For optimum efficiency you don’t want to oversize your heat pump but the
output of your old gas boiler may well not be a good guide what with
changes to insulation levels over the years and the fact that the original
boiler may never have been sized correctly in the first place.

I came across this interesting video about a simple “rule of thumb” guide
to heat pump sizing that no doubt folk can pick holes in but it would be
interesting if those folk on the group with heat pumps could
retrospectively do the sums (all you need is your annual gas consumption
assuming you were heating by gas).

https://youtu.be/hCeghKa3liM?si=YgjVctmdejT2IJDb

In summary, take your annual gas consumption in kWhrs, divide by 57.3 and
multiply by 20 to get the output of heat pump in Watts required

Anyhow, I thought it was interesting and it might help folk avoid the
pitfall of being sold a heat pump much bigger than they need.

Tim

--
Please don't feed the trolls

Tim+ <tim.downie@gmail.com> wrote:
> For optimum efficiency you don’t want to oversize your heat pump but the
> output of your old gas boiler may well not be a good guide what with
> changes to insulation levels over the years and the fact that the original
> boiler may never have been sized correctly in the first place.
>
> I came across this interesting video about a simple “rule of thumb” guide
> to heat pump sizing that no doubt folk can pick holes in but it would be
> interesting if those folk on the group with heat pumps could
> retrospectively do the sums (all you need is your annual gas consumption
> assuming you were heating by gas).
>
> https://youtu.be/hCeghKa3liM?si=YgjVctmdejT2IJDb
>
> In summary, take your annual gas consumption in kWhrs, divide by 57.3 and
> multiply by 20 to get the output of heat pump in Watts required

1200 litres of oil pa
~80% efficient rusty oil boiler (finger in the air)
10.35kWh per litre

1200*10.35*20/(0.8*57.3) = 5400 W

My installer's heat loss calcs came out at 5kW
My heat loss calcs came out at 8kW
My installer recommended a 10kW ASHP
I asked for a 13kW ASHP (dual fan so quieter)

The actual delta from 10 to 13kW was a couple of hundred pounds - it's a
bigger unit but only maybe 30cm taller. I sacrifice a bit of efficiency
that way but I'm happy with how it went.

One thing about a smaller heat pump is that it takes longer to swing the
house around - eg if you need to warm it up from cold - and it reduces the
recharge time when making hot water.

Theo

On 13/09/2023 17:38, Tim+ wrote:

> In summary, take your annual gas consumption in kWhrs, divide by 57.3 and
> multiply by 20 to get the output of heat pump in Watts required

On an average day, that could work, but it wont be good enough for the
coldest days, as it is averaging your use over the year.It is when the
most amount of gas is being used that you need to work out the heating
source size from. So the use of gas in January would be ideal.

Ive just done mine using the formula above, it says I need 3kW. Thats
bollocks, there is no way this house would be warm in the winter with a
3kW heat source for heating and water.

--
Remove the '+' and replace with 'plus' to reply by email

Alan Lee <alan@darkroom.plus.com> wrote:
> On 13/09/2023 17:38, Tim+ wrote:
>
>> In summary, take your annual gas consumption in kWhrs, divide by 57.3 and
>> multiply by 20 to get the output of heat pump in Watts required
>
> On an average day, that could work, but it wont be good enough for the
> coldest days, as it is averaging your use over the year.It is when the
> most amount of gas is being used that you need to work out the heating
> source size from. So the use of gas in January would be ideal.
>
> Ive just done mine using the formula above, it says I need 3kW. Thats
> bollocks, there is no way this house would be warm in the winter with a
> 3kW heat source for heating and water.
>

Ours works out at 5kW which seems low for a 5 bedroom house but that may
just be a reflection of our niggardly use of our central heating. We have
a log burner to “top up” and now we have an air/air aircon/heating unit
that should warm a significant portion of the house so it’s possible that 5
kW would work for us if we went for a “wet” heat pump system.

Tim

--
Please don't feed the trolls

Theo <theom+news@chiark.greenend.org.uk> wrote:

> One thing about a smaller heat pump is that it takes longer to swing the
> house around - eg if you need to warm it up from cold -

That makes sense.

> and it reduces the
> recharge time when making hot water.

