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Ground Source Heat Pump Questions

ham1sh

Standard Member
I'm hoping some of you guys can help me out with a few questions I have about aboput ground source heat pump systems.

Is it better to dig trenches and lay the pipes or go the bore hole route?
From what I can understand a bore hole would be more expensive, any ideas how much roughly? And which method provides the most effecient system?

Also as i have a young family that need baths etc every other night, would I also need to install solar panels to heat the water, or can the heat pumps these days, do it all? Can the solar panels also power the heat pump?

It is intended to install underfloor heating on the ground floor, but I haven't decided what to install on the first floor yet, possibly just standard radiators. Any advise on an alternative to radiators?

Cheers
Hamish
 

deckingman

Well-known Member
I don't know a great deal - hopefully someone with more knowledge will jump in here.

AFAIK, ground source heat pumps are really only suited to under floor heating. I read somewhere that the water doesn't get hot enough for conventional radiators (which work more by convection) or domestic hot water use. It takes qite a bit of electricity to run them.

I think you get out something like 4 times what you put in, so say if you needed say 8kW of heat, you need to supply 2 kW of electricity. If that's the case, then you need to work out how heat you need and then calculate how much power will be required from your solar system. Don't forget that you'll need to store power in batteries if you want to run the heat pump directly from the solar (like when it's dark).
 

ham1sh

Standard Member
Thanks Deckingman.
After reading up a bit more, I don't think solar is going to give sufficient output to drive the heat pump. Some of these pumps require a 3 phase supply apparently.
I'm still hoping to use the heat pump for radiators upstairs, (even though it's not ideal) as I can't think of a suitable alternative.

I suppose the next step will be to get a company round to give me a quote and some advice. There are a few companies up here (NE Scotland), that do this type of work, although I don't know how good they are. In fact I don't know anybody that has this type of system, so it's going to be a leap of faith, in more ways than one.

Thanks
Hamish
 

setjellyfish

Active Member
I was looking at heat pumps and when I worked out all the figures it's 4 times more expensive to install compared to getting a new gas boiler and marginally less expensive to run. All in all not worth the hassle yet.
 

mrm3

Active Member
I was looking at heat pumps and when I worked out all the figures it's 4 times more expensive to install compared to getting a new gas boiler and marginally less expensive to run. All in all not worth the hassle yet.

'only marginally less expensive to run' seems wrong ?

I thought the point when installed heating is virtually free !
 

setjellyfish

Active Member
'only marginally less expensive to run' seems wrong ?

I thought the point when installed heating is virtually free !


That's what I thought too but you still use electric to run the heat pump and when you work out the amount of electric you need to use compared to the gas used to run a boiler it's nearly the same cost. It's like all these new 'green' techs great in principle but expensive to install and take decades to recoup the costs.
 

gavan

Well-known Member
That's what I thought too but you still use electric to run the heat pump and when you work out the amount of electric you need to use compared to the gas used to run a boiler it's nearly the same cost. It's like all these new 'green' techs great in principle but expensive to install and take decades to recoup the costs.


That doesn't sound right - got any figures to back up your claim?
 

robh2002

Active Member
Unless you can get extremely good heat pump systems with a very high coefficient of performance (COP) then the costs could very well be close to that mentioned above compared to gas.

Burning gas in a new boiler will be done with a thermal efficiency of up to around 90%. Generating electricity to run the heat pump (say using a gas turbine, coal, nuclear etc.) might do so at an efficiency of say 30-40% (some higher - some lower). While the heat pump generates more heat that it uses in electricity you still have to factor in the efficiency of the electricity generation in the first place and its cost. Electricity is around 2 - 3x more expensive than gas (VERY roughly!) because of the efficiency of generation.

Perhaps very new heat pumps might have a higher COP making up for the low electricity generation efficiency, but if you have access to gas, it is usually cheaper to use this. If you have no gas then a heat pump will definitely be the way to heat a house.

Hope that makes sense - been a long day...
 
