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Plumberpro, Home Appliance Technician
Category: Appliance
Satisfied Customers: 634
Experience:  Heating and hot water heating appliances experienced
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Wiring instructions the Honeywell ST9420C central

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wiring instructions for connecting the Honeywell ST9420C central heating programmer to a baxi 105he

Hi , are you using a room stat as well or just the programmer? If just the programmer, then run a 3 core cable from boiler to the programmer. Live and neutral from boiler to programmer. 4 out from prog( heating on ) into switched live in boiler

This will be number 2 in boiler . you may have to remove a small link wire between 1 and 2 in no clock has been used before
Customer: replied 2 years ago.

The boiler has got a 24 hour mechanical time clock fitted when I remove this I take it I will have to replace the links I took out when I fitted the mechanical time clock.


David Heath

Hi , no .I'm pretty sure the clock wire out is what you will need for the switched live, as old clock and new will both be doing the same thing , is switching on the heating. So don't replace the link. But put heating out from prog into boiler terminal 2
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