Don’t understand this bit though.

Tim

--
Please don't feed the trolls

On 13/09/2023 17:38, Tim+ wrote:
> For optimum efficiency you don’t want to oversize your heat pump but the
> output of your old gas boiler may well not be a good guide what with
> changes to insulation levels over the years and the fact that the original
> boiler may never have been sized correctly in the first place.
>
> I came across this interesting video about a simple “rule of thumb” guide
> to heat pump sizing that no doubt folk can pick holes in but it would be
> interesting if those folk on the group with heat pumps could
> retrospectively do the sums (all you need is your annual gas consumption
> assuming you were heating by gas).
>
> https://youtu.be/hCeghKa3liM?si=YgjVctmdejT2IJDb
>
> In summary, take your annual gas consumption in kWhrs, divide by 57.3 and
> multiply by 20 to get the output of heat pump in Watts required
>

Output or input? If the output includes the COP you could be under
sizing :)

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

On 13/09/2023 18:56, Alan Lee wrote:
> On 13/09/2023 17:38, Tim+ wrote:
>
>> In summary, take your annual gas consumption in kWhrs, divide by 57.3 and
>> multiply by 20 to get the output of heat pump in Watts required
>
> On an average day, that could work, but it wont be good enough for the
> coldest days, as it is averaging your use over the year.It is when the
> most amount of gas is being used that you need to work out the heating
> source size from. So the use of gas in January would be ideal.
>
> Ive just done mine using the formula above, it says I need 3kW. Thats
> bollocks, there is no way this house would be warm in the winter with a
> 3kW heat source for heating and water.

Could that 3kW be input power, which could equate to between 2 and 4
times that as output power.

SteveW <steve@walker-family.me.uk> wrote:
> On 13/09/2023 18:56, Alan Lee wrote:
>> On 13/09/2023 17:38, Tim+ wrote:
>>
>>> In summary, take your annual gas consumption in kWhrs, divide by 57.3 and
>>> multiply by 20 to get the output of heat pump in Watts required
>>
>> On an average day, that could work, but it wont be good enough for the
>> coldest days, as it is averaging your use over the year.It is when the
>> most amount of gas is being used that you need to work out the heating
>> source size from. So the use of gas in January would be ideal.
>>
>> Ive just done mine using the formula above, it says I need 3kW. Thats
>> bollocks, there is no way this house would be warm in the winter with a
>> 3kW heat source for heating and water.
>
> Could that 3kW be input power, which could equate to between 2 and 4
> times that as output power.
>
>

I had a quick search of heat pumps and they are all generally rated by
their output power, not their energy consumption.

Tim

--
Please don't feed the trolls

On 13/09/2023 18:56, Alan Lee wrote:
> On 13/09/2023 17:38, Tim+ wrote:
>
>> In summary, take your annual gas consumption in kWhrs, divide by 57.3 and
>> multiply by 20 to get the output of heat pump in Watts required
>
> On an average day, that could work, but it wont be good enough for the
> coldest days, as it is averaging your use over the year.It is when the
> most amount of gas is being used that you need to work out the heating
> source size from. So the use of gas in January would be ideal.
>
> Ive just done mine using the formula above, it says I need 3kW. Thats
> bollocks, there is no way this house would be warm in the winter with a
> 3kW heat source for heating and water.
>
Indeed. Its the 'renewable' fallacy. That what counts is the average
output of e.g. a windmill.

Well that is where the money comes from, but the *utility* comes from
its *guaranteed peak output*, which is zero.

You can jump on cheapoJet and fly in a plane that is stressed to be able
to handle the *average* flight conditions with all its engines running,
but the rest of us would rather fly in a plane that is stressed for the
worst turbulence it will ever experience, and then some, and can fly
happily with one engine shut down.

I'll omit hot water because it really is very very small in terms of
overall power needed, and look in general at house heating.

House heating is proportional to the temperature difference between
inside and out.

The colder it is outside, the more heat you need to pour in.
The average outside temp in the UK is about 9°C. But the worst case is
- on really cold winter days - 0°C. Or even 0-5°C in some parts of e.g.
Scotland.

Its not hard to see that to *keep* your house at say 20°C, is going to
take double the *average* energy in winter, and possibly no energy at
all in summer.

