Ground Source Heat Pumps

Strummer22

How's everyone's COP so far this autumn? We're still getting used to our heat pump which was installed in March this year. So far though it seems to be performing admirably, I think because of the mild weather and that we've got the heating set to 17.5C most of the time as this is comfortable enough and we're trying to save energy. Our average COP since turning the central heating on is about 5.1.

How does this compare to others? Did you get a better COP in the first year of use (or to put it another way, does your heat pump slowly deplete the available heat in the ground over a number of years), and how much does it tend to drop as winter goes on with increased demand and decreased ground heat available?

beardymarrow

I don't have any way of seeing the COP on my IVT :-( It wouldn't have been difficult for them to implement, it would just need to know the flow rate as it obviously already knows dT.
I have not noticed any reduction in performance over the years, you wouldn't deplete the heat in the ground. Only reduction would be due to wear of parts, sludging up of rads etc.
5.1 is an impressive COP. What system do you have?

beardymarrow

COP will reduce with increased demand and reduced external temp though, for definite. At 0/35degC mine is officially 4.3 and at 0/50degC it is 3.1.

Strummer22

beardymarrow said:

5.1 is an impressive COP. What system do you have?

It's an EcoForest EcoGeo 5-22kW. Official SCOP for RHI purposes is 3.54 (at 50C flow temp).

Our EPC says space + water heating demand is 30,313 kWh so we could expect our heat pump to use 30,313/3.54 = 8,563 kWh of electricity a year.

Heating + DHW electricity usage so far in November is about 11kWh per day. This seems pretty good and I hope it continues to perform well. I'd budgeted for over 50kWh per day in January, anything less would be great! We'll see.  

beardymarrow

Strummer22 said:

beardymarrow said:

5.1 is an impressive COP. What system do you have?

It's an EcoForest EcoGeo 5-22kW. Official SCOP for RHI purposes is 3.54 (at 50C flow temp).

Nice! The newer style heat pumps that modulate are the way forward. Mine is just on or off  

ChapelBarn

Some help please - I have 2 x Greenline IVT installed and I am getting a recurrent error on one of the pumps saying "Delta across the HTF is too high" with a suggestion that the "HTF pump set too low" as a possible cause
The error seems to reset itself even if I do not acknowledge it - but the pump then goes into Summer Mode so not sure it is contributing to the heating of the house. 
My second pump is working fine.

Can anyone help with what to do with "HTF pump set too low"?

Patrol

Can anyone help with what to do with "HTF pump set too low"?

Hello. My IVT manual for "High Heat transfer fluid delta" has two possible causes. I think this is the same type of error as you are seeing.

1 Not enough flow over the heatpump. Action: 1 Check that the heat carrier pump has not jammed. 2 Check that all the valves are open.

2 The particle filter on the hot side is clogged. Action: 1 Clean the particle filter.

The filter is supposed to be user-maintainable so I would check that first as below (I've checked mine in the past). If that was fine I'd be looking for a service engineer as unless someone has fiddled with valves or turned radiatiors / underfloor heating valves off it sounds like a pump may need to be replaced.

Do you have a manual? Page 30 of mine describes how to check and clean the filters as below
1 Shut down the heat pump using the On/Off button

(a bit here from me, the hot filter will be in your heat pump. I can remove my front cover with two screws at the top, and the filter is towards the top on the left (next to the black cassette cylinder and under some U shaped pipework. The valve is a lever handle that rotates 90 degrees from on to off from memory)

2 Close the valve and unscrew the sealing cap
3 Loosen the circlip holding the screen in the valve. Use the supplier circlip pliers

(a bit here from me, the pliers taper to fine points so you can put them into the two small holes in the circlip. Be careful not to drop the circlip)

4 Lift out the screen from the valve and wash clean with water 

(a bit here from me, the screen is like a small metal thimble)

5 Refit the screen, the circlip and sealing cap

6 Open the valve and start the heat pump using the On/Off button

Patrol

Strummer22 said:

How's everyone's COP so far this autumn?

Also no option for me to see this, a bit frustrating to see @beardymarrow say that could have easily be done as it would be something I'd really like to monitor, along with actual kW used instead having to approximate with operating hours x 1.4-1.7kWh for my IVT.

Your average COP sounds impressive. From what I understand, the less heat a GSHP has to produce, the higher the COP. e.g. hot water at 51c is more efficient than hot water at 55c, and underfloor heating at a lower temperature will lead to a better COP than radiators requiring higher temperatures. Also a well insulated modern house will help?

I have mostly underfloor heating but 4 radiators and 3 radiator towels, would guess my 2009 year IVT's COP is not at the same level as your Ecoforest. In October total household consumption was 13kWh per day, the heat pump was running 2.07 hours a day over that time so 2.9-3.5kWh per day.

The two 38 metre ground loop trenches don't appear to be any different to the surrounding ground and 15 years later there is no sign where they are. I would say my heat pump has been running more efficiently over time due to optimising the original settings based on discussions held here. e.g. for the first 7 years it used 1100 hours of additional heat, for the last 7-8 years it has only used 86 hours of additional heat. At 6kWh per hour that's a huge improvement for moving away from the initial settings the installer used (to be fair, it was probably hard for them to find a good compromise as every property is different and they can't be running back to remote installs to fine-tune settings if the householder is cold). I'm not certain but I think this is one area where modulation helps.

Strummer22

Ours has modulation and weather compensation so only heats central heating water to high 30s degrees in the current weather. That definitely helps. We absolutely do not have a modern or particularly well insulated house…

ChapelBarn

Patrol said:

Can anyone help with what to do with "HTF pump set too low"?

Hello. My IVT manual for "High Heat transfer fluid delta" has two possible causes. I think this is the same type of error as you are seeing.

1 Not enough flow over the heatpump. Action: 1 Check that the heat carrier pump has not jammed. 2 Check that all the valves are open.

2 The particle filter on the hot side is clogged. Action: 1 Clean the particle filter.

The filter is supposed to be user-maintainable so I would check that first as below (I've checked mine in the past). If that was fine I'd be looking for a service engineer as unless someone has fiddled with valves or turned radiatiors / underfloor heating valves off it sounds like a pump may need to be replaced.

Do you have a manual? Page 30 of mine describes how to check and clean the filters as below
1 Shut down the heat pump using the On/Off button

(a bit here from me, the hot filter will be in your heat pump. I can remove my front cover with two screws at the top, and the filter is towards the top on the left (next to the black cassette cylinder and under some U shaped pipework. The valve is a lever handle that rotates 90 degrees from on to off from memory)

2 Close the valve and unscrew the sealing cap
3 Loosen the circlip holding the screen in the valve. Use the supplier circlip pliers

(a bit here from me, the pliers taper to fine points so you can put them into the two small holes in the circlip. Be careful not to drop the circlip)

4 Lift out the screen from the valve and wash clean with water 

(a bit here from me, the screen is like a small metal thimble)

5 Refit the screen, the circlip and sealing cap

6 Open the valve and start the heat pump using the On/Off button

Hello - OK thanks for that. I have a C series pump and so the valve is external to the pump. I have located it and cleared out the particle filter using the instructions above (and have just located my original manual)

I'll keep and eye on the alarms and see whether they return. At the moment it does seem to be working normally.