Calorex Pool Heater

[airefresco]

Yet another heat pump. Normally this would be no problem, however there are a few issues which worry me with this one. I´ve made a new thread so not confuse the other thread further, (Nike )

I went to the same site yesterday and this particular heat pump was fine then. I went back today to do something else and noticed that this particular heat pump had a band of ice across the centre of the evaporator. I checked it out and the suction (all the way to the compressor), the expansion valve and distributor were all frozen too. I switched it on and let defrost. Turned it back on and took some readings after about 10 minutes of running, by this time it was already icing up again.

Suction Pressure: 22 psi
Suction Temp at bulb: 0.5ºc
Discharge Pressure: 180 psi
Discharge temp (at compressor): 81.3ºc
Liquid line temp (off condenser): 23.2ºc
Water In: 25ºc
Water out: It´s not possible to get an accurate reading
Air on: 18.4ºc
Air off: 14.4ºc

The sight glass was full, no bubbling or flashing gas. To me it looks like it is short of refrigerant, but what I don´t understand is, if it is, why is the suction line frozen and why is the sight glass full?

I tested the expansion valve, and with the bulb warmed up the pressure rose to about 40psi, when put back, pressure eventually dropped back to where it was before. Tried adjusting the valve 1 turn each way and it made very little difference, if any at all.

Air flow is good, and evaporator is clean, water flow is definitely good.

[nicolacozma]

Which is the type of refrigerant inside the heat pump?

[airefresco]

Oh sorry, it´s R407c

[nicolacozma]

Your evaporator is starved because the superheat is too big. Also subcooling is towards high limits, this means the condenser contain the major quantity of refrigerant.
This behavior could happend when you have a restriction on liquid line.
Same phenomena could be also when you have a leak on system and the proportion on R407C are damaged.
Maybe is better to check for leakage on the system and then to replace the refrigerant with a new one.

regards

[nike123]

This heat pump have these symptoms:

• Medium discharge temperature (81.3°C)
• High evaporator superheat (16K)
• Normal condenser subcooling (6K)
• Low evaporator pressure/temperature (-15,5°C while it should be around 0°C considering air on temp of 18,4°C and normal air evaporator TD of 16-20K)
• Low condensing pressure/temperature (29,7°C while it should be around 40°C considering water in temperature of 25°C and and normal water condenser TD of 15K)

Symptoms of low refrigerant charge:

• Medium to high discharge temperature
• High evaporator superheat
• Low condenser subcooling
• Low compressor amps
• Low evaporator pressures
• Low condensing temperatures
• Low amp draw

Your case doesn't match in one symptom for low charge:
Low condenser subcooling
For low amp draw we don't have data to discuss

Symptoms of liquid line restriction after receiver (filter drier , line restrictions , TXV screen ) :

• Higher than normal discharge temperatures
• High superheat
• Low evaporation pressure
• Low condensing pressures
• Normal condenser subcooling
• Low condenser TD
• May be local cool spot or frost after the restriction
• Bubbles in sight glass if restriction is before him
• Low amp draw
• Low pressure switch activation

Your symptoms match everything here.
For amp draw and low pressure switch activation we don't have data to discuss.

I would say that restriction is in TXV or in pipe after sight glass to the TXV. Also, if filter drier is placed after sight glass, it could be filter drier restriction.

But, I suggest that you proceed as Nicola already said and first recover and weigh refrigerant charge because you will do it anyway.

[nike123]

Same phenomena could be also when you have a leak on system and the proportion on R407C are damaged.

Some readings about that possibility:

Servicing Systems With R-407C


What should a service engineer do if a system has lost part of its charge (leaked)?
It goes without saying that the first action should be to locate and correct the leak. Once the leak is eliminated, for normal (not critically charged) systems it is usually appropriate to “top off” the system to return to the standard refrigerant charge level, using R-407C, provided this charge is correctly transferred from the liquid phase in the container. System performance will return to normal.
In the case of critically charged systems (e.g. in many split systems including VRF systems) then, just as in the case of R-22 systems, the residual charge has to be recovered (removed from the system), and the precise specified quantity of R407C charged to the system.
In this respect the procedure for R407C is similar to that for R-22.

Can the composition of R407C in a system change?

R-407C is a zeotropic mixture. Its EQUILIBRIUM vapour and liquid compositions are different. What are the implications?
a) Refrigerant leaks: If the leak is only of vapour, at a location where both liquid and vapour co-exist in thermodynamic equilibrium then, as a consequence of the leak, a change in composition can occur.
In an operating system this scenario is uncommon. In practice leakage from the vapour phase only (where two the phases are in contact) is most likely to occur at a liquid receiver (or possibly an accumulator during transient conditions when liquid is present).
Leaks which occur in either the evaporator or condenser, where the liquid and vapour phases are in thermodynamic equilibrium during operation, do not result in composition shifts in practice because the leak is of both liquid and vapour – the two are not separate in the region of the leak. This has been confirmed by extensive testing.

A vapour leak can result in a change in composition of the residual charge during system shut-down (e.g. of an air conditioning system during the winter).

