Replaced thermostat 3 times in a year?


Old 02-17-18, 08:28 PM
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Replaced thermostat 3 times in a year?

Hello all and thanks for taking time to read this. I purchased my house about 2 years ago and my 2nd floor thermostat has been a problem since we moved in. I have a old boiler system ( oil ) . I have two 120 volt thermostats one on the first floor and one on the second floor. And I also have a 24v thermostat in what was the garage but the previous owner had converted to a small studio apartment. I am confused because I did not know you could run both low voltage thermostats and line voltage on the same boiler? When I have tried to replace the 2nd floor 120v thermostat it would call for heat but then not turn off when heat was reached? Also it seems that my 2nd floor thermostat is tied to my 1st floor thermostat. Is that normal ? I thought they needed to run back to the boiler directly? If anyone can offer any advice I would greatly appreciate it. Thanks
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Old 02-17-18, 08:48 PM
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Welcome to the forums.

With a system like that.... the wiring can be completely random.
A lot of information is needed and if you don't consider yourself knowledgeable with wiring.... hire in help.

We need to know the wiring colors at all the thermostats.
We need pictures of where they connect at the boiler.
Do you have multiple circulator pumps ?

Old 02-17-18, 10:06 PM
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Thanks for responding, Iíve attached a bunch of pics of the boiler and the thermostats the 2 line voltage thermostats are worked using 14wire Romex, the one on the first floor is a 3 wire that is using the red and white to attach to the line voltage thermostat. It looks like from that box there is a 2 wire Romex running to the thermostat location on the second floor. The wire from the 1st floor tstat to the 2nd fl tstat is showing 120volts with the white as the hot and the black is the common. ( I used a multimeter to test this),
the low voltage tstat uses common tstat 2 wire I believe it is a 18/2, that wire runs back to the device mounted on the side of the boiler unit.
I tried to install a Honeywell round tstat on the 2nd floor and it burnt up the tstat . I was running another 120volt tstat in that location for about 6 months and it would work but when it called for heat it would stay on even after it got to temp,
thanks again

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Last edited by PJmax; 02-17-18 at 11:01 PM. Reason: cropped/enhanced/reoriented pics

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