Ground Source Heat Pumps

matelodave

beardymarrow wrote: »

Thanks. With the recirc I can literally get in to the shower on the 2nd floor (HP and DHW tank is in the basement) and switch the water on while stood under it and it's immediately the right temperature. I'm prepared to forgo that luxury if it's costing me a fortune in DHW production though .

By very short time, what are we talking about? The HP coming on for 5 mins every hour, something like that (assuming no usage of DHW)? I just want to know what I'm aiming at, so I'm not chasing the impossible. Of course I know some of the on time might be because the ground loop isn't up to pressure, but the off time should still be OK.

Yes, mine comes on at about 49, and goes off at 54C.

I'd guess that with a hot water circulating pump that not only are you using 30-50watts whilst it's running (possibly 24/7) so costing you about £30-£50 a year it is also dragging heat out of your hot water tank and dispersing it throughout the pipework to gently heat the house and other places that don't need heating. Even a normally insulated hot water tank will lose 1-3kwh a day, pumping the hot water round the house will probably double or even treble that, depending on the length of the pipe runs, size of the pipes and how well they are insulated. It may save water but it sure doesn't save energy.

LittleVermin

arvysingh wrote: »

Hi,

As part of my final year dissertation on Ground Source Heat Pumps in the UK, I have set up an eight question survey.

I would be grateful if you/anyone could spare a few moments to assist me in my educational endeavours.

Please note this is for my dissertation and not for general release and not for any commercial interests.

All responses are anonymous.

Your participation is greatly appreciated.

Please refer to the link below if you wish to take part in the survey.

surveymonkey.com/s/TTW9CPV

Many Thanks.
Arvy

http://surveymonkey.com/s/TTW9CPV


Good luck, Arvy!

beardymarrow

matelodave wrote: »

I'd guess that with a hot water circulating pump that not only are you using 30-50watts whilst it's running (possibly 24/7) so costing you about £30-£50 a year it is also dragging heat out of your hot water tank and dispersing it throughout the pipework to gently heat the house and other places that don't need heating. Even a normally insulated hot water tank will lose 1-3kwh a day, pumping the hot water round the house will probably double or even treble that, depending on the length of the pipe runs, size of the pipes and how well they are insulated. It may save water but it sure doesn't save energy.

Thanks Dave,
I've done some timings, and I'm losing from 55.6 to 49.9 degrees in a 280l tank in 27 minutes!
So if, (roughly speaking) 1kWh = 1000kcal, then I'm losing 1.6kWh in 27Mins or 3.5kWh per hour. This is with the recirc pump off (it's on a timer).

I have 3 rad pumps on my GSHP (one for the UFH, one for ground and 1st floor rads and one for 2nd floor rads). They are permanently on, regardless of whether the HP is on. Is there any way that my DHW can be being piped through the rads (seeing as the rad and DHW returns are connected together in the HP) and that is cooling it down?

I might time the heat loss again with the valves on the rad pipes into the GSHP switched off to see.

beardymarrow

beardymarrow wrote: »

Thanks Dave,
I've done some timings, and I'm losing from 55.6 to 49.9 degrees in a 280l tank in 27 minutes!
So if, (roughly speaking) 1kWh = 1000kcal, then I'm losing 1.6kWh in 27Mins or 3.5kWh per hour. This is with the recirc pump off (it's on a timer).

I have 3 rad pumps on my GSHP (one for the UFH, one for ground and 1st floor rads and one for 2nd floor rads). They are permanently on, regardless of whether the HP is on. Is there any way that my DHW can be being piped through the rads (seeing as the rad and DHW returns are connected together in the HP) and that is cooling it down?

I might time the heat loss again with the valves on the rad pipes into the GSHP switched off to see.

I think I'm getting somewhere on the heat loss from the DHW tank.

This morning I lost 6.6deg in 22mins (with the recirc off).

This afternoon I disconnected the 3-way valve actuator, and manually moved it to DHW, closed the valves on the rad inlet and outlet above the HP and switched the external rad pumps off.

I then lost 2 deg in 1Hr 20Mins. However, the pump in the bottom left that pumps the water from the rads/DHW through the heat exchanger was still running and it was hot. Not sure if this is a problem though? The HP would have thought that the 3-way was in rad mode, but it was in DHW.

So, I opened the rad valves back up, put the 3-way valve back on, allowed it to reset to rad.

I then lost 2 deg in 9Mins.

So, somehow, something on the rad side is draining all the heat out of my DHW tank. What could be causing that? Is it possible that even though the 3-way seems to be moving OK, that the DHW water is being pumped through the rads via the 3-way?

Cheers

Beardy

lovesgshp

Still think it is a problem with the 3 way valve.
Fairly simple check. With the pump operating in DHW mode, hold the heating pipe on the top of the pump. If the valve is operating correctly, then there should be a virtual immediate temperature rise in the heating flow as the valve switches over from DHW.

beardymarrow

lovesgshp wrote: »

Still think it is a problem with the 3 way valve.
Fairly simple check. With the pump operating in DHW mode, hold the heating pipe on the top of the pump. If the valve is operating correctly, then there should be a virtual immediate temperature rise in the heating flow as the valve switches over from DHW.

Hi,
So, in DHW production mode :-
DHW out was Hot
DHW In was Hot
Rad out was cool
Rad In was warm

When DHW stopped :-
DHW out slowly went cool
DHW In stayed warm
Rad out immediately got hot, and then slowly cooled back down to cool
Rad In slowly went cool

Beardy

lovesgshp

OK. Is the temp in GT1 rising, as if the water is being somehow drawn of the tank then this would show.

beardymarrow

lovesgshp wrote: »

OK. Is the temp in GT1 rising, as if the water is being somehow drawn of the tank then this would show.

Hi, GT1 is 27.4 and is stable. I don't know how it's 27.4 though as the HP hasn't been producing any heating today.

DHW in to the HP is also still very warm, even 10 minutes after the HP switched off. DHW out is cool. Something must be drawing water out of the tank through the HP for DHW in to be warm still, but with DHW out cool?

I've checked and the engineer that is coming on Friday will have a replacement 3-way with him, so at least if that is still a problem (and I'm with you, I can't see how it is anything else), then he can replace it.

lovesgshp

Thanks for that info. Think you are going to have to wait for the engineer to arrive, as it is difficult to analyse some problems without being in front of the unit.
Hope you will update on his findings.

beardymarrow

lovesgshp wrote: »

Thanks for that info. Think you are going to have to wait for the engineer to arrive, as it is difficult to analyse some problems without being in front of the unit.
Hope you will update on his findings.

Yes, certainly will. We've improved my usage from 80kWh a day to about 60, already, so thank you so much for your help so far.