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setjellyfish

Active Member
I'm not claiming anything I was really hoping it was going to be cheaper and was already to dig up my garden. I did have figures but it all got binned along with the idea.
 

ham1sh

Standard Member
That's what I thought too but you still use electric to run the heat pump and when you work out the amount of electric you need to use compared to the gas used to run a boiler it's nearly the same cost. It's like all these new 'green' techs great in principle but expensive to install and take decades to recoup the costs.

Yeah, the amount of time to recoup the initial cost is a concern, but at least I'll know the CO2 emissions will be lower during the 10 years or so that it takes.
It seems like if I go the Borehole route as opposed to digging trenches, I could be up to £5000 more expensive, so I've kind of ruled that out as an option.
Mains gas unfortuantely isn't an option either, so it's either this or an Oil bolier I think.
 

miceri

Active Member
I have such a heat source for my house, COP=5.03.

The borehole depth is 180m (Deeper is better, but costs more initially).

Here in Sweden, it is very common, so the prices are not so bad. I have a large house (Over 3,500sq ft) so heating before was approx 44,000kw/year.

After the heat pump installation, already (without other changes such as radiators -> floor heating, heat exchanger ventilation system , full triple glazing etc) the cost is down to 23,000kw/year.

On this saving, pay-off is approx 6.5 years. After that, I get 1/5 price heat and hot water. Incidentally, I have chosen a 'green' supplier of my electricty (Wind, water turbines etc). I paid extra for a double mantle water tank, 500l. Which is 'prepared' for solar heating connections.

The heat / hot water to my house is constant, this installation is always considered a 'must' investment for larger houses.

Hope my info helps...

PS - What size house are you planning to heat, the heat pumps come in a variety of sizes...
 

robh2002

Active Member
Indeed - a very useful post!

What temperature do you have set for the water to be delivered from the heat pump and what is the borehole temperature? Do you have access to gas?

Many thanks,
Rob.
 
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ham1sh

Standard Member
I have such a heat source for my house, COP=5.03.


Miceri, a COP of 5.03 is quite good from what I understand. What make is your Heat Pump?
Is there a particular manufacturer you'd recommend, or are they all as good as each other?

Hamish
 

miceri

Active Member
Thanks Miceri for the info. Very helpful.
The floor area I'm looking at is approx. 255sq Mtr.

Hi ham1sh,

For a property that size, I would almost rule out the ground source pump, as it feel's a bit like over-kill (Read expensive).

I would suggest you look into Heat Inverter Air Pumps:
Air Conditioning - Climate Control Systems - Ground Source Heat Pump - Mitsubishi Electric

This is from a Swedish website, although I think you can see that the COP is claimed to be quite high:
Canvac - Q Heat SE luftvärmepump

Or are you looking at Heat Inverter pump that can also partially heat your water?

*EDIT* I also have a Heat Inverter Pump, that is set relatively low to 'top up' the airflow temp around the house. Actually, its mainly for the lounge, which has a 4m high sloping ceiling to a wall of windows, an so doesn't get that much heat from the wee little radiator's under them.
 
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miceri

Active Member
Indeed - a very useful post!

What temperature do you have set for the water to be delivered from the heat pump and what is the borehole temperature? Do you have access to gas?

Many thanks,
Rob.

Hi Rob,

The water is set at 50C, so not scalding, but 300l always available, 200l in the 'double mantle' partially heated, and it also has a heat element for those very wet nights with the kids.

Once a month, I believe the temp is 'spiked' to 60C to ensure no legionnaires business.

The technology is not what you seem, we do not 'set' our required water temp from the borehole. It goes something like this:

1 sealed system (Brine type alcohol) is fed down and up the borehole in a double pipe arrangement. My readout currently says '6.1C in, 6.7C out' at idling, and just now it is pumping this around at '4.9C in, -0,3 out'.

This is then passed through the compressor in the heat pump which then takes this constant temperature difference to heat our water to 50C, radiator system to 33C.

These C figures might seem quite low, but remember it is constantly available, always cycling around, the return heat from the radiators is not so much different either. So a 5C difference is actually quite high.

This entire system is linked to the outside thermostat, so that we set the heat requirement we want, and the system takes care of the rest.

