Boiler has no power after draining and refilling

Daboosa

Oil steam boiler MST396.

It needed maintenance. I turned off the switch. Drained the rusty water. Turned on the switch. Nothing happened. The Google nest thermostat shows "no power". Even the water auto feeder display was dark. Pressing the manual "feed" button did nothing.

First I thought it's the low water cut off stopped the electricity to the entire unit so I took off the safety valve and manually added water higher than the water level probe. Turned on the switch. Nothing happened. (Not sure if it need a reset or it even matters)

I checked the breaker box at the electricity main but nothing jumped there. (Although I didn't flip everything off and on just to make sure, maybe I should)

Does low water cut off stop power to the entire unit including thermostat and auto water feeder?

Thoughts? Thanks!

109A_5

Hello Daboosa,

Oops, what happened ? " Does low water cut off stop power to the entire unit including thermostat and auto water feeder? " It shouldn't but if someone wired things wrong… I think you may have noticed that by now.

If I had to guess from here I'd say the switch you used to shut off the system may have failed and did not turn back on. Or a wire was bumped and fell off. Someone with a multi-meter and knows how to troubleshoot wiring should be able to locate the defect quickly.

HVACNUT

Check the molex plug and make sure the control relay is plugged in all the way.

On more than one occasion I didn't have power after servicing and it turned out to be the switch itself.

yellowdog

Follow the path of power from the panel with a meter or a non contact tester. You will find where it is and where it isn't.

Daboosa

Thanks guys! I'll check the power switch next.

Is it possible the low water cut off was wired wrong to trip the whole circuit? Could that be the case and the system could still run fine for years as long as the water level never dips to trigger it? Does low water cut off need to be manually reset if that's the case?

Thanks!

Jamie Hall

Some systems are wired so that the low water cutoff will kill power to the whole system. Not the best way to do it… or is it? I think one could have a debate on that. Whatever, some are. And it iis possible that that cutoff is a manual reset, particularly if you have two low water cutoffs (the upper one should also trip the autofeeder, and be automatic).

109A_5

If the LWCO kills the power to the system and 'its self', how do you get the system to work in the first place ???

Daboosa

https://forum.heatinghelp.com/discussion/comment/1835587#Comment_1835587

Thanks! That's my system. Last night it's dark and I was tired. This morning I found the hidden manual reset button on the low water cut off. Pressed it and power kicked on.

Daboosa

My system is wired like that. The low water cut off still had an indicator light on though when power was out for everything else. I pressed the reset button on it and all is good now.

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1835685#Comment_1835685

So there's two Low Water Cut Off controls? One auto reset, one manual?

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1835676#Comment_1835676

Peerless boilers, at least in 2019, have a 120v LWCO that cuts off the 120v supply to the boiler and its 24v transformer. The LWCO is the power "gatekeeper". Of course, the LWCO doesn't shut off power to itself.

EBEBRATT-Ed

If you have a manual reset button on the LWCO on steam you need an additional LWCO that is not manual reset.

Maybe someone installed the wrong LWCO as one is all that required on steam AFAIN unless it was commercial