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Domestic Heat Pumps

V

Vinny

pfm Member
I can't find the recent thread, but there was an interesting and surprisngly fact-filled item on R4 You And Yours today - just on, around 12.30, including contributions from one of the Manufacturers - Worcester-Bosch?

Well worth a listen as there seemed to be some conversation about limitations that I've not heard before. I can't remember the actual numbers, but the current estimate is that less than half the number of homes "officially" thought to be suitable, actually are.

Three things stuck in my mind in particular - modern micro-bore systems can't be re-used, you need something to provide hot water, which many more modern homes is a combi, which is not ideal, insulation rating has to be C or better.
 
Yes, interesting point about microbore tubing.

My parents installed a microbore system back in 1974 - big mistake.
 
I remember a friend installing microbore. He pushed 20 or 30 feet down a hole in the floorboard to get across a 9 foot room, wondering where it was all going...
 
Heat pump heating systems only get up to about 40C so if you replace a gas boiler with a heat pump you need larger radiators. They are often used with underfloor heating for this reason. To be worthwhile you need high levels of insulation so they are not practical in older homes. It isn't a straight plug out plug in swap.
 
I have looked into it for our current house renovation, some basic requirements which meant it was not suitable for us in an older 1950s home:
  • Good/great insulation and seals around the house (no open chimneys)
  • Lots of wall space for larger radiators and/or underfloor heating in large parts of the house
  • Outdoor space for the condenser unit, mindful of noise
Also, at the moment, although they are very efficient, its still cheaper to go with gas. However, it IS the way to go in the future, when more 'green' and cheaper electricity is powering the grid.

I believe it can be a more cost effective solution if you don't have mains gas, and oil fed/standard electric boiler.

We also looked into Ground Source rather than Air Source, great if you have the space in the garden, we could not do it as we have TPO's on one boundary so can't excavate in the garden. Piling is effective but a lot more expensive.

Solar panels, Tesla Battery and a Air/Ground Source Heat Pump system is the dream, if still expensive to install.
 
Hoopsontoast said:
I believe it can be a more cost effective solution if you don't have mains gas, and oil fed/standard electric boiler.
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I've been looking into it for our weekend place - there is no mains gas there so it's got an oil fired boiler instead. It's got a very large garden but the by the time you consider the upgrades that would need to be done to the house (it's from 1776 and although it was modernised etc. about 15-20 years ago it's not likely to have insulation at anywhere near the levels needed) the costs and disruption are prohibitive.
 
In 2013 DGHP Housing association removed my open fire with back boiler and 6 radiators which gave enough heat to have windows open in winter whilst sitting in pants and fitted a Daikin altherma heat pump system and new radiators to my uninsulated and draughty late 80’s built 1 bed bungalow in Galloway, part of some bullshit government scheme to claim they were going green, there is no gas supply where I live. My electricity costs went from £10ish to £40+ per week in winter as the system doesn’t work in low temps nor with the build quality in the house. Two years ago they fitted a Tesla power wall battery to attempt to offset the running costs, saved a couple of £ but still bloody useless.

So I knocked back through the bricked up fireplace and fitted a wood burning stove/lined the chimney as I have access to unlimited seasoned logs from a friends farm/forest. This caused much upset from the housing association and they threatened me with eviction so I paid for an independent report regarding the fitting of such a heat pump to my poorly insulated house which showed that it was an unsuitable system to install and should not have been fitted.

In a new house built to modern insulation standards with underfloor heating I imagine they are a great choice but not in a 40yr old draughty poorly constructed and insulated bungalow, especially as I have secondary progressive MS and need heat & warmth
 
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Somafunk said:
my uninsulated and draughty late 80’s built 1 bed bungalow in Galloway
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Ye Gods - if it can't work in sunny and mild Galloway....... :)

They may have been within the trial scheme run by government - free trial installations of heat pumps in 3(?) areas, including one area of Scotland.
Whatever, they absolutely did not do ANY homework before fitting the system, obviously.
 
They were fitted to approx 300 houses up in the Black Isle (Inverness) and had to be removed as they were ****ing useless.

I withheld £1500 rent to pay for the purchase and install of the stove along with independent report on air source heat pump installation, 8 years later I still get letters threatening to take me court and eviction unless I pay within 28days…… yadda….yadda.

