In article
, Lee
Nowell writes
Thanks very much for the reply.

The trouble I have is that I am not confident enough to grow one from
scratch. Whilst I think I understand the basics and logic, the wiring
bit (e.g. use of PLC/ relays) is a bit beyond my comfort zone...

Also, from what I can see, I have an additional problem to yours in
that I need to run the UFH with seperate pump and actuators in
addition to all the zones.

Maybe I could split the problem into 2
- UFH
- Non-UFH

and wire the demand from each in parallel to the boiler? Not sure
whether that resolves the relay problem though - I'm not sure why I
need them at all to be honest...

You'd might be surprised at how simple the wiring can be.

Yes, you can separate that UF and conventional heating, that would be a
sensible place for a break but unless you use a truly synchronised
controller for the 3 conventional zones you are likely to run into short
cycling problems which may not be obvious but will stress the boiler
unnecessarily.

As I said, you could make this a lot easier with a bit of thermal
storage in the heating loop but it sounds like you have it already built
and aren't keen for that kind of change.

Relays can be a handy way to combine demands that need to be otherwise
isolated eg. in your case, where you have a pump for UFH and one for
conventional, using relays would let you combine those 2 demands to call
for heat at the boiler without switching on the pump on the other
circuit at the same time. Shout if you want a circuit.

Have you had a look at the uk.d-i-y heating wiki?
http://wiki.diyfaq.org.uk/index.php?...tegory:Heating
--
fred
BBC3, ITV2/3/4, channels going to the DOGs