Best Of

What gave me/us the most problems? The panic of customers in the month of October. This is the month in my area where and when the weather would change, and all manner of need for our services came charging in all at once. I started to call the month of October "A month of Mondays."

@Intplm.

Yes October/November. They knew they had a problem and hoped it would magicly heal over the summer

Here is a resistance chart from the manual of the other model in the other thread I posted. Keep in mind this is for thermistor type sensors. Self resetting Snap type thermal switches are usually open (infinite resistance) or closed (low resistance). I believe 1/2 of the ARHL (Auto Reset Hi-Limit) is NOT a thermistor and actually is a Snap type thermal switch. Having thousands of Ohms resistance in series with the 24 VAC current path to the Gas Valve makes no sense.

I believe the dual sensor is (1/2) sensor is a thermistor (S1 on the diagram), so variable high resistance that changes with temperature, usually NTC (Negative Temperature coefficient), temp goes up the resistance goes down. The other (1/2) sensor is a (needs to be) thermal snap switch type (Auto Reset Hi-Limit, Orange / Gray wires) which when closed at room and normal boiler operating temperatures has a very low resistance, like less than 1 Ohm to support the load current of the Gas valve. At least that is what the wiring diagrams are telling me. You should have the original documentation, are they significantly different than my postings ?

You may have the wrong sensor. Or your new sensor is defective. If you prefer chase out the 24 VAC that powers the Gas Valve and see where it stops.

Additionally the flame proving time should be long enough for a digital meter to settle if normal voltage is actually present. So an analog meter or and indicating load (such as lamp(s) that I like) should not be needed in this case.

If you replace the Gas Valve you probably need to do a combustion analysis. A combustion analysis may not be a bad idea for a tuneup when you get it running.

I like the new o-ring seals vs. fiber washers.

it is a very old school hygromteter, i think it was in my elementary school science books that were published in like 1970 and i think one of the middle school science rooms had one. i'm guessing they've been around since the 20's or 30's. that tube in the middle fills with water and keeps the wick wet.

I am a boiler operator. Fire‑tube boilers are more suitable for low‑pressure (<1.8 MPa) applications in the 2–30 t/h range, while water‑tube boilers are typically used for high‑pressure, high‑temperature industrial processes. Neither type is inherently “better”—you select the boiler that best fits your specific process requirements.

If you have any questions, you can read the blog I wrote on my personal website：