Wiser hub replacing Honeywell ST9400C & CM727

23 Sep 2020
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United Kingdom
Hi I am looking to install the Wiser 2 zone kit, I currently have Honeywell ST9400c controlling my hot water and Honeywell CM727 wireless thermostat controlling my heating,
The ST9400c is next to my boiler but the CM727 wireless receiver BDR91 is in my loft
Where would I install the wiser hub, is it on the existing ST9400c wall plate or in the loft where the BDR91 is?
Any help appreciated
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The Two Channel Wiser needs to be connected to the heating and hot water system wiring....


....so it would be impossible to use it to replace the Room Thermostat as there won't be any wires there relating to the control of the hot water system. It replaces the programmer that has both hot water and heating control wiring present.

The room thermostat can then be removed and a small wiring modification will be required to complete the circuit.
Thanks, I took the ST9400c off and there are only 3 wires so looks like I need to get another cable in and change wiring at my connection box
It appears then that you may only have the hot water control wired to the ST9400c and its central heating channel isn't used for anything, the central heating control wires having been moved to the room thermostat receiver instead. In which case you will only have wires connected to ST9400c N, L and 3.

If that is the case, you are right, rewiring to bring them both back to a central point is required.

Whoever installed the wireless thermostat should really have changed the programmer to a single channel version. Usually the wiring is left in place and the user told to leave the central heating control time permanently on.
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Yes you’re correct N,L & 3, I’ll check again to see if any old wiring was disconnected & left behind pipes
Thanks again for help

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