Honeywell DT92 thermostat, overiding central heating timer.

12 Oct 2011
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United Kingdom
I've just had new Worcester Bosch boiler installed with a timer for both the water heating and central heating.
The central heating is additionally controlled by a Honeywell DT92 wireless room thermostat.
The problem is that the thermostat overrides the timer. If the room temperature drops below the set temperature on the thermostat the central heating comes on, even if the timer is switched off.
If this a feature of the DT92 and to get more control I'll have to upgrade to a Honeywell 927 programmable thermostat, or has the boiler been wired up wrong?
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It sounds like it is wired incorrectly. The contacts of the DT92 should be in series with the CH output of the programmer so that you only get a demand for heat when the programmer CH output is ON and the thermostat contacts are closed.

Were these the existing controls before you had the new boiler installed? Whatever, your installer should have ensured that the system works correctly.
Many thanks for your responses
The boiler is a Worcester Bosch Greenstar 18 Ri and the timer a Plumb Centre EHE0200160 2 channel Programmer.
When the installer left, the system appeared to be working okay, and we have enjoyed 5 weeks of hot water controlled by the timer and hot water tank thermostat.
However, last week when we came to put the central heating on, initially it seemed to be working okay, but we came to realise that the heating would switch on and off controlled only by the temperature of the wireless room thermostat.
The thermostatic would override the timer like in frost protection mode.
I'm not sure if this is how it is supposed to work, because the next model up from the DT92, the Honeywell CM927 has a timer facility but still uses the same HC60NG receiver.
Thanks again
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Without checking how its wired in the wiring centre, sounds like it's wired up wrong, get the installer back to check it.

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