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Hi All,

Is it acceptable (building regs) for me to have a back boiler plumbed to a suitable sized radiator via thermosiphoning, and only attached to the hot water tank with a pump?

The problem that I have is that the bathroom (with airing cupboard) is the other side of the house to the lounge fireplace, so the pipes would run up 8' then along 20' then into the tank. I am assuming that this is not good for thermosiphoning (?), so instead i am suggesting that i put a radiator matched to the back boiler (8000Btu for example) in the bedroom above the stove, and have a pipe thermostat to switch on a heating pump. This will mean that during a power failure the back boiler will dump heat to the rad, but the rest of the time it will dump some to the rad, but most to the tank.

What do you think?

AB.

I don't think there'd be any issues with building regs. there (providing you do the actual plumbing OK). What you describe sounds plausible, and probably quite practical too.

Don't forget that you'll also need some kind of expansion facility - typically a small header tank above the highest point of the system.

I'd go for relatively small-bore pipe (15mm) for the long runs - it'll speed the water up, and cut your heat losses a bit - you may be wise to invest in 'Armaflex' high temperature pipe lagging - the ordinary stuff melts too easily!
(beware, it's about £3.50 a metre!)