Air source heat pumps - any advice/experience?

[dcawkwell]

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?

A better option would be lpg boiler with a couple of 47kg bottle. I have a neighbour he has just had all the central heating done insulation etc and a heat pump put it old gas boiler taken out. He still had a wood burning stove as a booster for heat.
A 12kW heat pump in freezing conditions is producing about 6kW of heat. It isn't enough to heat a house unless it is a modern well insulated house.
40 degree in the radiators just isn't enough to get some real heat in the building.

 

[snb]

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

There has been a lot of problems with the ecodans setups

their software was factory set so the compressor wouldn't start until flow temps had got to 20 degrees and it used the backup immersion to raise the temp.

you could alter the parameters but only down to 15.

Nearly all the current crop of air source units will operate the compressor from flow temps down to minus 5.

The other reason for high electric usage was customers not allowing the units to run for long enough periods.

I had an estate with these where we altered the ecodans to be on 24/7 and their operating costs dropped by over 50% compared to those where we allowed the customers to choose when they on.

You can get a lot of info from EST website which has a load of case studies with various setups and also some changes that were done and the improvements.

With both air source and ground source it is vitally important that design flow temp for heating be as low as practically possible as this has a huge impact on running costs as the system efficiency decreases as the flow temp increases.

 

[JulianP]

A 12kW heat pump in freezing conditions is producing about 6kW of heat..

That's not right, you have to account for that lost 6kw somehow.

What I think you mean is that it's working at a COP of 1.5 So a 12Kw heat pump would be producing 18kw of heat?

 

[Corgigrouch]

A 12 kW heat pump has a maximum output of 12kW at a specific ambient temp.... As soon as the ambient temps drop, it's output reduces.... A major issue with airsource is how frequently it has to defrost its coils and from where it finds the energy to reverse its cycle and pass hot refrigerant through its outdoor coils... every time it defrosts not only is it producing no heat but it is absorbing heat from the heating circuit. The UK is famous for cold damp Winters and hense the coils clog with ice frequently in a British winter

 

[dcawkwell]

A 12kW heat pump in freezing conditions is producing about 6kW of heat..

That's not right, you have to account for that lost 6kw somehow.

What I think you mean is that it's working at a COP of 1.5 So a 12Kw heat pump would be producing 18kw of heat?

No a 12kW heat pump produces 12 kW at whatever temperatures the manufactures quote. As temperature drops the amount of heat the pump is producing is reducing. So although they quote 12kW this is in fairly mild conditions when it starts to get cold it will only product 6-7kW. The electric consumption in my pump is fairly static at about 3-4kW to run the compressor. That combined with defrost cycles to stop the coil freezing up.
You won't heat all but a very insulated house on 6-7kW output.

 

[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

There has been a lot of problems with the ecodans setups

their software was factory set so the compressor wouldn't start until flow temps had got to 20 degrees and it used the backup immersion to raise the temp.

you could alter the parameters but only down to 15.

Nearly all the current crop of air source units will operate the compressor from flow temps down to minus 5.

The other reason for high electric usage was customers not allowing the units to run for long enough periods.

I had an estate with these where we altered the ecodans to be on 24/7 and their operating costs dropped by over 50% compared to those where we allowed the customers to choose when they on.

You can get a lot of info from EST website which has a load of case studies with various setups and also some changes that were done and the improvements.

With both air source and ground source it is vitally important that design flow temp for heating be as low as practically possible as this has a huge impact on running costs as the system efficiency decreases as the flow temp increases.

Never had that problem on our site as a lot of occupants turned the the immersion off as they were ****scared of using electricity.
We always advised to have it on constant especially with uf heating which I think when the occupants came to get use to it they did,but they would whack stat up to 23-27 so therefore the dan was working flat out I suspect.
We had major problems with u1 faults & after continuously checking the obvious mitsi still couldn't Suss it,sothey sent 2 of the boffins over from japan and since then have updated the software, I don't know if this has resolved the problem as I left that site last summer and majority of problems was occurring mid freezing winter.
Saying that I think mitsi are the market leader in ASAP & have the best model on the market from what I have read up on

 

[snb]

forget what i said about ecodans. was confusing with daikin althermas

 

[crashndie]

air source is good and works well underfloor heating wants to run at 45~50c tops the thing is you cant stick a heat pump on to old rads that was on a gas boiler they are undersized for a air source pump and designed to heat the room at 60~80c flow temps.. i read a post about some one having one fitted and the rads never get past 40~50 c thats because a low temp heat pump will never get hotter than this EVER ....

if your looking to keep small rads or existing system then get a Dakin altherma hi-temp system http://issuu.com/denv00/docs/lr_ecpen13-726_daikin_altherma_high_temperature_en?e=1731482/2513626 this will do 60c hot water and 75c flow temps to rads they are the dogs bocs

a poorly sized/designed system will not work do it once do it right i have fitted dakin althermas in place of gas /oil boilers i really can not rate this equipment enough

 

[Plick]

Hi guys, sorry about the hijack but im looking for some info on ashp, LPG or oil, I have already submitted another thread but no luck there, I'm hoping you guys could offer some help! Thanks



Hi,

I am just weighing up my options for heating a standard 3 bed 1930's semi. At the moment it has no central heating at all and a small wood burner in the lounge.

When the extension is finished it will have upstairs;
4 beds (1 in the loft)
2 ensuite shower rooms (1 in the loft)
1 family bathroom

And downstairs;
Kitchen
Utility with small wc in.
Dining room
Lounge (log burner)

Could someone offer some advise on what would be the best way to heat the property, as it has nothing but the log burner it is effectively a blank canvas so I'd like to get the correct equipment in now.

I'm open to all suggestions, air source, combi, LPG, anything, I'm leaning toward ashp after reading more about it on here, is this wise?

obviously the more economical to run the better. And the cheaper to install for the plumber the better - If that is possible.

Thanks in advance

 

[Norcon]

Hi guys, sorry about the hijack but im looking for some info on ashp, LPG or oil, I have already submitted another thread but no luck there, I'm hoping you guys could offer some help! Thanks



Hi,

I am just weighing up my options for heating a standard 3 bed 1930's semi. At the moment it has no central heating at all and a small wood burner in the lounge.

When the extension is finished it will have upstairs;
4 beds (1 in the loft)
2 ensuite shower rooms (1 in the loft)
1 family bathroom

And downstairs;
Kitchen
Utility with small wc in.
Dining room
Lounge (log burner)

Could someone offer some advise on what would be the best way to heat the property, as it has nothing but the log burner it is effectively a blank canvas so I'd like to get the correct equipment in now.

I'm open to all suggestions, air source, combi, LPG, anything, I'm leaning toward ashp after reading more about it on here, is this wise?

obviously the more economical to run the better. And the cheaper to install for the plumber the better - If that is possible.

Thanks in advance

Go with a heat only boiler and boilered stove and look for a renewables installer who is up too speed with the latest technology.
But dump the hydronic heat from the stove to upstairs only and have it sized for upstairs only!

A combi piddling out 12l/min is a waste of time for your gaffe.

 

[Corgigrouch]

To get hot water into the shower room in the loft, then you will need to either pump the water from a conventional cylinder, link your boiler and solid fuel boiler to an unvented via something like a dunsley neutraliser or use a thermal store...Obviously this all depends on the flow of water coming in to the property... I would say a solid fuel stove with a boiler built in and a pellet boiler but since install price is at a premium, an oil heat only boiler may work out cheaper...Sadly the cheaper the heating is to run, the dearer it is to install. For your property, unless you were to insulate it to the current requirements, I would not point you at air source