And the amount of energy you need to *get it to 20°C if you switch the
heating off in the day is going to be even higher. (god knows what heat
pumps will do to the evening peak electricity times)

I haven't actually had any heating in in the house for several months.
Its maintaining 20°C from just me, and bits of equipments and sunshine.
In winter I struggle to keep it warm with 12kW input.

*Getting* it warm with 12KW input can take all day.

If your average needs are 3KW I would suggest a minimum of twice that,
and better still 4 times that as the peak rating for your heating system

--
If I had all the money I've spent on drink...
...I'd spend it on drink.

Sir Henry (at Rawlinson's End)

On 13/09/2023 20:16, SteveW wrote:
> On 13/09/2023 18:56, Alan Lee wrote:
>> On 13/09/2023 17:38, Tim+ wrote:
>>
>>> In summary, take your annual gas consumption in kWhrs, divide by
>>> 57.3 and multiply by 20 to get the output of heat pump in Watts
>>> required
>>
>> On an average day, that could work, but it wont be good enough for
>> the coldest days, as it is averaging your use over the year.It is
>> when the most amount of gas is being used that you need to work out
>> the heating source size from. So the use of gas in January would be
>> ideal.
>>
>> Ive just done mine using the formula above, it says I need 3kW.
>> Thats bollocks, there is no way this house would be warm in the
>> winter with a 3kW heat source for heating and water.
>
> Could that 3kW be input power, which could equate to between 2 and 4
> times that as output power.
>
"In summary, take your annual gas consumption in kWhrs, divide by
57.3 and multiply by 20 to get the *output* of heat pump in Watts
required".

My rough guess is take the average, divide by the number of hours in the
year and multiply by 4.

to get peak desirable KW.

so the conversions factor to watts would be about 0.5

whereas the quoted one is 20/57.3 = 0.35 appx, so close , but no cigar.

Tim+ is saying he couldn't make it on 3KW, I am saying he probably could
, on 5kW.

People massively overestimate how much energy they need to keep warm.

For 9 months of the year this house runs on less than a kW from the AGA.

But during the coldest days of winter I need every ounce of 10-12KW plus
wood burners and supplementary stuff.

--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14

On 14/09/2023 05:21, The Natural Philosopher wrote:
> The colder it is outside, the more heat you need to pour in.
> The average outside temp in the UK is about 9°C.  But the worst case is
> - on really cold winter days - 0°C. Or even 0-5°C in some parts of e.g.
> Scotland.

Yes, heat loss surveys are generally calculated for an indoor
temperature of 21 degrees C, with the lower limit set according to the
region in the Country. South East England at -1, the Scottish Highlands
at -5.

> Its not hard to see that to *keep* your house at say 20°C, is going to
> take double the *average* energy in winter, and possibly no energy at
> all in summer.

Actually, its a bit less than half at 0 degrees, each degree rise uses
the same amount of energy. If its 9 deg average outside, then there
needs to be a 12 deg rise to get to 21. If its 0 deg, it needs a 21 deg
rise, so 75% more power required at 0 deg compared to 9 degrees outside.
Of course, if it goes to -5, that will mean a 26 degree rise needed,
but, we dont see those temperatures for more than 2 weeks in most of the
UK below the Scottish central belt.
If, as it should be, your heating system is designed for, say, a range
of -3 to 21 degrees, then at any temperature below -3, your heating
system will not be able to get it up to 21 degrees. It is designed for a
range of 24 degrees, and cannot cope beyond that, so an extra heat
source will be required to get to 21 degrees. (of course, it could be
designed for -10 to 30 degrees, but efficiency will not be good at lower
levels of need, unless the heat source can be modulated down correctly.)

This is becoming more important. Boilers have been over specced for many
years. The plumbers dont calculate the heat loss, they just put in
whatever they have fitted before, so a 24 or 30kW boiler is fitted to
most new builds. That is far too big, as the typical heat loss in a new
house will be less than 10kW (and according to the new building regs,
should be around 6kW). Of course, the extra capacity of the boiler will
help on the coldest days, it's not been designed, its just been fitted
with no regard to efficiency. The householder will always be warm, but
bills will be high to get that warmth, as that boiler will be cycling
far more than necessary (the worst way for wasting gas), and will
probably not be condensing either, as the plumber just turns it up to
maximum when they fit it. This has to change, and HPs are forcing this
change, as anyone who doesnt design the system properly will never get
the HP to work efficiently.

