Air source heat pumps

[PlasmaParticipant @plasma]

<p style=”text-align: left;”>Mark,</p>
I did mine the other way round. Got solar pv and batteries in 2 years ago and have decided on a heat pump to augment that system.

Together we should start seeing some real savings.

I’m not one of those who demand to know when the outlay will pay for itself, it’s just not on my radar. I didnt buy a car with an eye on when it would pay for itself in savings s I’d make not paying for public transport. Same thing with this, its about too many things to just look at numbers alone.

 

[Mark RandParticipant @markrand96270]

I did have the solar and battery before the heat pump. Heat pump decision was based on a boiler heat exchanger leak (fixed that, but the only part of the boiler I haven’t replaced was the steel casing 😀 ) and SWMBO stating that she wanted rid of the bath and a shower putting in for our old age (boiler’s in the way, in the bathroom). When I put in the solar panels and battery for the shed roof, I was worried about ROI, but I think they’ve actually paid back in three years! I’m not that bothered either any more, so I’m happy to take any ‘short term’ loss to help the environment. I remain ‘slightly niggled’ over the obvious bullshite and larceny of those who are purveying grant subsidised heat pump installations…

[BaldricParticipant @baldric]

As we moved in May 2020, and in September replaced the oil system with ASHP, I can’t compare the running costs or performance, all I can say is how we find the ASHP. The reasons for replacement were that the water tank was on its last legs & boiler was rather old, the most important reason was the oil tank was in the way of the planned workshop! Other reason for ASHP, was there is no gas in the village.

We live in a bungalow, built in about 1960, with solid floors, probably no insulation in the floor, cavity walls, with insulation, loft insulation & double glazing, probably not the ideal  house for an ASHP. When fitted, a few radiators needed changing to either slightly larger ones or double radiators instead of single ones. We have had no issues with the system heat wise, it runs 24×7 as both of us work from home. The system is very quiet, outside you can hear the unit if you are next to it, go round the corner & can’t hear it at all. At the time we had the ASHP installed, the scheme was we paid for it, but over the next 9 years we get several payments a year, totalling about £9000, not covering all the original outlay, but better than nothing.

We have had issues, that was a pump & the room thermostat, both which could cause an issue on a gas/oil system.

Overall we have been happy with our choice & don’t have to worry about when we need to order oil, plus reducing our use of gas with it’s volatile prices.

We have also had solar panels fitted for a few years now, facing a mix of east & south, so again, not ideal, but that is the way the roofs face where it made sense to fit panels. The panels do help significantly from March to November, lowering our usage, by about 40-50%, plus exporting a reasonable amount, although the export was not enough to pay for the installation on their own.

Mark.

[Charles LamontParticipant @charleslamont71117]

Anyone considered or installed a ground source system?

[PlasmaParticipant @plasma]

Looked at ground source, we don’t have the area available for a useful system.

It’s also a lot more expensive to install.

Developers building a new site where a number of houses can be supplied from ground source seem to be the best way to go about installing it.

This is all according to second hand information by the way.

[PlasmaParticipant @plasma]

<p style=”text-align: left;”>So, after encountering one firm who were clearly more interested in the government grant (not the same now closed down firm in the news) we have decided on a system from a reputable installer that has been optimised for our home.</p>
With luck it will be in and running within a month so we will be able to see how it runs prior to any cold weather.

I understand that a heat pump delivers heat in a different way to a gas boiler so there will be an adjustment period until we learn how to regulate things.

We will then see if the system can deliver heating as promised.

I guess you could say it’s a gamble, but then everything is. Research can only take you so far before a theory has to be tested.

Mick

[Charles Lamont]

On Charles Lamont Said:

Anyone considered or installed a ground source system?

Not for about forty years … I was more interested in such things back-then, before all the the ‘missionary-zeal’ bombarded us.

For what little it’s worth: I convinced myself at the time that the best return on investment would be a ‘running water’ source … but of course we never found the dream-home with a stream 🙁

MichaelG.

[John MCParticipant @johnmc39344]

i keep an eye on the heat pump stuff because I will, eventually, replace the solid fuel with a heat pump.

I recently has a chat with a guy at the “The National Self Build & Renovation Centre” in Swindon.   Very useful it was too.

I always thought the best system was ground sourced.  Not necessarily, apparently.  If we had a prolonged cold spell the efficiency of that system would reduce as the ground around the pipework warms up.  Not much difference in efficiency, but detectable.

Air sourced seems to be the way forward for most.  If I lived by and owned a waterway then water sourced would be the best.

 

[PlasmaParticipant @plasma]

The plumbing team foreman came today to walk through the installation with me.

Basically he writes a job book for the team of installers with photos and dimensions to make the install go smooth.

I have a couple of jobs to do such as moving a few bits of furniture out of the way and building a platform in the loft to carry the hot water cylinder.

In a couple of weeks the plumbers and sparky will arrive to fit the system.

I will be there throughout to help things run smoothly.

 

[BazyleParticipant @bazyle]

Any info available as to total cost and amount of subsidy and how much of the subsidy is absorbed by consultant’s fees and kickbacks form his mandatory contractors.

Is there a combined ground source and air pump? it would make sense to switch between the two according to weather.

