Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Weird symptoms: related to LWCO?

Ken C.
Ken C. Member Posts: 267
I was called to the house of a customer with a gas-fired steam boiler. His automatic water feeder wasn't working. My meter showed that there was only 10 volts going to the feeder (it was a 24-volt model).

The low water cut off was getting 24 volts, but it didn't always shut the burners off when the water level was drained down. It was a McDonnell Miller probe-style LWCO with a test light. When pressed, the amber light glowed brightly, which indicated a grounded probe, according to the troubleshooting chart.

During one of the times I drained the water down, I heard a sputtering noise. It was actually the burners running, but not running very well. The homeowner said the burner runs normally when the water level is full.

I'm wondering if a grounded (or intermittently grounded) probe could be the reason only 10 volts was going to the water feeder? Could it also allow the main gas valve to partially open, hence the sputtering flame?

By the way, the MM literature mentioned that chemicals may need to be added to the boiler water to maintain conductivity. Could someone please elaborate on this (what product/chemical, when or how often would it need to be added, etc.)

Comments

  • Tony_8
    Tony_8 Member Posts: 608
    Probes

    Need to be visually checked and cleaned periodically. Don't depend on the test light. The switch contacts are in the box with the lights on it, so if it's only letting 10 through it's probably not the probe itself. I would probably replace the whole LWCO. It doesn't sound safe to me if the gas runs when the LWCO should've killed it.
  • Ken C.
    Ken C. Member Posts: 267
    I'm changing it

    I will be returning there tomorrow to replace the whole LWCO.
This discussion has been closed.