My boiler is kettling and needs replacing, it's quite old, supplied by
British Gas, and has a flue that goes straight through the wall, some work
would be needed to replace it including a new upright flue. I have a quote
of £4K from the local plumber (who has done a fair bit or work to my
central heating and has a good team of people).

I have been reading up on heat pumps and I'm struggling a bit to see how
they can extract heat from cold air. Seem to me to be a bit like
windmills, the more you need them the less efficient they are.

Anybody actually had one fitted? Can you give some idea of how it works
compared to what you had previously and whether it's saving or costing you
money please?

--
Jeff Gaines Dorset UK
The only thing necessary for evil to prevail is for good people to do or
say nothing. (Edmund Burke)

Jeff Gaines wrote:

> I have been reading up on heat pumps and I'm struggling a bit to see how
> they can extract heat from cold air.

It helps if you think of temperatures in Kelvin, rather than Celsius.

Extracting some energy from air at 270K to warm some water to 310-330K
(depending if you have UFH or rads) sounds more reasonable ...

On 25/02/2024 15:19, Jeff Gaines wrote:
>
> My boiler is kettling and needs replacing, it's quite old, supplied by
> British Gas, and has a flue that goes straight through the wall, some
> work would be needed to replace it including a new upright flue. I have
> a quote of £4K from the local plumber (who has done a fair bit or work
> to my central heating and has a good team of people).
>
> I have been reading up on heat pumps and I'm struggling a bit to see how
> they can extract heat from cold air. Seem to me to be a bit like
> windmills, the more you need them the less efficient they are.
>
> Anybody actually had one fitted? Can you give some idea of how it works
> compared to what you had previously and whether it's saving or costing
> you money please?
>

You need a property with above thermal characteristics (not
guaranteed by just slapping on more insulation) before you
should even think about. If you are on mains gas then stick
with it (and still upgrade the insulation).

If you have a bungalow with a solid floor then you already
have a possibly worse perimeter to area ratio, especially
if it has had hotch-potch extensions in the past and this
means a lot of heat loss through that 1 metre strip of floor
all around the perimeter, next to external walls, which cavity
wall insulation will not improve.

Refer to Part L of the buildings regs for details

On 25/02/2024 15:35, Andrew wrote:
> You need a property with above thermal characteristics (not
> guaranteed by just slapping on more insulation) before you
> should even think about. If you are on mains gas then stick
> with it (and still upgrade the insulation).

Thats a fallacy. All heat sources are improved by more insulation, it
isnt just heat pumps.
A well designed and fitted ASHP should have a SCOP of 3.5 or more,
making it , currently, the same price for use as a gas boiler.
In future, I can see the gas prices rising more than electric, which
will make the HPs cheaper to run, but, at the moment, there is a very
artifical political decision to keep gas prices at the same ratio with
electric prices, even though there are now some very low cost ways of
producing electricity.

> If you have a bungalow with a solid floor then you already
> have a possibly worse perimeter to area ratio, especially
> if it has had hotch-potch extensions in the past and this
> means a lot of heat loss through that 1 metre strip of floor
> all around the perimeter, next to external walls, which cavity
> wall insulation will not improve.

And fitting any type of heat source will have the same problem of losing
too much heat through the fabric of the building. Gas has been cheap for
the last 50 years, those days are ending, so we cannot carry on wasting
it as we've been doing. With ASHPs, proper design has to be done for
domestic heating, something that has hardly happened for the last 40
years, and being as gas was cheap, the fitters have got away with it.

On 25/02/2024 17:53, Alan Lee wrote:

> even though there are now some very low cost ways of
> producing electricity.

Only if you conveniently ignore the extra cost of the infrastructure to
support them and the need to supply backup generators when they fail to
work when needed most.

>
> And fitting any type of heat source will have the same problem of losing
> too much heat through the fabric of the building. Gas has been cheap for
> the last 50 years, those days are ending, so we cannot carry on wasting
> it as we've been doing. With ASHPs, proper design has to be done for
> domestic heating, something that has hardly happened for the last 40
> years, and being as gas was cheap, the fitters have got away with it.