Nope, no gas. Gas systems are very rare in Sweden.
 

miceri

Active Member
Miceri, a COP of 5.03 is quite good from what I understand. What make is your Heat Pump?
Is there a particular manufacturer you'd recommend, or are they all as good as each other?

Hamish

Hi Ham1sh,

Here is a swedish PDF:http://www.nibeonline.com/pdf/639250-2.pdf
Should keep you busy! You can see the COP value quite easy.

Take a a look at the pictures [Berg is the borehole method], might help a little also.
I am having trouble finding English material based on this, so if you have any question from the PDF let me know, and I can translate.

Wouldn't say one manufacturer is that much better than the other, there are different compressor technologies, scroll etc. For us, and many others it comes down to which installors have the best deals that include drilling down. they are usually tied to manufacturers, so you essentially get a pump that they can provide.
 
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miceri

Active Member
I also have a 'heat exchanger' ventilation system ready to install. This takes cold air in, heats it slightly, pumps it around.

Then it sucks it back in (including the heat you have generated from radiators, floor heating, heat inverter system etc) and uses this to 'heat slightly' the incoming air. Nice fresh clean air constanly changing in the house.

This method means you can 'seal' you house very tight, to minimise heat loss. I wouldn't recommend doing this without a ventilation system.

Sorry to drift off topic, but I think it is important to see the benefits of all these systems working together.
 
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robh2002

Active Member
Great - much appreciated! I know the theory (well I should as I lecture on it!), but the practical information is just what I wanted. Thanks again.
Rob
 

ham1sh

Standard Member
Hi ham1sh,

For a property that size, I would almost rule out the ground source pump, as it feel's a bit like over-kill (Read expensive).
I was at an exhibition in Aberdeen at the weekend, and spoke to various people about heat pumps, solar PV etc. and one of the guys I spoke to thought I might need 2 bore holes to accomodate a property of my size, I presume he's exaggerating then?

I have had a look at Air source heat pumps as well (same manufacturers as the ground source pumps), but they seem to be very different from the Mitsubishi ones you highlighted.

Or are you looking at Heat Inverter pump that can also partially heat your water?
Yes, the Heat pumps I've looked at, have either had water tanks built in, or the option of hooking them up to an external tank.

Hi Ham1sh,

Here is a swedish PDF:http://www.nibeonline.com/pdf/639250-2.pdf
Should keep you busy! You can see the COP value quite easy.
Nibe was one of the manufacturers I've been looking at. Overall I think their kit has impressed me the most.

Take a a look at the pictures [Berg is the borehole method], might help a little also.
I am having trouble finding English material based on this, so if you have any question from the PDF let me know, and I can translate.
Thanks for that, good pictures.
I've no problems regarding information after the exhibition at the weekend. I've obtained literature from Nibe, Danfoss and Worcester Bosch. I've just got to read through it all now :rolleyes:

Wouldn't say one manufacturer is that much better than the other, there are different compressor technologies, scroll etc. For us, and many others it comes down to which installors have the best deals that include drilling down. they are usually tied to manufacturers, so you essentially get a pump that they can provide.
Yeah, i'll have to get a few companies round to give me estimates at some point. No way near that stage yet though, just gathering information.

Thanks very much for your help.
Much appreciated :thumbsup:
Hamish
 

miceri

Active Member
255sqm :eek::oops:

I read sqft :suicide:

In sqm, my house is 290sqm heated and another 37sqm for the non-heated attached garage.

We only have 1 bore hole, I know of people who have drilled 2 for similar and smaller properties. 2 bore holes are required to 'cycle' less, but you also must factor in the costs of drill an additional hole. I also think that not all of the pump units are equipped for that... They also must be a certain distance apart, or you will be drawing geothermic heat from the same place.

So he wasn't pulling a fast one!

It also depends what else you will do with the house in terms of additional / complementary heating & ventilation systems. As I said previously, I am planning floor heating (waiting for the daft builders to send estimates in), heat efficient ventilation, triple glazing etc.

So, 1 bore hole was plenty enough for me.

As I now understand you have 255sqM, then forget the heat exchanger method, you do need something more substantial.

