HughF

This…. I’d ignore it and just crack on.

Everyone on our terrace has done rear extensions - no-one had a PWA, we just got on with it

Couldn’t see the add-on coils available separately, but their pricing is certainly attractive.

I already have the TS, 500ltr jobby (although it’s really a buffer as it doesn’t have a coil in)… options are cut it open and add a pair of stainless steel pressure washer coils in series, cut it open and add my own coil (I have a big enough lathe to swing a suitable former), or do dhw with a shunt pump and a plate heat exchanger and flow switch… I do like the coil idea as it doesn’t need moving parts.

Having to play catchup only affects COP if you have load compensation adjusting your LWT upwards to speed the recovery... If the recovery method is as simple as 'room is below setpoint, turn on heat pump' then the LWT will sit at the same point on the WC curve as if the HP was already running. In fact, it might end up running at a greater COP because it isn't cycling, instead running into a cold start scenario.

Anyone got an idea on the coil size in this? I’m looking to make/find/buy a coil that I can add into a 500ltr thermal store that will be heated by a chp plant, with a view to providing dhw through this coil. A 50m length of 22mm gives me a little over 3.5m2 of surface area, ideally I’d like a bit more than that.

I’d have gone for one if it was available when I did my conversion…. Be nice to have something in the cylinder cupboard that was the same size as the vented that came out.

Yep, just watched the video. Standard thermal store with a coil for dhw. Could do the same with a small direct cylinder, a phe, flow switch and shunt pump.

Yep, manufacturers data sheet…

I’d pick the unit with the widest modulation ratio, ignoring the type of refrigerant used.

Thinbed foam popular for internal walls in NL too

Split if you’ve got a long (>20m) pipe run externally…. Personally I wouldn’t bother with the f-gas bod and would just get on with it, but then I’ve got the gear from doing r290 mini splits and r134 cars. Monobloc is better in that you don’t need to find room for any internal components (provided you don’t get a Samsung )

The other thing to be aware, if your heat pump only had a dhw valve live (or a heating valve live) output, instead of a separate switched live for each valve, you’ll need some relay voodoo to control the 2x 2 ports. luckily mine has both, but I ended up using a 3 port anyway because it was already on the cylinder.

Yep, I figured most people will be running with radiators, hence my statement…

Best controls (room stat will auto-adapt your weather comp curve for you, yes I know Mitsubishi also has auto adapt). Best backup if you’re an installer (vaillant take care of it all)