Ground Source Heat Pumps

Patrol

@DeeWestern will be interesting to hear if the noises reduce or stop as a result of repositioning the sensor.

lstevensuk said:

thanks again @beardymarrow! Does the valve go the heat pump end with the actualor? I will run the wires anyway in now and then worry about it when we replace the ground source with an air source one day in the not too distant future

Any reason why you mention replacing a ground source heat pump with an air source heat pump. My understanding was that ground source was more efficient during colder months, and unless I could not source another GSHP I would not consider switching to an ASHP.

beardymarrow

Strummer22 said:

Our GSHP was installed last year and the installer gave us the first annual service free. I’ve been advised that future services will cost £250 each (I’ve not signed up to a service plan or anything, it would be PAYG). Does that sound reasonable to service a GSHP? 

I need to check whether an annual service is required for the warranty to be valid, if not then will it be ok to service it less frequently?

Sounds about right for a service, but there's really no point. Do it yourself in 30mins.

Clean the filters on the hot and cold side
Top up the cold side expansion tank to between 1/3 and 2/3
Check for leaks
Bleed the hot water tank
Check for air bubbles in the refrigerant
Check pressure on the central heating circuit and top up if needed

All this is detailed in the manual, and it's dead easy. You're paying for someone's travel time to get to you really.

beardymarrow

DeeWestern said:

Spent some more time diagnosing, as everything just got hotter and hotter other than the hot water itself! The water tank had a Worcester white container with a front that has never come off, it had been bodged on by the installer - but I attacked it with a spanner and got it off - the problem was clear!

Someone had taken out the GT3 probe, which dangled down through a hole in the top of the outer white container of the hot water tank. They they then put it back down the hole... but inadvertently put it on the outside of the insulation, rather than the inside. So the hot water was super hot, and the return to the GSHP was hot, but GT3 returned a low value. I've tucked it in to the insulation now, so hopefully the GSHP will run smoothly now its not being overtaxed.

Got the cover off!


Tucked the GT3 probe in:

Wow! Who would have done that! That's going to have caused the compressor a world of pain :-(

I think on mine there's a little tube welded flat to the outside of the metal tank (under the insulation about 1/4 of the way up) that the temperature sensor slides into. It just holds the sensor tight against the side of the tank. Either that or I'm remembering an old tank at previous house.

How is the compressor noise now? Those noises you sent over are very wrong. You should just get a hum.

The heat exchanger can get sludged up, but much more likely too are the two flexible hoses. I replaced mine and just flushed the heat exchanger out with a hose, but to be fair it was actually not too bad, even after 15 years.

beardymarrow

Patrol said:

@DeeWestern will be interesting to hear if the noises reduce or stop as a result of repositioning the sensor.

lstevensuk said:

thanks again @beardymarrow! Does the valve go the heat pump end with the actualor? I will run the wires anyway in now and then worry about it when we replace the ground source with an air source one day in the not too distant future

Any reason why you mention replacing a ground source heat pump with an air source heat pump. My understanding was that ground source was more efficient during colder months, and unless I could not source another GSHP I would not consider switching to an ASHP.

Exactly. ASHPs have improved in efficiency and slightly caught up with GSHP, but GSHP has improved too (variable duty compressors for example) and is still more efficient (unless the bulk of your usage is during summer, which would make no sense unless all it heated was a swimming pool :-) ), so unless you didn't already have the ground loops, I can't see why you'd go for noisier, less efficient and physically larger ASHP.

Strummer22

beardymarrow said:

Strummer22 said:

Our GSHP was installed last year and the installer gave us the first annual service free. I’ve been advised that future services will cost £250 each (I’ve not signed up to a service plan or anything, it would be PAYG). Does that sound reasonable to service a GSHP? 

I need to check whether an annual service is required for the warranty to be valid, if not then will it be ok to service it less frequently?

Sounds about right for a service, but there's really no point. Do it yourself in 30mins.

Clean the filters on the hot and cold side
Top up the cold side expansion tank to between 1/3 and 2/3
Check for leaks
Bleed the hot water tank
Check for air bubbles in the refrigerant
Check pressure on the central heating circuit and top up if needed

All this is detailed in the manual, and it's dead easy. You're paying for someone's travel time to get to you really.

