Heating Control

6 Feb 2009
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United Kingdom
can anyone advise if it's possible to change a prog. timer from a 1 channel to a 2 channel? if so, will there be wiring problems? i am considering a honeywell st9400c prog and a cm927 wireless prog thermostat.

current setup is a potterton combi he30 directly connected to honeywell st6100a1001 (1channel) programmer. hot water is instantaneous on-demand. there is no thermometer gauge on the boiler to indicate the temperature.

thinking of replacing the prog with a st9400c and cm927 to control the heating temp. in so doing, how can i ensure hot water on demand? any wiring problems? any advice is greatly appreciated
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All you should need is the CM927.

This will time the ch and control the room temp.

The HW should be instant all the time and needs no timer on it, as long as you wire the 927 properly into the external controls terminals.
thanks gas4you for your clear advice.
by external controls terminals i take it that you meant the honeywell junction box.
may have to come back to you on wiring just to be sure. hope you won't mind.
you should not have a junction box, if it is still there, your wiring is highly suspect
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Slowboat what do you mean there is nothing to indicate the temp is it a potterton performa 30HE do you currently have a roomstat
is the wiring highly suspect bengasman? i thought the junction box is to facilitate easier wiring between the boiler and the programmer, is it not?
Why is that bengas?

May have mistakenly interpreted the op as referring to the wiring centre.
The st series timer probably gave me that idea.
i don't install poxis for obvious reasons, but i do seem to remember they come with a built in timer, or at least can use one.
this would be a whole lot easier than hooking up some external timer.
namsag, i was wrong. actually there is a temp indicator. it is not in a gauge format. the boiler is a potterton performa 30he with 2 dials for hw and cw temp control respectively. presently, there is no roomstat. i thought gas4you suggestion of a cm972 sounded good.
of course all advices will be greatly appreciated.
Yeah i was gonna say what do you think the pretty lights are for :LOL:

Leave your junction box there take a LNE from fused spur into it then from it take a LNE to your boiler LNE connections on terminal strip.
Also take a LN to the receiver unit of the honeywell stat,
Then from boiler terminal strip connections 1 and 2 take a wire to honeywell receiver connections A and B if i remember correctly.
Flex used to the boiler should be .75 heat resistant

And you dont need your existing clock
yeah! those pretty bright red lights. :LOL:
thanks namsag for your clear and concise instructions. i will certainly give it a go. may have to trouble you if i get stuck

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