[PlasmaParticipant @plasma]

<p style=”text-align: left;”>Ground source is very expensive to install and needs a lot of space to be useful.</p>
You can never know how much you are being taken for when there is government money on offer. There’s obviously a massive incentive to the installer to get money from the customer and the free cash from HM department of useless spending.

The grant is currently £7,500 towards the total cost. For our installation we have to pay £5,000 in addition to the grant.

There will.aways be unscrupulous contractors out there but I think we have found a good one. They were recommended by a close friend and were a couple of grand cheaper than a firm who were very definitely not looking after our best interests.

 

[Nigel Graham 2Participant @nigelgraham2]

Hmmm…

Can’t see this being ever more than an academic question for me….

However, I have one question about ground-source heat-pumps I have yet to see addressed, except implicitly by the default position of all heat-pumps being air-to-water (or air-to-air) ones. It is this:

How does one avoid depletion?

Analgously to over-drawing a water well; so in the coldest weather the result is a very cold garden, no heat output and a long recovery time? In favourable conditions a depleted water-well might recover fairly soon. I can’t imagine some tens of, perhaps a couple of hundred, cubic metres of ground regaining a considerable amount of heat back to original temperature very rapidly.

How would it affect the topsoil in which all the plant-roots, mico-organisms, fungi and invertebrates are over-wintering? Or tree-roots at greater depths?

For any given land the heat content and recharge rate will likely be very individual too, affected by the local geology and hydrology as well as meteorology. If a whole housing-estate is fitted with GSHPs, would the depletion be quicker and the recharge even slower?

I recall someone on this site once suggesting “they” will make it illegal to freeze the worms (which incidentally do burrow quite deeply below bad near-surface conditions).

I do not recall much serious public encouragement to use ground-source heat-pumps, only air ones; suggesting they are not adviseable.

….

Regarding stream-source pumps… maybe for a few homes and a large river; but what of the ecological effect of a lot of them chilling the water? And the point that as you go downstream the amount of heat available will be less because your upstream neighbours have snaffled much of it?

[Nigel Graham 2]

On Nigel Graham 2 Said:

Hmmm…

[…]

How does one avoid depletion?

[…]

….

Regarding stream-source pumps… maybe for a few homes and a large river; but what of the ecological effect of a lot of them chilling the water? And the point that as you go downstream the amount of heat available will be less because your upstream neighbours have snaffled much of it?

You’re on the ball, Nigel

You may have noticed my somewhat cynical use of the term ‘Missionary Zeal’ … This often carries the baggage of un-comprehended dogma 🙁

Incidentally, there is an excellent little booklet about the ‘wars’ between the mill-owners of Stockport … who did many dastardly deeds tapping water from upstream of their competitors !

MichaelG.

.

Ref. https://stockportheritagetrust.co.uk/shop/rivers-under-your-feet/

[Nigel Graham 2]

On Nigel Graham 2 Said:

Regarding stream-source pumps… maybe for a few homes and a large river; but what of the ecological effect of a lot of them chilling the water? And the point that as you go downstream the amount of heat available will be less because your upstream neighbours have snaffled much of it?

Surely the simple answer to that is a few upstream thermal power stations using the rivers for cooling!

 

[Charles Lamont]

On Charles Lamont Said:

Anyone considered or installed a ground source system?

You should ask the residents of Cleat Hill about that…..

https://www.bbc.co.uk/news/articles/cvgxdnlzkjzo

Houses destroyed by gas explosion when they didn’t have gas.

Robert.

[Charles LamontParticipant @charleslamont71117]

As I understood it, ground source is mainly using geothermal heat, especially if it is the deeper borehole type rather than the shallower grid. Below about two metres depth the ground temperature does not vary much from summer to winter. A cellar in the UK maintains a reasonably stead temperature around 10°C. This is connected with the character of British ‘warm’ beer.

The efficiency of a heat pump depends on minimising the temperature difference between the source and the sink. On a cold day in the UK, when heating is most needed, a ground source will be at a significantly higher temperature than air.

“If we had a prolonged cold spell the efficiency of that system would reduce as the ground around the pipework warms up.”

The ‘as’ does not make sense. The efficiency will be reduced if the ground temperature drops, and until it warms up.

I did not know about the Cleat Hill incident, which brings attention to a risk when boring, but would be ‘whataboutery’ if used as an argument against the use of heat pumps.

[John MCParticipant @johnmc39344]

Charles, my mistake, I should have written ““If we had a prolonged cold spell the efficiency of that system would reduce as the ground around the pipework cools down.”

Apologies for that.

I do wonder if the winters with prolonged cold spells are a thing of the past?   Then the increasing temperature differential between ground and working fluid will be minimal, maybe not worth considering?

[Mark RandParticipant @markrand96270]

As for water source heat pumps, cooling one litre per second of water by 1°C will release 4kW of heat. I could heat my house using the storm drain under the back garden as the heat source and that’s not much more than a trickle. Dunno what Severn Trent would have to say about it though.

[noel shelleyParticipant @noelshelley55608]

Mark, keep the water murky and they may never know ? I won’t tell. Noel.

[PlasmaParticipant @plasma]

Well the system has been installed and is running for the first time today.

It took one full day for the plumbing work and half a day to wire up the system.

Setting the thing up will be key to getting the best out of the system and there is going to be a period of learning for me to optimise settings.

It looks very slick and is much quieter in operation than the combi boiler it replaced.

Let’s see how things go.

[Author]

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