Altherma frequent compressor cycling

[afternine]

Hi!

I'm a new member here, so I would like to say hello to everyone first! I hope you can cope up with my writing since I'm not a native English speaker.

I have a new house with a 6kW of heating power needed at -10°C ambient temperature, heated by an Daikin Altherma 8kW model (using Daikins swing compressor), driving a combination of underfloor heating and oversized radiators (connected on the same loop and using the same water temperature as the underfloor heating, always below 35°C ). I have no buffer tank. Indoor temperature regulation is done using Altherma's weather dependent water set point.

Altherma can regulate heating power from 4kW to 8kW. House needs 4kW at 0°C outside, so at higher outside temperatures (like these days as it is 7°C to 10°C outside) it has to work in intervals. Here comes the problem with cycling :
- altherma switches on for 2 minutes, starting with an higher compressor frequency and then gradualy reducing it, unitl it switches off at the end of this 2 minutes interval (since there is not enough heat demand).
- it waits for 2 minutes (nothing is running, not even circulation pump)
- switches on only the circulation pump for 2 minutes to read the water temperature - it is cold enough to cause it to start the compressor and starts the cycle again.

So I have a compressor start every 6 minutes - it means 10 in an hour -> more than 200 per day! :eek:

I believe that such a number of compressor starts is a recipe for heatpump failure, not to mention that it makes it difficult to maintain constant indoor temperature.

I guess I could install an indoor temperature thermostat but I would prefer not to do it, because of the slow response from underfloor heating and low house temperature inertion (it is made of light prefabricated insulated elements) - it means that at quick outside temperature variations the indoor temperature would lag behind. Maybe a buffer tank would help but I have no space reserved for it (water unit is located under the staircase). I found no way to reduce the number of cycles using user modifyable settings.


Is anyone else experiencing such problems with frequent starts/stops? Or am I just making an elephant out of a fly? Can a swing compressor withstand such a frequent cycling? I guess the same goes for pipes and heat excangers - is there a chance of early failure because of frequent pressure cycles? It is our first "real" heating season, heat pump was installed a year before (nov 2008), but rarely used since the house was not finished inside and we did not move in. I have another year of 3 year warranty period. I hope it does not break down the next day warranty expires. Can it last 10 years with such working regime?


Kind regards

[VRVIII]

Hi,
Does the system control on water temperature only? No room stats or zone valves etc.
Does the system incorporate a bypass regulating valve? The min water volume must be at least 10L when valve is in bypass.
Do you have commissioning data indicating the water flow rate?
Have you checked the water strainer is clean?

I would recommend installing a room thermostat, the weather dependant function can still be used.

[afternine]

Does the system control on water temperature only? No room stats or zone valves etc.
Yes, the only control is Altherma's own weather dependent control.

Does the system incorporate a bypass regulating valve?
No. No bypass valves are installed.


Do you have commissioning data indicating the water flow rate?

No, the water flow was not measured, but it should be enough, since we managed to get the "not enough flow"
error only when calibrating the flow through individual floor loops on first (lowest) pump speed with all the radiators "closed". In no other case this error occurs, so the flow rate should be high enough. The circulation pump has 3 possible settings - on highest and mid speed the water flow is high enough to cause hissing noise in the pipes (loud enough it can be heard throught the floor!), so I guess it is enough. The circulation pump is operating on middle speed, since at highest the noise realy gets "noticed".

Have you checked the water strainer is clean?
No, I talked to my installer and he said that because all piping is new the strainer should be clean. I have to say that I tried the running the circulation pump on each of three speeds, and after the system (water and floor temperature in function of the new flow rate) stabilises after about 10-12 hours , the behaviour is the same.

I would recommend installing a room thermostat, the weather dependant function can still be used.
As I said, I would prefer not to install a room thermostat, because the room thermostat signals the need for heating when room temperature has already fallen. By the time the underfloor heating builds up enough heat, I'm affraid it would be already quite cold inside the house because of the low thermal inertia of the house (I gets cold inside quickly), so I would prefer to have only weater dependant control, as it signals the need for heating as soon as it is needed. In this way the underfloor heating is "quick" enough to maintain constant inside temperature. I have to say that this system works remarkaby well with outside temperatures below 3°C since the working intervals become longer and power regulation is in effect.

I guess the best solution would be to have a modfied firmware for the controller with a wider heating hysteresis, but I guess this is something only guys from Daikin can provide.

I hope my answers explain the situation a bit.

[mad fridgie]

I am not sure of your product, but principles do not change.
I suggest that you have to much flow through your radiators (this is conterdictory to rads only) I suspect that the rads are unable to release the energy at at rate equal to the energy production. More flow through the floor is accebtable due to the ability of the floor to absorb larger amounts of energy compared to that of air. This should reduce the number of cycles, and I also think noise?? It should also smooth temp swings within the house (increased thermal storeage)
More flow through the heat pump is always a benefit.

[afternine]

Hi!

Thanx for suggestion - at first I had the same flow through all the pipes (checked with flow rate indicators on the manifolds), but this logic is flawed since hot water returns too quickly through radiators or the shortest floor loops. So I calibrated them in this way:
- closed the valves (for the tested floor loop or radiator)
- waited long enough for the radiator or floor to cool down (12-24 hours)
- open the valve by 1 milimeter and then wait for the flow to have effect (to warm up the radiator or floor)
- repeated the proces of opening of the valves by tiny bit and then waiting, until (in a few repetitions) the required heat output is obtained.

In this way, there should be no short circuit of returnig hot water.

I even tried with all the radiators closed, but the ciclying did not stop.

However, this is my configuration:
- 1. floor: 3x100m loops (living room, kitchen, dining room) + 2x50m loops (bathroom, hallway)
- 2. floor: 1x75m loop (bathroom) + 3x Korado type 22 radiator of heating surface of 12m2 (aprox. the same as the room surface, so heat output is "almost" the same as with floor heating).

Any other idea how to make it stop cycling?

[mad fridgie]

So your unit, uses return water temp as the control method, the set point is adjusted in relation to the ambient.
Lower ambient, higher set point.
Higher ambient, lower set point.
Is there a hysterises setting (differential)
Is your house being at the right temp (It is working well apart from the short cycling)
I am trying to get some feel for your system

[afternine]

So your unit, uses return water temp as the control method, the set point is adjusted in relation to the ambient.
Yes, precisely. It is also written in the Service manual for the Altherma models 11kW - 16kW (my is 8kW, but the service manual for 8kW model does not explain the compressor frequency control). Maybe the algorithm for frequency control is the same, or it may be not the same. I got the manuals from the Daikin extranet

Lower ambient, higher set point.
Higher ambient, lower set point.
Yes, current setpoints are 38°C at -10°C outside, 28°C at +15 outside.

