correctly sizing radiators for a ASHP

Have you worked out how many kWhrs of sunlight goes into a modest sized law in a year? And how many you might extract? And after several years of operation what the ground temperature might be?

No, I didn't think so. I suspect it's beyond you and all you can voice is false rhetoric. Trump would be proud of you.

A typical art student belief who hasn't a clue about the greenhouse effect and denial that CO2 is transparent to light but absorbs IR

You seem to assume many things, including a misunderstanding of the greenhouse effect.

Pretty similar. Because it's an air to water system, the wet side of it has decent thermal mass. So you don't notice the defrost cycles because the outdoor unit simply stops generating hot water for a while, just circulating the existing water. There's enough volume in the heating loop to keep going for a while as it does so. You don't notice the radiators going cold or anything like that.

I can't say I've measured them, but I'd guess a defrost cycle might be a few minutes an hour sort of frequency, on a freezing-fog kind of day.

Theo

No-one has actually been allowed to properly try it.

The one test well that was being drilled was stopped because it exceeding the artifically low limits set for earth tremors (headlined by the anti-frackers as Earthquakes), depite the surface effect being lower than a passing truck! The limits were clearly set to ensure that fracking would fail in the UK.

While I have not, I have seen articles stating that domestic GSHPs are likely to exhaust their heat supply in as little as 50 years.

A few days ago we got a leaflet through the door telling us that British Gas could install an ASHP for £4999. Some small print mentioned ‘depending on what we need to do inside your home’ (or words to that effect). A government grant of £5k was also mentioned.

The device shown was by Vaillant and the claim was it would last 20 years.

It would apparently be installed by a tattooed young lady from an ethnic minority.

I chucked it in the bin.

I confess I haven't, but after a search this is the first one I saw with real numbers and a reasonable study:

ROFLMAO!

For a boiler replacement I've been looking at my heat loss calculations that I performed 30 years ago. Since then various items in my property have been replaced or improved which has resulted in less heat loss. All those years ago I added multiple (5 to 10%) factors of safety to the calculations and assumed too high a temperature difference by a few degrees*. The radiators were also selected to fit in the selected space and rated just above the elevated heat loss calculation(s).

My original calculations for whole house heat loss was around 11kW but now closer to 8kW. This latter figure seems to be close for the average quoted for a 3 bed house in the UK (during February). My radiators are close to being 40% oversized, especially in the rooms used most for relaxation. I may/will use that to experiment reducing the flow temperature and hence return temperature and gain a few percent more efficiency in the condensing boiler.

Apart from the boiler replacement in a slightly different location and changing an open vent system to a pressurised system no other changes will be made to the rest of the central heating.

Yes, you did say otherwise.

Upthread as I have quoted you said "The colder it is the less a solar power station will produce." which is not correct.

I think we're on the same page though; solar power is great for running your aircon, but not for keeping the lights on.

Andy

Yes, it's rather unfortunate that heating installers have got away with 'finger in the air' heatloss calculations, and then ignored them and fitted the largest boiler they could. Those kinds of numbers sound reasonable - my own calcs came to 8kW losses, but the offical ones came to 5kW. I think there's some amount of leeway given things you don't really know (eg construction materials, air changes due to ventilation, complicated roof structures).

Theo

Who knows? The BG leaflet was a bit short on real information.

Where does the government always find its cash :-(

It is correct,

Let me spell it out for you.

Winter is cold, because there is less solar energy reaching the ground, for a shorter time per day. Therefore the colder it is, the less a solar power station will produce.

In summer, a cloudy day is a colder day, therefore the colder it is, the less a solar power station will produce.

Until Tin Lizzie and Kwackers got into Downing ST, the government always relied on pension funds and overseas investors (and a lot of pension funds there too) to buy the debt that HMG issued in the form of IOU's or gilts.

Suddenly that changed over one weekend.

Today has been cloudy nearly all day, and the solar farms will not be doing well. Yet it's unseasonably warm.

Sometime we get a patch of clear cold air from Siberia. It's _really_ cold, even though it's bright and sunny. The solar farms will do quite well.

Temperature is not the relevant factor.

But I think I'm banging my head on a brick wall here.

Andy

Winter is not unseasonably warm, Winter is when its cold. Winter is when solar output is at a minimum due to short days, and low azimuth of the sun

And it is the short days and low azimuth that are the reason for the low output, not the cold temperatures.

Andy