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.

Temporary bypass of ps-802-u-24 LWCO

In August 2012 I replaced my boiler, along with all associated controls. Unfortunately, the McDonnell & Miller ps-802-u-24 just sustained water damage from a first floor burst pipe.  It powers on, goes through its initial cycle correctly, but then (unnecessarily) calls for water - all despite visible damage on the circuit board.  I should say "called for water" as I ultimately decided to touch the discolored diode/transistor (?) whereupon it just about crumbled.

I ordered a replacement yesterday and, within the last hour, learned that the distributor didn't in fact have "4 in stock." I cancelled my order, not wishing to wait the "3-5 business days from M&M, then we'll ship to you." Instead, I will find a local supplier first thing tomorrow.

In the meantime, I've already sustained two, 32-degree (indoor) days and would like to temporarily bypass the control.

The boiler is a Utica Peg-C, intermittent gas, for a single pipe steam system.

According to the manufacturer's wiring diagram -as implemented by the installer- I believe the LWCO can be bypassed by temporarily removing its brown, red and white wires from inside the wire connections box, and connecting the red wire from the Pressuretrol to the brown (L1, hot) from the transformer?

Thanks in advance.


  • todd_ecr
    todd_ecr Member Posts: 91

    The low water cutoff is a safety device.  DO NOT under any circumstances bypass the low water cutoff.  Doing so can result in property damage, serious injury or death.
  • gazzerp
    gazzerp Member Posts: 14
    All is well...

    Thank you for your post.

    I fully understand the purpose of the LWCO -along with the remaining, in-series safety devices.  My intent was solely temporary; I would have been occupying the basement during its operation, beginning the clean-up process, and therefore frequently monitoring the water level.

    I used the past tense above as, this morning, I installed a replacement and all is well.  Thankfully, it was the only device to have been rendered inoperable.

    While I'm sure the damage was caused by the burst domestic water pipe, this incident has identified an exposure I never knew existed. That is, should the LWCO ever again register a "false" reading (regardless of how this could occur) then I see the benefit of having a "high" water sensor installed between the LWCO and the automatic water feeder I have.