New, free central heating, was re: boiler sizing

Which is true of anywhere you fit it. Fitting it in a living room where you would normally sit watching TV etc. rather than doing anything physical is the best compromise.

Also variable speed pumps

That is why I mount mine in a hallway. It's generally a thoroughfare.

That's traditionally where they were, in my experience.

I went the whole way and we have individual timer/stats in every room - each with it's own motorised valve - only affordable as a) I did it all, b) Maplin were selling timer/stats for £14 each and the local B&Q were selling off their stock of motorised valves at half price for some reason.

How have you arranged the boiler call for heat?

Chris

The setup is that each timer/stat operates its own valve and the limit switches on the valves are all paralleled to call for heat.

The actual setup is a box in the airing cupboard with transformer and relays, so the timer/stat contacts only see a fully isolated 12V, while the valves are operated by and feed back 240V for the boiler and pump. There is a second box under the floor downstairs for the downstairs radiators. The two boxes are connected with triple and earth cable, for L, N, E and switched live coming back.

The reason for using an isolated 12V was that I could retrofit the thermostats using unobtrusive alarm cable running up the edges of door frames, only burying cables as each room becomes due to redecoration. It also meant that I could have a timer/stat in the bathroom, rather than having an uncontrolled loop in there.

I did worry about the effect of moisture on the timer/stat in the bathroom, but it has been fine for 18 years so far.

The downstairs box also has a triple and earth to the conservatory, where a timer/stat operates a valve and second pump, for the underfloor heating there, with its own blending valve to provide the right water temperature in the loop.

It's a Greenstar 2000.

- Mike