> And the amount of energy you need to *get it to 20°C if you switch the
> heating off in the day is going to be even higher. (god knows what heat
> pumps will do to the evening peak electricity times)

No, its pure physics. To get a 10 degree rise needs a set amount of
energy, whether it is 0 to 10, or 10 to 20, both use the same amount of
energy for the 10 degree rise.
The building fabric has an effect, in absorbing heat, this can affect
how long heating takes (and subsequent cooling), but for that building,
it will always take a set amount of energy to keep it at a set
temperature, in relation to the outdoor temperature.
Thinking now is that keeping the heating on all day when absent, is a
bad thing, unless the house is very well insulated, as the energy in
keeping it at 21 degrees is being lost at a rate of 3kW or so, so for
gas boilers, just turn it on when you want it if the insulation is not good.
HPs like to tick along quietly,so they are best left on, with a setback
temperature of 16 to 18 degrees, and , of course, if you have a HP
installed, you should be aware of the benefits of insulation, so the
house should be well insulated, which helps more than anything to keep
energy in the house, and bills low.

--
Remove the '+' and replace with 'plus' to reply by email

Tim+ <tim.downie@gmail.com> wrote:
> Theo <theom+news@chiark.greenend.org.uk> wrote:
>
> > One thing about a smaller heat pump is that it takes longer to swing the
> > house around - eg if you need to warm it up from cold -
>
> That makes sense.
>
> > and it reduces the
> > recharge time when making hot water.
>
> Don’t understand this bit though.

I meant *increases* the recharge time for hot water. ie it takes 9.31kWh to
heat 200 litres of water from 10C to 50C. If you have a 5kW heat
pump it'll do it in 2 hours, if you have a 10kW heat pump it'll take 1 hour.

Theo

Theo <theom+news@chiark.greenend.org.uk> wrote:
> Tim+ <tim.downie@gmail.com> wrote:
>> Theo <theom+news@chiark.greenend.org.uk> wrote:
>>
>>> One thing about a smaller heat pump is that it takes longer to swing the
>>> house around - eg if you need to warm it up from cold -
>>
>> That makes sense.
>>
>>> and it reduces the
>>> recharge time when making hot water.
>>
>> Don’t understand this bit though.
>
> I meant *increases* the recharge time for hot water. ie it takes 9.31kWh to
> heat 200 litres of water from 10C to 50C. If you have a 5kW heat
> pump it'll do it in 2 hours, if you have a 10kW heat pump it'll take 1 hour.
>
> Theo
>

Your cunning use of the word “reduces” was just to throw me off the scent
then? ;-)

Tim

--
Please don't feed the trolls

You mention insulation. The problem is there is a huge number of dwellings
like mine around with single brick walls and no matter what you do with the
loft and windows and doors, you would one imagines have to insulate under
the boarded floor of the ground floor and somehow insulate the outside walls
as well, before you really did get an internally stable environment. You
would also need windows that do not heat inside in summer due to some kind
of coating.
These houses are often terraced like mine though in which the middle ones
only have two outside walls but the semi detached on the ends have 3.

Obviously this will assume nobody leaves doors and windows open as well, so
you end up wondering exactly what is cost-efficient. Heating with storage
heaters or a boiler in the winter, and cooling with air con in the summer,
or get a heat pump that can work in both situations. Sadly, the power needed
for these two would seem to be variable according to the whether, so how
could wonder tell how big your installation should be, and what it uses for
the outside part of the system?

Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"Tim+" <tim.downie@gmail.com> wrote in message
news:1212891807.716314744.530527.tim.downie-gmail.com@news.individual.net...
> For optimum efficiency you don't want to oversize your heat pump but the
> output of your old gas boiler may well not be a good guide what with
> changes to insulation levels over the years and the fact that the original
> boiler may never have been sized correctly in the first place.
>
> I came across this interesting video about a simple "rule of thumb" guide
> to heat pump sizing that no doubt folk can pick holes in but it would be
> interesting if those folk on the group with heat pumps could
> retrospectively do the sums (all you need is your annual gas consumption
> assuming you were heating by gas).
>
> https://youtu.be/hCeghKa3liM?si=YgjVctmdejT2IJDb
>
> In summary, take your annual gas consumption in kWhrs, divide by 57.3 and
> multiply by 20 to get the output of heat pump in Watts required
>
> Anyhow, I thought it was interesting and it might help folk avoid the
> pitfall of being sold a heat pump much bigger than they need.
>
> Tim
>
>
> --
> Please don't feed the trolls

On 14/09/2023 07:59, Alan Lee wrote:
> On 14/09/2023 05:21, The Natural Philosopher wrote:
>> The colder it is outside, the more heat you need to pour in.
>> The average outside temp in the UK is about 9°C.  But the worst case
>> is - on really cold winter days - 0°C. Or even 0-5°C in some parts of
>> e.g. Scotland.
>
> Yes, heat loss surveys are generally calculated for an indoor
> temperature of 21 degrees C, with the lower limit set according to the
> region in the Country. South East England at -1, the Scottish Highlands
> at -5.
>
>> Its not hard to see that to *keep* your house at say 20°C, is going to
>> take double the *average* energy in winter, and possibly no energy at
>> all in summer.
>
> Actually, its a bit less than half at 0 degrees, each degree rise uses
> the same amount of energy. If its 9 deg average outside, then there
> needs to be a 12 deg rise to get to 21. If its 0 deg, it needs a 21 deg
> rise, so 75% more power required at 0 deg compared to 9 degrees outside.
> Of course, if it goes to -5, that will mean a 26 degree rise needed,
> but, we dont see those temperatures for more than 2 weeks in most of the
> UK below the Scottish central belt.
> If, as it should be, your heating system is designed for, say, a range
> of -3 to 21 degrees, then at any temperature below -3, your heating
> system will not be able to get it up to 21 degrees. It is designed for a
> range of 24 degrees, and cannot cope beyond that, so an extra heat
> source will be required to get to 21 degrees. (of course, it could be
> designed for -10 to 30 degrees, but efficiency will not be good at lower
> levels of need, unless the heat source can be modulated down correctly.)
>
> This is becoming more important. Boilers have been over specced for many
> years. The plumbers dont calculate the heat loss, they just put in
> whatever they have fitted before, so a 24 or 30kW boiler is fitted to
> most new builds. That is far too big, as the typical heat loss in a new
> house will be less than 10kW (and according to the new building regs,
> should be around 6kW). Of course, the extra capacity of the boiler will
> help on the coldest days, it's not been designed, its just been fitted
> with no regard to efficiency. The householder will always be warm, but
> bills will be high to get that warmth, as that boiler will be cycling
> far more than necessary (the worst way for wasting gas), and will
> probably not be condensing either, as the plumber just turns it up to
> maximum when they fit it. This has to change, and HPs are forcing this
> change, as anyone who doesnt design the system properly will never get
> the HP to work efficiently.
>
>> And the amount of energy you need to *get it to 20°C if you switch the
>> heating off in the day is going to be even higher. (god knows what
>> heat pumps will do to the evening peak electricity times)
>
> No, its pure physics. To get a 10 degree rise needs a set amount of
> energy, whether it is 0 to 10, or 10 to 20, both use the same amount of
> energy for the 10 degree rise.

No. You have entirely missed the point. I am not talking about
maintaining a temperature, I am talking about how much power you need to
heat all the thermal mass inside the insuslations TO that temperature.

e.g. if I let my UFH zone get cold, it can take around 12 HOURS to get
it to 19°C, pumping in 12KW.

Once there, its happy to use around 5-6kW except in vilely cold weather.

My boiler really needs to be specced to around 20kW to reduce warm up
times on the sold screed floor

> The building fabric has an effect, in absorbing heat, this can affect
> how long heating takes (and subsequent cooling), but for that building,
> it will always take a set amount of energy to keep it at a set
> temperature, in relation to the outdoor temperature.

