JohnMo

So is your heat pump oversized to allow this?

Definitely found that with mine, certainly once you get cycle times below about 10 mins, you may as well give up.

So that is just the restart hysterisis. Doesn't the lower pump speed, just drive a lower output of the radiators, and then drive shorter boiler cycles, as there is less to take the boiler heat away?

If settings don't give the behaviour you expect set them back to default. What thermostat are you using? Is it an on off one or opentherm?

Read an article the other day saying electric prices in the UK are set to drop like a stone. As our price is directly linked to gas wholesale prices, which due to the glut of LNG on the world market is falling, and due to fall even further. Several countries are reducing their uptake of LNG due to more renewables coming stream and less reliance on imported gas.

How do you do your schedule?

Unless you couple that with a battery. Then low and slow wins.

That's a strange lunch your cooking up.

Here's a few things to read UFH-System-Design.pdf UFH output calculation.pdf

If they are quoting a buffer it isn't an expansion vessel. A buffer requires secondary pumps, a volumiser doesn't. A buffer provides hydraulic seperation and therefore needs a pump(s) for the heating circuit. Samsung Gen 7 schematic don't compel the use of a buffer, if your are doing an open system. They show a volumiser on the flow to heating circuit. Cylinder size is basically worked out as follows, 45L per bedroom, plus 40L. Reheat time assuming 300L and a 5kW output will be around 1hr and 20 mins to 50 degs, assuming bulk average temperature is about 30 degs.

Out of the parties that doesn't agree has the design flare? They are right. For me it's my wife, I have a say, then I'm told what going to happen. Simple.

Generally never required with sensible design. What size? Good. So basically the design should look something like this. Two floors if the same design flow temp no mixing should be needed. If one floor needs a higher flow temp some mixing may be required, this should be fine with an electronic mixer not a mechanical one. But if well insulated upstairs should really need much or any heating. So I would be tempted to flow a single flow temp to both floors and balance as needed with flow rates. So next is system capacity. You will need at least 20L per min kW output of the heat pump. If you don't comply with that add a volumiser on the return line prior to tee coming back from cylinder. Then run open loop from ASHP on weather compensation. Alarm bell - if you are bigger that 6kW, find a different installer. Alarm bell installer talks about a buffer, find a different installer. You want an efficient system you want a heat pump that modulates to at least half your heat loss at -3, then the heat pump ticks away all day at 7 Deg outside and maybe above that. Would suggest you heat loss is is in the 2.5 to 3kW range from what you have said. If so a 4kW would-be good.

Stops it floating away when you screed?

I just used PIR (70mm) didn't bother with the expansion strip. It purpose is to make up the expansion and contractions of the screed, as the UFH temperature cycles. A second (minimal) benefit is a small thermal break, to decouple the floor. I get the impression it's for retrofit applications where flow temps can be high.

Chocolate, new wallet to replace the one stolen in Paris, socks. I'm easy to please.