Air source heat pumps - any advice/experience?

[swanny65]

Hello, my names Kev Fisk of K Fisk Plumbing, best thing to do is give me a call .............., I have an air source pump running my house and use it as a test unit to show people that want to view an actual system, your welcome to pop over and have a look and further chat, also oil is no problem but once you've done the maths with the government grants there won't be a lot in regarding install price.

Not an expert by any means. However my brother has this system in the house he built. It has UFH throughout and works like a dream. Been fitted over 2 years and he is very please with it.

 

[Norcon]

"They do work in the right situation"

So would a batch of candles if the heat loss is only a few kilowatts.

 

[dcawkwell]

12kW heat pump running at my house right now.
It ain't doing it! It struggles to heat half my radiators (about 6) to anything over about 40-45 degrees.
Good job I have my lpg boiler to cut in as a booster.

If you have reasonable insulation and double glazing an air source will do some of the year but wouldn't consider one as the sole heat source of the house especially once temperature start to drop below about 10 degrees outside.

I also have 3 air con units and they work wonderfully to heat the rooms or cool them down. These begin to struggle as the temperature gets to
zero in heating mode.

I think that you need to speak to your installer as he has gotten something badly wrong..

My home isn't suitable for air to water without major alterations... Decent quality units work well in lower temperatures but can struggle in cold humid conditions so only a fool would try to install airsource without a reliable back up for those days...It was true 25 years ago when I first got involved in reverse cycle heat pumps and is still true today.

I am the installer and all the units are whatever the government payments name is. I forget. I implemented the unit I have because it was available. I know it isn't up to it. But given the amount of electric it uses I wouldn't even try to find a unit that could do the house. The electric bill would be frightening.

 

[roguetrader]

Today spoke to the the developer who owns two three bed semis in which we installed Dimplex ashp's last year, ufh downstairs and rads upstairs.
Both have electric bills amounting to circa £750 for the last year.
I pay that a quarter for my house gas and electric.

 

[Norcon]

That sounds good but they must have very low heat losses.
Like about not much more than 6 to 10 kilowatts.

Any boiler in that situation will show results.

I've cut my heating bill in half this winter so far just by switching to solid fuel.
Intend fitting solar panels next.

 

[Corgigrouch]

I am the installer and all the units are whatever the government payments name is. I forget. I implemented the unit I have because it was available. I know it isn't up to it. But given the amount of electric it uses I wouldn't even try to find a unit that could do the house. The electric bill would be frightening.

So let us get this right.... You installed an air source heat pump to heat your home based on what you could get your hands on rather than the correct size. knowingly fitting a unit too small for the job and you are slating it because your home is cold?

It is a real shame that we don't have a face palm icon..

And yes, I guessed that you had fitted your own.....

 

[roguetrader]

That sounds good but they must have very low heat losses.
Like about not much more than 6 to 10 kilowatts.

Any boiler in that situation will show results.

I've cut my heating bill in half this winter so far just by switching to solid fuel.
Intend fitting solar panels next.

Yep, only small units, but just goes to prove they do work in the right situation.

 

[dcawkwell]

I am the installer and all the units are whatever the government payments name is. I forget. I implemented the unit I have because it was available. I know it isn't up to it. But given the amount of electric it uses I wouldn't even try to find a unit that could do the house. The electric bill would be frightening.

So let us get this right.... You installed an air source heat pump to heat your home based on what you could get your hands on rather than the correct size. knowingly fitting a unit too small for the job and you are slating it because your home is cold?

It is a real shame that we don't have a face palm icon..

And yes, I guessed that you had fitted your own.....

Yes. Provided I can heat some of the house in the winter with the air source it is fine. My units came in to my possession at next to nothing but have a retail price of £3000 each so well worth putting it in.
I don't think trying to heat the house which is quite large on air source would be possible at an economic cost. It is a saving with the air source.
My heating with lpg could easily run through £1500-£2000 if I let it.
So I am happy I have a mix of heating. Coal fires, lpg gas fire, lpg boiler, air con units and electric air source. But I wouldn't recommend to anyone to try and heat a larger house with just air source.

 

[Corgigrouch]

Irrespective of the size of house, air source will work well provided that the application is suitable.

My only reservation is that it may struggle in prolonged cold weather or freezing fog and so I would always reccommend that a back up heating system is retained as the electric heating elements provided are very inefficient.

 

[Kev F]

If you can get away with one heat pump I'd just run that, I've proved more than once its easy, either way I'd just use one heat source, it is far too costly combining.

