In article
, Lee
Nowell writes
Hi,

I have a relatively complex setup and was wondering if anyone had any
views on the best way to wire it all up... Also, any advice on whether
a wiring centre is a good idea as they seem to be very expensive given
what they appear to be....

Setup is....
-----------------
3 x radiator heating zones timed centrally and operated by 2 port
motorised valves
1 x towel rail heating zone timed centrally and operated by 2 port
motorised valves
1 x hot water tank heating timed centrally and operated by 2 port
motorised valves
1 x secondary hot water loop timed centrally.
2 x underfloor heating zones with 2 wire actuators, pump, manifold,
controlled by a prog room stat
zone 1 has 1 actuator
zone 2 has 5 actuators

All ideas appreciated.

When I set up my system I did it with 9 zones (1 per room) but was
frustrated with the lack of multizone controls available at a reasonable
(or unreasonable) price.

In the end I have grouped rooms into 3 zones and used Honeywell
programmable stats to control the zones with TRVs in rooms not currently
directly stat controlled. The system is not without its problems however
as the demand from the stats is not synchronized[1], meaning that one
zone can call for heat and be satisfied just in time for another zone to
call for heat. The staggering of the zones can cause repeated light load
firings of the boiler which are inefficient and wasteful[2].

Your life will be made a lot easier if you have some kind of thermal
store on the heating side of the system, that way if one of your small
zones kicks in it doesn't need to fire the boiler to get heat. The last
thing you want is your boiler (which I assume is large) to be short
cycling repeatedly to satisfy the demand of a towel radiator. If you do
this, you don't need to synchronise your controls meaning you could
break the system down into smaller and more manageable blocks. You could
use a PLC to control those sub-blocks but I don't know of a controller
that will do the job as a whole.

If you don't have the hot water linked to your store then you can still
have the heating side flow at a temperature that suits best efficiency
for a condensing boiler.

I think your system is too complex for a single wiring centre to handle,
I would wire all your controls back to a single point and grow your own
wiring centre using a large shallow electrical installation panel filled
with DIN rails and rail mounted terminals, leaving plenty of space for
other DIN rail goodies to be added at a later date. Document the system
very well.

[1] Up to 4 Honeywell wireless programmable stats can be synchronised in
one of their moderate systems but there was I reason I didn't like it. I
think it was an insistence that you use RF controlled radiator valves to
control the heat.
[2] Made worse by Honeywell's (compulsory) proportional control system
which forces the boiler to be cycle at least 3 times an hour when the
temperature is in the proportional zone.
--
fred
BBC3, ITV2/3/4, channels going to the DOGs