Ground Collector Heat Pump performance problem

2500w

Since the cold spell began in late November our heat pump can only heat the UFH circuit to about 25 degrees ( I know thaht 35 degrees is ideal). Does this indicate a problem with the horizontal ground collector not being deep enough?

rayh

From the information you supplied and at a distant, I would firstly suggest that you check you ESB meter and compare the readings with your latest bill. You could also check your daily readings over a short period and I find below 10 units per day very good - 10 to 15 average, but above 20 you should start to investigate.
Geothermal systems use electric energy to capture heat energy at generally about 4 to 1, but if the system becomes inefficient for a number of reasons, the ratio of input to output can change radically.
If as I would suspect your electricity usage has gone through the roof – have you heat pump checked by a competent engineer and or supplier.

KAGY

I second checking the ESB usage. Other things that you could check yourself are
* is the compressor louder than normal
* is there a sight glass, this should be nearly free of bubbles when running, if it's mostly gas with a little liquid you've got a refrigerant leak.
* what the pressure on the secondary glycol circuit (assuming it's closed) if it's dropped to zero you could have a leak there.

BTW where are you measuring the temperature?

2500w

The temperature is displayed on a small control panel on the heat pump.

I have been measuring heat pump running hours and ESB meter readings for a month!

The HP is running for 11 hours every 24 hours (of which 5 at night rate).
It always uses 2.9 KW (when circ pumps are taken into account). So its using 32 units out of the 48 per day.

The supplier is blaming the poor performance on the greater heat loss that the building is suffering. However even today with the increase in outdoor temp to 11 degrees the UFH water reached only 26 degrees.

rayh

2500w wrote: »

The supplier is blaming the poor performance on the greater heat loss that the building is suffering. However even today with the increase in outdoor temp to 11 degrees the UFH water reached only 26 degrees.

Just as a matter of interest;
a) Who or how was the original specifications for the plant determined?
b) Has the supplier carried out any analysis of your heat energy load or do you know what it actually is?

2500w

a. I believe the spec was calculated by the installer taking the floor area (240 sq m) and multiplying by 40 (assuming heat loss of 40 w per square metre). This gives 9.6 KW. So they concluded that an 11 KW heat pump would be more than ample.

b. IU have just googled heat energy load and NO this much effort has not been invested in caclculating this figure. Would you recommed that I do it?

No6

2500w wrote: »

a. I believe the spec was calculated by the installer taking the floor area (240 sq m) and multiplying by 40 (assuming heat loss of 40 w per square metre). This gives 9.6 KW. So they concluded that an 11 KW heat pump would be more than ample.

b. IU have just googled heat energy load and NO this much effort has not been invested in caclculating this figure. Would you recommed that I do it?

9.6 kw sounds like a very small heat load for a 240m² house unless its very very well insualted A rated level at least!!! Sounds to me like your heat pump is undersized.

rayh

2500w wrote: »

a. I believe the spec was calculated by the installer taking the floor area (240 sq m) and multiplying by 40 (assuming heat loss of 40 w per square metre). This gives 9.6 KW. So they concluded that an 11 KW heat pump would be more than ample.

b. IU have just googled heat energy load and NO this much effort has not been invested in caclculating this figure. Would you recommed that I do it?

Rule of thumb are not a very satisfactory system of measurement and 40 would be considered on the low end.

To get this system to a satisfactory level of performance will require a good thermal performance of the building fabric and optimium performance from the plant itself

sinnerboy

rayh wrote: »

Rule of thumb are not a very satisfactory system of measurement and 40 would be considered on the low end.

To get this system to a satisfactory level of performance will require a good thermal performance of the building fabric and optimium performance from the plant itself

If it is not too self contradictory of me say ......

Whilst agreeing that rules of thumb are not satisfactory ...... I would actually use a rule of thumb of 80w/m2 for a B rated house - i.e. insulation and (air tightness) in excess of 2005 regs .....