Hi Kev,

My wife and I are doing a self build, we're planning on going for an ASHP to run underfloor on the first 2 floors, and a couple of large rads in the loft rooms. Unvented cylinder, also having a log burner, along with mechanical heat recovery and ventilation. Which heat pump would you recommend? The house is a 3 bed , with 2 extra loft rooms, 168sqm plus the loft space. 100mm cavity, 50mm celotex, 50mm air gap. We're also outing insulated plasterboard on the internal side of the external walls.

Cheers,

Dom

I personally fit Samsung, its a very easy to use system and you can extend warranty to 7 years, I'm a service agent also so get great support

 

[Kev F]

"They do work in the right situation"

So would a batch of candles if the heat loss is only a few kilowatts.

Funnily enough myself and the main man at Samsung met one day and had a play around, we got a room to resemble a code 5 insulated house, the 50" TV heated the room in 30mins. 3-4 bed houses in next 5 years will be running on around 5kw

 

[Kev F]

Irrespective of the size of house, air source will work well provided that the application is suitable.

My only reservation is that it may struggle in prolonged cold weather or freezing fog and so I would always reccommend that a back up heating system is retained as the electric heating elements provided are very inefficient.

I appreciate that thought but can confirm Samsung inc my jobs have all worked over some serious weather conditions, I've had a couple of hitachi units again been in over 3 years and have had no issues at -5

 

[Norcon]

Or the sane way would be to feed both heat sources into a thermal store and feed hot water, rads and underfloor from there....

It doesn't sound so insane when you have a client with a two storey dwelling who has expressed a wish to have a back boilered stove to supplement his UFH heating.
Then on the first floor only, fit radiators in the bedrooms for the sf hydronics. The ufh remains autonomous with the condensing oil boiler (or heat pump) for maximum efficiency. That gives you instant zoning without any controls!
And complete separation with no cross over flows cooling the stove return or heating the heat pump or condensing boiler return ruining efficiency!

One rad (heat leak) is gravity so it operates in a power cut as usual and the other few pumped.
Nested twin coils (or triple for solar) in a vented gravity fed cylinder which are cheap compared to unvented and thermal storage (aka sludge buckets)

The main controls you need for the stove ( hi-lo stats ,injector T and circulator, avta cooling valve optional) will cost £400 which you've already saved. The only extra cost is the radiators in the bedrooms and leaving the system adaptable for up grading to a mains pressure HW module in the future for upstairs showers only.
Then you have back up when the mains water supply fails (ie -frozen pipes, utility works in operation, failing pressure etc etc)

When the electricity supply fails (some people were off for weeks in the recent storms which battered the country) you still have hot water at the taps and two rooms fully heated. Ten kw is the maximum stove size needed and no need for a navvy slave to shovel coal or chop sticks.
Downstairs areas will benefit from the stove heat just by leaving doors open. The property design may lend itself to that anyway.
(ie- stove in open planned hallway)

Divide and rule and you have a completely hybrid superior system with minimum controls and implementing part off its design from the ole days with none of the disadvantages of the modern day sludge buckets, crappy combi's, or expensive, troublesome and restrictive unvented cylinders for very little extra cost.

 

[Deano72]

I was an engineer on a site where they had upto 300 eco dans installed, all new builds with uf heating & heat recovery units.
The bills the majority of occupants had was herrendous,some anywhere between £800-£1000 per quarter.its bit unfair to go pointing the finger solely at the ashp as a lot of these occupants would have tv, tumble dryers ,wash machines on all day but that was probably the same with there previous houses and there's bills were a lot less.
The end user needs to understand how to use the system and how to get the best out of the system for the best economical results,there designed more for comfort heating 21c
The only way I would have one would be if I was to build/super insulate the house my self then go around around with a infra red heat gun to make sure there was minimum heat loss...
So in a nutshell if you have a system that is designed & installed correctly in your super insulated house and you understand what to exspect to achieve from it , then yes go for it

 

[Clere3]

Our house is currently 90sqm, built in the 1950's, so not insulated to modern standards (or any standards even!), but we having the cavities done, 300mm in the loft, we've had new double glazing installed and removing the airbricks. The underfloor heating will be the retrofit style - with a small amount of celotex underneath it. As I understand the water only needs to be heated to 40 degrees to get and effective result.

We've had a couple of quotes, and no one has suggested we need a second heat source - surely if the pump is the correct spec it should be able to operate as our sole source of heating? We will have the ability to heat the water to 60 degrees to kill legionella - couldn't we use this if the weather really was bad? Surely cheaper on the odd occasion than the several thousand pounds to install an oil backup, along with paying for oil?