Wrong again. It takes a set amount of POWER to maintain heat and extra
ENERGY to get it hot in the first place

> Thinking now is that keeping the heating on all day when absent, is a
> bad thing, unless the house is very well insulated, as the energy in
> keeping it at 21 degrees is being lost at a rate of 3kW or so, so for
> gas boilers, just turn it on when you want it if the insulation is not
> good.

Its very very arguable. No Swedish house would for example dream of
letting it get cold during the day. It is all about the function of
internal thermal mass and boiler efficiency at various power outputs. If
you have a lot of thermal mass or a boiler that is less efficient at
'full throttle', you may consider leaving it on.

Old houses with low insulation and low thermal mass definitely want a
timed schedule.

Modern houses with high thermal mass, modulating boilers and stonking U
values possibly do better at a constant temeparatures.

....I had no choice if I wanted a warm UFH zone BUT to run it 24x7, but I
am building a new heating controller now that will micromanage any
number of time/temperature periods, so i can what you call 'set back' to
say 12°C during the week and then let it burn all saturday to get it
warm (19°C) for the weekend

> HPs like to tick along quietly,so they are best left on, with a setback
> temperature of 16 to 18 degrees, and , of course, if you have a HP
> installed, you should be aware of the benefits of insulation, so the
> house should be well insulated, which helps more than anything to keep
> energy in the house, and bills low.
>

I did all the heat calcs when I built my house. I know quite a lot about
heat calcs and the like.

My biggest mistake was not thinking about over provisioning the boiler
for cold days. It tends to run for about 6 hours to get things warm and
then when it tries to restart it trips out and wont start till its
electronics cool down :-)

Really with in screed UFH you probably want about twice the 'keep the
house warm' power to GET the house warm in the first place.

The problem is that the screed will cool down when the heating is off,
to match the room ambient temperature, but to really start kicking heat
out that screed needs to get up to around 40°C, so you have a thwacking
great lump of screed that sucks in heat until it gets to 40°C or so.

Hence my idea to let it get cool, but not cold, with infinitely
adjustable time/temperature controls.

We will see how it pans out this winter.

--
“It is dangerous to be right in matters on which the established
authorities are wrong.”

― Voltaire, The Age of Louis XIV

On 14/09/2023 07:59, Alan Lee wrote:

> HPs like to tick along quietly,so they are best left on, with a setback
> temperature of 16 to 18 degrees, and , of course, if you have a HP
> installed, you should be aware of the benefits of insulation, so the
> house should be well insulated, which helps more than anything to keep
> energy in the house, and bills low.
>

If you are going to spend upgrading your insulation to make a HP viable
with a reasonable electricity bill then the same degree of insulation is
also going to benefit your pocket in the way of lower gas bills.

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

On 14/09/2023 13:31, alan_m wrote:
> On 14/09/2023 07:59, Alan Lee wrote:
>
>> HPs like to tick along quietly,so they are best left on, with a
>> setback temperature of 16 to 18 degrees, and , of course, if you have
>> a HP installed, you should be aware of the benefits of insulation, so
>> the house should be well insulated, which helps more than anything to
>> keep energy in the house, and bills low.
>>
>
>
> If you are going to spend upgrading your insulation to make a HP viable
> with a reasonable electricity bill then the same degree of insulation is
> also going to benefit your pocket in the way of lower gas bills.
>
>
indeed. Currently the cheapest way to heat a house is oil....

--
Karl Marx said religion is the opium of the people.
But Marxism is the crack cocaine.

