Ämne: IVT Greenline HT Plus "High Pressure Switch (HP)" / "Pressostat höj" error

[Kristian Lautrup]

Hi,
Recently our 10 years old IVT Greenline HT Plus 9 started giving the "Compressor Temperature T6 (GT6)" error first about once per day escalating to several times times per day often also with the "Low Pressure Switch (LP)" error popping up.

Our local plumber suspected it was the Expansion Valve, so I ordered a replacement Expansion Valve which he replaced.

Since then the "Compressor Temperature T6 (GT6)" and the "Low Pressure Switch (LP)" went away, but instead I now get the "High Pressure Switch (HP)" error after the compressor has been running for about 8-10 minutes (seems only to happen when heating the usage water).

I have tried some minor adjustments on the screw on the Expansion Valve turning it both clockwise and counter clockwise.

However, the "High Pressure Switch (HP)" is consistently showing up after 8-10 minutes or so.

These are examples of the temperatures I see just before the error (hot water target temperature set to 49 degrees):
GT2 (Outside): 14,5
GT3 (Hot water): 50,9
GT6 (Compressor): 78,9
GT8 (Heatpump out): 54,3
GT9 (Heatpump in): 49,0
GT10 (Earth collector hose in): 6,2
GT11 (Earth collector hose out): 2,2

Turning the Expansion Valve screw clockwise seems to raise the GT6 temperature (if I turn it to much it goes above 100 degrees) and turning the Expansion Valve screw counter clockwise seems to lower the GT6 temperature (too much and it goes below 0 degrees). However, I don't see turning the screw either direction having much impact on the other temperatures.

I also tried to change the flow of the circulation pump on the hot side between level 1,2 and 3. Setting it lower seems to raise the gap between the GT8 and GT9 temperatures which I guess is because a lower circulation flow when heating the Hot Water allows the Hot Water to absorbe more of the heat.

But no matter what I try to adjust I keep getting the "High Pressure Switch (HP)" which I didn't get prior to the expansion valve was changed.

Any good suggestions what might be the problem?

Best Regards,
Kristian

[25fOCUS]

Check the electric valv for usage water  it can be  block , dont working

[Carl N]

This is not an expansion valve issue.
It looks more like the temperature gets to high when heating hot water.
First check the venting nipple on the top of the hot water heater, it can be air in it.

Otherwise the hot water sensor (GT3) may show a few degrees to low temperature, it sould be same as heatpump out (GT8) when heating hot water.
If you lower the temperature on hot water 3-4 degrees in menu 2.3 the issue should disappear.

[Roland]

I agree with Carl, this is a new problem which is not related to the expansion valve. An IVT HT plus pump should be able to produce heat up to a temperature of 65 degrees. 54 degrees is far from that.

I do not think there is a problem with the GT3 sensor. It is located low on the water heater and normally shows a lower temperatur than GT8.

When you have a GT6 temperature below zero it is likely that compressor is fed with liquid refrigerant which can destroy the compressor. I recommend that you call a technician who can measure the pressures in the system and check whether there is something wrong with the high pressure sensor and set the expansion valve correctly.

[Carl N]

Maybe it can produce 65 °C water, but it is return temp that is the problem.
I think the flow should be lower if the heatpump out temperature should be higher. 
Maybe that is an option to lower the speed of the circulation pump.

[Kristian Lautrup]

Hi,
Thank you for the suggestions.

I already vented the ventilation screw on top of the water heater and there is no air.

I only saw the GT6 temperature below 0 degrees if I turned the expansion valve adjustment screw to much counter clockwise.

If I disable the compressor operation only allowing the heat pump to heat the hot water by electricity I see pretty much the same GT3+GT8+GT9 temperatures and even if I set the hot water target temperature higher than the 49 degrees for instance 51 degrees I don't see the high pressure switch error. So it only happens when the compressor is running and it never happened before the expansion valve was changed.

What is the best way to check whether GT3 shows the correct temperature?
You write that it is located low in the water heater. If I let the hot water run for some minutes on the closets tap and measure the temperature there should that then be close to GT3, or is there a more accurate way to determine whether GT3 is accurate?

I read some other articles suggesting that the high pressure switch error could be cause by the switching valve not completely closing causing some of the circulation to got to the radiator circuit when it should go to the water heater.
And some other articles suggest that the soft hoses or the heat exchanger could be clogged with dirt.
Are those likely reasons on a almost 10 years old Greenline HT Plus (I'm not sure whether there should be a filter anywhere in that circuit)?

[25fOCUS]

Look after samthing like this close open and clean it

[Carl N]

Difference between GT8 and GT9 is OK, I don't think there is any problems with the flow. 
If the hoses is clogged then difference tends to increase.
I think there might be an issue with the HP sensor. 

[Roland]

Maybe it can produce 65 °C water, but it is return temp that is the problem.

I do not think so. The return temperature on my pump is limited to 48 degrees but it must be higher on a pump which can produce heat at 65 degrees. 

I think ther might be an issue with the HP sensor. 

Agree, but why should it start making problems after the expansion valve was changed? Anyhow there seems to be no problem with the flow.

