NY <me@privacy.invalid> wrote
> Rod Speed <rod.speed.aaa@gmail.com> wrote

>>> In the event the house that we bought is heated by gas boiler and
>>> radiators, plus a gas Aga in the kitchen and (for the evenings) a
>>> wood-burning stove in the lounge using free wood from all the trees
>>> we've pruned.

>> Lot more farting around than with a properly designed
>> air sourced split system.

> If it was a new house, where the air ducts, the hot water heater, the
> heat exchanger box etc could all be designed in before construction, an
> air-source heating system might be feasible,

And split air sourced systems don't need any of that and
work fine in existing houses when designed properly.

> though I'd probably want a Calor gas heater and cooker hob in reserve,
> just in case of power cuts -

We get very few of those and I just use the camping gas stove if required.

And just go to bed if it gets too cold.

> the problem with going all-electric is that you are putting all your
> eggs in one basket.

But it is perfectly possible to have a generator. I have one that cost
me peanuts at a garage sale and have never needed to use it in more
than a decade now. We did have a mega storm which took out lots
of trees and one of the power poles that has the 11KV supply on it
that took a while to stand up again, but that doesnt happen often
enough to matter.

> But retrofitting ducts, boiler, huge and unsightly heat exchanger fan

You don't need anything like that with a SPLIT SYSTEM.

> in an existing house (some of which dates back to 1800s) is not
> affordable.

But a split system is.

> It so happened that we did need a new boiler shortly after we moved in
> because the hot water cylinder developed a leak and the engineer
> discovered that the boiler was about to corrode through, so we went for
> combi boiler heating water on demand rather than heating a cylinder of
> water. But the crucial thing was that it used all the existing radiators
> and CH/HW piping. So the disruption was confined to the boiler room and
> the airing cupboard where the cylinder had been.

> In hindsight, would we have been better off going for oil rather than
> gas?

Nope, we gave up on oil almost half a century ago now.

> Well both have increased in price dramatically, but hopefully things
> will get back to normal eventually.

But as you get older, you will find cutting up all that wood stops being
feasible. But you will still be able to flick a switch for much longer.

> And at least it works, without cold draughts, dust and a godawful
> moaning whine through the house.

Nothing like that with a properly designed air sourced split system.

> And no unsightly and throbbing fan-box bolted on the outside of the
> house.

There is no throbbing with a well designed system and it is easy
to do it so you can't see it.

> If a ground source / air source heating system could heat water for
> conventional radiators, then it might be worth considering. But my
> experience with my parents' puny ducted air heating puts me off that
> technology (how ever the air is actually heated).

It is silly to reject any approach just because one implementation is
fucked.

On Tue, 19 Apr 2022 20:20:20 +1000, Theo
<theom+news@chiark.greenend.org.uk> wrote:

> NY <me@privacy.invalid> wrote:
>> Do air source heat pumps actually work? Do they actually get the house
>> as
>> warm as radiators heated by gas or oil can do?
>
> Yes and no. Work they do. They don't get *as hot* because boilers
> output
> water at say 70C while heat pumps prefer 45-55C. You can make them
> hotter,
> at the expense of efficiency. But it's much better to run them at lower
> temperatures to make them more efficient. That means larger heat
> emitters.

That isn't true with split systems.

> Basically you *can* drop in an ASHP for a boiler, but the efficiency is
> worse than doing a proper system design. Given lack of efficiency will
> cost
> you over the lifetime of the unit, it makes sense to get the design
> right to
> begin with.
>
> Replaced a 14kW boiler with a 13kW ASHP, house is just as warm overall -
> the
> ASHP doesn't actually need to work very hard. We did upgrade the
> radiators
> to cope with the lower flow temperature, and the installer failed to
> balance
> them so there was some unevenness between the rooms. After 3 months they
> came back to fix their (numerous) mistakes, although we now can't test
> that
> until winter.
>
>> I ask because my parents had a house that was heated by ducted air and
>> a)
>> it was always bloody freezing, and b) the house was always dusty because
>> of the dust that the ducted air circulated.
>>
>> When we were looking for a new house a couple of years ago, we saw one
>> that had air source heating installed by the owner who was a heating
>> engineer. He raved about the heating system, but there were cold
>> draughts
>> in every room and an inescapable whine permeated the whole house.
>
> That's an air to air heat pump. With an air to water version the
> radiators
> are silent, just like boiler rads. The outdoor noise is quieter than the
> old boiler, although more continuous.
>
> Our water ASHP also does cooling (down to 7C). It works very well, but
> radiators aren't good 'cold emitters'. I'm looking at fitting fan coils.
>
>> In the event the house that we bought is heated by gas boiler and
>> radiators,
>> plus a gas Aga in the kitchen and (for the evenings) a wood-burning
>> stove in
>> the lounge using free wood from all the trees we've pruned. It's
>> costing a
>> lot more than it did before the gas prices went up, but we've reduced
>> gas
>> consumption by turning the heating down a degree or so, and we keep room
>> doors closed and don't heat the corridor outside the rooms. Our
>> economies
>> have reduced the daily gas usage from 5 cubic feet (2021) or 5.8 cubic
>> feet
>> (2020) to 3.5 cubic feet (2022) for March. So far, we only have
>> comparative
>> figures for March because we didn't start the economies until the end of
>> February this year.
>
> Our ASHP takes 2-25 kWh per day, depending on the outside temperature.
> In
> March usage was average 10kWh per day. That includes hot water of
> 1-2kWh.
>
> 1 cubic foot of gas is 0.29kWh, so your 3.5cuft is roughly 1kWh. Given
> the
> Ofgem average heating load is 12000kWh per year, I'm a bit dubious about
> your numbers. Do you mean cubic metre? (10.55kWh)
>
> Theo