Is there a hysterises setting (differential)
No, there is no user settable hysteresis. I guess this would be the solution to my problem.


Is your house being at the right temp (It is working well apart from the short cycling)
The temperature control works beautifully at low ambient temps, but it tends to overheat at high ambient temperatures because of fixed time intervals (2 minutes compressor operation every 4 minutes) and high starting compressor frequency, which gives too much heat.

Thanx for your time.

[Gary]

Hi!

I'm a new member here, so I would like to say hello to everyone first! I hope you can cope up with my writing since I'm not a native English speaker.

I have a new house with a 6kW of heating power needed at -10°C ambient temperature, heated by an Daikin Altherma 8kW model (using Daikins swing compressor), driving a combination of underfloor heating and oversized radiators (connected on the same loop and using the same water temperature as the underfloor heating, always below 35°C ). I have no buffer tank. Indoor temperature regulation is done using Altherma's weather dependent water set point.

Altherma can regulate heating power from 4kW to 8kW. House needs 4kW at 0°C outside, so at higher outside temperatures (like these days as it is 7°C to 10°C outside) it has to work in intervals. Here comes the problem with cycling :
- altherma switches on for 2 minutes, starting with an higher compressor frequency and then gradualy reducing it, unitl it switches off at the end of this 2 minutes interval (since there is not enough heat demand).
- it waits for 2 minutes (nothing is running, not even circulation pump)

I'm wondering why the circulation pump stops.

[mad fridgie]

At the higher ambient, your units heating out put increases (2.5% per C).
I would wasy we need to dampen the effect on the temp sensing probe. (without getting into the electronics)
The probe needs to be removed from the pocket. (no longer in the direct water flow)
Some form (an aluminium block, or a seal ed piece of pipe with some oil in) of mass needs to fixed onto the water pipe. The temp probe need to be fixed to this mass (opposite side to water pipe) This then need to be well insulated.
you will get over and under shoot (short term), but a better averaged temp and reduction in short cycling.
( aliitle hard to sort problems, when somebody elese has written the software)

[Gary]

I have no experience with these particular systems, but it seems to me the pump should run 24/7 throughout the heating season.

[afternine]

@Gary
This is another thing I also tried - I did force the circulation pump to work all the time (it is written in the user manual how to do it), but this did not improve the cycling. Since it did not matter, I put it back to default operation (on/off). Maybe they switch it off to save electricity, but I guess it only strains the pipes with flow starting/stopping.

@mad fridgie
As far as I could see, the Altherma has the temperature probes on the tubes, not directly in the waterflow - it has an insulation sleeve over the tube and a wire going in between the tube and the inslulation. I would post a picture, but the forum does not let me post html links yet.

But I think your suggestion might work! I have to talk to my installer about this modification (I guess someone could tell without a doubt that sensor has been tampered with) so I don't get my warranty void.

Is it possible that such modification (delayed reading of correct return flow temperature) breaks something (i.e. compressor overload or something similar)???

[mad fridgie]

Your are not running the machine at extremes, so slight overshoot will not have an effect the the running gear (comp, etc)
Your present probe is position is effectively is in the flow. (quick reaction)
a simple test, get some aluminium foil (or foil tape) add aprox. 40mm around the pipe, add probe at about 30mm. (add some insulation old socks just for test)

[Gary]

@Gary
This is another thing I also tried - I did force the circulation pump to work all the time (it is written in the user manual how to do it), but this did not improve the cycling. Since it did not matter, I put it back to default operation (on/off). Maybe they switch it off to save electricity, but I guess it only strains the pipes with flow starting/stopping.


I wouldn't expect it to improve right away. The water would need to circulate for a while, but would eventually even out the temps.

[afternine]

@Gary
I had it on 24/7 for about 45 days - I knew it would take a while to get things in balance, but sadly it did not improve the cycling.

@mad fridgie
You surely got me fired up, I will take a look tomorrow how to try it out (it's almost midnight here and everyone is already sleeping, so makeing noise this very moment is not an option).

On the other hand, I guess I run the machine at full power sometimes - I'm sorry I did not tell it before, but Altherma is used for heating the hot sanitary water, too. When heating the HSW, the water temperature gets to about 50°C, which is Alterma's max water temperature. Is there anything that can go wrong because of the modification when heating HSW?

Right now I try to reduce cycling by using the built in timer and alternating intervals with lower temperature and higher temperature than it would be normal. Needless to say that this is not the desired operating mode.

[mad fridgie]

I wouldn't expect it to improve right away. The water would need to circulate for a while, but would eventually even out the temps.
This maybe true for fixed water temps, but these system the temps change.
If you imagine that the house heat exchangers (rads and underfloor) are added together and have a total total rating of 0.3Kw/C (based on linear, not quite true put good enough) ie; house 20C water 25C heat released would be 1.5kw
So when cold outside, water is 38C so heat rejected into the house is 5.4kw (this would balance roughly with units performance all fine)
When mild ambient (15C) water is at 28C, so heat rejected 2.4Kw, but heat output would be at least a good 10kw. the nett effect si the the water warms very quickly. Unit turns off, but does not have enough time to change the thermal mass temp with in the house, so short cycling.
Many ways to fix in design, but trying to find one without major mechnical or electronic changes.

[Gary]

This maybe true for fixed water temps, but these system the temps change.
If you imagine that the house heat exchangers (rads and underfloor) are added together and have a total total rating of 0.3Kw/C (based on linear, not quite true put good enough) ie; house 20C water 25C heat released would be 1.5kw
So when cold outside, water is 38C so heat rejected into the house is 5.4kw (this would balance roughly with units performance all fine)
When mild ambient (15C) water is at 28C, so heat rejected 2.4Kw, but heat output would be at least a good 10kw. the nett effect si the the water warms very quickly. Unit turns off, but does not have enough time to change the thermal mass temp with in the house, so short cycling.
Many ways to fix in design, but trying to find one without major mechnical or electronic changes.

I would tend towards major changes. :)

For starters, I would add a separate pump for the rads and run it off a room thermostat.

[afternine]

You explained it very well. I thought that a producer like Daking would have sorted such things out, but I guess they did overlook this situation. BTW, is there any way to get in touch with Daikin and let them know about this problem?

