Latest Altherma simulator

[colder123]

I am new to this forum and somewhat relieved to find out we are not the only ones having problems with a heatpump in winter...

This is our third winter with the Outdoor ERHQ014AA and
Indoor EKHBX016BB3V3 + 300l hot water tank. Outdoor unit was replaced by Daikin last winter and they tuned the waterflow which helped above 0. Then extreme ice builds up on side, top and bottom even with the bottom-plate mounted. At temperatures below 0 the performance drops, unit runs constantly and room temp is not above 18-19.

Thermography photos have shown some heat losses in insulation which I have fixed, but although they have some effect if the unit had some spare capacity it probably would be able to compensate this 1-2kW loss and not have iced up -right?

Using the simulator 3.3.2 and 7.1.9 I discovered this combination has a negative spare capacity and below -7 doesn't have enough capacity.

Anyone can send me a link or mail the latest software 3.5.3 and 7.5.4 database so I can check and fiddle around with the figures being given to me by our installer. Their data shows there is should be no problem...

thanks

240m2, Netherlands, Amsterdam, 10,5kW in both a 240V and 400V

[DTLarca]

Then extreme ice builds up on side, top and bottom even with the bottom-plate mounted.

A major problem - robbing you of perhaps 80% capacity - what are you doing about this?

[desA]

I cannot, for the life of me, understand why people would subject equipment to this kind of abuse. Surely installers think about the most appropriate position in terms of weather extremes?

That this machine has come thus far, is a miracle.

[MikeHolm]

Des,
This unit seems to be on a roof where we find a lot of units, in a crowded city. It appears to be out in the open and therefore get good airflow so what is wrong with the position of the unit in this installation?

[charlie patt]

hell fire is that a ice cube or a condensing unit keepus informed

[desA]

Des,
This unit seems to be on a roof where we find a lot of units, in a crowded city. It appears to be out in the open and therefore get good airflow so what is wrong with the position of the unit in this installation?

Fair comment, but - ouch! Wind chill, evaporative cooling & defrosting water will surely love each other.

I would suggest using an outside wall, in similar fashion to an a/c outdoor unit - if a suitable sheltered location cannot be found.

When I see this kind of thing I can honestly say that perhaps the inappropriate selection of technology has been offered.

[al]

Heat pumps in general are sized at +7, below this capacity drops off, sizing a unit to account for this reduction can be expensive and lead to a unit installed that is massively oversized 11 months of the year, i presume you had a few quotes for this job, did you go with the most expensive?

It would help to raise the unit by a few inches to allow the defrost water drain off which would keep the lower part of the coil clear.

I have had a few calls to competitors equipment where i've had to teach the staff to put the unit in test cool to defrost the outdoors a few times a day:)

alec

[Bigfreeze]

Heat pumps in general are sized at +7, below this capacity drops off, sizing a unit to account for this reduction can be expensive and lead to a unit installed that is massively oversized 11 months of the year, i presume you had a few quotes for this job, did you go with the most expensive?

It would help to raise the unit by a few inches to allow the defrost water drain off which would keep the lower part of the coil clear.

I have had a few calls to competitors equipment where i've had to teach the staff to put the unit in test cool to defrost the outdoors a few times a day:)

alec

Anyone sizing a HP at +7 should be shot. I know alot of companies work the numbers in order to increase the COP of their units in the sales pitch and even thats bs

[colder123]

thx. I don't think they should be shot however:)

[colder123]

thanks Alec. It was quite expensive. Raising it a little was suggested as an improvement by the installer recently. I knew then it needs a backup to overcome -5 or less and perform likely better in the other 11+ months. But as calculated in the simulator, from -7 it needs 6kW backup instead of the 3kW that's installed now. Just trying to figure out from the last software whether it even delivers 10,5kW including backup @ -7,4: they say it does and the tables from the databook say not...

[colder123]

A major problem - robbing you of perhaps 80% capacity - what are you doing about this?

finding proof it wasn't sized right - and make them exchange it for a heat-pump that works at low temperature at affordable running cost - any suggestions?

