Heat pump switch off with HP or LP alarms ?!?

[2v6]

Hello,

Last days I have digging around a 30 kW heat pump.
It is Bright air-water split system with R407c.
There was a leakages and very often with LP1 alarm.
So the pipes was repaired and recharged with fresh refrigerant. In manual the quantity was 13 kg.
After starting in heating mode the pressure goes up very fast and HP switch turns off the machine. I have drain back about 3 kg of the refrigerant in order to keep out pressure under the limit of the HP switch (2.7 MPa, 27 bar, 390 Psi).
Even that the out pressure is high the low pressure is very low, near to LP switch limit (0.7 bar, 10 Psi).
Also time to time the compressor switch off with alarm tP (there is a thermal sensor in the compressor).
The condenser temperature is about 35 degC, but inlet pipe is very hot (above 90).

Where could be the fault?

[install monkey]

were the driers changed and was it vacced out,was a torr gauge used?

[2v6]

were the driers changed and was it vacced out,was a torr gauge used?

No, the drier wasn't changed.
The system was vacced out.
What is "torr gauge"?

[frank]

Sounds like you do not have sufficient water flow through the condenser.....check your pump ......
"pressure goes up very quick"

or it's full of non condensibles

[install monkey]

http://www.google.co.uk/search?q=tor...w=1366&bih=622

[2v6]

Yes, I also have check...
Could you sugest a supplyer for a good torr gauge?
What values have to reach for good vacuumation of this system?

frank, the flow was first check, but I think is OK. 44 degC out when 38 degC water in to the heat exchanger. This is with HP about 22 bar and LP 1 bar.

http://www.google.co.uk/search?q=tor...w=1366&bih=622

[Emmett]

(1) I am not familiar with heat pumps but 38 deg c condenser water? sounds way too high to me, perhaps someone can explain if it isn't, why it isn't
(2) I would think that if the drier were plugged you would trip on low pressure not high as this would act like a pump down solenoid (correct me if I'm wrong install)
(3) are your gauges steady or does the high side bounce around rapidly?

[2v6]

(1) I am not familiar with heat pumps but 38 deg c condenser water? sounds way too high to me, perhaps someone can explain if it isn't, why it isn't
(2) I would think that if the drier were plugged you would trip on low pressure not high as this would act like a pump down solenoid (correct me if I'm wrong install)

(3) are your gauges steady or does the high side bounce around rapidly?

The water inlet temperature is as what is needed for the heating instalation. Heating system is not very good for heatpump...
Could you explain more detail about (2)?

The gauges are steady. Last days the EV start working after defrost with high noise. What could be the reason?

[Bigfreeze]

How long does it take to trip out. Quick tripping is a sign of poor flow through the condenser. Also you should check the expansion valve is not excessively closed. That would also give the same symptoms.
A heatpump will normally pull very low backpressure for the first two mins or so until a balance is found.

If excessive pressure builds up behind the EV its not unusal to hear them whistle when the machine shuts down as the system trys to equalize, especially if its a EEV.

[2v6]

How long does it take to trip out. Quick tripping is a sign of poor flow through the condenser. Also you should check the expansion valve is not excessively closed. That would also give the same symptoms.
A heatpump will normally pull very low backpressure for the first two mins or so until a balance is found.

If excessive pressure builds up behind the EV its not unusal to hear them whistle when the machine shuts down as the system trys to equalize, especially if its a EEV.

Which condenser you mean? In cooling mode the system seems that operates normal, but with other EV near to heat exchanger.

It trips from HP sometime very short (about 10-20 sec) after defrosting, sometime very long (about 20-30 min) when the water goes above 40 degC.
Also sometime it trips with alarm tP, which comes from thermoprotection contact inside the compressor (SANYO, scroll).

What means "excessively closed EV" and how to check?
Is "EEV" an expansion valve with equalisation line?
The noise from the EV start about 10-20 sec after defrosting and continue about 1 min.

[Bigfreeze]

The expansion valve in use on cooling mode is probably shut down to much. I'm taking that its a TEV (Thermostatic expansion valve) and not an EEV (Electronic expansion valve). There is a screw under the cap on the back of the valve, Mark its point as it is set now, Then open the valve a quarter turn. It may need to be opened further but I'm pretty sure thats your problem. The valve is letting through some refrigerant but not enough and the pressure builds up behind the valve. Try this and see, you can always return the screw to the marked position.

Best time to do it is in the first few secs of defrost, you'll actually hear the change in the strain on the compressor.

[Bigfreeze]

What are your discharge temperatures also. Very unsual for a thermistor to trip a compressor condensing at 40C. Are you sure your not undercharged and running a very high discharge temp?

[desA]

Sorry if I missed this part : what type of defrost mechanism is it? Hot-gas bypass / electric strips / reversing valve?

[2v6]

The expansion valve in use on cooling mode is probably shut down to much. I'm taking that its a TEV (Thermostatic expansion valve) and not an EEV (Electronic expansion valve). There is a screw under the cap on the back of the valve, Mark its point as it is set now, Then open the valve a quarter turn...

Both are TEV.
Because it was triping with HP (the outlet at the compressor goes very fast above 25 bar and more) I just turn quarter after quarter to the end of the counter clock wise possition. In this possition compressor works with about 22 bar pressure out.

What are your discharge temperatures also. Very unsual for a thermistor to trip a compressor condensing at 40C. Are you sure your not undercharged and running a very high discharge temp?

The discharge temperature is awlays vary high, sometime more than 90 degC.
Is possible that it is undercharged. On the docs the charge quantity was 13 kg but it was not possible with this to run longer without HP alarm. After discharging of about 3kg the HP alarm not comming.

Sorry if I missed this part : what type of defrost mechanism is it? Hot-gas bypass / electric strips / reversing valve?

The defrosting is with 4-way valve - the system start work in cooling mode with switched off external fans.

[desA]

The defrosting is with 4-way valve - the system start work in cooling mode with switched off external fans.

Could the 4-way valve be sticking in such a position as to cause high back-pressure?

[2v6]

Could the 4-way valve be sticking in such a position as to cause high back-pressure?

Do you mean to continue work in cooling?
No, when the valve is switch on the evaporator (external air HE) going cold to about -15 degC and condenser (internal water HE) going hot (water in/out temperatures are 39/45 degC). There is also 15kW electric heater after the water HE. dT of the electrical heater is about 3 K so if the dT of the heatpump is 6K I think that also it heating power is OK.

[dukesos]

same HP fault here, after a 10% over-charge on R407c, thankyou all for the posts.
Compressor discharge also very hot, still running over 26Bar with pool water at 40 degrees Celsius, so will perhaps try opening the expansion valve a little.

[2v6]

Hi,

Today I have take a picture of the inside unit.
Is the installation of the cooling TRV OK?

28122011548.jpg