By using aluminium foil -> you mean the foil my wife has in the kitchen for wrapping food? I guess it takes many wraps to make it 40mm thick! ;)

[mad fridgie]

I suspect when you do your domestic hot water (HSW), run time will be of some length, so dampening is reduced, and overshoot is reduced, this is not a major!

[mad fridgie]

You explained it very well. I thought that a producer like Daking would have sorted such things out, but I guess they did overlook this situation. BTW, is there any way to get in touch with Daikin and let them know about this problem?

By using aluminium foil -> you mean the foil my wife has in the kitchen for wrapping food? I guess it takes many wraps to make it 40mm thick! ;)
Yes just ouy of the kitchen, Fold foil into a saugage first (to make fatter) less times to wrap, need not be perfect!

[afternine]

Yes, heating HSW takes 40+ minutes, so I guess dampening would not be an issue.

@Gary
I would really like to try the alternatives which require no major $ or € or ...

[afternine]

OK, I'll see if I can try the "sausage" fix... I'll try to wrap it up tight first to get good thermal conductivity and small dampening and if it does not help then loose it up to make dampening bigger.

[mad fridgie]

OK, I'll see if I can try the "sausage" fix... I'll try to wrap it up tight first to get good thermal conductivity and small dampening and if it does not help then loose it up to make dampening bigger.
This is a bit trail and error, at this stage just proving that it works (it will, in a fashion) It is alittle easier for me when I can touch and feel, so can only give basic indications.
Once proved you install company should be able to knock something up, that is a bit more prescise.
Go to bed, I hear your wife call!:D

[afternine]

He he, wife already sleeps for about 2 hours :).

I will post as soon as I get some results. I just hope not to break something - you know - just finished the house and moved in - so no surplus of cash at the moment for a replacement heat pump. :p

Is there any way to contact Daikin and get this fixed as it should be - with software upgrade? I can try writing to support@daikin.com but I guess it is a long shot.

[VRVIII]

Your are not running the machine at extremes, so slight overshoot will not have an effect the the running gear (comp, etc)
Your present probe is position is effectively is in the flow. (quick reaction)
a simple test, get some aluminium foil (or foil tape) add aprox. 40mm around the pipe, add probe at about 30mm. (add some insulation old socks just for test)
Mad fridgie,
I understand your thought process but there is a couple of problems with it:
1/ The unit has 3 water sensors (+1 in DHW tank)
2/ The sensor is also used to calculate required outdoor capacity, so reducing the sensor temp will increase capacity.


I suspect when you do your domestic hot water (HSW), run time will be of some length, so dampening is reduced, and overshoot is reduced, this is not a major!
The DHW tank has an idependant sensor and a larger dead band which is adjustable.

[mad fridgie]

Mad fridgie,
I understand your thought process but there is a couple of problems with it:
1/ The unit has 3 water sensors (+1 in DHW tank)
2/ The sensor is also used to calculate required outdoor capacity, so reducing the sensor temp will increase capacity.


The DHW tank has an idependant sensor and a larger dead band which is adjustable.
I do not know the product, good that you have practical experience.
We are not reducing the sensor temp, but reducing the reaction time.
I suspect (but could be wrong) when these start up, that after a short period, they ramp to full speed, (possibly for a number of reasons) when getting close to set point unit will ramp down (more than likely many smarts controlling) i did state that the ubit will under and over shoot.
This is a compremise,.
maybe there are more changes to be made in the software at a higher level than the operator can access. One presumes he has already contacted his specialist.

[afternine]

Hi guys, I'm not in bed, yet...

I did contact my installtion specialist and he did measure the compressor frequency - fast start then slowing down. He said everything is OK and that I have to live with it .:confused:

[Gary]

Yes, current setpoints are 38°C at -10°C outside, 28°C at +15 outside.

The temperature control works beautifully at low ambient temps, but it tends to overheat at high ambient temperatures...

This would seem to indicate that 28C@15C is too high.

[afternine]

Originaly it was set to 25°C at +15°C outside (it can not be set lower than 25°C) but I also got overheating. I tried to rise it up a bit to lenghten the working interval and (hopefully) the stop interval, too. Sadly, it didn't work out this way, and I left it on 28°C, as it didn't do any difference. I will put it back to 25°C.

[mad fridgie]

How is it going?

[Brian_UK]

I know that you are concerned about compressor starts but a brief read of the manual indicates that the room sensor, if fitted, is designed to stop overheating by switching the system off.

Perhaps this may be worth investigating as the outdoor unit is oversized for the heat load.

[afternine]

Hi!

While rereading the entire thread again, the reply from Gary (... This would seem to indicate that 28C@15C is too high ...) got me thinking for the milionth time:

I can not set lowest setpoint lower than 25°C (factory setting, although there is a setting 9-01 "Heating set point lower limit. which I set to 15°C, so it should let me set the low setpoint lower than 25°C, but it does not). Than I got the idea: 25°C is at 15°C outside - maybe I can "move" the 15°C outside - indeed I could set it, I set it to 11°C - this is equivalent to 22,5°C at 15° outside. In this way I can lower the low end of the heating curve.

Then I removed the units cover, set the circulation pump to "always on" and waited for a couple of hours - and I have a little difference! Today it was cloudy with almost constant temperature between 9°C and 10°C and the compressor makes 2 to 3 cycles (2 minute on, 4 minutes off), then "sleeps" for about 8 minutes (skips 1 to 2 cycles), then it repeats 2 to 3 cycles, sleeps for 8 minutes... I guess it is some improvement, although really not much.

While the cover was off, I took a look at thermistors: there are 4 thermistors:
- inlet return water
- outlet water heat exchanger
- refrigerant liquid side heat exchanger
- outlet backup heater

Here is a copy/paste excerpt from the Service manual regarding frequency control:

3.3 Frequency Control
Outline
Frequency will be determined according to the difference between water and set temperature.

The function is explained as follows:
How to determine frequency.
Frequency command from a hydro-box (the difference between the water temperature and the
temperature set by the remote controller).
Frequency command from a hydro-box.
Frequency initial setting.
PI control.


Determine command frequency
Command frequency will be determined in the following order of priority:
Limiting frequency by drooping function
Input current, discharge pipes, low Hz high pressure limit, peak cutting, freeze prevention, fin
thermistor temperature.
Limiting defrost control time
Forced cooling
Indoor frequency command

Determine upper limit frequency
Set a minimum value as an upper limit frequency among the frequency upper limits of the following
functions:
Compressor protection, input current, discharge pipes, Low Hz high pressure, peak cutting, freeze
prevention, defrost.

