ST9100C & Grant Combi 21e - thermostat wiring problem

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Hi,

I've recently moved in to a new house and am having difficulty with the thermostat.

I have a Honeywell ST9100C, it is set to run and the stat is calling for heat - but this won't fire the boiler, the only way to get CH on the boiler to run is to switch the boiler from timed to continuous, but then it is only controlled by the thermostat on the boiler, not the external one.

I have found a wiring problem with the ST9100C - the mains earth cable had been wired to terminal 1 on the back plate, rendering the entire boiler without an earth connection.

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Terminal 4 on the stat is wired to 19 on the boiler (CH Timed on)
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I'd appreciate any help, thanks!
 
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your roomstat is not wired up correctly. there is a link in 25& 26 on the boiler connections. that is why the roomstat is not working

ideally if you are not able to do it yourself you should get someone in.
much safer in the long run.
 
no because the switch wire from the Honeywell ST9100C (4) to 19 on the boiler switches the ch on.

25 and 26 need to go to a roomstat.

forgot to say the Honeywell ST9100C is not a roomstat its a timer.
;) y
 
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Isn't that inside the timer?

I know that is working as the demand light is on when I raise the temp on the stat
 
Sorry to bump, I also failed to mention that there is no voltage through wire 19 when the boiler switch is in the time position but there is voltage when it is in the constant or off pos.
 
The fault is at the Honeywell ST9100 - YOU MUST FIT A LINK between "L" and "1" - 9100 is a single channel timeclock with VOLT FREE CONTACTS!!

link L-1 all will work OK from there! ;)
 

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