ASHP

Puff

Member
My place in Wales has one of these for heating/hot water in the main house. It works but bloody hell, is it expensive in electricity to run, probably about 10000kwh pa and that's set at a reasonable temp with a wood stove backing it up. *

Obviously bearing in mind that I would need it more in Winter than Summer for heating, what recommendations would people have in terms of Solar PV and/or Wind for something that will provide enough power to keep these bills down? Obviously not worried about exporting.

* Double glazed, roof insulation, nothing else I can do there :(
 

akaPABLO01

Member
If you are using 1kW of electricity for 1kW of heat then an ashp will give you 3.3kW of heat for 1kW of electricity.

It is something you should look into. Maybe compliment it with a small solar to help it generate hot water in summer.

Loft insulation is very important some 300mm or more to help keep the heat in.

To correctly size a pump means a heat loss calculation needs to be done, room by room.

Do you have a full wet system radiator in place? A heat loss will determine the size of rads needed also and whether copper pipe runs need upgrading such as 10mm.

You say main house, if you have another unit like converted stables or barn you should also consider ground source heat pump on district heating. Gshp is more expensive then ashp to install but gshp will pay you on district heating for 20 years and single unit heated 7 years Rhi.

Both system generate heat at a low temperature so sizing rads as well as the heat pump is very, very important and could mean either not enough heat is generated or rads aren’t able to circulate the heat efficiently.

You definitely need a heat loss calculation done.
 

Exfarmer

Member
Location
Bury St Edmunds
I am very dubious about ASHP for use in this part of the world. Having run one for 8 years to heat a swimming pool we normally give up in the winter.
They are very good in the summer giving a very high return of heat for electricity input. However in the winter they often spend more time in de ice mode than actually heat capture mode.
I run my 6 KW unit / 18 KW output in combination with 8KW of solar PV
However how much of the solar we capture I have no idea as my meter does not show export.
I believe these units are a con for anyone hoping to provide heating in the winter cheaply and suspect they would show very little improvement over direct electric heating.
 

f0ster

Member
yes when the temp drops the cop of these drops to well below 2:1 and some of them even have an electric immersion heater inside to top up the last 10 deg, they need solar to subsidize them.
 

akaPABLO01

Member
Strange @Exfarmer as all my heat pumps are functioning beyond expectation.

I’ve attached a small screenshot, room temperature top right and hot water temperature bottom left. All made good progress through the minus temperatures we had.
 

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akaPABLO01

Member
the good progress is not in dispute it is the running cost of these when the temp gets down that costs
Personally I’d say the design and heat loss calculations are the important side. Undersize and cop isn’t there oversize and stop start burns cop. Then coupled with emitter to disperse the warmth is last. Undersized rads means overworked pump.

Heat pumps can definitely handle our climate you just need correct calculation with 10% added in size for rural areas.
 

f0ster

Member
one kw of electricity will give you 3.3kw of heat but only under ideal conditions, with our climate the very time you need the kw the conditions are not ideal for the heat pump. the manufacturers COP gives the output at different temperatures which is why they are expensive to run and need an alternative supply of power to subsidize them such as solar.
 

akaPABLO01

Member
Then adjust output temperature flow to 35 degrees at -7 still has 2.41 cop. Sure you’ll pay 5.8p /kW of heat @ 14p / electrical unit but in the summer or when ourside temps above 10 you’ll get cop upward of 3.96 making overall annual saving as temperatures increase. Adjust output flow is key but as I said before, if you circulate the heat through 10mm pipe carcass and rads aren’t big enough then loss in transfer is problematic. Insulation factored in, correct calculations made makes a heat pump install work.

As my m8 @Still Farming will agree, there’s plenty of sharks out there that look at an EPC stick a wet finger in the air and install a heat pump with no correct heat loss done. You’ll find a correct heat loss will be higher than an EPC but installing a domestic doesn’t need this and run straight from epc for payments. Do as my m8 did and buy a bigger boat with a good captain.

