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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 19079
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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I have an old boiler in floor heating system in the house I

Customer Question

I have an old boiler in floor heating system in the house I rent. There are 4 zones each controlled by a thermostat. There are, naturally, four "relay" boxes with small slider on the top.
The problem is that the system does not operate according to the thermostat. I understand these levels can stick. One time when the thermostat was turned off and I left the house, when I returned a few days later it was 100 degrees and it has consumed 10% of the propane tank. I manually slid all four sliders to the off position, but suspect one came on automatically one time.
Question: If I replace these four zone relays, will that likely fix the problem? And how much would it cost to place them? ( I have a picture of the relay boxes but can't upload them on an initial question.
Submitted: 6 months ago.
Category: HVAC
Expert:  Rick replied 6 months ago.
You have to determine the source of the problem. It could just as easily be a bad thermostat or a dead short in thermostat wiring. Go ahead and post your picture by clicking on ADD FILES next to the SEND button and we can go from there. A couple pictures of the boiler and piping might help too
Customer: replied 6 months ago.

did you get the pic?

Expert:  Rick replied 6 months ago.
Ok, those aren't relays they're zone valves. If you moved the lever to the notch then you've permanently opened them manually.
Expert:  Rick replied 6 months ago.
If they were in the manual open position then that would explain the heat running wild
Expert:  Rick replied 6 months ago.
I probably should edit the previous post. They aren't permanently open in that you can move them back to automatic operation.
Expert:  Rick replied 6 months ago.
To be clear the proper position for the lever (so the zone valves function as they should) is not in the notch
Customer: replied 6 months ago.

Right. They were never in the notch. That I understand is a permanent open. I moved them to the right away from the notch, which I assume is closed. But it seems that one came on despite this fact, and the fact that all thermostats are turned into the lowest position. Also the level doesn't seem to move smoothly. So I suspect that this "box" will have to be replaced?

Expert:  Rick replied 6 months ago.
To the right is manual open but that depends on how the head is oriented. Was it only 1 zone that ran wild?
Customer: replied 6 months ago.


Expert:  Rick replied 6 months ago.
Ok so you need to determine if you have a bad zone valve or a bad thermostat or a dead short in the thermostat wiring between the thermostat and the zone valve. Are you onsite so we can do a little trouble shooting?
Customer: replied 6 months ago.

Not onsite. But I will contact you when I have access and a bit of time to do it. The thermostat seems a new model, and the runaway heat only happened once. However, none of the zones have operated truly well or accurately controlled. I assume there is a time delay for the system to turn on and off, but it seems worse than expected. This winter, before I knew about the notch, the system turned off and would not turn ON in any zone at all despite all thermostats being turned fully up.. Then suddenly it came on the next day. Thanks for the help so far.

Expert:  Rick replied 6 months ago.
Radiant heat is very slow to respond and is never used with a set back/programmable thermostat for this reason. Even so it's much more efficient that other type of hot water heat even with a programmable thermostat. So the temp should be set at given temp (usually 68 since it feels warmer than with heat that heats the air not the objects in the room). I'm online until ~7 pm EDT and back in the morning around 8 am