Determine lower limit frequency
Set a maximum value as an lower limit frequency among the frequency lower limits of the following
functions:
Four way valve operating compensation, pressure difference upkeep.

Determine prohibited frequency
There is a certain prohibited frequency such as a power supply frequency.


Indoor frequency command (∆D signal)
The difference between the outlet water temperature and the temperature set by the remote controller will be taken as the “∆D signal” and is used for frequency command.

Frequency initial setting
When starting the compressor, or when conditions are varied due to the change of the room, the frequency must be initialized according to the total of a maximum ∆D value of the hydro-box and the Q value of the hydro-box.
Q value: hydro-box output determined from hydro-box.


PI Control (determine frequency up/down by ∆D signal)
P control
Calculate ∆D value in each sampling time (20 seconds), and adjust the frequency according to its
difference from the frequency previously calculated.

I control
If the operating frequency is not change more than a certain fixed time, adjust the frequency up
and down according to the ∆D value, obtaining the fixed ∆D value.
When the ∆D value is small...lower the frequency.
When the ∆D value is large...increase the frequency.

Limit of frequency variation width
When the difference between input current and input current drooping value is less than 1.5 A, the
frequency increase width must be limited.

Frequency management when other controls are functioning
When frequency is drooping;
Frequency management is carried out only when the frequency droops.
For limiting lower limit
Frequency management is carried out only when the frequency rises.

Upper and lower limit of frequency by PI control
The frequency upper and lower limits are set depending on hydro-box.
When outdoor unit low noise or quiet commands come from hydro-box, the upper limit frequency
must be lowered than the usual setting.

If I'm right, the main thing that regulates the compressor frequency is the ∆D, which is "the difference between the outlet (which oulet???? heat exchanger or floor heating manifold) water temperature and the temperature set by the remote controller". Maybe someone can see some other way to lenghten the cycles.

I guess the only thing that would fix cycling is "sausage fix" or updated software.

Before atempting the sausage fix I will contact my installer and discuss it with him.

I have no room sensor fitted in the house. As for the oversized outdoor unit - every Altherma under the 8kW range has minimum power output of 4kW - even the smallest 6kW unit (so I guess it is not much of an inverter). The only difference between units in 6 - 8 kW range is max compressor frequency. I don't know about bigger Althermas (11-16kW range) as they don't have stated minimum power output and have different type of compressor (scroll).

[Gary]

Six cycles per hour is widely considered acceptable.

I would be more concerned with the overheating in milder weather.

And I would think twice before messing with the frequency controls.

[afternine]

Six cycles per hour is widely considered acceptable.
OK, but what would be an optimal number of cycles in such mild conditions? What number of cycles per hour would you like to see if it was your heatpump?


I would be more concerned with the overheating in milder weather.
With the new lower setpoint setting I hope it is resolved. As for what I could see today I think overheating won't be an issue any more.


And I would think twice before messing with the frequency controls.
That's why I want to talk to my installer - I do not want to fry something and be left without warranty.

Today I heard one possible reason why is such cycling designed - Althermas in 6-8kW range do not have a crankcase heater - could be power cycling needed to keep the compressor from cooling down too much???

[Gary]

, but what would be an optimal number of cycles in such mild conditions? What number of cycles per hour would you like to see if it was your heatpump?

Without a buffer, it either runs more often or has wider temp swings... pick your poison. Six per hour is acceptable.

[mad fridgie]

Without a buffer, it either runs more often or has wider temp swings... pick your poison. Six per hour is acceptable.
Agreed,
I think this must be a well insulated house (or very small), and a quick acting system.

[afternine]

I'd prefer a little bit wider temp swings and a compressor that runs for 20 years. As it is now, I hope it runs for 10 years.

The house is a 2 store high light prefabricated construction with 20cm of isolation on walls. It does not need much heating power, but once you switch heating off it cools down rather quickly because of low mass. This is the reason I opted for underfloor heating - needed to have a mass that keeps temperature stable. I would not have installed radiators, but wife insisted not to have ceramic tiles in bedrooms.

[mad fridgie]

I'd prefer a little bit wider temp swings and a compressor that runs for 20 years. As it is now, I hope it runs for 10 years.

The house is a 2 store high light prefabricated construction with 20cm of isolation on walls. It does not need much heating power, but once you switch heating off it cools down rather quickly because of low mass. This is the reason I opted for underfloor heating - needed to have a mass that keeps temperature stable. I would not have installed radiators, but wife insisted not to have ceramic tiles in bedrooms.
Play with the sausage, this will give the swing (under/over shoot)

[frank]

I can not set lowest setpoint lower than 25°C (factory setting, although there is a setting 9-01 "Heating set point lower limit. which I set to 15°C, so it should let me set the low setpoint lower than 25°C, but it does not).
This is to stop "over condensing" and liquid return to the compressor. When the water temp is 16C or below, the Hydrobox will engage the back up heater to raise the water circuit temp before allowing the compressor to run.


regulates the compressor frequency is the ∆D, which is "the difference between the outlet (which oulet???? heat exchanger or floor heating manifold)
It is the outlet from the Hydrobox as there is no sensor on your underfloor manifold.
The compressors do not need a crankcase heater as they pass a small current through the windings during the off cycle, to warm the oil.

[afternine]

Frank, thax for clarifying things.


It is the outlet from the Hydrobox as there is no sensor on your underfloor manifold.
He he... sure there is no sensor on manifold ;) :o

Now I'm in doubt if the "sausage fix" would work - we were talking about delaying readings from the inlet return water thermistor of the heat exchanger (thus prolonging the diference between the return flow and the setpoint), not the outlet (difference between momentarily achieved water temperature and set point).

Now the question is: should the sausage fix be applied to the outlet water heat exchanger thermistor, too? Maybe only to the outlet thermistor? The Service manual is not clear about this - all it says is "the difference is computed between the outlet and setpoint".

I know this is becoming a little bit silly (delaying readings here and there), but I would like to grasp the theory correctly.

[mad fridgie]

This is making sense, and makes worse. The higher the ambient the hot water coming out.
When you have the pump turning on and off, how long is the pump on after the comp turns off?

[afternine]

When you have the pump turning on and off, how long is the pump on after the comp turns off?