They are useful for lighting the fire. :)
 
ASHP’s may be possible in most houses but what about tower blocks? They are heavy, they vibrate and they need to be serviced, so fitting them at height on external walls is probably impractical. I was looking into putting one on the roof of the extension but as my house is constructed from stone and mortar it looks like that’s not possible as it would probably shake the wall apart and be next to a bedroom. Which is a shame as it would be easy to get a supply to it and it would be close to the central heating pipes. If it has to go on the ground then everything becomes more of a problem even if I can find the space. The hot water tank needed with heat pumps is also going to be a problem for some, as a normal sized tank is only going to hold enough water for one good bath and will probably only get heated during the night or when the house is unoccupied, so how will that work in a typical household with 2 adults and two children?

My house was built in 1890’s and is a typical 2 up, 2 down (+extension) miners cottage so is probably poor in thermal efficiency and is heated by a solid fuel stove. I am in the process of adding insulation everywhere I can. Last winter I calculated how my stove compares to the CO2 from my new (28kW) gas boiler. A by-product from the math was the kWh for the stove which except for the really coldest days came to about 1.5kWh. Once it’s lit it runs 24/7 for months and I run it at the lowest level possible without it going out (and even that can be too warm). The CH water temperature is normally 35-40C so in theory an ASHP should work. When I bought the house it had an open fire in every room so I fitted the central heating system and used the largest radiators that would fit which probably helps mitigate the low water temperature and underflooor heating is on the list. With an ASAP (and the gas) all the heat will all be through the CH system but is a very different sort of heat. My stove only puts about 600W into the CH (calculated by the time it takes to heat a tank of water when the CH is off) with the rest as convection and IR and as it is built into the thick external wall between the front room and bathroom that wall gets warm and acts like a large thermal store. So I think the concern about the low temperature of heat pumps isn’t a major problem as long as you run it 24/7 keeping the house a semi constant temperature and not in the heat on demand method possible with a very powerful gas system.

The other downside with ASHP’s is the noise. At the moment on a still night I can lie in bed and listen to the brook about 200mtrs away burbling down the valley. I suspect that when everyone has an ASHP all you will hear is fans rattling away 24/7.

P.S. The CO2 from the stove for a day is about the same as the gas burner burning for about 6.5hrs (new modulating boiler with smart thermostat (Vaillant) set to 52C so that it’s within the Combi heat recovery operating range) and the cost of gas vs coal is about the same but probably shouldn’t be. So why do I still use the stove? The gas boiler can heat the house but having an IR source in front of you is just so much more pleasant. When they increase the tax on solid fuel and make the cost prohibitive I will go 100% gas and get an IR panel as a supplement in the main rooms.
 
How does Air Source heatpump work when the air temperature is below freezing? I would imagine icing problems.

I live in the tropics and I can assure you that the noise of the outdoor airconditioning unit fans is a big problem between neighbours
 
davidsrsb said:
How does Air Source heatpump work when the air temperature is below freezing? I would imagine icing problems.
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They take heat from the internal system (water tank in attic has electrical heating coils inside which with a shite system like mine is necessary to provide hot water to a 60dg temperature to avoid legionella) and circulate it through the condenser unit that is fitted outside the house, it only works down to a certain temp before it all goes pear shaped as I found out when we had that extended cold spell a number of years ago. We had 17 days of below freezing temperatures and a low of - 16 which caused my outside condenser system to fail spectacularly and spew its guts and gases everywhere.
 
davidsrsb said:
How does Air Source heatpump work when the air temperature is below freezing? I would imagine icing problems.

I live in the tropics and I can assure you that the noise of the outdoor airconditioning unit fans is a big problem between neighbours
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I think it depends very much on what heat pump you have, taking Somafunk's reply.
We have 5 x Air / Air 'Inverter' types (Toshiba)
They work entirely as air/air.
Below -15 they are not going to do so well, if work at all.
At -5 to -10 we are fine in work.
Their heating efficiency obviously drops the colder it is, and a change in the type of gas used a few yrs back also changed some specs.
At this moment in time, the efficiency on cooling is not brilliant as the temps are up..
Depends how comfortable you want the building to be temp wise.

Our building is some 300 yrs old, with a lantern roof, so was just a little on the draughty side.
Liteally tons of rockwool later, many thousands of tubes of mastic, a fair few plaster boards, and we have a draught free , comfortable environment.
It took a long while for me to achieve, but I am happy with the results.

The outside units are not that bad sound wise, being inverters they can vary the fan speed at will.