I hasten to add I am not a heating engineer , I "borrowed" this from an M+E pal

2500w

While 9.6 KW seems low the actual heat pump that the supplier went for is rated as 11.7 KW. I would have thought this would be adequate. Although I must add that our house has 60 mm cavity wall insulation but no dry lining. The dormer ceiling space has 5 inches of rigid insulation. I would class it as well insulated but definitely not over 2005 spec.

While 40 w per sq metre might be low would 80 w not be a bit high. Take for example my neighbours house 300 sq metres and a 13.5 KW heat pump is heating the house and the garage with energy to spare. His system seems to be coping a lot better than mine hence my concern turning to the ground collector being too shallow. The analog dials for the heat ground collector supply are reading 0 degrees.

What should the next step be?

rayh

2500w wrote: »

What should the next step be?

This is a very interesting point in this thread and at the risk of again been accused of a rant can I summarise as I see it.

This is a relatively new dwelling and will be requiring a heat energy source for a century or more and will only be seeing a fossil fuel source for probably 1/5 of its life or probably about ½ of your life. Therefore to solve this problem by increasing the energy inputs may have some short term cost benefits. Long term, you have only one option and that is to reduce you energy load by improving the thermal performance of the building fabric.

Against this background and at some distance from the actual problem can I would suggest that you have an energy audit and advisory report prepared to determine your energy load and the options for reductions in your current and future energy requirements.

hogandrew

Has anyone who bought a heat pump on this looked into buying it abroad... I am just about to buy one for my new house and was thinking of going to sweden for a few days to buy one... Sorry for changing the direction of the thread

2500w

How do you find somebody suitable to do the energy audit?
Ideally somebody who understands Geothermal heat pumps.

rayh

Go to http://193.178.2.42/SearchAssessors.aspx

dryan

rayh wrote: »

From the information you supplied and at a distant, I would firstly suggest that you check you ESB meter and compare the readings with your latest bill. You could also check your daily readings over a short period and I find below 10 units per day very good - 10 to 15 average, but above 20 you should start to investigate.
Geothermal systems use electric energy to capture heat energy at generally about 4 to 1, but if the system becomes inefficient for a number of reasons, the ratio of input to output can change radically.
If as I would suspect your electricity usage has gone through the roof – have you heat pump checked by a competent engineer and or supplier.

Rayh,
After reading your post above, i monitored my heatpump for a few days - the last few days (with the mildish weather) it has used on average 20 units/24hours.
Back in the really colder snap, it was burning on average 40 units a day.

What are you basing your figures above on?
I expect that this changes relative to the seasons when the ground temp fluctuates a bit?

2500w

dryan

How do you know the heat pump was using 40 units. ie how do you seperate heat pump ESB usage from your total usage.

I do so by knowing that my heat pump and all its associated circulating pumps uses 2.9 kw. Thats 2.9 units for every hour that it runs. If I know the hours the heat pump ran for that day ( and I do from ITS statistics) then I multiply running hours by 2.9. At the moment it is running for 10-11 hours each day, so about 30 units every day for the past month.

My point is you cannot estimate this figure based on your ESB meter deltas unless you rated every appliance in your house and calculated its average daily running time. The method above is a better way to cost the heat pump usage. Maybe you're doing this anyway? If so then 20 units might be good if you're happy with the heat levels, BUT THAT DEPENDS ON THE RATING FOR YOUR HEAT PUMP. You have not told us its power consumption. Did you recently measure your brine temperatures and if so how do you do it?

rayh

dryan wrote: »

Rayh,
After reading your post above, i monitored my heatpump for a few days - the last few days (with the mildish weather) it has used on average 20 units/24hours.
Back in the really colder snap, it was burning on average 40 units a day.

What are you basing your figures above on?
I expect that this changes relative to the seasons when the ground temp fluctuates a bit?

Sorry dryan, but previous expenience with the Moderator prevents me from going on "Rants" but if you would like to PM me your energy rating, floor area and annual electricity usage. I will respond to you.