:)

[nike123]

That much icing could be also if unit is not working properly or defrost function is not executed fully/properly.

[frank]

That much frosting could also be a sign that the gas charge is slightly short.

[back2space]

Very similar to the post over here...

http://www.refrigeration-engineer.com/forums/showthread.php?t=29395

[brunstar]

Looking at the installation of this unit it is evident that the unit is not mounted up off the ground. If the unit is not mounted up off the ground then when the unit carries out a defrost the condensate does not have free egress out of the unit.
If it is mounted so close to the ground, the condensate will then freeze and block the holes in the bottom of the unit and this is when the next defrost runs over the top of the next.
It is the same principle as making a candle, you start with the wick then you coat it cool it and continue to coat it, the candle gets thicker and thicker.

From a refrigeration point of view you can simulate this in your cold room FDC (Forced Draught Cooler). Block the drain in the FDC, raise the humidity in the cool room and see what happens to your FDC.

I hope that this makes sense.
No heat pump located in cold climates should be mounted directly on the ground.

If the unit is to be raised then the platform should only be the width of the feet beneath the unit.

[nevgee]

Looking at the installation of this unit it is evident that the unit is not mounted up off the ground. If the unit is not mounted up off the ground then when the unit carries out a defrost the condensate does not have free egress out of the unit.
If it is mounted so close to the ground, the condensate will then freeze and block the holes in the bottom of the unit and this is when the next defrost runs over the top of the next.



I hope that this makes sense.
No heat pump located in cold climates should be mounted directly on the ground.

If the unit is to be raised then the platform should only be the width of the feet beneath the unit.


I'm sorry to disagree here. The level of the unit above ground is completely irrelavent. the actual physical arrangement of the built unit allows for a natural drain from the drip tray however the location..... even if the drain from the tray was blocked the only out come would be for condensate to over flow the level of the drip tray and then pour over the top of the tray lip and out of the unit through the casing.

The pic shows quite clearly there is a problem with the defrost cycle or the performance of the unit as a whole. A blocked drain would not cause the whole of the casing , especially at hig hlevel , to frost over.

This unit appears to have bee running without a defrost cycle being activated. Quite possibly, I'm guessing here, someone has caused the defrost cyle to be overriden to make the unit run longer in the hope of more output. ;)

[brunstar]

I'm sorry to disagree here. The level of the unit above ground is completely irrelavent. the actual physical arrangement of the built unit allows for a natural drain from the drip tray however the location..... even if the drain from the tray was blocked the only out come would be for condensate to over flow the level of the drip tray and then pour over the top of the tray lip and out of the unit through the casing.

The pic shows quite clearly there is a problem with the defrost cycle or the performance of the unit as a whole. A blocked drain would not cause the whole of the casing , especially at hig hlevel , to frost over.

This unit appears to have bee running without a defrost cycle being activated. Quite possibly, I'm guessing here, someone has caused the defrost cyle to be overriden to make the unit run longer in the hope of more output. ;)

We can disagree and that is ok, if a unit had been running without a defrost then the whole coil MUST have frost on it as the evaporator will have even distribution across it.

If the ground is zero the ice will freeze which will block the holes in the unit then the unit will not be able to drain away.

If you would like to back up your assumptions please carry out tests.

[colder123]

We can disagree and that is ok, if a unit had been running without a defrost then the whole coil MUST have frost on it as the evaporator will have even distribution across it.

If the ground is zero the ice will freeze which will block the holes in the unit then the unit will not be able to drain away.

If you would like to back up your assumptions please carry out tests.


Looking at the installation of this unit it is evident that the unit is not mounted up off the ground. If the unit is not mounted up off the ground then when the unit carries out a defrost the condensate does not have free egress out of the unit.
If it is mounted so close to the ground, the condensate will then freeze and block the holes in the bottom of the unit and this is when the next defrost runs over the top of the next.
It is the same principle as making a candle, you start with the wick then you coat it cool it and continue to coat it, the candle gets thicker and thicker.

From a refrigeration point of view you can simulate this in your cold room FDC (Forced Draught Cooler). Block the drain in the FDC, raise the humidity in the cool room and see what happens to your FDC.

