Steam boiler won't kick on. Voltage drop? Mystery!

nburgess

We have a Bunham Independence steam boiler. We've lived here for five years, and the boiler is about 20 years old. It's still working fine other than this one issue, and it's had maintenance, been flushed regularly, etc.

Ever since we moved here, we've had this intermittent issue, and it's gotten worse lately: the boiler will work, generate heat, and then either when it kicks off or sometime after (forgive me for not knowing all the terminology), it will basically go to sleep, and the thermostat will not wake it up. You can tell it's gone into this state because the LED on the low water cutoff goes dim. Then, if you press the manual feeder button, even for a split second, the LED goes bright again and everything turns on. If the thermostat is calling for heat, you'll hear an ignition within seconds. It will work for a while, and then it might keep working, or it might go back to "sleep." At that point, we'll notice the heat isn't on, go to the basement, hit the manual feed button for half a second, and we have heat again.

When we first moved in and had this issue, a plumber suggested we buy a new low water cutoff. So, we did, and we continued to have the problem. Same issue, same temporary solution of pressing the feeder button. Other plumbers looked at it and thought it was possibly sludge in the boiler messing with the LWC's readings, but then they looked at it and thought it was relatively clean. Also, the LWC does not show a red LED when this problem is happening--it's always just dim.

Recently the problem was getting worse, where it would happen a few times a day. I called in an electrician, and he replaced a bunch of wires and redid connections in the junction box. My theory was that the dim LED was showing that there was too little voltage getting to the LWC, and it might be a wiring issue. This WORKED... no issues for 3 weeks. The boiler would start up, shut down, do everything on its own as it should. But it started again out of the blue a few days ago. Same exact symptoms as before.

It seems like it's clearly an electrical issue, and the fact that rewiring made it get better for weeks makes me think we were on the right track. But why would it suddenly stop working again? And why, this whole time, as pressing the manual feeder button seemingly made the voltage increase and stay increased until the boiler shuts down, at which point it falls? It seems like the boiler doesn't realize the LWC is there until it's drawing more power, but we had this issue before and after replacing the LWC.

Here's an image of the boiler. I can provide closer shots of anything. The rust on and around the LWC is from an unrelated leak issue that was fixed a few years ago and didn't really seem to affect this (it looks fine inside).

Would LOVE to at least hear some theories on what could be going on here.

Oh, and the LEDs on the zone switching relay stay bright the whole time. It's only the one on the low water cutoff that goes dim.

EBEBRATT-Ed

I am an electrician myself but a plumber and an electrician may not be the best people to call. You need a service technician. You or someone with an electrical meter need to catch this when you are having the problem. With the thermostat calling and the boiler off with the dim light they need to trace the limit circuit and find where the problem is. It could be the low water cutoff or something else.

Big Ed_4

Check the dip switches , are they set to unit match ? After that , was the probe replace with the new LWCO ? Was teflon tape used ?

109A_5

Hello @nburgess
So this rusty box (the LWCO) has been replaced ? And the circuitry inside is corrosion free ?


Assuming the LWCO is not contaminated or defective, looking at a wiring diagram that may be similar to your system, the Yellow and Blue wires should have 24 VAC across them continuously. This needs to be verified when the LED is dim. The 120 VAC side of the transformer could have issues causing the 24 VAC side to be low. Someone with a meter needs to do some measuring when it acts up, and not move things when doing so. Moving things just seems to prolong the aggravation.

Or an alternative is every connection 24 VAC and 120 VAC from the LWCO all the way back to the circuit breaker panel should be thoroughly inspected and maybe replace the service switch, maybe even the circuit breaker.



http://bostonheatingsupply.com/Burnham/Burnham Independence I&O Manual.pdf

mattmia2

Anyone replace the water feeder? Sounds like the contact that tells the lwco that it is done feeding isn't making when it finishes feeding.

mattmia2

Or does the feeder tell the lwco it is done feeding or does the lwco just go on the water level? they hydrolevel instructions don't show schematics, just ambiguous terminals wired together.

nburgess

109A_5 said:

Hello @nburgess
So this rusty box (the LWCO) has been replaced ? And the circuitry inside is corrosion free ?

Inside is corrosion-free. Thankfully that rust is all on the surface. It looks bad, but the issue pre-dates the rust, and didn't really get worse after.

Thank everyone for your input!

Right now the best theory I have is that the transformer might be damaged from years and years of crappy wiring. The electrician who was here could not test it while it was not working, because it was fine at that moment, and I can't force the problem to happen. I can test it myself next time it happens.

@Big Ed_4 I'm not sure if the probe was replaced, but the probe was inspected last month, for what it's worth.

@mattmia2 I don't really know anything, but I think the LWCO just goes by water level. As far as I know, if the LWCO detects low water, a red LED goes on, which is not happening. The way it's (not) working right now, it seems more like the boiler doesn't even think the LWCO is installed.

Intplm.

@nburgess

Ah yes! The transformer. Yup. Was thinking the same thing. Hopefully replacing it will do the trick


And if all else fails......years ago, and this is a long shot. I had a customer who was at an odd spot in their neighborhood. There was no transformer on the poll nearest their home. The utility company came and corrected this by adding or replacing a transformer at the street.
This was a long time ago as to which one they did (replace or add I'm not sure) but this similar problem as yours went away. Some food for thought.
Hope the transformer replacement on the boiler does it for you.

Sootmaster

The back of the low water cut off where it connects to the probe needs to be clean and Brite for the control to get a good ground connection to the probe. The dim light makes me think something is up with that and then when you come along and "jiggle the handle" by hitting the feed button its enough to get the connection back. 

Probably not related, but I would check the pigtail on the high limit. When they are partially blocked they can give you some mystery problems like shutting down and then coming on again many hours later.

pedmec

I would cut out the molex connectors and go right to the screw terminals. my guess is the or1 connection is loose in the molex connector. Hitting the manual feed is just causing the wires to move as its a quick opening valve and the water pipes generally move due to the quick opening of the solenoid water valve in the water feeder.