Air heat pump

Martisha

Does anyone have this source of energy in their home? Is this cheaper to run than gas boiler?

I am interested in buying a house with air heat pump and not sure what to check?

[Deleted User]

It depends how much you pay for your electricity. At the moment, with gas prices rising fast, it's probably going to be a bit cheaper.

Think of the long term though. Gas is only going to get more expensive, and everyone will have to switch from a gas boiler to a heat pump sooner or later, for environmental reasons. So buying this house saves you a potentially large cost to convert later on, and the gap between the cost of a boiler and a heat pump will only continue to increase.

Just make sure it's been installed properly. Heat pumps need more surface area to work, i.e. very big rads or underfloor. Also check if it offers cooling as well. As climate change bites you may want some cooling in the summer.

ProDave

Simple answer is no it is not cheaper than gas, but in a well designed system should be almost the same.  That may change in time as gas is likely to continue rising faster than electricity.

But if you have no gas at all, you will save on not paying the gas standing charge.

A more important question is how old is the house how is the heating delivered (radiators or under floor heating) and how well insulated is the house?

A modern house, designed from the outset with low temperature under floor heating is likely to work very well with a heat pump.  An old Victorian house with poor insulation and radiator heating is likely to perform very badly with a heat pump.

I have a very well insulated self built new build with an air source heat pump and it works very well indeed.

babyblade41

I'm at the start of a large conversion & have looked at so many heat sources.

We are going for an air source heat pump with under floor heating and big industrial rads.

The conversion is complete open plan except for 2 beds & bathroom in a large area, an old concrete block industrial warehouse .
I'm thinking of future prices ..plus no mains gas .

I did look at a bio mass boiler but just the size of the thing was a bit off putting 

FreeBear

babyblade41 said: I did look at a bio mass boiler but just the size of the thing was a bit off putting 

There are some quite compact little biomass (pellet) stoves/boilers available. It is the storage space required for the fuel that is a problem for most. It needs to be somewhere dry, and if the system uses a self feeding mechanism, the store needs to be very close.

Martisha

Its a new build house with underfloor heating downstairs and radiators upstairs, also storage tank.

how this all work? Do you set it a timer to heat water or is it running constantly?
does it require yearly service like a gas boiler?

babyblade41

FreeBear said:

babyblade41 said: I did look at a bio mass boiler but just the size of the thing was a bit off putting 

There are some quite compact little biomass (pellet) stoves/boilers available. It is the storage space required for the fuel that is a problem for most. It needs to be somewhere dry, and if the system uses a self feeding mechanism, the store needs to be very close.

Yes we did seriously think of going this way but the whole mechanics of it (size, log storage, maintenance etc) & if summers are going to get hotter then the one we have decided on blows cold air too 
We have a good supply of logs & storage isn't too much of a problem but add it all together  for the huge space we have to heat we changed direction

ProDave

Martisha said:

Its a new build house with underfloor heating downstairs and radiators upstairs, also storage tank.

how this all work? Do you set it a timer to heat water or is it running constantly?
does it require yearly service like a gas boiler?

Hot water always comes from a hot water tank with a heat pump.

There is usually some form of programmer with an ASHP sometimes just like a normal boiler programmer though some are a bit more complicated, but there should be an option to have the heating on all the time or at programmed times.

Heat pumps differ to gas boilers in that they are usually much lower power so it is often better to leave them on all the time.  There will be multiple room thermostats with under floor heating so the house won't overheat and waste energy.

gm0

Heat pumps and Under Floor Heating are slow to heat you up compared with gas and radiators at higher temperatures.  You don't want to let the house get cold, come back and want it warm "now" as there will be a delay while the 30C - 35C water circulates and then does its work slowly.  A big UFH pad can take a long time to heat from truly cold (and more positively a long time to cool down too).

60C water would do the same room air heating from rads from a gas boiler more quickly but that's fossil boilers not heat pumps.   If you run the heatpump like a gas boiler - it will likely disappoint on performance and cost. 

You want to top up your UFH regularly in winter using the heat pump.  But you want to do it when electricity is cheap if your tariff does that across 24 hours and use the slow release of stored heat across the day.  A different approach to programming to a gas boiler where time of day is irrelevant bar occupancy and comfort.

