On Sun, 10 Jan 2010 23:34:10 +0000, Calvin Sambrook wrote:

Presumably your system designer did heat loss sums for the extension.
You don't tell us much about it but let's assume it's a fairly normal
room built to today's insulation standards, not stupidly long and thin
or uninsulated etc. UFCH product from the major players claims about
100W/m2 which for most normal rooms works well. UFCH is getting a bit
like lego now, buy the standard bits, plug them together and it simply
works, so it's hard to see how the designer could have gone very wrong.

Your builder had more latitude to mess up, often they are not
experienced in exotic things like UFCH. The spacing between the pipes
is important as too wide a spacing limits heat output.


What's perhaps not so readily appreciated is that the length of the loops
of pipe making up the UFH circuits is important too. For example in a
recent installation one area was about 16m^2, and I needed 83 Watts/m^2
to heat it. With a 5C drop between flow and return and I'd have had needed
almost 1 bar to pump the required amount of water around a single pipe
loop - far higher than a typical central heating circulator ("pump") can
manage. However by splitting it into two loops it only requires about 0.16
bar.



--
John Stumbles -- http://yaph.co.uk

Fundamentalist agnostic