And the problem still exists both with gas and ASHP. A lack of skill in
the industry to correctly design the system. With so many cowboys
entering the solar/ASHP market in order to suck up all the grants the
chances of having a correctly designed ASHP system may be less than
having a correctly installed new gas boiler.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 25/02/2024 15:19, Jeff Gaines wrote:
> I have been reading up on heat pumps and I'm struggling a bit to see how
> they can extract heat from cold air. Seem to me to be a bit like
> windmills, the more you need them the less efficient they are.
>
> Anybody actually had one fitted? Can you give some idea of how it works
> compared to what you had previously and whether it's saving or costing
> you money please?

Its a long explanation. Andy previously has said it really. Basically,
the idea is to suck in loads of air, the refrigerant is cooler than
that, it gets warmed by this hotter air, expands, is then compressed,
releasing the energy it has abosrbed.A heat exchanger then warms the
water passing through the outside unit. ( there are some that have
indoor and outdoor units, these are split units, though they all work
the same way).

Currently you can get a £7500 grant to take out a gas boiler and have a
G/ASHP fitted. Usually this £7.5k is not enough to pay for the full
install. Mine has cost around £8k for the parts (full heating system),
there is easily 2 weeks work for a full CH system to be fitted, so
labour will be £3k or so, hence a total cost to the customer of around
£3 -4k.

Octopus have been fitting a lot recently, and giving such good prices
that it's daft to not take up their offer. However, there are some
downsides to their offerings. From anecodatal evidence, they are
designing them to run at 50 degrees. This will get the house warm, but,
it will cost around 25% more to run than one designed for 40 degrees.
British Gas also do the same thing, they guarantee that your house will
be warm. Thats easy, if its too cold, they turn up the flow temperature,
and for each 1 degree increase in flow temp, you'll be paying 2.5% more
for your electric.

Design is the key. Get it designed to run at 35 degree flow temperature,
and you'll be seeing COPs of 4+. The downside to that is that most of
the radiators in an existing installation will be too small. Radiators
in the 60's/70's were designed for a radiator temperature to room
differential of 50 (DT50). Even now with new gas boilers, this will not
work using the quoted figures for radiator output, as new boilers are
now limited to a flow temperature of 55 degrees. If you have a room
temperature of 20 deg. then your DT will be around 25 (55 flow, 35
return = 45 mean -20 = 25), so the quoted radiator output is roughly
half of the actual figure.
With a well designed HP running at 35 degrees, with a return of 30 deg,
the Mean Water Temperature is 32.5 deg, minus the room temp of 20 gives
a radiator DT12.5, so the radiator quoted at 1000 watts at DT50, now
only gives out around 250 watts (it isnt quite as straightforward as
that, there is an equation to get the output correct).
So from that, you can see that your radiators will probably not be big
enough to run really efficiently at 35 degrees flow, and be able to warm
the house, as they are just not big enough to emit the required heat. In
the real world it normally isnt quite so bad, as plumbers just chucked
any rads in that fit, and they were mostly over sized, as, well, gas was
cheap, and no one moans if the house is too hot, but they are on the
phone immediately if its too cold.
If you are going for one, your house needs a proper heat loss survey,
not a 10 minute look around. A proper survey should take at least a hour
to measure up everything in the house, then at least another hour
working out the results. Each room needs to be assessed to see what the
heat requirement is for that room. To get the Grant, the house also
needs to meet some insualtion requirements. An open barn will not get a
grant.

Alan Lee wrote:

> Basically, the idea is to suck in loads of air, the refrigerant is
> cooler than that, it gets warmed by this hotter air, expands, is then
> compressed, releasing the energy it has abosrbed.A heat exchanger then
> warms the water passing through the outside unit.

For anyone who wants to go into it any deeper, I found that Stiebel
Eltron have a few hours of videos and tests you can sit through to
improve your understanding ... you get a pretty worthless certificate too!

<https://www.stiebel-eltron.co.uk/en/service/Services-for-partners-and-installers/Training/HeatPumpPass.html>

On 25/02/2024 18:27, Alan Lee wrote:

> Even now with new gas boilers, this will not
> work using the quoted figures for radiator output, as new boilers are
> now limited to a flow temperature of 55 degrees.

Are they? My "new" gas boiler had a default flow temperature or 75C but
easily changed to be a lot lower.

> If you are going for one, your house needs a proper heat loss survey,
> not a 10 minute look around. A proper survey should take at least a hour
> to measure up everything in the house, then at least another hour
> working out the results. Each room needs to be assessed to see what the
> heat requirement is for that room.

