correctly sizing radiators for a ASHP

More than I expected. I guessed 350W each So this guy is saying that rooms needs 1.6Kw, three rooms like that and thats your heat pump maxed out on 5Kw

Well, its not though is it. He's probably quoting/mistaking the output required to get the room from 5 degrees up to 20 degrees. Once it is above 18 degrees, it will only need a small amount of power to reach 20 degrees, unless it is a very poorly insulated room, which is unlikely. There is a lot of maths involved in getting the heat output correct before fitting an ASHP, and if insulation is poor, that should be pointed out, so the ASHP and radiators can be sized correctly to heat the house to the required temperature.

True but you size radiators to get from the 5 to 20 degrees.

Looking back on my calculations from many years ago one of my rooms was calculated at around the 1.5kW heat loss and the single radiator sized accordingly. With a conventional boiler of the time and with much higher flow temperatures the radiator is approx third of the size of the radiators fitted in that room. At the time the very large windows were single glazed - now double glazed and with insulation in the previous empty voids behind the frames.

Various control systems limit the flow of water through the radiators, or shut off or reduce the modulation on the gas boiler when the desired temperature is reached.

Despite the title of the video this guy is having a dig at a few Youtube heating engineers that say that ASHP do not work. He is advocating that if do the maths first and correctly size your system then ASHP do work well.

What this video probably confirms is that bolting a ASHP to an existing hot water radiator distribution, without modification and without existing underfloor heating, is unlikely to give acceptable results.

The specification on the label on the heat pump

Heating Capacity 15.3kW , COP 3.8

The latter two parameters are starred so likley to be under certain limited operating conditions.

Yes, it is.

He's probably quoting/mistaking the output

I dont think you understand heat loss.

My house was calculated to need 10kW to *maintain itself* at 19°C with an outside temperature of 5°C. Built to 2000 building regs for insulation.

I looked at a heat pump - it needed something like a 15kW unit on 3 phase power. £20,000. Cost of 12KW oil boiler., £1500 (then)

And yes, in very cold days it struggles to jeep the house warm

Indeed. My point being that houses need a lot of peak capacity to stay warm in very cold weather, and as with all things 'renewable' and green, the heat pump efficiency is lowest when you need it most. When there are low outside temps.

Ground source is better, because the soil deep down is a fairly stable temperature source.

NB I did the maths and so did a consultant heating engineer. In general I found that for my very large rooms around 50W/sq meter was needed to keep them warm My mistake was in not putting in 100W/sq m and a 20kW boiler in order to warm the place up in less than 5 hours. I leave the UFH on 24x7 in winter. If I switch the heating on at all, which I probably wont do that often this winter.

Modern homes constructed with 6+" of insulation and pressure tested with carefully controlled ventilation are obviously going to be better, but that home there was an old bay windowed Edwardian property, that has probably just got DG and cavity wall.

Hence the need for such large radiators

The point being that older housing stock needs a lot of heating, and a ASHP running off what - a 30A circuit, probably around 7kW, and only having a 2:1 power uplift when air temps are around freezing, is going to struggle.

And will need a lot of radiator. Which is why UFH is far more effective. Floors are big radiators

What he is probably saying is that if you just follow the hype and install an ASHP its not going to work very well,

Its a serious exercise in heating design and insulation

Ultimately I think we will move to ASHP, unless nuclear electricity is so cheap we just run heating cables under the floor. But you need uprated electricity feeds to the house - especially if you also want to charge an electric car. And you need massive rads if you don't have UFH.

What this means is that older houses are at a severe disadvantage. You can run 3 phase power into new builds, and you can, given enough garden, easily install deep ground source heat exchangers . And you can stuff massive insulation and heat exchange ventilation in. To the point where passive houses become possible

But older houses are neither built like that or equipped with decent electricity feeds, nor is the grid itself sized to cope.

In France, nuclear power makes electricity so cheap that they don't bother with heat pumps. Its direct electrical heating. IIRC my sisters house in Sweden was directly heated electrically as well. Nuclear plus hydro plus Scandinavian insulation levels ensured it wasn't expenesive

In this country renewable energy is so expensive and unreliable that many people who install heat pumps will be in for a massive shock, when the power cuts begin. And the grid will need a 3:1 upgrade at every level to accommodate all the electricity we will need, but be unable to supply.

Especially now we have the massively incompetent lapdog Rishi back on the 'green' bandwagon banning fracking.

I cant think of a better way to destroy a nation.

Yup. 3.8 is rather optimistic and utterly infeasible at low air temperatures*. Its likely to be half that at best when you need it the most.

And that is the killer. The colder it is the less the heat pump will produce.

The colder it is the more a nuclear power station will produce. The colder it is the less a solar power station will produce.

• "Your heat pump may not work as efficiently when the outdoor temperature falls to below -5 ℃. When the temperature outside is around

(

Given the jury is out on whether fracking is economically viable in the UK, with unknown, perceived small amounts of methane from fracking, you haven't been keeping up, have you?

You're a typical art student, making ludicrous claims you know nothing about.

The jury is out because research into it has been stymied. You say yourself the amount of gas that might/might not be produced is unknown, so how about we find out, eh? The Yanks seem to produce a lot.

With ASHPs making such demands as dramatically improving insulation and adding UFH, a large part of the UK’s housing stock is going to cost a fortune to ‘upgrade’, as well as upgrading the generation capacity and distribution network. And on a per-house basis it will cost a lot to run.

With a couple of blocking high-pressure areas this winter, on top of the rolling blackouts, things are set to look ‘interesting’.

And the benefits from all this are questionable at best.

Its extremely well known to within broad limits that fracking will release a given percentage of the gas there, and the gas there is a function of the shale size.

So we do roughly know, certainly well enough to asses commercial viability. Well enough to order its banning by whoever it is who has Rishis leash in their grubby paws.

And the sheer chutzpah of Rishis faux science 'until science proves its safe' is beyond contempt.

The words were probably written by an Arts Graduate Civil Servant.

Very different geology.

I wonder how a gas powered heat pump would fare? A gas ICE to both run the pump and top up the pumped heat.

That was my take too. Some people aren't able to take a balanced view.

It would take low grade heat and convert it into higher grade heat + bit more.

It may well not be viable to extract it, but is that any reason to ban someone from trying? You never know, they may be proven right.

Yes, what I meant was, how much better that a normal boiler while using the existing radiators, IOW how much of a saving in gas.

Err, it won't be stable as you progressively suck the heat out. Only light sandy soil will allow radiant heat from the sun to warm it up quicker and to a greater depth but that is the same soil type that loses its heat quickly in winter, naturally.