A tank is usually DHW but could be a buffer tank for the heatpump to work on when UFH and rads stop asking for heat to manage cycling.  If the latter it will probably be near the heatpump.  If it's huge then it could be a heatstore.  A design where heat goes into a large body of water and is pulled out again by the various circuits for rads, dhw, ufh etc.  But less common than the other two.

There have been a few generations of heat pumps already and the sophistication of controllers varies.  In a decently insulated house built with it in mind (such as UFH) but also - air sealing, perhaps MVHR, good glazing, loft and wall insulation etc.  Can be a great solution.  Retrofitted to a draughtier house with old poor windows and walls.  Gimmick.  Will disappoint via lack of winter comfort and high  electricity bills.  Look at the situation as a whole.  UFH is a positive indicator. But assess the other aspects of the house which contribute to how much heat this house needs at winter peak and over the year.  Does that seem consistent with modern eco heating.

Sadly there *are* monstrously badly specified systems out there with cheapest bidder tech from already defunct suppliers put in by cost focused developers and even HAs. Not very many such but they *do* exist.  So it is caveat emptor.  Best to find out *what* heat pump it is and whether it is from a supplier that is reputable and still exists.    I have seen older rural property for sale in the summer where the heatpump has been fitted but the (expensive and disruptive) demand reduction work seems mysteriously absent.  Naive seller dressing for sale with a life expired boiler or just a chancer pulling eco wool over prospective buyers eyes.

This is just the same as taking a view on whether a boiler is "new and good for a decade" or may need replacing immediately and adjusting your view on house value by 5k or 10k (size, age what else is needed). With fossil you might find a Worcester Bosch boiler or a "Who is that ?" cheap and nasty boiler.  So it is with heatpumps which depending upon size can be more expensive than boilers.  

They do need periodic checking DIY or paid.

If this house is consistently built with modern heating in mind.  Then lucky you.  The work is already done.

I would not now buy a house to live in long term with a cheap fossil boiler and terrible cheap windows which will need replacing as part of migrating off gas.  Developers are gradually starting to do heating and car chargers properly. But it is still very patchy.  Insulation and air seals and vapour membranes done right costs time and money and the buyer can't easily see good from bad.  British building is sadly a byword for "that'll do" board it up.

Mr.Plinky

Hi query for us here in the Uk Im really not convinced on heatpumps at this time and want to check somepoints:

1) Hot water - Ive been informed they heat to a maximum  50 degrees max - this appears to be insufficient, looking for opinions.

2) Which heat pumps should we be considering in the UK - initial research indicates any external temperature below 40 degrees F/circa 3 degrees Cent or less means the pumps are very inefficient.

3) We would not have the scope for underfloor heating and from reading this thread slow to heat up and cool down, so if you want a simple heat burst in the evening seems pretty useless. Would we be using the existing radiators or need new. Im getting very confused here.

4) They seem overly expensive for what they are vs new gas boilers and whilst gas prices are currently rising - not forever we all hope, I cant see the financial benefit (Im sorry green is a luxury for the more affluent and we have a family).

Any tips, pointer and advice welcome.

Thanks
M

ComicGeek

1] The heat pump only heats the cylinder to 50 degrees as it becomes very inefficient heating it higher. Baths/showers normally only run at 38 degrees, so you don't really need 60+ degree water. The system does a pasteurisation cycle every week to heat up the cylinder to 60 to make sure no harmful bugs are forming in the cylinder due to lower storage temps.

2) Any from main manufacturers (Mitsubishi, Daikin, Nibe, Samsung, Vaillant etc) have reasonable efficiencies below 3 degrees, but the actual number of hours below 3 degrees is fairly small so most people are interested in the key temperatures - efficiencies normally quoted at 3 and 7 degrees. Efficiencies are much higher once the outside temperature rises.

3) The UFH is slow to heat up and cool down, not the heat pump. So radiators fed from heat pumps would still be quick to respond, albeit not so hot to touch as with gas boilers as the water temp is lower with heat pumps. You would likely need new radiators if you're not also upgrading insulation etc in the rooms.

4) The main financial benefit is against oil, LPG or direct electric, although with current high electricity prices that is debatable at the moment. I personally don't see a need to rush to switch from gas to heat pump, although it is fairly inevitable that it will happen at some point in the future. Small changes now, like oversizing new radiators, installing new insulation anywhere you can, will help to reduce future installation costs.