Heat pump operates when it shouldn't - any suggestions as to why?

record

Hi,

If anyone can help me I would be very grateful...

I have an air-to-water heatpump that supplies me with hot water and also underfloor heating (UFH).

However, when the UFH system is set to "auto", the heatpump operates for up to an hour per day for no apparent reason - i.e. no room stat is calling for heat / it is not on a timer, etc. I have been taking detailed readings to confirm this and discovered that it is switching itself on up to 6 times per day for short periods at a time.

The company that installed the system has gone bust, so I can't go back to them.

Many thanks in advance for any thoughts on the matter.

Mike2006

You will need to get somebody who is either familiar with the unit or just a good general electrician to troubleshoot the issue for you.

Most likely the unit is not starting for no reason, so you have to find out what is 'calling' for it to start.
Is it a room stat, a water stat or an internal parameter which has been set on the unit itself to start at pre-determined times..

No easy way to do it really..

Mike.

ninjaBob

I had to troubleshoot my own system so that I could pair up the loop & stats

With my System I can set the stat to 7 degrees and the heatpump will only come on if Hotwater is requesting it.

Additionally I can turn off each loop on the manifold (at the contact and at the pipe it self).

By doing this you can rule out the underfloor calling it (even which stat), it would also be worthwhile seeing if any of your stats are on external walls, in areas of draught etc.

If you have your manual for the heatpump you can see if there is a feature to ignore hot water. I think on mine I can set it to party or holiday mode and it will ignore the hotwater. Set it to this mode after ruling out the stats and see if it comes on.

Hope that helps a little, but I would try and get someone with experience with your particular heatpump to look at it.

record

Thanks for the replies.

ninjaBob wrote: »

I had to troubleshoot my own system so that I could pair up the loop & stats

With my System I can set the stat to 7 degrees and the heatpump will only come on if Hotwater is requesting it.

Additionally I can turn off each loop on the manifold (at the contact and at the pipe it self).

By doing this you can rule out the underfloor calling it (even which stat), it would also be worthwhile seeing if any of your stats are on external walls, in areas of draught etc.

If you have your manual for the heatpump you can see if there is a feature to ignore hot water. I think on mine I can set it to party or holiday mode and it will ignore the hotwater. Set it to this mode after ruling out the stats and see if it comes on.

In relation to the above ninjabob, I have ruled out the stats as the cause of the problem (by trial and error with the stat settings and by alternately turning them off).

When the system turns itself on for no apparent reason, about 3 or 4 of the pipes on the manifold start to get warm - the problem seems to be more than just one faulty stat or one control on an individual loop.

It sounds like your wall controller is the same as mine - a Luxtronic - is that the case?

Mike2006 wrote: »

You will need to get somebody who is either familiar with the unit or just a good general electrician to troubleshoot the issue for you.

ninjaBob wrote: »

I would try and get someone with experience with your particular heatpump to look at it.

I take your points re getting someone out, but I just want to see if I can narrow the problem down first - time is (an awful lot of) money with these guys, and they are often shooting in the dark from my experience!

Could a leak somewhere on the system be causing the problem?

Mike2006

I suppose it could be a leak.
Do you have an auto fill loop fitted to the system? This could hide a leak.

If it is coming on for just a short burst many times a day it sounds like it maybe is not set up correctly or maybe it is meant to heat on demand as opposed to storing thermal energy..

If it is meant to operate like that, it sounds like it is releasing a small amount of heat at a time and having to top it up. A leak would have this effect...

If it is happening every day though, I would imagine that you would have spotted a leak by now...

Sorry if I am not answering your question directly.. It might jog your train of thought though....

Mike

paddy236

Can you name the make and model of heat pump?
What is the temperature in the inlet/outlet of the heat pump when it turns on/off?
Does it happen at random times each day or at the same times?
If you set the heat pump to turn just once a day, instead of auto, does it still turn itself on at various other times?
Can you read the ambient air temperature of the heat pump from your controller? If that stat was faulty it could bring on the heat pump as part of the frost protection.

Paddy

record

Many thanks Paddy for your reply.

paddy236 wrote: »

Can you name the make and model of heat pump?

It's an Alpha Innotec, 12KW Air-to-water heatpump (model LW 120M-A/XS).

paddy236 wrote: »

What is the temperature in the inlet/outlet of the heat pump when it turns on/off?

Don't know the answer to this, although I can take readings easily if required. What could these readings indicate?

paddy236 wrote: »

Does it happen at random times each day or at the same times?

It seems to just come on at random times of the day. Although I couldn't be certain of that, I'm almost sure that is the case.

paddy236 wrote: »

If you set the heat pump to turn just once a day, instead of auto, does it still turn itself on at various other times?

I actually don't know how to set the heatpump to come on just once a day, although I'd say I could figure it out. Are you asking this question to try to narrow it down to / rule out a possible timer fault?

paddy236 wrote: »

Can you read the ambient air temperature of the heat pump from your controller? If that stat was faulty it could bring on the heat pump as part of the frost protection.

I have been taking readings twice daily of the ambient temperature - average of around 14 degrees. In this instance, are you referring to the stat outside at the heatpump itself which could be faulty? However, I don't think a frost protection fault is the issue as the heatpump is only coming on for very short periods of about between 5 and 20 minutes at a time, albeit doing this up to 6 times per day.

record

Mike2006 wrote: »

If it is coming on for just a short burst many times a day it sounds like it maybe is not set up correctly or maybe it is meant to heat on demand as opposed to storing thermal energy..

If it is meant to operate like that, it sounds like it is releasing a small amount of heat at a time and having to top it up. A leak would have this effect...

Hi Mike, thanks for your reply. I don't have an auto-fill system, but I will check the pressure reading to ensure that there is no leakage.

What do you mean by "heating on demand" as opposed to "storing thermal energy"?

paddy236

Your heat pump should have some built in temperature stats; one on the inlet pipe to the heat pump, one on the outlet pipe to the heat pump and an ambient temperature stat. Your controller should be able to read the temperatures from these stats and it will then decide if it should turn on/off etc.
The controller for my heat pump displays the inlet and outlet temperatures on the screen along with some other information. You need to be able to read these values on your controller. When your heat pump turns on by itself you need to read the inlet/outlet temperature. When it turns itself off again you need to read the inlet/outlet temperature. Do this over the course of the day. If the inlet/outlet temperatures were the same then the controller has been programmed to turn the heat pump on once the temperature drops below a preset temperature and then turn it off once it reaches another preset temperature. If the temperatures were different then something else is telling the heat pump to turn on.
You can monitor the times the pump turns itself on and see if there is any pattern. If there is then the heat pump could be programmed to turn on at set times during the day.
You should be able to get your controller to display the ambient air temperature also. If the sensor is faulty it could be telling the controller that it is freezing outside and the controller is turning on the pump as part of the frost protection.
Your temperature gun can tell you actual temperatures of pipes but you need to get the temperature readings from the built in stats so you can know what temperatures the controller is actually seeing.

Have you got the user manual for the heat pump and controller?

Hope this makes sense.
Paddy

record

Thanks for the reply Paddy, that does indeed make sense.