On Thursday, 14 September 2023 at 14:47:27 UTC+1, The Natural Philosopher wrote:
> On 14/09/2023 13:31, alan_m wrote:
> > On 14/09/2023 07:59, Alan Lee wrote:
> >
> >> HPs like to tick along quietly,so they are best left on, with a
> >> setback temperature of 16 to 18 degrees, and , of course, if you have
> >> a HP installed, you should be aware of the benefits of insulation, so
> >> the house should be well insulated, which helps more than anything to
> >> keep energy in the house, and bills low.
> >>
> >
> >
> > If you are going to spend upgrading your insulation to make a HP viable
> > with a reasonable electricity bill then the same degree of insulation is
> > also going to benefit your pocket in the way of lower gas bills.
> >
> >
> indeed. Currently the cheapest way to heat a house is oil....
>
>
> --
> Karl Marx said religion is the opium of the people.
> But Marxism is the crack cocaine.
Can't be arsed to wade through this whole thread but thinking back a few years I recall debates in the group about efficient use of fuel and design of heating systems for the typical "working" household where comfort was required for a period in the morning for getting up, breakfast and going out to work. This being followed by coming home for tea and comfortable evening occupation prior to going to bed
If my memory serves correctly the ideal for minimising losses required rapidly raising the room temperatures then modulating the input down to maintenance heat level. Optimum switch off times reduced waste of energy. Losses through floors, walls, ceilings etc being measurable but following the laws of physics. Allowing the interior to cool when unoccupied reduced heat energy leakage. The proponents of heat pumps seem to disregard Newtons laws of cooling and seem quite content to accept room temperatures well below what I find comfortable in my 1980s brick/block built house with cavity wall insulation, double glazing and loft insulation.

On 16/09/2023 20:50, John J wrote:
> On Thursday, 14 September 2023 at 14:47:27 UTC+1, The Natural Philosopher wrote:
>> On 14/09/2023 13:31, alan_m wrote:
>>> On 14/09/2023 07:59, Alan Lee wrote:
>>>
>>>> HPs like to tick along quietly,so they are best left on, with a
>>>> setback temperature of 16 to 18 degrees, and , of course, if you have
>>>> a HP installed, you should be aware of the benefits of insulation, so
>>>> the house should be well insulated, which helps more than anything to
>>>> keep energy in the house, and bills low.
>>>>
>>>
>>>
>>> If you are going to spend upgrading your insulation to make a HP viable
>>> with a reasonable electricity bill then the same degree of insulation is
>>> also going to benefit your pocket in the way of lower gas bills.
>>>
>>>
>> indeed. Currently the cheapest way to heat a house is oil....
>>
>>
>> --
>> Karl Marx said religion is the opium of the people.
>> But Marxism is the crack cocaine.
> Can't be arsed to wade through this whole thread but thinking back a few years I recall debates in the group about efficient use of fuel and design of heating systems for the typical "working" household where comfort was required for a period in the morning for getting up, breakfast and going out to work. This being followed by coming home for tea and comfortable evening occupation prior to going to bed
> If my memory serves correctly the ideal for minimising losses required rapidly raising the room temperatures then modulating the input down to maintenance heat level. Optimum switch off times reduced waste of energy. Losses through floors, walls, ceilings etc being measurable but following the laws of physics. Allowing the interior to cool when unoccupied reduced heat energy leakage. The proponents of heat pumps seem to disregard Newtons laws of cooling and seem quite content to accept room temperatures well below what I find comfortable in my 1980s brick/block built house with cavity wall insulation, double glazing and loft insulation.

One solution often does not fit all. Saving on your fuel bills may
involve different strategies depending on the lifestyle. As you say, a
working household may result in a property being unoccupied for most of
the day while the opposite is true with many households where people are
retired. Having a system that requires the temperature to be maintained
at a near comfort level 24hours a day may be uneconomic for many people.

However going green is not about saving money!

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

On 14/09/2023 07:59, Alan Lee wrote:
> Actually, its a bit less than half at 0 degrees, each degree rise uses
> the same amount of energy. If its 9 deg average outside, then there
> needs to be a 12 deg rise to get to 21. If its 0 deg, it needs a 21 deg
> rise, so 75% more power required at 0 deg compared to 9 degrees outside.
> Of course, if it goes to -5, that will mean a 26 degree rise needed,
> but, we dont see those temperatures for more than 2 weeks in most of the
> UK below the Scottish central belt.
> If, as it should be, your heating system is designed for, say, a range
> of -3 to 21 degrees, then at any temperature below -3, your heating
> system will not be able to get it up to 21 degrees. It is designed for a
> range of 24 degrees, and cannot cope beyond that, so an extra heat
> source will be required to get to 21 degrees. (of course, it could be
> designed for -10 to 30 degrees, but efficiency will not be good at lower
> levels of need, unless the heat source can be modulated down correctly.)
>
> This is becoming more important. Boilers have been over specced for many
> years. The plumbers dont calculate the heat loss, they just put in
> whatever they have fitted before, so a 24 or 30kW boiler is fitted to
> most new builds. That is far too big, as the typical heat loss in a new
> house will be less than 10kW (and according to the new building regs,
> should be around 6kW). Of course, the extra capacity of the boiler will
> help on the coldest days, it's not been designed, its just been fitted
> with no regard to efficiency. The householder will always be warm, but
> bills will be high to get that warmth, as that boiler will be cycling
> far more than necessary (the worst way for wasting gas), and will
> probably not be condensing either, as the plumber just turns it up to
> maximum when they fit it. This has to change, and HPs are forcing this
> change, as anyone who doesnt design the system properly will never get
> the HP to work efficiently.

