Ground source heat pumps

[advancedplumber]

you have had a lot of good feed back here with loads of good guys with loads of good experience. my opinion, well geo thermal is a great theroy, suppose to date back to roman times when they had fires under ground heating running water. it doesn't use any fosiel fuels? well it is essential that it has a 3 phase 415 volts power supply for a start. the same electric requirements for a small engingeering or industrial workshop. etc. and thats just for a house the cost of a local electrical supplier to take 3 phase to any dwelling intatially in costly never mind running a 3 phase underfloor heating system, running at low temperature 24/7 well if that isn,t using fuel from some where well and the best bit is that because geo only achives temperatures of 30 to 45 degees c it can't heat ur domestic hot water so u r reliaing on electric immerions to heat ur cylinder for hot water. the big key the geo thermal is in the insulaltion of the dwelling. building sound cavity wall with heavy 50 mm foiled back insulation and then studding the insude walls with drylining and putting insulation in that again an awful lot of bother. i have personally been to a lot of houses lately and reinstalling a standard oil/ gas heating system for one of thses geo thermal unit.

 

[charliechaplinspants]

Wow! ........The first official Waffling Noob.......Congrats...

 

[doitall]

AdvancedPlumber.

You can get units up to 12Kw on single phase electric, which is more than enough for most average sized properties.

Because of the high start up load, most good units limit the start up to 5 in any 24 hour period, another good reason for stores or buffer tanks.

At the exhibitions we had a working model, that took heat from a minus 12c block of ice, and fed the radiators at 55c, obviously not ideal as you want to avoid freezing the collectors at all cost if you want the unit to be efficient, but it did work and was on show for all to see.

Absolute cold is something like -320c, anything warmer and you can harvest the energy, 12c being the optimum temperature.

Any system be it heat pump, or solar should have a second back up to boost the temperature for cleanse cycles once a month.

Properly installed an gshp will supply all the hot water and heating, but as lcgs said the quality of the refrigerant makes a lot of difference, we always used "MonoEthyleneGlycol" at 20% solution.

 

[doitall]

And for the record a heat pump is no more reliable than your every day fridge, in fact other than an heat exchanger and a few stats there ain't much more in a fridge, except it works in reverse.

 

[Silinman]

Why anyone would want to fit radiators in a new built is mind boggling, absolutely no sense whatsoever.

We could get 55c from our heat pumps (Alpha Inatec) so oversized rads and you could get away with it.

Sorry doitall, I'm confused here. You say its daft to fit rads in new build, and then in your next line you talk of oversized rads and getting away with it - away with what, please explain.

confused self-builder

 

[Paul Barker]

Some clients don't want to go to the extent of UFH in which case oversized radiators might just about heat the house with 55 degrees centigrade.

UFH takes less energy to make you comfortable, so when you are doing a project to save energy you would not be true to your stated aims if you used radiators.

 

[doitall]

Probably the way it's worded, nothing new there then

You can get away with over sized radiators with most heat pumps, based on 45-50c and good insulation.

Under floor heating is 10 x better for low temperature heating, and doesn't take up half the wall, and is cost affective in a new build.

 

[Silinman]

Probably the way it's worded, nothing new there then

You can get away with over sized radiators with most heat pumps, based on 45-50c and good insulation.

Under floor heating is 10 x better for low temperature heating, and doesn't take up half the wall, and is cost affective in a new build.

Ok understood thanks - what about hot water? Do most people have separate hot water heating, given that the circulating temperature of the GSHP is relatively low?

 

[doitall]

Hot water you should look at solar as well.

A tank full of hot water at 45c + will be more than suitable for most needs.

What you need is an alternative heat source for the cleanse cycle once a month, whereas you take the temperature up to 60c to kill any bugs.

 

[ajstoneservices]

I have no knowledge of the installation of these systems, just their use. My sister lives in Devon, and has one of these systems fitted in her cottage.

The only advice I can give you concerns noise. The pump and associated plant for my sisters system is in the kitchen. Be warned these systems can be quite noisy, especially when they start up. In the kitchen, its not such a problem, but you wouldn't want the equipment near your lounge or bedrooms. See if the equipment can go in an outbuilding, etc.

Its just one thing to consider at the planning stage.

That's the reason for this http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MESELX:IT&item=250434784364

 

[simond]

If you get an invertor driven unit it has less noise and startup current.

The older designs still have a fixed rate compressor which is noisier, needs buffer tanks in most cases, and uses more Kwh.........

 

[Silinman]

Thanks all - the advice is much appreciated.

 

[Agile]

None of you have mentioned the real disadvantage of heat pump systems!

In the UK we use fossil fuels to make out electricity. This process is not very efficient and so the electricity here costs about four times the cost of gas.

So there is no significant fuel cost advantage if a mains gas supply is available.

An air to air system is usually far cheaper to install than a ground source although in very cold weather it can almost fail completely.

In countries where the electricity is produced from hydro electric sources like the Cariba and Zambesi then there is a great reduction in the CO² emissions if heat pumps are used. Also like France where its largely nuclear the same applies although there can be other environmental aspects to take into the equation.

Unfortunately at the moment all the heat pumps are far more expensive to buy than gas boilers and have a very short warrantee.

Tony

 

[simond]

Whilst I concur with your argument about Co2, Tony, Mitsubishi Ecodan have carried out some real life trials with a suburban house and found that their air source pump works out around 20% cheaper than a gas fired heating system.

However, as you point out, the capital cost of the equipment is higher.

The lifespan of these systems is likely to be longer than a run of the mill new condensing gas boiler, at 20yrs.

 

[Agile]

Mitsubishi Ecodan have carried out some real life trials with a suburban house and found that their air source pump works out around 20% cheaper than a gas fired heating system.

The lifespan of these systems is likely to be longer than a run of the mill new condensing gas boiler, at 20yrs.

I have this feeling that Mitsubishi may well be the manufacturers with a vested interest!

I would only take serious notice of a totally independent test organisation. Even universities are no longer independent now as they receive funding for the research they do.

If the lifespan for a heatpump was expected to be 20 years then why do Viessmann only give a 12 months warrantee? At least they give 5 years on their boilers!

Tony