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Heat Pumps

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 MeMeMe 29 Jul 2020

Anyone have any personal experience with air or ground source heat pumps?

We’re investigating installing one so have looked into the technicalities of it but we’re lacking any kind of opinion from anyone who’s actually got one...

 Sealwife 29 Jul 2020
In reply to MeMeMe:

I don’t personally have either but both types are very, very common where I live.

Ground source ones - need a fair bit of ground available for your trenching, I believe it can sometimes be achieved with a borehole but not seen that done locally.  Most folk I know who have ground source have it feeding into a wet system of underfloor heating which doesn’t get really hot but keeps a steady, comfortable temperature.  Often used in conjunction with a small multi fuel stove on really cold nights.

Air source more popular in towns, units usually bolted to outside of houses, but rattly in the wind but nobody seems that bothered.  Usually feed out into house through warm air ducts.  Friend who had it put into 3 bedroom 1970s terrace said it’s improved the warmth and comfort of his house whilst cutting electric bills (previously he had storage heaters).

1
 SAF 29 Jul 2020
In reply to MeMeMe:

The fitters left about half an hour ago!!

We have had a grant air source heat pump fitted to replace oil and will be claiming from the renewable heat initiative. 

The main factors for success seem to be having all the radiators changed to bigger ones due to the lower hot water temperature in the system and having a well insulated house .

The company from Durham (we are in North Wales) who fitted it were awesome. Sent a massive team out and did it all in a day. 

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 MeMeMe 29 Jul 2020
In reply to SAF:

Durham you say? What's the company? We've struggled to get multiple quotes and we're a lot closer to Durham than North Wales is!

How does yours heat the house? Via hot air? We've currently got underfloor heating (downstairs a least) so it would feed into that.

 SAF 29 Jul 2020
In reply to MeMeMe:

It's a wet system, using standard radiators but bigger than normal to account for the fact the heat pump only heats water to 55C rather than 65-70C that an oil or gas system heats water to.

Project heating solutions in Doncaster (the fitter I was chatting to was from Durham).

 Deri Jones 29 Jul 2020
In reply to MeMeMe:

We've not installed the GSHP yet, but have had the system designed to include it down the road. We went with Chelmer and have had good service, good design backup with any queries our plumber had.

Get your head around the design principles of using lower temperature systems - as SAF says, we've got big radiators and big bore plumbing. We've installed a lot of woodfibre insulation (think 280mm in roof, min of 80mm on internal walls etc) but the rads have ended up physically the same size as before to make the system efficient. Our advice was to get the place as well insulated as was reasonable, then sort out a rad/ufh system sized to suit lower temp heating using a heat store, then finally look at the inputs to that system, so you're heat pump is as small as possible and can work economically. Just replacing a gas/oil boiler without sorting the other bits wasn't a good use of the heat pump. There's a good Excel spreadsheet from the Buildings research establishment that roughly models heat requirements/insulation and gives you an idea of the wattage for radiators required at different heating system temperatures. As a rule of thumb, I think it is 2.5x the standard rad sizes. I've found the Passivhaus handbook to be invaluable in plotting out trying to make a 200+ year old farmhouse as non oil guzzling as possible.

Hope that helps

 Philip 29 Jul 2020
In reply to MeMeMe:

ASHP for 6 years in Staffordshire. Really impressed with it.

Nibe.

 Brown 30 Jul 2020
In reply to MeMeMe:

I've not got experience of them in a small domestic setting but have been specifying them for non-domestic and multiresidentual a lot in the last few years.

There has been a tipping point with the decarbonisation of the grid due to renewables leading to heat pumps now being lower carbon than natural gas boilers. If you have a focus on carbon and local air quality they are a good choice.

If you have access to natural gas it still works out a little cheaper to use that but if you are off the gas grid I'm sure it's cheaper than oil, batch purchase ofoof gas or electric panel heaters.

If you then sign up to a fully green energy tariff you can be zero carbon.

The ability to generate large amounts of domestic hot water using them is limited and if you are a big user (large family) that might be something to consider.

It is also vitally important to get them appropriately sized. Their efficiency can collapse if they are worked too hard. Also watch out the method you use them. There are products that are highly effective when running 24h day which are outrageously expensive if used traditionally with on off periods. 

Post edited at 14:07

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