On Tue, 19 Apr 2022 20:30:04 +1000, Theo
<theom+news@chiark.greenend.org.uk> wrote:

> NY <me@privacy.invalid> wrote:
>> But retrofitting ducts, boiler, huge and unsightly heat exchanger fan
>> in an
>> existing house (some of which dates back to 1800s) is not affordable.
>> It so
>> happened that we did need a new boiler shortly after we moved in
>> because the
>> hot water cylinder developed a leak and the engineer discovered that the
>> boiler was about to corrode through, so we went for combi boiler heating
>> water on demand rather than heating a cylinder of water. But the crucial
>> thing was that it used all the existing radiators and CH/HW piping. So
>> the
>> disruption was confined to the boiler room and the airing cupboard
>> where the
>> cylinder had been.
>
> Air sucks as a heat transmission medium, because the specific heat
> capacity
> is so low. That's why you need to blow a lot of air to get much heat
> transfer. Lots of blowing = noise, dust.

You don't get any of that with a split system.

> Water has a much higher specific heat, hence it's much easier to install
> pipework.

Even easier with a split system.

Convection can be silent, whereas transferring heat by
> conduction
> usually needs forced movement.

But perfectly possible to do that silently.

> Heat pumps can use either. Each have their pros and cons, especially if
> you
> want them to do cooling as well as heating.
>
>> In hindsight, would we have been better off going for oil rather than
>> gas?
>> Well both have increased in price dramatically, but hopefully things
>> will
>> get back to normal eventually. And at least it works, without cold
>> draughts,
>> dust and a godawful moaning whine through the house. And no unsightly
>> and
>> throbbing fan-box bolted on the outside of the house.
>
> With oil you need a 1000+ litre oil tank outside of the house, so I don't
> think that wins on the unsightliness. We've actually regained a good
> chunk
> of garden by removing our oil tank.
>
>> If a ground source / air source heating system could heat water for
>> conventional radiators, then it might be worth considering.
>
> They can, and they do.
>
> Theo

On Tue, 19 Apr 2022 21:26:16 +1000, Andy Burns <usenet@andyburns.uk> wrote:

> NY wrote:
>
>> Do air source heat pumps actually work? Do they actually get the house
>> as warm as radiators heated by gas or oil can do?
>
> Depends, keeping radiators with an ASHP (air to water monobloc) is not
> ideal as the efficiency goes down with higher flow temperature, adding
> UFH with lower flow temperature usually not practical, alternatively you
> could use a split system with internal wall or ceiling mounted fancoil
> units
>
>> I ask because my parents had a house that was heated by ducted air and
>> a) it was always bloody freezing, and b) the house was always dusty
>> because of the dust that the ducted air circulated.
>
> ASHP certainly doesn't mean switching to ducted air heating
>
>> When we were looking for a new house a couple of years ago, we saw one
>> that had air source heating installed by the owner who was a heating
>> engineer. He raved about the heating system, but there were cold
>> draughts in every room and an inescapable whine permeated the whole
>> house.
>
> certainly there's a lot to get right,

Not with a split system. Just size the outside part so it doesn't ice up.

> and it makes more sense for new builds rather than refits

Wrong with split systems.

newshound <sradcliffe544@gmail.com> wrote
> The Natural Philosopher wrote
>> NY wrote

>>> Do air source heat pumps actually work? Do they actually get the house
>>> as warm as radiators heated by gas or oil can do?
>>>
>> An air source heatpump certainly can work, but you need to understand
>> its inhernet limitations
>> Firstly, it is at its most efficient when raising temperatures by the
>> smallest amount, So you can get out up to 4:1 more heat than dierect
>> electrical when you are heating water from say 5°C outside to say 40°C
>> water temperature.
>> However that raises further issues
>> - that water temperature is well below what any conventional gas or
>> oil boiler can deliver, so a one for one replacement will be hopelessly
>> inadequate. You need larger areas to radiate sufficient heat at 35°C
>> compared with radiators at 50-60°C, so in order to use the pump to its
>> greatest efficiency, you will need to install underfloor heating, most
>> likely. And the attendant insulation. I.e its a pretty hopeless choice
>> for an existing building upgrade...
>> - the water temperatture itself depends on there being external heat
>> to pump. If it goes below zero outside - air temperature wise - that
>> heat pump will struggle. Like all 'renewable energy' technology it lets
>> you down when you need it most.
>> Ground source pumps are better - the soil rarely freezes at depth, and
>> there is a far greater thermal store to tap than there is with air
>> source.
>> - because water temperatures are typically too low for a domestic hot
>> water system most air source heat pumps add in immersion heaters to
>> raise the DHW temperature enough to sterilise it and make it usable.
>> They often will add those immersion heaters to the heat pump output for
>> room heating as well, which reduces the overall efficiency of the heat
>> pump just when it needs to be outputting its maximum - especially if
>> the heat pump is cheap and undersized - leading to almost no pump gains
>> at all and a shocking electricity consumption under very high output
>> conditions in very cold weather. Ground source pumps are generally
>> better in this respect.
>
> Perhaps you need to put the electric heating on the input air too :-)

Not when it's designed properly. Yes, I saw you smirking.

>> Scandinavian houses seem to use direct electrical heating or ground
>> source. Go figure.

On 19/04/2022 11:30, Theo wrote:
> With oil you need a 1000+ litre oil tank outside of the house, so I don't
> think that wins on the unsightliness. We've actually regained a good chunk
> of garden by removing our oil tank.

When I had my new mancave built I allocated 2m square to hold the oil
tank. It's in its own fireproofed room. It confuses all the delivery
drivers no end!

Keeping it in the dark I hope will help tank life, and it must be a lot
harder to steal from.

Andy