Boiler won’t shut off despite reaching desired thermostat temperature

ryanhare37

Hi everyone,

My knowledge about my one pipe boiler and steam system is minimal. I recently had a gas fireplace installed, in the process the workers installing the gas line from piping that goes to my furnace accidentally caused a disjoint in the thermostat wiring to the wire that goes to the furnace. I reattached the wiring but since then my furnace will not shut off when it reaches the desired temperature on thermostat or even when I turn thermostat to “off.” I assumed I re-attached the wires incorrectly and have tried several different combinations with the same result. The wire to the furnace has a red and white, the wire from thermostat has two whites. I feel like I have tried every possible attachment combination (maybe not?). Is it possible the wiring or unit are just bad or short circuited to due the tampering? The thermostat and wiring are very old. I am thinking the easiest solution may be to just have new wiring and unit replaced altogether, but my hunch is it may be a very simple fix? I appreciate any advice or help.

Thank you,
Ryan

KC_Jones

There is a high likelihood they shorted the wires from the thermostat and now it’s acting like a continuous call for heat. If that’s the case it needs rewired, but probably don’t need to replace the thermostat.

ryanhare37

Okay, thank you very much for the help!!

Jamie Hall

It should be a simple fix. if your thermostat has just the two wires (they should be white and red, but no matter) it is, basically, just a simple switch.

So.

Start with the red and white wire from the furnace. The furnace should turn on when the two are hooked together, and should turn off when they are separated (best to do the hooking together and unhooking with the power off... although if you really know what you are doing you can get away with doing it live). Does it pass that test? If the furnace runs whether or not the red and white from the furnace are hooked together, it is likely that there is a short between the red and the white wires. It is usually easiest to run new wire rather than try to find it. If it passed, now hook the white wire from the thermostat to the white wire, and the other thermostat wire to the red wire. With the thermostat off, does the furnace run? It shouldn't. If it does, you either have a short between those two white wires from the thermostat or the thermostat has a problem. To find out, take the thermostat off the wall and unhook the two wires. Leave them separated. Now does the furnace run? It shouldn't. If it does, at this point you're pretty sure to have a short between those two white wires, and the simplest thing to do may be to fish a new wire pair through. If it passes that test, hook the thermostat up again and leave it off. Dos the furnace run? It shouldn't, an if you've gotten this far it's likely the problem is in the thermostat somehow.

JUGHNE

If you disconnect the wires from the tstat does the boiler stay on? If so then disconnect the wires from the boiler....does it shut off then?
Can you post a picture of where they "disjointed" your wire?

They actually owe you for this grief BTW.
Probably do not want them to "fix" it though.

ryanhare37

Thank you for the thorough response I’ll try this procedure!

ryanhare37

Thank you, I disconnected them all, attached is the photo. The red and white over blue pex is coming from boiler, two whites split are coming from thermostat

Intplm.

When you did this, what happened?

ryanhare37

It stops running when they all are disconnected, however I turned the power off first before disconnecting them.

mattmia2

How did you splice them when you re-connected them? Did you use a wire nut or something or at least some tape to keep them from shorting?

JUGHNE

My suggestion was to do that in 2 steps.
1. Remove tstat and disconnect wires at wall.......do you still have the burner?

2. Leave the tstat removed as above and take apart the splice we see in your picture.........do you still have the burner on?

Can you show us where/how the cable was cut by FP people?
Or did they just pull this connection apart??

Jamie Hall

ryanhare37 said:

It stops running when they all are disconnected, however I turned the power off first before disconnecting them.

OK,,, but what about the rest of the troubleshooting steps I gave you?

ryanhare37

All those steps were spot on! I figured it out following that process, I didn’t suspect the thermostat since wires were clearly disconnected and seemed to be obvious problem, however somehow the thermostat shorted. I had to go through whole process in the steps you gave to figure it out. After i replaced the thermostat, everything is functioning great. Thanks to all for the help,

Jamie your steps were perfectly explained, and troubleshooted the problem for me. Thanks so much for the thorough reply! I am very appreciative!

-Ryan