What type of terrain / location is your house?
You can also get heat pumps very similar to this that can be installed in a lake / sea if you have water very close, you can also have your entire garden dug up, and masses of piping laid to act as a collector in the ground. This is pretty useful for new builds.
 

ham1sh

Standard Member
We only have 1 bore hole, I know of people who have drilled 2 for similar and smaller properties. 2 bore holes are required to 'cycle' less, but you also must factor in the costs of drill an additional hole. I also think that not all of the pump units are equipped for that... They also must be a certain distance apart, or you will be drawing geothermic heat from the same place.
Yeah that makes sense, and like you say an additional hole is probably going to double the cost.:rolleyes: Hopefully I'll be able to avoid that.

It also depends what else you will do with the house in terms of additional / complementary heating & ventilation systems. As I said previously, I am planning floor heating (waiting for the daft builders to send estimates in), heat efficient ventilation, triple glazing etc.
It will definitely be undefloor heating on the ground floor, and probably radiators on the 1st floor. From what I understand these will have to be bigger than the norm, due to the lower heat output from the heat pump. Not too worried about that though.


What type of terrain / location is your house?
You can also get heat pumps very similar to this that can be installed in a lake / sea if you have water very close, you can also have your entire garden dug up, and masses of piping laid to act as a collector in the ground. This is pretty useful for new builds.
The ground is quite hard about 1ft down, which is why I was thinking of going down the bore hole route. There's also a soakaway which could impede things via the trenching method.

There is a park which may available nearby, and apparently the ground isn't so hard there, so I'm hoping I'll be able to use that. :)
 

miceri

Active Member
If you are thinking of mixing floor heating and radiators, then look carefully at which equipment you buy.

Floor heating temperature is significantly less than radiators. You will need a unit than is equipped to distribute 2 separate water flows. Otherwise, you risk damaging the under floor pipes.

The heat pump we got 'Nibe Fighter 1135' is prepared to do this, others are not - However, most have an optional uint you can buy to enable this. I would assume the plumber / installer would spec this out with you first.

Think about where the pump will be placed also, the Nibe range has a relatively noisy compresssor, but we have ours hidden in room that in effect 'swallows' this noise. Other rooms, especially next the bedrooms are not so lucky.

My neighbour did his at the same time as us, and choose a Bosch system, as it was quieter, because it was to be placed nearer to the lounge. Had a lower COP value though...

Are you thinking of having an 'all in one' unit, where the water tanks in enclosed with the pump unit? As we dimensioned for 4 people, 2 showers, 1 bath, 1 corner spa, then we choose the smaller stand alone pump, and a separate larger water tank.
 

ham1sh

Standard Member
If you are thinking of mixing floor heating and radiators, then look carefully at which equipment you buy.

Floor heating temperature is significantly less than radiators. You will need a unit than is equipped to distribute 2 separate water flows. Otherwise, you risk damaging the under floor pipes.

The heat pump we got 'Nibe Fighter 1135' is prepared to do this, others are not - However, most have an optional uint you can buy to enable this. I would assume the plumber / installer would spec this out with you first.
Thanks again miceri, I never knew that, but I suppose it makes sense when you think about it.

Think about where the pump will be placed also, the Nibe range has a relatively noisy compresssor, but we have ours hidden in room that in effect 'swallows' this noise. Other rooms, especially next the bedrooms are not so lucky.

My neighbour did his at the same time as us, and choose a Bosch system, as it was quieter, because it was to be placed nearer to the lounge. Had a lower COP value though...
We will be installing the pump in the garage, so hopefully noise won't be too much of a problem, but I'll keep this in mind when I eventually choose which system to go for.

Are you thinking of having an 'all in one' unit, where the water tanks in enclosed with the pump unit? As we dimensioned for 4 people, 2 showers, 1 bath, 1 corner spa, then we choose the smaller stand alone pump, and a separate larger water tank.
We will be going for a separate water tank as well. We have 2 young kids at the moment, and with all the baths and showers etc we tend to use quite lot of hot water. The washing machine seems to be running all day every day! :eek:
 

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