The circluation pump switches off at the same time as the compressor. From that moment outside fan runs for another minute, but the circulation pump sleeps for 2 minutes. Then the circ. pump goes on for 2 minutes to get the water temperatures right. Ater this second 2 minutes interval, the compressor starts.

Right now I have the circulation pump on "always on" setting.

[mad fridgie]

I need to find out when the comp and pump turns off, what then turns the pump back on.
A; Just temp setting
B: Pump pulses every so oftern to ensure that probe is reading the right temp.
To test set pump back to on/off mode.
Adjust set point high, run until water temp is high, then turn to low set point.
All should turn off, watch pump, how long before pump comes back on?

[afternine]

I need to find out when the comp and pump turns off, what then turns the pump back on.

The circulation pump goes on 2 minutes after the compressor stopped, and stays on (it does not turn off until next compressor stop)


Adjust set point high, run until water temp is high, then turn to low set point. All should turn off, watch pump, how long before pump comes back on?

I currently do this strategy (high temp then low temp) with timer (runs for 3 hours at the weather dependent set point +3°C , then for 5 hours at -5°). This way I use underfloor heating as buffer tank for radiators (room temperature does not swing more than 0,5°C) and somewhat lower the number of compressor starts. The circluation pump runs as described above. Compressor start is triggered when water gets cold enough for the current setpoint.

[mad fridgie]

OK, not what I wanted to hear!
Increase water flow would help, but noise is a problem.
The foil will still dampen the effect. (not quite as good as on the return)
Set controller back to original settings, but have set point at 25 not 28. (at 15 ambient)
Have ago! It should increase run times and increase of times.

[Brian_UK]

I'm getting confused with the water sensor positions, it's me, don't worry ;)

On an underfloor system using a heating boiler the normal control would be aiming for a set point temperature on the flow to the manifold.

The set point would be controlled by a mixing or diverting valve on the underfloor water circuit.

So the Altherma is trying to achieve set point temperature by modulating the compressor speed whilst the set point is being modulated itself by the weather compensation software in the system.

Also, if the pump stops with the compressor off mode then whenever the pump starts, in a temperature sampling, then is it monitoring the temperature of the water returning from the underfloor system or is it checking the temperature from the hydrobox?

It seems to me that the underfloor loops are not maintaining a stable temperature (maybe that's the way it is designed?) which goes against the design of underfloor heating; correct me if I'm wrong here.

If we assume that a heating cycle has completed and the pump has shut off then, with your low heat retention, the water in the pipe loops will begin to cool quite quickly.

The pump kicks in to check the system status and gets a slug of overcooled water. So the system starts up with the compressor heading for maximum capacity to compensate.

I think that you should keep the pump running to provide a more steady load on the controls.

[mad fridgie]

I sort agree Brian, I would not control a system as descibed, but what do I know.
With how it seems set up, and the temp settings, there simply is not enough run time to introduce energy energy into the underfloor (thermal storage), so regardless if the pump runs or cycles, water temp will fall quickly.
This system also has rads, so heat is lost very quickly from these (no thermal mass)
There seems to be no method of adjusting diff or dead band on these units.
All problems can fixed with $$$$
Normally, i control on return water temp (cold into the heat pump) and have room control via a stat in the concrete (Not in the air, no good for underfloor heating with a heat pump)
Increaseing the flow through the cond, would reduce the TD between water in/out and would introduce more energy into the floor, and make the system more stable, but at high flow noise seems to be a problem.

[afternine]

So the Altherma is trying to achieve set point temperature by modulating the compressor speed whilst the set point is being modulated itself by the weather compensation software in the system.
Exactly.



Also, if the pump stops with the compressor off mode then whenever the pump starts, in a temperature sampling, then is it monitoring the temperature of the water returning from the underfloor system or is it checking the temperature from the hydrobox?
It has a termistor before and after the heat excanger in the hydrobox. While the compressor is off, the water passing through heat excanger is not heated, so both thermistors read the same value. Altherma displays on the control panel the temperature that is on the heat exchanger outlet, so when compressor starts you can see water temperature raising, but you can not see the water temperature coming from the manifold (return flow) any more.



It seems to me that the underfloor loops are not maintaining a stable temperature (maybe that's the way it is designed?) which goes against the design of underfloor heating; correct me if I'm wrong here.
The underfloor loops keep rather stable temperature, since there is 15cm of insulation beneath the loops, and they are covered with 6cm of concrete, on which ceramic tyles are laid. The water from radiators is joined (mixed) with water from underfloor loops before going to heatpump. As far as I could observe it looses (the mixed water) about 1°C in 2 hours. This is not an exact measurement.



I think that you should keep the pump running to provide a more steady load on the controls.
That's why I set it to "alwasy on".

[Gary]

Increaseing the flow through the cond, would reduce the TD between water in/out and would introduce more energy into the floor, and make the system more stable, but at high flow noise seems to be a problem.

I'm wondering if decreasing the water flow wouldn't stretch the run time and thus lengthen the cycles.

[afternine]

Increaseing the flow through the cond, would reduce the TD between water in/out and would introduce more energy into the floor, and make the system more stable,
There was an idea to switch the pump to slowest speed to let the water to really cool down before returning to heat pump, thus increasing dT. Needless to say that did not work. Then we tried on max speed for a entire day to let it stabilise - also did not work.



but at high flow noise seems to be a problem.
yes, on max speed it is unaceptable, so it is runinng on middle speed always on.



There seems to be no method of adjusting diff or dead band on these units.
This is the source of "all evil"

[afternine]

I'm wondering if decreasing the water flow wouldn't stretch the run time and thus lengthen the cycles.
It seem that at min speed the all the heat generated can not get transfered to water quickly enoug, so the compressor stops.

It seems that even at max speed the heat can not get transferred quickly enoug from water through pipes to concrete to cool it down to have a large enough temperature difference on return. On the other hand, when concrete is heated enoug - it can not accept any more heat (energy is transfeered only from higher temp to lower temp - when there is no heat difference, there is no energy transfer, so a wider band would be needed.

[afternine]

A little off topic - is there a way to edit a post after it has been submited? Since English is not my first language I find it difficult to get the right words, then after rereading I would often edit something, but I can not find how to do it.

[Toosh]

A little off topic - is there a way to edit a post after it has been submited? Since English is not my first language I find it difficult to get the right words, then after rereading I would often edit something, but I can not find how to do it.

Hi When you make a post at the bottom you will see an edit button click it make your changes then click edit and then save changes. Hope this helps

Toosh

[mad fridgie]

Without going to high expense, dampen the probe (reduced response time) Nothing to loose, all to gain!