+1
And don't be surprised if more than a boiler/ASHP swap is required.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 25 Feb 2024 at 18:27:13 GMT, Alan Lee wrote:

> On 25/02/2024 15:19, Jeff Gaines wrote:
>> I have been reading up on heat pumps and I'm struggling a bit to see how
>> they can extract heat from cold air. Seem to me to be a bit like
>> windmills, the more you need them the less efficient they are.
>>
>> Anybody actually had one fitted? Can you give some idea of how it works
>> compared to what you had previously and whether it's saving or costing
>> you money please?
>
>
> Its a long explanation. Andy previously has said it really. Basically,
> the idea is to suck in loads of air, the refrigerant is cooler than
> that, it gets warmed by this hotter air, expands, is then compressed,
> releasing the energy it has abosrbed.A heat exchanger then warms the
> water passing through the outside unit. ( there are some that have
> indoor and outdoor units, these are split units, though they all work
> the same way).
>
> Currently you can get a £7500 grant to take out a gas boiler and have a
> G/ASHP fitted. Usually this £7.5k is not enough to pay for the full
> install. Mine has cost around £8k for the parts (full heating system),
> there is easily 2 weeks work for a full CH system to be fitted, so
> labour will be £3k or so, hence a total cost to the customer of around
> £3 -4k.
>

Just to say . . . I had a quote a month or so ago - £15k. And that was the
basic pump and hw tank install only - no other work or alterations. Totting up
the parts came to about £6k - so £9k labour.

I was at a gathering of about 100 retrofit people the other day, and
anecdotally there's a number of companies taking, er, liberties with the
pricing in view of the grant. And some deep cynicism around the MCS
certification/qualification, with painters/decorators jumping on board etc.

FWIW I'm not going with an ASHP for now - going to concentrate on insulation
and mechanical ventilation. I'm also looking at solar, but I'm not fixated on
economic returns. I'll look at ASHPs again once (and if) that little lot's
sorted, and I can afford it.

RJH wrote:
> £15k. And that was the
> basic pump and hw tank install only - no other work or alterations. Totting up
> the parts came to about £6k - so £9k labour.
You can guarantee the labour is going to be at least £7k to "soak up"
the jobs for the boys grant ...

On 25/02/2024 in message <xn0oihyed4kas6500i@news.individual.net> Jeff
Gaines wrote:

>Anybody actually had one fitted? Can you give some idea of how it works
>compared to what you had previously and whether it's saving or costing you
>money please?

Many thanks for all the replies on this.

Is seems to me that sticking to gas is probably the best bet for now, I'm
76 so unlikely to see any pay back on a heat pump.

You've got me a bit frightened with all the calculations! It reminds me of
the first CH system I was involved with at an uncle's house when I was 11
years old. I was given a book showing the heat loss per hour in BTUs for
all the materials found in a house and depending on the direction they
were facing. I don't know how well I did with the calculations but I do
know that house always felt blooming cold!

--
Jeff Gaines Dorset UK
The only thing necessary for evil to prevail is for good people to do or
say nothing. (Edmund Burke)

On 25/02/2024 21:50, Jeff Gaines wrote:
> On 25/02/2024 in message <xn0oihyed4kas6500i@news.individual.net> Jeff
> Gaines wrote:
>
>> Anybody actually had one fitted? Can you give some idea of how it
>> works compared to what you had previously and whether it's saving or
>> costing you money please?
>
> Many thanks for all the replies on this.
>
> Is seems to me that sticking to gas is probably the best bet for now,
> I'm 76 so unlikely to see any pay back on a heat pump.
>
> You've got me a bit frightened with all the calculations! It reminds me
> of the first CH system I was involved with at an uncle's house when I
> was 11 years old. I was given a book showing the heat loss per hour in
> BTUs for all the materials found in a house and depending on the
> direction they were facing. I don't know how well I did with the
> calculations but I do know that house always felt blooming cold!
>

I believe these days the regulations with regards changing a gas boiler
also require a house heat loss calculation to be performed in order to
fit the correct size of boiler.I'll bet that most installations will be
a like for like capacity boiler which may not result in the best fuel
efficiency with modern condensing boilers.

