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Ground sourced heat pumps - how they work

Discuss Ground sourced heat pumps - how they work in the Green Energy Forums | Green Energy Hub area at

The Title should read Air Source Heat pumps, as that's what the article is explaining.
With Ground source the evaporator coil is buried in the ground either horizontally-ish or vertically-ish.

This guardian article explains it really well with awesome graphics.

How many of you guys are into this?
They work well in well designed and insulated properties and in climates that are more stable than the UKs.

All things being equal, in an equally well insulated property with a well designed emitter system, they only out perform a gas boiler, on cost, above 5⁰C (ish) ambient temperature.

Below 0⁰C they perform well but are more expensive than Gas.
Above 5⁰C they perform well and can be cheaper than Gas.
Between 5⁰C and 0⁰C they can be hideously expensive and unreliable. Icing up is the bane of heat pumps. Loss of heat production and expensive to run are the good consequences, smashed fans and split coils the worst and I've seen plenty.

There really is no cost arguments that heat pumps win, you will never recoup the investment cost without very generous government subsidies.

Retro-fitting to old properties is prohibitively expensive, if an honest appraisal is presented to the client then none would be sold.

Heat pumps are relatively cheap, probably 25-50% the cost of a well designed installation (property dependant) but they are not a fit-and-forget solution the way a combi is. Regular servicing repairs and maintenance must be factored in. They will deteriorate in performance as evaporators degrade. Fans will become noisy as bearings fail. They reach a point 5-7 years where replacement parts become close to replacement value of the heat pump.

Only ever consider one as an option if you are not on the gas grid.

There may be some merit in making one work in tandem with a combi but the payback period probably wouldn't stack up.

Technologically they have not changed significantly since I installed them, maybe on a software level but the guts are the same.

I installed, not designed the install, hundreds over a three year period, six years ago. For an installer they have to be a fit and forget product to make any financial sense. If you end up on the hook for poor performance and maintenance they will cripple you, in fact they did me.

Very rarely are issues the fault of the machine, they are predominantly installation design and environmental.

If you are looking at installing them do only that and make sure you are only on the hook for that.

If you are buying one be very, very careful. Make sure your property is as well insulated as it can be, your emitter system is suitable and, factor in maintenance costs. If a salesman glosses over this stuff find another because they WILL deliver a system that is expensive to run and unreliable.

Slowly, and as funds allow, I'm upgrading my insulation levels and emitter sizes to make the transition a painless as possible as I've a feeling this will be forced upon us.
A very good summary from GBDamo.

I did the heat pump online course from STIEBEL ELTRON earlier in the year, mainly for my own interest (I also completed the online tests for the CPD certificate). If you are considering a heat pump and have the time, I'd recommend doing one of these (free) courses. Of course it will be biased towards their own brand equipment, but tells you how it all works, and gives you an online tool to work out the efficiency to expect.

In the UK, our gas (or oil) heating systems mostly use radiators designed to run at circa 70 degrees C, whereas these heat pump systems work much better at much lower temperatures, e.g. at 40 degrees C, with under floor UFH systems. So unless you have or are planning UFH, I'd be quite wary of converting an existing radiator system.
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