If I disable the compressor operation only allowing the heat pump to heat the hot water by electricity I see pretty much the same GT3+GT8+GT9 temperatures and even if I set the hot water target temperature higher than the 49 degrees for instance 51 degrees I don't see the high pressure switch error. So it only happens when the compressor is running and it never happened before the expansion valve was changed.

It is as it should be. When the compressor is not running the pressure in the condensor is low. The HP alarm cannot be triggered.

What is the best way to check whether GT3 shows the correct temperature?
You write that it is located low in the water heater. If I let the hot water run for some minutes on the closets tap and measure the temperature there should that then be close to GT3, or is there a more accurate way to determine whether GT3 is accurate?

As GT8 was 54 degrees, a temperature the pump should have no problem with, before it stopped, GT3 cannot be the problem. There is a reasonable difference between GT8 and GT3. The temperatur of the hot water at the tap should be roughly the same as the GT8 temperatur. GT3 is mounted so low that you need to withdraw more than 100 L. Besides GT3 does not measure the hot water temperature but the temperature of the circulating water heating the hot water.

I read some other articles suggesting that the high pressure switch error could be cause by the switching valve not completely closing causing some of the circulation to got to the radiator circuit when it should go to the water heater.
And some other articles suggest that the soft hoses or the heat exchanger could be clogged with dirt.
Are those likely reasons on a almost 10 years old Greenline HT Plus (I'm not sure whether there should be a filter anywhere in that circuit)?

In all these cases the temperature difference between GT8 and GT9 is much higher due to low water flow through the condensor, 15 degrees or so instead of 5. 
 

[Kristian Lautrup]

I realise that when the heat pump running on the compressor is heating hot water the switching valve does not seem to completely shut of the outlet to the radiator circuit. Touching the pipe leading to the radiator circuit about 1,5 - 2,0 meters away from the heat pump it is consistently warm even when the heat pump has been heating hot water for 10-15 minutes.
I unmounted the small "motor" that pushes in the pin in the valve when running in hot water heating mode and the pin is completely pushed in (I can't push it any further manually), but still hot water is circulating to the radiator circuit.

The valve is supposed to completely shut off the radiator circuit when heating hot water right?

Strange thing is that when I disable the compressor only heating the hot water by electricity the outlet pipe to the radiator circuit does not become hot, so that only seems to happen running on the compressor. Does that make any sense?

[Roland]

The radiator water circuit should be completely shut off when the pump i heating hot water. Only a few decimeters should be warm due to conduction. It does not make sense to me that it occurs only when the compressor is running and not when using the electrical heater.

I forgot to mention one thing. It is possible that the GT9 sensor is mounted on the return pipe from the radiator system before the T-connection where it meets the pipe to the pump and pipe coming from the bottom of the water heater. In that case it does not measure the true return temperature when making hot water. It will then show a too low temperature. Anyhow, 54 degrees out from the pump should be no problem. 

[lödläckan]

ang. exp ventilen. är bulben fastsatt med pasta och isolering!!

[Kristian Lautrup]

Ok it seems the company who changed the expansion valve have realised they have put on 0.5 kg too much which when removed will hopefully explain the "High Pressure Switch (HP)" error.

A couple of further questions I hope you can me answer.

The bulb connected via a metal cord to the expansion valve is placed on the cold pipe going in on the top of the compressor. The bulb is placed just next to the place on the cold pipe where the smallest pipe on the expansion valve is connected to that cold pipe.
That is the correct placement of the expansion valve right?

Other question is that I have received a quite aggressive bill from the company where a huge part if for 1.5 kg new coolant costing almost 1.900 DKK incl. VAT (about 2.450 SEK).

Is it normal to add new coolant instead of reusing the old coolant?
I imagined that the old coolant would be good enough, so it could be put back after changing the expansion valve?

Even if new coolant is required I feel the price for 1.5 kg new coolant is too high.
Does anybody know how much that would usually cost?

[Kristian Lautrup]

Ok it seems the company who changed the expansion valve have realised they have put on 0.5 kg too much coolant on the system which when removed will hopefully explain the "High Pressure Switch (HP)" error.

A couple of further questions I hope you can me answer.

The bulb connected via a metal cord to the expansion valve is placed on the cold pipe going in on the top of the compressor. The bulb is placed just next to the place on the cold pipe where the smallest pipe on the expansion valve is connected to that cold pipe.
That is the correct placement of the expansion valve right?

Other question is that I have received a quite aggressive bill from the company where a huge part if for 1.5 kg new coolant costing almost 1.900 DKK incl. VAT (about 2.450 SEK).

Is it normal to add new coolant instead of reusing the old coolant?
I imagined that the old coolant would be good enough, so it could be put back after changing the expansion valve?

Even if new coolant is required I feel the price for 1.5 kg new coolant is too high.
Does anybody know how much that would usually cost?

[Gipskatten]

At least for car A/C systems it's customary to re-use the coolant. Maybe tolerances are lower in heat pumps, if too much oil is added efficiency is compromised which doesn't matter much in a car A/C but may be detrimental for picky COP hunters

Have no idea of prices for coolant, nor which type is used in your pump, but click the link to the left ("Fyll din AC", don't want to post direct link since I guess Rickard gets a dime or two for a click on the ad) and you get swedish prices for kits to fill R134A in AC's. Coolant AND gear, much cheaper than your bill.