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 26/02/2024 in message <l42nogF15htU1@mid.individual.net> alan_m wrote:

>On 25/02/2024 21:50, Jeff Gaines wrote:
>>On 25/02/2024 in message <xn0oihyed4kas6500i@news.individual.net> Jeff
>>Gaines wrote:
>>
>>>Anybody actually had one fitted? Can you give some idea of how it works
>>>compared to what you had previously and whether it's saving or costing
>>>you money please?
>>
>>Many thanks for all the replies on this.
>>
>>Is seems to me that sticking to gas is probably the best bet for now, I'm
>>76 so unlikely to see any pay back on a heat pump.
>>
>>You've got me a bit frightened with all the calculations! It reminds me
>>of the first CH system I was involved with at an uncle's house when I was
>>11 years old. I was given a book showing the heat loss per hour in BTUs
>>for all the materials found in a house and depending on the direction
>>they were facing. I don't know how well I did with the calculations but I
>>do know that house always felt blooming cold!
>>
>
>I believe these days the regulations with regards changing a gas boiler
>also require a house heat loss calculation to be performed in order to fit
>the correct size of boiler.I'll bet that most installations will be a like
>for like capacity boiler which may not result in the best fuel efficiency
>with modern condensing boilers.

I'll have to brush up on my BTUs (or is it BThUs?)!

--
Jeff Gaines Dorset UK
Here we go it's getting close, now it's just who wants it most.

On 26/02/2024 08:17, Jeff Gaines wrote:
> On 26/02/2024 in message <l42nogF15htU1@mid.individual.net> alan_m wrote:
>
>> On 25/02/2024 21:50, Jeff Gaines wrote:
>>> On 25/02/2024 in message <xn0oihyed4kas6500i@news.individual.net>
>>> Jeff Gaines wrote:
>>>
>>>> Anybody actually had one fitted? Can you give some idea of how it
>>>> works compared to what you had previously and whether it's saving
>>>> or  costing you money please?
>>>
>>> Many thanks for all the replies on this.
>>>
>>> Is seems to me that sticking to gas is probably the best bet for
>>> now,  I'm 76 so unlikely to see any pay back on a heat pump.
>>>
>>> You've got me a bit frightened with all the calculations! It reminds
>>> me of the first CH system I was involved with at an uncle's house
>>> when I  was 11 years old. I was given a book showing the heat loss
>>> per hour in  BTUs for all the materials found in a house and
>>> depending on the  direction they were facing. I don't know how well I
>>> did with the  calculations but I do know that house always felt
>>> blooming cold!
>>>
>>
>> I believe these days the regulations with regards changing a gas
>> boiler also require a house heat loss calculation to be performed in
>> order to fit the correct size of boiler.I'll bet that most
>> installations will be a like for like capacity boiler which may not
>> result in the best fuel efficiency with modern condensing boilers.
>
> I'll have to brush up on my BTUs (or is it BThUs?)!
>

Even when I first calculated my heat loss, perhaps 40 years ago, the U
values for various walls/roof/windows etc. were quoted in Watts per
square metre (per degree C)

Btu to kW, divide by 3412

--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On 26/02/2024 in message <l431i0F2j38U1@mid.individual.net> alan_m wrote:

>>>>You've got me a bit frightened with all the calculations! It reminds me
>>>>of the first CH system I was involved with at an uncle's house when I 
>>>>was 11 years old. I was given a book showing the heat loss per hour in 
>>>>BTUs for all the materials found in a house and depending on the 
>>>>direction they were facing. I don't know how well I did with the 
>>>>calculations but I do know that house always felt blooming cold!
>>>>
>>>
>>>I believe these days the regulations with regards changing a gas boiler
>>>also require a house heat loss calculation to be performed in order to
>>>fit the correct size of boiler.I'll bet that most installations will be a
>>>like for like capacity boiler which may not result in the best fuel
>>>efficiency with modern condensing boilers.
>>
>>I'll have to brush up on my BTUs (or is it BThUs?)!
>>
>
>Even when I first calculated my heat loss, perhaps 40 years ago, the U
>values for various walls/roof/windows etc. were quoted in Watts per
>square metre (per degree C)
>
>Btu to kW, divide by 3412

I'm talking 66 years ago!

--
Jeff Gaines Dorset UK
I take full responsibility for what happened - that is why the person that
was responsible went immediately.
(Gordon Brown, April 2009)