Recent content by primping-swashing

What is the receiver you describe here? The ST6400C downstairs has only connections for live/neutral/earth and HW+CH on, so that can only control the HW and downstairs CH zone valves. The CM67 upstairs has only two wires so presumably also controls a single zone valve upstairs (and, as far as I...

We just moved into a house that has two heating zones. Downstairs has a Honeywell ST6400C programmer and a wall thermostat, upstairs has a programmer/thermostat Honeywell CM67. There are two loops and two valves, but it seems the upstairs zone cannot heat if the downstairs zone isn't already...