I suspect my EcoForest is designed to stop an amateur accessing some of the bits that need servicing. That said, I'll check the manual and see whether I'd be confident to do it myself. 

beardymarrow

Strummer22 said:

I suspect my EcoForest is designed to stop an amateur accessing some of the bits that need servicing. That said, I'll check the manual and see whether I'd be confident to do it myself. 

My bad, I forgot you had an EcoForest, not an IVT/Bosch. You might well be right. I'd like to think you can still check and clean the filters, bleed air from the hot water cylinder and check and top up pressure on the central heating at a minimum.

Strummer22

beardymarrow said:

Patrol said:

@DeeWestern will be interesting to hear if the noises reduce or stop as a result of repositioning the sensor.

lstevensuk said:

thanks again @beardymarrow! Does the valve go the heat pump end with the actualor? I will run the wires anyway in now and then worry about it when we replace the ground source with an air source one day in the not too distant future

Any reason why you mention replacing a ground source heat pump with an air source heat pump. My understanding was that ground source was more efficient during colder months, and unless I could not source another GSHP I would not consider switching to an ASHP.

Exactly. ASHPs have improved in efficiency and slightly caught up with GSHP, but GSHP has improved too (variable duty compressors for example) and is still more efficient (unless the bulk of your usage is during summer, which would make no sense unless all it heated was a swimming pool :-) ), so unless you didn't already have the ground loops, I can't see why you'd go for noisier, less efficient and physically larger ASHP.

My GSHP - which has a variable duty compressor - managed an average COP of over 4 during winter. Actual SCOP is somewhere around 4.5, against a design SCOP of 3.54. I don't think anyone's ASHP will get close to 4.5. 

I achieved an improved COP by:

• Setting the thermostat to 17.5-18C during the day, and 16.5 at night. This is colder than we'd prefer to but obviously energy costs being what they were we tried to save where we could. 
  
• turning down the max compressor load to 50%, except during the very coldest weather. The efficiency is much better at 50% than 100%. Although it takes a bit longer to heat the buffer tank I'm happy with the trade-off.   
• Adjusting weather compensation to the lowest possible temp, again except during the very coldest weather when the radiators couldn't quite heat up enough to maintain indoor temp. This means the heating was on longer but again the heat pump was more efficient. 
• Programming the heat pump to turn off space heating in the evening and come back on early morning.
• Programming hot water to turn off overnight. I have since adjusted this further to just an hour in the morning and a couple of hours in the evening. There's no point cycling to maintain temp in the hot water tank if it's just going to cool down again without being used.

Do ASHP users typically report they can beat the design SCOP of their systems?

Patrol

Strummer22 said:

Do ASHP users typically report they can beat the design SCOP of their systems?

I imagine it is very difficult to know unless the heat pump shows it, hopefully most/all recent models do but my IVT GSHP does not.

Does your heat pump have "additional heat" or a cassette etc. When I turned my hot water from continuous to only heat 6am-10pm I found it used more electricity as the additional heat kicked in every morning (bear in mind I had a faulty 3 way valve some time later so it is possible that the hot water was cooling quicker than it should have done). I haven't changed settings for a while now as am happy with it, and not tried overnight reductions for 10+ years

Strummer22

Patrol said:

Strummer22 said:

Do ASHP users typically report they can beat the design SCOP of their systems?

I imagine it is very difficult to know unless the heat pump shows it, hopefully most/all recent models do but my IVT GSHP does not.

Does your heat pump have "additional heat" or a cassette etc. When I turned my hot water from continuous to only heat 6am-10pm I found it used more electricity as the additional heat kicked in every morning (bear in mind I had a faulty 3 way valve some time later so it is possible that the hot water was cooling quicker than it should have done). I haven't changed settings for a while now as am happy with it, and not tried overnight reductions for 10+ years

Yes it’s got a backup immersion heater, but it doesn’t need to use it on current settings.

lstevensuk

I currently use Sentinel R500c transfer fluid in my heat pump. Is there a cheaper alternative? (Still have leak)