Our first house was specced with the heating OK down to that zero degree
outside temperature.

The second winter we were there we had a long cold spell.

Once the outside temperature got to zero the heating was running flat
out all the time.

As the temperature outside went below zero the inside temperature
started to follow it down.

IIRC it got down to -10 or so outside. We were having to top up with fan
heaters inside.

You need to design for worst case, not just average.

Andy

Vir Campestris <vir.campestris@invalid.invalid> wrote:
>
> Our first house was specced with the heating OK down to that zero degree
> outside temperature.
>
> The second winter we were there we had a long cold spell.
>
> Once the outside temperature got to zero the heating was running flat
> out all the time.
>
> As the temperature outside went below zero the inside temperature
> started to follow it down.
>
> IIRC it got down to -10 or so outside. We were having to top up with fan
> heaters inside.
>
> You need to design for worst case, not just average.

But what if “worse case design” results in an inefficient system for the
other 99% of the year? It might well be more economic to “top up” in other
ways.

Tim

--
Please don't feed the trolls

On 22/09/2023 21:50, Vir Campestris wrote:
> On 14/09/2023 07:59, Alan Lee wrote:
>> Actually, its a bit less than half at 0 degrees, each degree rise uses
>> the same amount of energy. If its 9 deg average outside, then there
>> needs to be a 12 deg rise to get to 21. If its 0 deg, it needs a 21
>> deg rise, so 75% more power required at 0 deg compared to 9 degrees
>> outside.
>> Of course, if it goes to -5, that will mean a 26 degree rise needed,
>> but, we dont see those temperatures for more than 2 weeks in most of
>> the UK below the Scottish central belt.
>> If, as it should be, your heating system is designed for, say, a range
>> of -3 to 21 degrees, then at any temperature below -3, your heating
>> system will not be able to get it up to 21 degrees. It is designed for
>> a range of 24 degrees, and cannot cope beyond that, so an extra heat
>> source will be required to get to 21 degrees. (of course, it could be
>> designed for -10 to 30 degrees, but efficiency will not be good at
>> lower levels of need, unless the heat source can be modulated down
>> correctly.)
>>
>> This is becoming more important. Boilers have been over specced for
>> many years. The plumbers dont calculate the heat loss, they just put
>> in whatever they have fitted before, so a 24 or 30kW boiler is fitted
>> to most new builds. That is far too big, as the typical heat loss in a
>> new house will be less than 10kW (and according to the new building
>> regs, should be around 6kW). Of course, the extra capacity of the
>> boiler will help on the coldest days, it's not been designed, its just
>> been fitted with no regard to efficiency. The householder will always
>> be warm, but bills will be high to get that warmth, as that boiler
>> will be cycling far more than necessary (the worst way for wasting
>> gas), and will probably not be condensing either, as the plumber just
>> turns it up to maximum when they fit it. This has to change, and HPs
>> are forcing this change, as anyone who doesnt design the system
>> properly will never get the HP to work efficiently.
>
> Our first house was specced with the heating OK down to that zero degree
> outside temperature.
>
> The second winter we were there we had a long cold spell.
>
> Once the outside temperature got to zero the heating was running flat
> out all the time.
>
> As the temperature outside went below zero the inside temperature
> started to follow it down.
>
> IIRC it got down to -10 or so outside. We were having to top up with fan
> heaters inside.
>
> You need to design for worst case, not just average.
>
Yup. And then there is warm up time

> Andy

--
Socialism is the philosophy of failure, the creed of ignorance and the
gospel of envy.

Its inherent virtue is the equal sharing of misery.

Winston Churchill