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What is this thing on my damper?

riles246 Member Posts: 3
edited December 2014 in Strictly Steam
TL;DR Version: The very last picture shows something that is acting up, what is it?

My system is acting up again. I recently replaced the Honeywell ignition module with an S8610U, which was a direct replacement (wire for wire, including TH-W/24v posts) and it solved all of my problems.

However, I just came home after a few days away and the heat is not working again. I've traced the issue to the TH-W wire- when I move the 24V wire from the 24V post to the TH-W post, the system fires up. This bypasses all of the safeties, though (i.e. pressuretrol and LWCO), so I'm only running it with me sitting right next to the boiler so I can keep an eye on the pressure.

Before getting started, here is a picture of my boiler and its wiring box:

Thermostat/Thermostat Relay:
I traced the thermostat wire with a voltmeter. I am seeing 24VAC from the thermostat wire into the relay on boiler, then 24VAC coming out of that relay going into the pressuretrol (goes in as a gray wire, comes out as a red wire). So I know the thermostat is working. Also, when I switch it from "heat" to "off", you can hear the relay tripping and cutting voltage to the next step.

The next step is the pressuretrol. The pressuretrol is fed from a gray wire which comes off of the thermostat relay. I see 24VAC on the gray, which goes into the conduit for the pressuretrol where it connects to the pressuretrol switch, and then goes into the red wire in the pressuretrol. I see 24VAC on both the gray and the red wire, meaning the circuit is close, which makes sense since the boiler is presently at 0 PSI. This means the pressuretrol is not the issue.

Next, the red wire from the pressuretrol goes back into the wiring box and then goes straight into the conduit for the LWCO, along with 120VAC white/black. Both 120VAC wires are reading correctly, and I'm seeing 24VAC on the red wire. The signal from the LWCO comes out as an orange wire, and I'm seeing 24VAC on that contact too. This makes sense since there is plenty of water, and this means that the LWCO is fine.

Unidentified Object #1:
From the LWCO, the orange wire carrying 24VAC goes back into the wiring box and is connected to a new red wire. That red wire goes into the boiler and attaches to this unidentified object. This object has two connections- a red wire (which comes from the LWCO) and a black wire (which goes to unidentified object #2). I tested both terminals, and both have 24VAC. That means that whatever this thing is, it's working fine.

Unidentified Object #2:
From object #1, the black wire goes outside the boiler, around the back, and into unidentified object #2. Object #2 has two connections- black (from object #1) and red (ultimately the TH-W wire). I've confirmed that the black wire is carrying 24VAC, but the voltage does not come back out of object #2 in the red wire (TH-W). So, what the heck is this thing? It is located underneath my automatic damper, but does not appear to be connected to anything else either electronically or mechanically. It has a jumble of numbers but does have "200F" on it and it's near the exhaust, so I'm thinking some sort of temperature sensor?


Am I safe to bypass this thing so that I have heat until I can get a replacement?

Thanks in advance!