Zone won't heat unless the other zone is also turned on


Old 01-25-16, 04:23 AM
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Zone won't heat unless the other zone is also turned on

I live in a home with an electric hot water boiler heating system with old school Radiators. There are two heating zones, one for each floor. Everything worked fine when I moved in. Each zone heated independently of the other.

A friend offered to replace my main floor thermostat with a programmable one. When he did it seemed my heat stopped working on that floor. After experimentation, I figured if the heat was on upstairs, the down stairs heat would also kick in.

I put the former thermostat back on in hopes that this would fix the problem. It did not. I switched the upstairs and downstairs thermostats just to see if it changed anything. It did not.

The only wires in the thermostat are a red and white wire. It doesn't seem like we could have messed anything up. ideas on how to fix it.

(If it makes any difference I have to heat the upstairs more than comfortable so that downstairs reaches a comfortable temp.
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Old 01-25-16, 04:44 AM
Join Date: Mar 2006
Location: Wet side of Washington state.
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What is with this term "old school"? Why can't we have some new school items? Why do they have to have any reference to school, old or new? Why can't you simply state that you have cast iron radiators?

Rant over.

Do you have separate circulator pumps for the two zones or a single pump and two zone valves? Obviously when your friend changed the thermostat he inadvertently did something to stop the system actuation from the thermostat signal.

Now your description of the downstairs zone heating IF the upstairs is also calling for heat reads like you have a single pump and zone valves. It also seems that the downstairs zone valve is opening, perhaps is always open, and this allows water flow whenever the upstairs thermostat calls for the pump to operate. This could be as simple as a failed "end switch" in the downstairs zone valve. It could be a relay failure as well depending on the type of zone valve and or interface between the thermostat, the zone valve and the circulating pump.

Several pictures of the control box(es) with the covers removed that are connected to the pump(s), thermostats and zone valves (if present) will help to narrow this down. Pictures need to be well lit and in focus or they are useless. Using a separate hosting site is with high definition pictures and the public URLs posted here is preferable to direct uploading to this site.

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