Ground Source Heat Pump Questions

miceri

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.

ham1sh

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

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

ham1sh

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.

miceri

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

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.

miceri

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

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.

robh2002

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.

ham1sh

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