HONEYWELL ST6400C / ST6450B Programmer wiring changes Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[marek]

Hi,
Can anyone out there tell me if the ST6400C is interchangable with an ST6450B programmer or do you have to change any of the wires. They look pretty identical. I wanted to check before replacing my faulty ST6400C with a ST6450B
Many thanks in advance
Marek