Extensive computer modelling, confirmed by field tests, has shown that “topping off” the charge with R407C (adding R407C to the depleted charge in the system to restore the charge to its correct mass level) will always tend to bring the composition back close to its correct formulation. The refrigerant, after such topping off, will have performance parameters very close to those for the standard composition. The performance of the system after a leakage which caused composition shift, and subsequent topping off with new R407C is not noticeably different from that of the system with standard composition charge. After a series of leak/recharge cycles in a fully instrumented test system under standard conditions, cooling capacity had dropped by ~5% and with even less impact on system energy efficiency. These tests and subsequent experience in the field has shown that R407C systems can be “topped off” after a leak and will operate normally. There is no need, except in the case of critically charged systems, to replace the entire charge after a leak.

b) “Segregation” within a system. One of the principal reasons that R407C is not used in “flooded evaporator” chiller systems is that liquid pooling occurs in the evaporator, resulting in a composition of the operating (circulating) refrigerant being variable and different from standard. This results in loss of proper control.

There have been a few isolated cases of anomalous operating behaviour reported in DX Air-Air systems which suggest that segregation with composition shifting might be occurring. The symptoms are manifested as sustained high condensing pressures and sometimes high compressor discharge temperatures. Such segregation can only occur if there is the opportunity for a significant volume of liquid refrigerant to “pool” – to remain static in physical contact with the circulating refrigerant mass. Pooling might occur in an accumulator, in a rising evaporator or other similar situation.
It must be emphasised that this will happen in only a very few exceptional circumstances
The solution to such a problem would be to modify the circuit (or correct an obstruction) to ensure that the whole refrigerant mass circulates through the system.

Conclusions: With some restrictions on its application use (namely for centrifugal compressors and flooded evaporator chillers) R-407C is now successfully used in the majority of air conditioning and comfort heat pump applications. Servicing R-407C systems can be carried out as if it were R-22, bearing in mind the additional care needed for moisture management and the use of the two (dew point and bubble point) saturation P-T relationships.

References:

Bivens D.B., Patron D.M., Yokozeki A., ASHRAE Trans. 1997, Vol 103

Original document

[airefresco]

Thank you for that document nike, very informative.

The low pressure switch never activated whilst I was there. However the defrost stat did, as the icing up section was were the phial is located.

The reason why I was at the site is they have been having issues with the contactors chattering. There are 2 systems and it was the other system that was causing this problem. I took a reading of both systems and i´m pretty sure this one was a little lower than the other heat pump on site, I think. The rated current I believe was 11Amp, and I think from memory this one was around 8 (+/-0.2)amps on all phases. But I can´t be sure of that.

I don´t remember seeing a drier in the system. The icing up seems to start at the TXV, everything before that is OK.

The charge is fresh. I repaired this system about a week ago. It had a fractured discharge line coming from the compressor. When I was there repairing that, the client said that this system iced up a lot around the centre of the evaporator. Both heat pumps are located inside the pump room and had poor ventilation, so I put it down to that. They have however, since improved the ventilation into the room and now it should be sufficient. It was working well after it was charged and the following day too, but this does seem to be a recurring problem only on this system. From reading what has been posted I would think it´s more likely to be a restriction at TXV or possibly the liquid line. How can I prove if it is the TXV? I have already proved the TXV is opening/closing but I guess there could still be a restriction there?

[nicolacozma]

How many circuits have your evaporator? Maybe one or more of them are blocked or have a restriction. But in this case SH will be lower and is not your case.

By other hand try to heat up the TXV body, if the pressure goes up means that you have a restriction on TXV due to moisture. If not then you have a mechanical restriction on TXV (have to change TXV).

[airefresco]

There is a distributor that comes from the TXV and splits into 6 or 7 smaller lines which feed the coil. They all return on a common header to the suction line. All of them were iced.

The pressure does go up if the TXV bulb is warmed. I tested this removing the bulb from the suction line and warming it in my hand while watching the gauges. It took a while (a minute more or less), but the suction pressure gradually started to increase, so I put the bulb back on the pipe and it started to fall again. However, i did not try to warm up the body of the valve, so I will try this. It´s difficult to get to the TXV because it is inside the evaporator section which you have to remove the cover to get to. If you remove the cover then you get poor air flow across the evaportor, which obviously drops the pressures anyway.

When I evacuated the system it was on for a good hour and the torr gauge was right down and holding, so I don´t think there is moisture in the system. However, if there is no drier fitted I suppose it could be possible somehow.

Thanks for your help.

[airefresco]

Progress. I left the Calorex off on Saturday after I left. I went back this morning and switched it on, straight away a huge improvement in performance,

Suction Pressure: 50psi
Suction Temp:18.5ºC
Discharge Pressure:175psi
Discharge Temp: 63ºC
Liquid Line Temp: 25.8ºC
Water on: 25ºc
Water off: Na
Air On: 19.3ºc
Air Off: 11.3ºc

Superheat: 19.5ºc
Subcooling: 1.7ºc
TD: 3.5ºC

(If someone could kind enough to check those last to make sure I worked them out right, I would be most grateful)

Liquid was flashing quite a lot in the sight glass and only a couple of the distributor lines were icing, other than that no more ice.

