Anybody got any experience of installing / operating this kind of heating. It's a 2 storey cottage and I'm considering installing 2 circuits (one upstairs and one downstairs) using a single 15mm pipe in one radiator and out the next. One of the reasons for this is that the walls are 2.5 feet thick. It will be fed from an eternal oil fired combi boiler.
That's not quite what a single pipe system is. Start by imagining a large loop of pipe with no radiators on it. Now you tap them in to the loop, but without breaking the loop. If you look at it like an electrical circuit, each radiator would seem to be shorted out by the loop, but that analogy is wrong as the radiator can be looked upon as a much thicker pipe which will therefore take the majority of the flow unless restricted by the valves.
Selection of radiator sizes is much more critical than with a parallel pipe system. Balancing is then done per loop, not per radiator. You should take into account the falling average rad temperature around the loop when sizing radiators.
I think you might struggle to find plumbers nowadays who understand single pipe systems, at least in enough detail to design one.
I thought the reason the radiators heat up is gravity feed, i.e. the cold water 'falls' into the pipe after the radiator and 'rises' into it at the beginning by virtue of the differing density. This would fit in with my experience (I have a one pipe system which I'm planning to be rid of) where the pipework all gets hot well before the radiators do. It's not a great system as Andrew said as there is a temp drop around the circuit.
To be honest there's not much more work involved in making a hole big enough for a pair of pipes compared to a single (again I have some experience as my walls are 2' thick so you're only ahead by 6"). It will then be easier to balance, more efficient/effective and any plumber who comes in subsequently will be able to work out what to do. I had real problems with mine when I had to change some rads due to them rusting through, ended up having to sort it myself.
Incidentally could you point us all in the direction of your boiler supplier, I would rather nbot have oil but the idea of having an "eternal boiler" strikes me as a good one!
Fash
There are two single pipe systems - one where the radiator sits on top of the pipe and would be connected via T pieces, and the other where the radiator is in series with the pipe and would be connected using elbows. It's the latter that I'm interested in.
Never seen or heard of this. You couldn't turn a radiator off, for one.
You've got internal walls 2.5ft thick in a cottage?
Even then I can't really see what saving you'd have since a one pipe system still has two pipes - it's just how those are tapped off to the rads which is different.
Both were common in the '50s and '60's. The series type was often seen in public buildings and schools - with cast iron pipes.
The later was often retro fitted in the '60's as a package. A house I work on has this. It isn't great - but not worth changing. Must have been installed in the Wimpy house in the mid-60's.
Long time ago I had a rented flat - part of a large house - with a communal heating system like that. Gravity circulation and the boiler was a non electric type - complete with clockwork timeswitch. The pipework was a work of art with beautiful welds in places. It was only designed for background heating of 55F on a cold day - and worked very well. Installed in the early '50s, IIRC.
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