Troubleshooting two-wire thermostat system

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Old 12-21-19, 12:54 PM
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Troubleshooting two-wire thermostat system

I recently installed a new thermostat and ever since, the heat in the house wonít turn off (two wire system, we use a boiler with radiators to heat house). Set point is around 60 and actual temp right now is 80. Working on troubleshooting (already tried 4 different wire configurations) but itís hot!! As a reprieve, I was thinking about connecting the R and W wires directly together behind the thermostat (just twisting the non-insulated part at the end so itís electrically connected). My thought is that this may cause the signal to stop telling the boiler to give more heat... Will this cause any issues if I were to do that?
 
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Old 12-21-19, 01:36 PM
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Welcome to the forums.

In order to get heat..... the thermostat shorts those two wires together.
Open the two wires and no heat.

So you may another problem other that then the thermostat.
Do you have multiple zones in the house ?
 
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Old 12-21-19, 01:41 PM
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Yes but this thermostat only controls one zone. So what if I connected only one wire (like white to W or red to R), but not both? Then it would be open and heat would stop right?
 
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Old 12-21-19, 01:47 PM
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Then it would be open and heat would stop right?
Then it would be open and the heat should stop.
 
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Old 12-21-19, 02:03 PM
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Ok I just disconnected red from R and left white connected to W (ie should be open). Flipped the breaker back on, weíll see if the heat stops. Any ideas what the problem could be?
 
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Old 12-21-19, 02:08 PM
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Well that might be working but I canít tell because thermostat gets power from R apparently (there is no power now). Maybe Iíll try the opposite (leave red connected to R and disconnect white from W, leaving it open)
 
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Old 12-21-19, 03:20 PM
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It doesn't matter which wire you disconnect. Nothing works on one wire. It needs two. You need two wires to call for heat. If you have a digital thermostat.... it's probably a battery thermostat.

I don't know what your problem is. If you have multiple zones then you have multiple circulator pumps or multiple zone valves. Each thermostat controls a zone pump or a zone valve.

If you don't know what you have..... post some pictures so we can identify it for you.
How-to-insert-pictures.
 
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Old 12-22-19, 04:20 AM
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What make/model of new thermostat are you using?

If the "thermostat gets power from R apparently" then that leads me to believe it is a power stealing type (Nest, for example). Sometimes to steal power enough trickle current is leaked through to keep the heat on.
 
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