"John Aston" wrote in message
.. .

If anyone else is reading this thread and wants some background
information,
I came across Warmrite's "Manual Of Modern Hydronics" at
http://www.heatinghelp.com/pdfs/156.pdf


I didn't know that was on the Heatinghelp website, thanks for that.


Remember this USA/Canda, where things are done a little different. There is
a diagram of a UFH system taken of the fresh water of a cylinder. Potable
water running through the heat emitters. Not allowed here.

The majority of US houses have a direct fired water heater. There are
companies in the US who are aggresively selling systems which use hot
water from a DHWS heater to supply UFH (e.g., Radiantec). I think that
the wording of the Warmrite manual was probably chosen to avoid any
legal action from such companies. They do say that the preferred
approach to such "dual use" systems is to separate the space heating
from those containing domestic water using a small stainless steel
heat exchanger.

This 'dual-use' system is banned in some states and there are many US
heating professionals who are vigourously opposing it's use.