I think a gold star is order for nicolacozma and Nike as I think maybe (somehow) the system has moisture in it and that was freezing at the TXV or somewhere in the liquid line. Tomorrow I am going back to fit a drier (it doesn´t have one, I checked) and I may as well recharge with fresh R407c.

Thank you for the help, and i´ll keep you posted how I get on tomorrow.

[nike123]

Progress. I left the Calorex off on Saturday after I left. I went back this morning and switched it on, straight away a huge improvement in performance,

Suction Pressure: 50psi
Suction Temp:18.5ºC
Discharge Pressure:175psi
Discharge Temp: 63ºC
Liquid Line Temp: 25.8ºC
Water on: 25ºc
Water off: Na
Air On: 19.3ºc
Air Off: 11.3ºc

Superheat: 19.5ºc
Subcooling: 1.7ºc
TD: 3.5ºC

(If someone could kind enough to check those last to make sure I worked them out right, I would be most grateful)

Liquid was flashing quite a lot in the sight glass and only a couple of the distributor lines were icing, other than that no more ice.

I think a gold star is order for nicolacozma and Nike as I think maybe (somehow) the system has moisture in it and that was freezing at the TXV or somewhere in the liquid line. Tomorrow I am going back to fit a drier (it doesn´t have one, I checked) and I may as well recharge with fresh R407c.

Thank you for the help, and i´ll keep you posted how I get on tomorrow.

Numbers looks good except subcooling (2,7K instead of 1,7K)

Now it looks like system is little undercharged!

For moisture check, use hot fan for paint removing and heat TXV body (after you see that ice is started to form in evaporator fins). If in short time ice melts and suction pressure get to normal, you are sure that moisture is case.


Good luck!

[airefresco]

Numbers looks good except subcooling (2,7K instead of 1,7K)

Sometimes I can´t read my own handwriting. I wrote 2.7K but it looks like 1.7K. I´m glad though I got the method right. Thanks for checking.

Would a turbotorch work with the flame on the lowest setting to heat up the TXV?

[nike123]

Sometimes I can´t read my own handwriting. I wrote 2.7K but it looks like 1.7K. I´m glad though I got the method right. Thanks for checking.

Would a turbotorch work with the flame on the lowest setting to heat up the TXV?

I would not do that! Here, we could buy hot fans for 10€. That is 5 beers in pub.

[CHIZEL010]

Hi, cant be bothered to read all those other comments to many numbers and stuff. But just to let you know all Calorex Heat Pumps are fitted with a drier, mostly a parker reciever drier which is black with a sight glass on the top. The only reason it would not have one is if someone took it out.

[airefresco]

I thought that was just a receiver. I have just done a search on google and yes, you are quite correct there is one of those.

So does it matter that it now has two driers on?

[CHIZEL010]

Having worked for and on Calorex for 20 years plus, you are not the first to fit a second drier. Parker driers have been on Calorex's for as long as i have been working on them. As long as the parker drier is not restricted in any way then it will probably be ok. Do not take out the parker drier and just leave the standard drier though, you need this because it acts as the reciever as well. If it is all working ok, then all well and good. But if not change the parker drier and remove the standard drier.

Hope this helps you out.

[CHIZEL010]

Oh and yes a turbo torch gently heating the valve is fine, I and every engineer i know does this. But as i said gently heat it.

[airefresco]

Thanks for the info.

Since you seem to be the Calorex expert do the model number mean anything in regards to capacity? For example, a Daikin TXS35G is 3.5kW.

I´ve not got this system running yet, as when I went to fit the drier, the place has had it´s power cut off. So I´m waiting for them to be reconnected, before vaccing and recharging.

[CHIZEL010]

I am not aware that the model no is to do with their capacity, Calorex model no's seem to be rather random. The last 2 numbers on the serial no determine the year it was made.
If you can source a parker drier i would replace it if i was you before vaccing and charging it.
Hope it all works ok.

[airefresco]

Cheers for the info. I was just curious about the model number that´s all.

The driers would probably be a an absolute nightmare to get.

This unit was installed 18 months ago and has worked for about 3 weeks in total.

[aircon50]

Hi Airefresco. New to this site, but not to refrigeration. Been on Tenerife for about 4 years installing a/c and pool heat pumps. Driers shouldn't be too much of a problem except that they may have to come from Tenerife or Gran Canaria. Check out Controles Tenerife (Conte), GesConfort or Distem. All Tenerife companies, but not sure if any have depots on Lanzarote. Best of luck
By the way - Is your name Stuart?

[airefresco]

No it´s Paul

We already use GesConfort for Daikin, But i´ll look into the others, none of them have places over here. All we have are 2 small local companies who are dealers for Pecomark and Eurofred. Normal driers like the copper ones or even Danfoss ones are easy to get anything else becomes a pain.
thanks.

[CHIZEL010]

I have about 10 parker driers in my stores, but thats not much use to you over there.
Calorex would supply to you direct, their No is on their web site and they are very helpfull.