[afternine]

Yes, I already contacted my installer and he said he will come one of these days. If the machine was out of warranty period I would try it out myself, but in this case...

When it is done I will surely post the results back. In the meantime, has anyone got a contact to some Daikin support? Here we have only authorised resellers, noone from Daikin around....

[Gary]

It seem that at min speed the all the heat generated can not get transfered to water quickly enoug, so the compressor stops.

It seems that even at max speed the heat can not get transferred quickly enoug from water through pipes to concrete to cool it down to have a large enough temperature difference on return. On the other hand, when concrete is heated enoug - it can not accept any more heat (energy is transfeered only from higher temp to lower temp - when there is no heat difference, there is no energy transfer, so a wider band would be needed.

Hmmm... At low speed there is insufficient flow. At high speed there is noise. I'm beginning to think you have a water flow problem. Possibly the branch/balancing valves are closed off too much.

[Gary]

Hi!

Thanx for suggestion - at first I had the same flow through all the pipes (checked with flow rate indicators on the manifolds), but this logic is flawed since hot water returns too quickly through radiators or the shortest floor loops. So I calibrated them in this way:
- closed the valves (for the tested floor loop or radiator)
- waited long enough for the radiator or floor to cool down (12-24 hours)
- open the valve by 1 milimeter and then wait for the flow to have effect (to warm up the radiator or floor)
- repeated the proces of opening of the valves by tiny bit and then waiting, until (in a few repetitions) the required heat output is obtained.

This seems backwards. I would start with all of the valves full open and close off a little at a time to balance the flow.

[afternine]

Valves on 3 longest loops (cca 100m) are fully open, since they have the highest hidraulic resistance (and are roughly the same length) I think there is no point in closing their valves

On the shortest loops I did start with closed valves and then slowly opening them to avoid thermal short circuit.

The valves of radiators are opened just enough to get enough heating in the room (also to avoid short circuit through radiator)

This way I tried to make sure there are no thermal short circuits and the longest loops also get enough flow to hopefully provide the buffer tank effect also.

I have to say there are no cold spots in the house - the heating is nicely even everywhere.

I would suppose that if the short loops are too short to provide enough heat with same water flow as the longer loops, they would need a higher flow and I'd get a short circuit through them. However, the flow meters on the manifold indicate that flow through the short ones is lower than through longer loops - if those meters are to be trusted - I don't put much faith in them.

Here's recap of my situation - each floor has it's own manifold:
- 1. floor: 3x100m loops (living room, kitchen, dining room) + 2x50m loops (bathroom, hallway)
- 2. floor: 1x75m loop (bathroom) + 3x Korado type 22 radiator of heating surface of 12m2 each (2 plates 180x60cm with folded fins between them)
There are no mixing valves, motorised valves and such things - it is kept as simple as possible - everything gets the same water te mperature.

[frank]

Are you able to measure the temperatures, fairly accurately, on the flow pipe and return pipe under the Hydrobox, just near the valves, when the unit is on full power?

[afternine]

Sadly no, I don't have a thermometer that is nearly precise enough to do such thing. Maybe I can get something in the afternoon, when I finish at work.

[VRVIII]

altherma switches on for 2 minutes, starting with an higher compressor frequency and then gradualy reducing it, unitl it switches off at the end of this 2 minutes interval (since there is not enough heat demand).


What is the full model number of your hydrobox?

When the outdoor is started the unit will enter start up control and operate with preset values for EEV opening, inverter frequency and pump control.
- Inverter frequency is limited to 55Hz 120secs then 70Hz for a further 80secs
- Preheat control may hold off the pump until desired heat exchanger temp is reached.
- The unit also incorporates a 3min anti recycling timer to prevent excessive tart/stops
- The water thermostat control sensor is R1T located between the heat exchanger and back up heater

As Frank suggested you could calculate an approx flow rate by checking delta T across the inlet/outlet water temps (normally around 5K)
- Switch off unit or lower set point to 25~30
- Start system when water temp is <30
- Temporarily increase set point to 40
- Wait for 10min to ensure system is operating at 100% capacity
- Check temperature difference across inlet & outlet water pipes at hydobox.

The 3 port valve for changing from DHW to Space heating (if applicable) must be a diverting valve not mid a position valve. It may be worth verifying the correct valve has been installed and is operating correctly (these are often miss wired)
.

[Brian_UK]

Sadly no, I don't have a thermometer that is nearly precise enough to do such thing. Maybe I can get something in the afternoon, when I finish at work.Good idea.

Although your flow indicators are working the measurement of the return loop temperatures would help you to balance the system better. You may actually have a short circuit through part of the system which will encourage early compressor shut down.

With the system running, work from the index fully open circuit and compare with the next circuit. Adjust flow valve to achieve the same, or closely similar, return temperature. Proceed through the whole system until all returns are at the same temperature.

[mad fridgie]

VRVIII, has given good information on how the unit operates, thought there was some other smarts controlling this.
I would not waste your time measuring temps to assume flow rates, +/-50% really means nothing. Unless you know the actual Kw output then all very big guess.
Lets look at some numbers
House 20C, so coldest possible water return temp 20C, ambient 15C, heat pump is likely to be giving 10Kw of heat energy (not lower levels as rated conditions) Set point 25C at outlet of heat pump. Presume flow rate of 0.3L/S (mid point for these types of circ pumps) Temp rise would just less than 8C, unit will turn off.
From what has been said the machine has the ability for an external thermostat. What is needed is 2 thermostats wired in parrallel, one measuring ambient and one measuring return water temp (with adjustable diffs)
1; ambient lets say set at 8C above this becomes open circuit
2 return water temp, lets say set at 24C, above this becomes open circuit.
The unit setting is maintained at higher set point lets say 32C.
This will allow for extended run times, and prelonged off times, whilst reducing temp swings. At lower temps, the system will revert back to original operation, which works fine as is.

[VRVIII]

VRVIII, has given good information on how the unit operates, thought there was some other smarts controlling this.
I would not waste your time measuring temps to assume flow rates, +/-50% really means nothing. Unless you know the actual Kw output then all very big guess.
Lets look at some numbers
House 20C, so coldest possible water return temp 20C, ambient 15C, heat pump is likely to be giving 10Kw of heat energy (not lower levels as rated conditions) Set point 25C at outlet of heat pump. Presume flow rate of 0.3L/S (mid point for these types of circ pumps) Temp rise would just less than 8C, unit will turn off.
From what has been said the machine has the ability for an external thermostat. What is needed is 2 thermostats wired in parrallel, one measuring ambient and one measuring return water temp (with adjustable diffs)
1; ambient lets say set at 8C above this becomes open circuit
2 return water temp, lets say set at 24C, above this becomes open circuit.
The unit setting is maintained at higher set point lets say 32C.
This will allow for extended run times, and prelonged off times, whilst reducing temp swings. At lower temps, the system will revert back to original operation, which works fine as is.

