On 2008-01-20 20:09:38 +0000, robgraham said:

Thanks David - headache will be that this is a traditional Scots farm
cottage and you will know how thick the walls are - and are usually
rubble in the middle so drilling holes for pipes is a bit of a
nightmare. Might have to think about microbore along the skirting.

Rob

May well not work because you may not be able to get enough water through it.

First thing is to calculate the heat loss and size the radiators.
Once you have the required heat output then you can calculate the
volume of water per second that has to pass through (using the formula
of mass x specific heat x temperature fall). The temperature fall
will be that across the radiators (12 degrees for a conventional
boiler, 20 for condensing). Using the amount of heat, you can then
calculate the mass of water using its specific heat.
1 litre of water weighs approx 1kg. so you can work out the volume per second.

Then refer to the pipe tables and work on the basis of a flow velocity
of no more than 1.5 metres/sec. It gets progressively harder to move
water faster than this in a small tube and noisier as well.

You can download a design guide from the Copper Development Association
web site www.cda.org.uk. Leaflet 150. 8 and 10mm tube will not
carry much heat very far, and you will probably need 4kW plus in a room
of that size in your part of the country.

If you are thinking that you might use gas, then the same principle
applies. Leaflet 124 is the one on that.