wonderful diagram of an ASP on EDF website

[Andy Burns]

This particular manufacturer specifically states they do not fit immersion heaters.

[Andrew]

But surely every domestic hot water tank normally sold in the UK has one or two immersion heater bosses fitted by the manufacturer ?.

[T i m]

Partially.

I thought the idea was that they were moving 'heat' (so both arrows might be red) from outside to heat on the inside, irrespective of how it's done?

So 'heat' is drawn from the (already cold) air outside, compressed and converted into a lower volume of air but at a higher temperature on the inside?

So I'd have a large light red arrow facing the outdoor rad and a smaller darker red arrow coming out of the rad on the inside.

Cheers, T i m

[Chris Green]

But doesn't all that inertia, super insulation and draught proofing make heating costs with conventional systems much cheaper too?

[alan_m]

The site is a bit more honest than some I've read but it still is a bit vague about how much heat air sourced can generate in the coldest months (I very much doubt their 300 to 400% figure is for winter) and how much insulation is appropriate. They mention a hybrid approach but fail to mention that they mean an electric conventional boiler. Run it off Eeconomy 7 and you have most of the disadvantages of storage heaters.

[The Natural Philosopher]

It is not. At zero outside you tend to be around 2:1 at best, and it gets topped up with straight immersion heaters. I think at -5°C you might as well have an electric fire...

[No Name]

Tangential thought.

A Evacuated solar tube on the roof can collect solar energy via water as its energy transfer medium... (it is accepted it is only harvesting energy during sunlight hours)

A Ground source heat pump requires underground pipework.....

Why not use the solar evac tubes to feed a GSHP's input ciruit and save on evacuating the garden for the underground pipework?

I would expect the solar heated water to be at least a few degrees higher than from the ground thereby improving teh COP of the heat pump and also be less costly to install due to not needing a digger.

(The solar evac tubes would supply hot water direct during the summer but then work via the GSHP to provide central heating and hot water)

[newshound]

Interesting idea although I'd still worry about the capital cost. Also, you *really* need to get plumbing with good long term reliability.

[Andy Burns]

Domestic GSHPs circulate 30 to 50 kg of brine per minute, think the solar tubes could constantly warm that quantity by 4 degrees?

Also the heat pumps don't actually like their inputs above about 15°C

[T i m]

When my mate (a heating engineer) installed the GSHP system in his place about 10 years ago (as a testbed with thoughts of doing so commercially), the biggest issue wasn't needing a digger (they did that bit by hand) but the drilling rig, drilling the vertical holes (~5 m deep I think) for the main heat collecting pipes.

I think there were 4 or 5 holes so 8 or 10 hoses that then came back into a manifold in the garage.

I think as the holes were drilled the debris was pumped out with some sort of heavy fluid that was left in the hole to keep it open. The flow / return pipes were then made up and lowered into the holes and the idea that over time the surrounding ground itself would fall back into the gaps, make contact with the pipes for good thermal contact.

He imported the actual heat pump directly from China and because the concept was quite new and the instructions not very good, he never really got it working. ;-(

If he did want to try it again he's done the hard work as all the plumbing is in place and he'd just need a working HP.

Cheers, T i m

[Brian Gaff (Sofa]

Do you think the person doing these drawings has done one for a Nuclear Power Station yet?

Brian

[No Name]

OK, expanding on the idea a bit more:

There would have to be a switching in/out arrangement where during the summer months, the Solar panels heats the thermal store directly for the hot water. The GSHP woul donly be switched in between teh Solar tubes and the thermal store during the winter months.

Then to gaurantee 15 deg max input, use a 22mm thermostatic mixer valve or a UFH blending valve to blend the "warmed" water from the Solar tubes with the cooled water output of the GSHP into teh GSHP's inlet?

[Andrew]

Most heat pumps are owned by people who don't have an acre or more of land, or a running stream, or suitable ground for a borehole so they have to use air source heat pumps. I'm sure these work better on a south facing sheltered wall that is a natural suntrap anyway.

If space was not a problem, maybe installed at one end of a polytunnel would boost their efficiency ?.

[John Rumm]

Although if fitting a tank into a place with not loft cistern etc, it would make more sense to go unvented.

[Tim Lamb]

I like the idea of using a running stream:-) Few second hand domestic radiators linked up:-) Sadly I doubt the EA would agree. I could use the R. Lea. Nice and warm downstream of Luton sewage treatment works.

A friend installed an air to wet underfloor system to a new build in Suffolk. Seemed to perform OK although there were 3 large fans on the outside unit. House was SIPP construction so very well insulated.

I never found out how she got DHW but there may have been a secondary thermal booster.

[Andrew]

According to my house deeds there is a 26 inch water main running across the bottom of my garden. It comes from Hardham and supplies ?Crawley or maybe even Croydon.

I have often wondered if the temp of the concrete cap on top of the pipe which must be at least 8 feet down, is high enough to make it worthwhile to put a ground loop on it and collect some free heat. Southern water might be bit miffed though.

A neighbour a few doors up has one fitted, but the house is a 1973 built detached house with plastic cladding in the front. Behind the cladding is an uninsulated 9 inch wall of hollow blocks which leaks heat like a sieve. The heatpump is on the other side, facing north and in permanent shade. Even after replacing all 8 rads with triple- panel ones (ouch) she says she is freezing in winter. Also for a while the Poxi-batterton supreme gas boiler ran in parallel so once a year a bloke would arrive to service the gas boiler, take one look at the controls and mutter "I don't know how to do this set up" and leaves. Gas boiler has now been disconnected, hence the 'freezing' internal environment.

Anyone planning to get a heat pump probably needs to be living south of a line from the wash down to Bristol, plus needs a house that is insulated to a far better standard than the original builder managed.

[Tim Lamb]

In message <rra13c$uot$ [e-mail]>, Andrew [e-mail] writes

Snip.

I have the land to do any of the current options. From a superficial investigation I decided, at my age, it was never going to pay back.

Other landowners have commented that dry soil is not good for the

*slinky* type. The twin borehole may bring comment from the EA as they stress about linking water bodies and worry about contamination. Air source you already know:-)

Ideally you need a modest lake in your garden!

[Andrew]

Err, you always plant trees for future generations though :-)

The best soil is clay I believe. The nice sticky sort that Sarah Beany is building her mansion on down in Somerset.

[Tim Lamb]

I have done some of that. Remains to be seen if the changes to the post Brexit CAP reward landowners sufficiently for significant tree planting. Most of my life trees have died inconveniently; Dutch Elm disease, now Ash dieback. All converted back to CO2 so I'm not sure planting here in exchange for the Amazon is anything more than political posturing:-(

[charles]

Like the factor at Balmoral who planted an area with trees and expected them to be harvested in about 500 years time.