Mad frigrie,

The nominal flow rate for a size 8 unit in heating mode 24 L/min, the flow switch will trip at around 12L/min.
The unit capacity can be found in the technical data book capacity tables, this gives unit capacities under various conditions.
i.e. ambient temp 7 CDB with a leaving water temperature of 35 C = 8.4kw (nominal)
If you divide the unit capacity by heat exchanger delta T then divide by 4.2 (specific heat value for water with no additives) = flow rate in L/s
i.e. 8.4(KW) / 5(ºC ∆T) / 4.2 = 0.4L/S X 60 = 24 L/min.
This would give a good indication of the flow rate providing the unit is operating at 100% capacity.

I could be wrong here but I’m sure there are room stats available which monitor room temp and slab temp, they have a self leaning logic to maintain an optimum room temp under various conditions.


Afternine,
What is the full model number of your Hydrobox?
What size of water pipes is connected to the Hydrobox? (These should be 28mm)

[afternine]

Hi!

Here are the facts:
- indoor unit model is EKHBH008AA6WN, manufactured in 2008, serial number 3800475. On the sticker there is another code: 3PW41657-25A
- printed circuit board in indoor unit:
- has the code (similar but not the same as on the sticker): 3PW43696-1A (should they be the same?)
- lot number: 788ß (yes, this is the "beta" sign - I hope this does not mean "beta" board as in software)
- the main chip on the PCB has a sticker on it: VP00203 V016

Outdoor unit:
- model ERHQ008ADV3
- manufactured in 2008
- serial number J002291

Sanitary Water tank model: EKHWSS200-300A3Z2

Now for the measurements: I borrowed an Minolta Cyclops 300af thermal camera to do the measurements (this thing was $2000 in 2004!):

- circulation pump is set to middle speed
- outside ambient temperature: 9.5°C
- starting water temperature value on controller: 24.4°C
- starting temperature of return flow pipe measured with Minolta: 24.7 °C

- water set point: 45°C
after 15 minutes the values are:
- on the controller: 38.4°C
- heated water pipe (measured with Minolta): 32.3°C
- return water pipe (measured with Minolta): 27.1°C

Since the measured pipe temperature and controller water temperature differed greatly, I took a look at the thermometers on manifolds; both read about the same value:
- heated water 39°C
- return water 33°C

@Brian_UK
I tried to measure the temperature of each pipe that returns to manifold and I had a "control" pipe - one radiator was closed (no flow through it). All pipes had about the same temperature, the pipe that comes from closed radiator was 2°C cooler than others. I did not find a pipe that is significantly hotter than others. I'll measure again, since the camera is better suited for measuring temperature of flat surfaces, on roud surfaces it can get a reading way off.

From what I see I guess there is enough flow and no obvious short circuits. Oh, and I found a sticker on the wire that goest to the flow switch - it says "setpoint 8l/min +- 1l".

30 minutes after the test the water temperature was 26.5°C

@mad fridgie
when using additional room thermostat Altherma "forgets" about its own controll.

It seems to me it will be either the sausage fix or the software fix - the first being more likely :(

[mad fridgie]

Mad frigrie,

The nominal flow rate for a size 8 unit in heating mode 24 L/min, the flow switch will trip at around 12L/min.
The unit capacity can be found in the technical data book capacity tables, this gives unit capacities under various conditions.
i.e. ambient temp 7 CDB with a leaving water temperature of 35 C = 8.4kw (nominal)
If you divide the unit capacity by heat exchanger delta T then divide by 4.2 (specific heat value for water with no additives) = flow rate in L/s
i.e. 8.4(KW) / 5(ºC ∆T) / 4.2 = 0.4L/S X 60 = 24 L/min.
This would give a good indication of the flow rate providing the unit is operating at 100% capacity.

I could be wrong here but I’m sure there are room stats available which monitor room temp and slab temp, they have a self leaning logic to maintain an optimum room temp under various conditions.


Afternine,
What is the full model number of your Hydrobox?
What size of water pipes is connected to the Hydrobox? (These should be 28mm)
Yes and No, (do not have manual) we are looking at 15 ambient water on at min 20C, so refrigeration capacity could be anything (basic principles indicate a 20% rise in heat of rejection), and is the machine running at 100% (there are likely to many things that effect the load profile, does it have predicitive load limiting, if so how, when is introduced) Yes at what speed is this pump flow rate, and at what water pressure drop. As it seems there is only one pump, it is driving through the heatexchanger, underfloor, rads and hot water. So it would expect that flow rate would be less, due to pressure drops. You can not use ratings as a guide unless you are at the rated condition. To make it worth doing to some level of reality real figures have to be used.
remember the system does work fine, the OP does seem to have a lot of understanding.
The question is "is there any way that the differential/deadband/reaction time/ramp period, can be adjusted", here lies the problem.

[mad fridgie]

Afternine, what great detail, I wish all could give this level of information. "welldone"
It would seem that you have a flow rate rate of around 0.35L/S which is OK.

[afternine]

@VRVIII:

Outer diameter of pipes is 34mm - here is a picture of my setup (hey, the forum lets me put links in posts now!):

http://www.4shared.com/file/74458060/6fefed70/hpim6992.html



As it seems there is only one pump
Yes, there is only one circulation pump

[VRVIII]

Yes and No, (do not have manual) we are looking at 15 ambient water on at min 20C, so refrigeration capacity could be anything (basic principles indicate a 20% rise in heat of rejection), and is the machine running at 100% (there are likely to many things that effect the load profile, does it have predicitive load limiting, if so how, when is introduced) Yes at what speed is this pump flow rate, and at what water pressure drop. As it seems there is only one pump, it is driving through the heatexchanger, underfloor, rads and hot water. So it would expect that flow rate would be less, due to pressure drops. You can not use ratings as a guide unless you are at the rated condition. To make it worth doing to some level of reality real figures have to be used.
remember the system does work fine, the OP does seem to have a lot of understanding.