I hope that this makes sense.
No heat pump located in cold climates should be mounted directly on the ground.

If the unit is to be raised then the platform should only be the width of the feet beneath the unit.

Thanks for your suggestions. the unit has the bottom plate heater option which ensures the holes in the bottom stay open.

With temperature around 0 this weekend, ice starts to build up, the effect seen is indeed the "candledripping" on the support but even at the side of the unit, floating freely 10cm above the floor. Any idea how this can happen?

The defrost cycle runs from time to time, I can see that by looking at the control panel and/or at the unit.

By the way this installation was done by Daikin themselves to replace a faulty unit. Apparently they don't do this according to their own installation manual which exactly prescribes mounting up off the ground...

[nevgee]

I am sure that there will be a problem with the defrost, this being iether not adequate as a whole, therefore the coil doesn't have suffient heat added long enough to defrost the whole coil. Or, the system is not getting adequate heat from the reverse cycle to clear the coil. So is it the programming at fault, timing at fault, or the heat sink /buffer is not adequate, system may be low on gas. Iether way the coil appears to be not receiving enough heat to clear totally each time a defrost is activated. This allows for ice to remain and accummulate over time. Ice candelling is another sign of insufficient heat being given up to the coil and surrounding areas. This can often be seen around evap casework inside coldrooms, when the defrost is not on long enough and the surrounding air temp is lower than 0C.

[nec0310]

We have installed hundreds of Altherma systems.
The model shown is a LT series 16-indoor unit, Series 14 outdoor unit. Your photo shows common issues with the twin fan outdoor unit;
1) external ambient temperature sensor is mid mounted to the rear of the evaporator. If this ices up or snow falls onto it, defrost cycle changes. Defrost is governed based on time, and or relationship between ambient sensor and evaporator sensor and refrigerant pressures. You must unclip the sensor and remove away from the coil- this is a standard procedure with our installations. Keep clear of snow and ice!!!
2) Out door unit needs at least 150mm clearance.
3) The volume of the hydronic heating system may be insufficient to develop complete defrost- always install Series 16 twin fan units and HT systems with micro buffers to provide at least 30 litres of additional system volume to ensure clean defrost. We have many systems- early units with no buffer have occasional icing issues. Units with buffers run clean. 3kW back up heater may be insufficent for clean defrost.
4) LT twin fan unit experiences liquid refrigerant wash at the bottom of the coil. More recent LT outdoor unit has hot gas bypass discharge to the bottom of the evaporator coil. Beware of over condensing at the indoor unit ie either excessive hydronic flow, over dimensioned heat emitter system. Daikin LT refrigerant system should operate on 6 degree C dT. Control hydronic flow by flow setters either on primary hydronic circuits or on individual circuits.
5) LT system must never be over dimensioned to heat emitter otherwise poor defrost will result!!! Major ice build up.
6) We install 100 litre wall mounted buffers to all our twin fan units- never any issues. Systems run well and inverter able to modulate through out heating season- very efficient operation. maybe you need to consider this.


I would suggest you need to revisit the initial design
Hope this helps

[Jon Glanfield]

Hi Nec

I would be interested to hear how you configure the buffer in terms of hydraulics and wiring.

Do you use a 4 or 2 tapping buffer?

Do you you still call the heat pump on via the room stat or leave this out of the heat pump and use it's on board sampling option?

Cheers

Jon

[nec0310]

Hi Jon,
For the Series 8 systems, we use 2 tapping buffer in series if the system free volume is below 10 litres.
For Series 16 (11.2, 14, 16 outdoor units) we use 4 tapping but only use 3 of the tappings ( one from indoor unit, one flow with secondary pump, one for common return from heat emitters and to Altherma. Three tappings allows hydronic balance towards the secondary circulation pump(s)-prevent flow short circuiting within the buffer.
Room stats control the secondary pump(s), zone valves etc. Altherma operates on sampling flow/return (ie indoor PCB S2-1 set to off) with timer control synchronised to the room stat controls/programmer.
Works very well for multiple altherma

Nec