With regards to icing up, then yes, obviously they do, rather a lot.
They have sensors, and when they reach a certain point, the heating shuts down, and they revers to fridges for a while, (5-10 mins) which heats the exchangers a little - all the ice melts, water runs off and freezes where it lands!
That can be problematic, as rivers of ice on a car park aint fun.
 
slavedata said:
Heat pump heating systems only get up to about 40C so if you replace a gas boiler with a heat pump you need larger radiators. They are often used with underfloor heating for this reason. To be worthwhile you need high levels of insulation so they are not practical in older homes. It isn't a straight plug out plug in swap.
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CO2 heat pumps get up to 75C, but there aren't so many of those available for domestic applications.
 
Sonority said:
With regards to icing up, then yes, obviously they do, rather a lot.
They have sensors, and when they reach a certain point, the heating shuts down, and they revers to fridges for a while, (5-10 mins) which heats the exchangers a little - all the ice melts, water runs off and freezes where it lands!
That can be problematic, as rivers of ice on a car park aint fun.
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We have hi-rise buildings bristling with aircon outdoor units on the side. Apart from being ugly, I would imagine that replacing the rain of air con drain that you get now with slabs of ice falling down would be very dangerous
 
There are some fundemental laws of physics involved that limit what can be achieved. They can be made more efficient to some degree, although I suspect that they are already pretty good, but that won't alter their many limitations and inconvenient aspects.

So far as ground source versions go, I can't help but think if large installations became common, refrigerating all of that soil cannot be a good idea.
 
@Somafunk , did you get a explanation as to why ASHP were installed in your place of residence? It is difficult to think of a less practical solution to water and space heating for an old and inefficient building.

I read an article about the use of ASHP in some run down council owned buildings (College View, owned by Wexford Council in the passive house plus magazine (online or hard copy)), where the residents moved out whilst the buildings were upgraded with very high level of insulation, heat recovery and ventilations system etc. This brought the buildings up to a level whereby an ASH could be used effectively and cheaply (installation and ASHP costs must still have been significant). The buildings were originally rated at G level and after the retrofit were at A2 or A3 energy ratings.

https://passivehouseplus.co.uk/issuu/digital-editions

Issue 37, page 52.


The cut off point, in terms of building energy rating, for where ASHP becomes a practical solution is difficult to predict, but it is clear that the better the energy rating, the greater chance that a heat pump can be used efficiently and effectively and currently this is only really practical for highly insulated buildings.

I cannot see how any heat pump solution is practical for most of the UK housing stock, unless a massive retrofit of current buildings happens to get buildings up to an A energy standard (based on one example of practical evidence that heat pumps are effective at this level in Ireland at least).

A friend of mine has installed 5 ASHP solutions in houses in France and Bulgaria. He upgraded the insulation levels in each of these buildings (3 of these he owned and lived in at various stages), he was all the time experimenting to learn more about ASHPs, how to size them, how to use them and what is needed to make them more effective. He was able to do this cheaply as he bought the units direct and developed his own control systems etc. Whereas if you go to one of the main suppliers the cost get very large, very quickly for larger buildings. The cost and effectiveness of any heat pump solution coupled with the energy rating of the building will limit their use for some time to come.
 
IanW said:
The cost and effectiveness of any heat pump solution coupled with the energy rating of the building will limit their use for some time to come.
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Insulating the whole or a major percentage of the UK housing stock to level C or better is never going to happen, so heat pumps are only ever going to be niche, although I suppose you could just make them bigger (unfeasilbly bigger).
I don't recall whether the man from Worcester-Bosch on the radio programme was talking about ground or air-sourced, but he was talking about 50C water being normal/achievable. The problem is that existing central heating systems are designed with water temperatures around 70C. As heat transfer rates are broadly proportional to radiator-room temeperature difference, assume 20C room temperature (comfortable-cool), and the sums are easy to see.
 
slavedata said:
Heat pump heating systems only get up to about 40C so if you replace a gas boiler with a heat pump you need larger radiators. They are often used with underfloor heating for this reason. To be worthwhile you need high levels of insulation so they are not practical in older homes. It isn't a straight plug out plug in swap.
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This is exactly our problem. We have oil heating, which still works well, but which is getting on in years, and which will need replacing in the short-medium term. Swiss local authorities are encouraging a change to heat pumps, and Mrs. Tones likes the idea, as she hates oil heating (endless procession of guys needed to tend to it). This is fine if you have floor heating, but we have radiators, and they would need to be substantially bigger to cope with the fact that heat pumps cannot (AFAIK) raise the temperature to the 60°C needed for conventional radiators. Hopefully someone will come up with a suitable solution for us, before the heater collapses.
 
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