Multi-zone thermostat control on old gas-fired boiler

Jeff Lawrence_25

SR502 control.

Ed_57

Multi-zone thermostat control on old gas-fired boiler?

Hi --
I have a problem that I thought would have an easy solution,
but I haven't found it yet. Two years ago I split my heating system into two zones (1984 100000 Btu Hydrotherm unit, 1911 House with a monoflow section now on one zone and a two pipe section on a second zone). The zoning was accomplished via the addition of a circulation pump for power the new two-pipe zone, not by adding a control valve.
I would like each thermostat to be able to fire the boiler and switch on it's respective pump. The latter is easy, but the former has proved difficult.

If I hook up voltage from both thermostats to the gas-control valve, the application of voltage from the second thermostat causes it to close. So now only the colder zone controls the firing of the boiler, the second thermostat simply turns on the pump, and if the other zone calls for heat too, everything is great.

I need a control board that will interpret the signals from the thermostats, close the voltage to the gas-valve to fire the boiler and independently switch power to the pumps when heat is called for from either thermostat. Does such a beast exist? Where can I find one? Or do I need to build one myself with radio-shack relays? I worry about doing this for reliability -- I don't want my home-made board to fail after a year or so... My local supplier looked at me blankly when I described this and I couldn't find anything in his catalog.

Thanks anybody!

Unknown

As Jeff says,

a Taco SR 502 relay should fit the bill for you.

Dave