The unit data book includes capacity table indicating capacity in kw at various ambient and water temperatures. However as you say it can be difficult to verify the unit is operating at 100% as the inverter controls incorporate various temperature and current limiting functions.



The question is "is there any way that the differential/deadband/reaction time/ramp period, can be adjusted", here lies the problem

As far as I’m aware none of these are adjustable.

[afternine]

As far as I’m aware none of these are adjustable.
Since you asked for exact hydrobox model I was hoping you knew some trick/way to adjust the parameters.

[VRVIII]

Since you asked for exact hydrobox model I was hoping you knew some trick/way to adjust the parameters.
Afternine,

It was only the hydrobox full model number I requested - EKHBH008AA6WN. This was to confirm which settings are available on your unit, the available setting can vary depending on series.




@mad fridgie
when using additional room thermostat Altherma "forgets" about its own controll.

If you connect an additional room thermostat the only Altherma controller functions that will be lost are space heating on/off button and space heating schedule timers.

[brunstar]

If you would like to reduce the capacity out of the machine and also reduce the compressor cycling, run the system on the night quite mode which will limit the upperlimit of the compressor frequency and also the fan speed which will also limit the capacity.

To run the indoor water pump continuously without a room thermostat you will have to isolate the unit, put a bridge wire across the thermostat terminals 1, 2 and 4 and turn dip switch 3 on on the indoor printed circuit board.
let us know how you go with this.

[brunstar]

i just looked at your pictures, have you installed the 3 port valve motor to the system? if you have not done this, this would also be why the unit is short cycling.
You have low resistance through the domestic hot water cylinder and flow = return will cycle the unit off...
have you installed the motor or do you leave the body in the mid position?

[afternine]

Hi everybody!

Sorry for being quiet so long, but in the meantime we had all sorts of things going on, including tornado speed winds with gusts topping over 240 km/h - yep, I thought we'll be blown off with the house and everything - this time I was sorry for not building with brick and mortar, however, luckily everything is fine. And Altherma worked fine in such wind, with no problems, keeping us warm! I expected it to get maybe a fan error since the wind was full frontal into the outdoor unit, but it just kept going.

Now, about the Altherma's cycling - I spoke with the guy who installed my system and he is NOT favorable to the idea of the "sausage" fix. He says that all small Althermas (6-8 kW) they installed all run with no problems and that I just keep looking at it too much :confused: . He said they had a few compressor failures with the bigger ones (11-16kW) but the small ones run totally fine as they come from factory. So as long as the machine is in warranty period I have to keep it as it is (if I want to keep it under warranty ;) - it expires in november 2011 ). So no sausage fix yet. Although this does not stops me from thinking that I could save a few thousand compressor starts and make it last quite a few years more, when the warranty will be long forgotten.

However, now, as the weather is getting warmer I'm even more disappointed in Altherma's software. There is a field setting 4.2 "heat pump off ambient temperature". When outside temperature is higher than the setting, Altherma effectively shuts down (not completely, the red LED stays on), but the circulation pump is off and everything else is off. I set the field setting to 15 °C (the factory default is 25°C), and this is what happened:
the outside temperature was around 15°C and the reading on the display alternated between 15.0°C and 15.5°C every second, so it did shut down and started up the circulation pump. Even worse! It did the same with the 3way motorized valve - switching it from domestic hot water to space heating and back! Why does it "play" with 3way valve I have no idea, since there was no need to heat the domestic water. And it did so every second!!!, until the temperature rised/fallen enough to make it decide what should it be!!! I could not believe my eyes when I saw this - I guess nobody at Daikin thought about too frequent state switching... Of course I immediately set the 4.2 field setting back to 25°C.

I think the Altherma's software is "only half baked" (I guess I'm a bit proffessionally deformed, since I'm a software engineer). However, I would never think that a company with a name as Daikin could sell something like this. It puts Daikin in a really bad light. If I knew how bad Altherma's software is, I would opt for a heat pump from a different manufacturer. I guess it is OK to keep things simple, but software THAT simple, without any state switching control, is just overkill.

@Brunstar
Thanx for tking a look at my pictures - yes, I have the motor on the 3way valve - the picture shown was taken during the system assembly. The motor was mounted by the installation guy, so I guess he put the motor on the valve correctly. I even checked it myself - I took the motor off the valve when it is in space heating position and the valve seems to be set OK - the way of space heating fully open and domestic hot water fully closed. I'm sorry I didn't take the picture with the motor off, but I may do it in future. I also thought of the thermal shortcut through the DHW some time ago, because when heating domestic water, the pipe that goes to space heating is also quite hot. This would indicate that the valve is not fully diverted in one/other way. Maybe the pipe just gets hot from the valve housing, since the pipe seems to be hot only near the valve, the further from valve the colder it is. I'll remove the motor and take a picture of the valve, so you guys can take a look at it if it is OK.

As for the suggestion of keeping the night mode, I thought of it also myself, however, sadly it does not make much/any difference. The only way to lower the cycling frequency I found so far, is to use the timer and make it work in intervals - but this is not the comfort I payed for.

[back2space]

All I can say is get back to your installer, he needs to check with Daikin if this is normal operation. Do not let the installers pull the wool over your eyes your system doesnt seem to be operating how it should be.

I had many problems with my lg system such as short cycling and all sorts and it turned out it was short on refrigerant amongst other issues.

If all else fails contact daikin yourself as he should be an accredited installer for the altherma system.

[back2space]

Without going to high expense, dampen the probe (reduced response time) Nothing to loose, all to gain!

How would you dampen the probe?

[multisync]

How would you dampen the probe?


Pour water on it?

[back2space]

Pour water on it?

He was talking of increasing a delay time so it dont cycle as much? Pouring water on it is not what I was asking!

I assume he means some sort of insulation?

[cadillackid]

if it is a thermistor you can also often put resistors in parallel with it..

putting the correct value resistors in parallel will require that there is more temperature swing up and down.. (the Daikin will 'see' the temperature swings as narrower than they really are) this will basically allow for longer cycle times off and on....
-Christopher

[The bone]

answer is simples.system requires 2 pump

[technicalm]

I have read this with great interest.

There are multiple issues coming to bear. Control, method of heat dissipation in the house, the behaviour of the weather compensation and heat pump sizing.

I wont tell you what I do for a living, but i can suggest that fitting a small buffer cylinder will largely make this go away.

Not complicated, cheap solution, tried, tested and reliable.

Good luck.

[donato35]

any news about this interesting post??
Tks