Ashp are by far the best heat producers costing less annually overall only surpassed by gshp which have a better cop.
 

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f0ster

Member
They can work better with underfloor heating due to the low temp required but with rads running at low temp it is a non starter. You have to increase the rad size to compensate for the low temp. Installing underfloor heating is a major upheaval. And you still need hot water at 60deg
 

Still Farming

Member
Mixed Farmer
Location
South Wales UK
Then adjust output temperature flow to 35 degrees at -7 still has 2.41 cop. Sure you’ll pay 5.8p /kW of heat @ 14p / electrical unit but in the summer or when ourside temps above 10 you’ll get cop upward of 3.96 making overall annual saving as temperatures increase. Adjust output flow is key but as I said before, if you circulate the heat through 10mm pipe carcass and rads aren’t big enough then loss in transfer is problematic. Insulation factored in, correct calculations made makes a heat pump install work.

As my m8 @Still Farming will agree, there’s plenty of sharks out there that look at an EPC stick a wet finger in the air and install a heat pump with no correct heat loss done. You’ll find a correct heat loss will be higher than an EPC but installing a domestic doesn’t need this and run straight from epc for payments. Do as my m8 did and buy a bigger boat with a good captain.

Ashp are by far the best heat producers costing less annually overall only surpassed by gshp which have a better cop.
Ho ho ho that's a cracker ???
 

Still Farming

Member
Mixed Farmer
Location
South Wales UK
I am very dubious about ASHP for use in this part of the world. Having run one for 8 years to heat a swimming pool we normally give up in the winter.
They are very good in the summer giving a very high return of heat for electricity input. However in the winter they often spend more time in de ice mode than actually heat capture mode.
I run my 6 KW unit / 18 KW output in combination with 8KW of solar PV
However how much of the solar we capture I have no idea as my meter does not show export.
I believe these units are a con for anyone hoping to provide heating in the winter cheaply and suspect they would show very little improvement over direct electric heating.
My so called M8 prof.renewables will tell you different !
 

Exfarmer

Member
Location
Bury St Edmunds
Can you explain how a heat pump,works when it is completely covered in ice, or when it is running backwards to De ice every ten - fifteen minutes.
I just dont understand this process at all.
They may extract heat very efficently in even very cold air if it is dry , but when the fins are completely blocked in ice there is not a cat in hells chance of it working.
 

phillipe

Member
Can you tell me something ,and yjis comes from a man who built one of the first berm houses in britain.once you have extracted the heat from around your pipes in the ground on your gshp,and the the winter is dark long and very cold ,where does the ground get its warmth from?
 
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Exfarmer

Member
Location
Bury St Edmunds
Can you tell me something ,and yjis comes from a man who built one of the first berm houses in britain.once you have extracted the heat from around your pipes in the ground on your gshp,and the the winter is dark long and very cold ,where does the ground get its warmth from?
This is one I can answer, it is important when planni;g and installing ground source heating to allow for sufficient length of pipe to only take the heat that naturally radiates up from the earth. Like any spring you will find running in winter always feel warm on a cold day.
The earth naturally is giving off heat from its inner core which can be harvested. If taken at the right speed you will have millions of years of free heat. If. You take it too quickly by having too short a pipe over too small an area it will certainly fail. Several large scale schemes in this country have failed as they overestimated the back ground heat available
 

Puff

Member
I'm doing a small barn conversion at some point this year, so it will be underfloor heating througout. With that in mind, will try and dig up some of the paddock and see whether I can get enough depth for a GSHP though I suspect it might be too rocky. Hadn't thought of tying two buildings together with it before.

Will also look into Solar Water to pre-heat the tank and Solar PV to cut down on (paid) electricity usage.

Strange @Exfarmer as all my heat pumps are functioning beyond expectation.

I’ve attached a small screenshot, room temperature top right and hot water temperature bottom left. All made good progress through the minus temperatures we had.

What's the App/device you're getting that from please? Don't mind installing a new controller if I am able to remotely manage it.
 

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