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Test bypass low-water cutoff

gattu_marrudu
gattu_marrudu Member Posts: 26
edited December 1 in Thermostats and Controls

Hi there,

My furnace suddenly stopped igniting, obviously in the coldest day of the year so far.

I have a steam system with an Utica boiler controlled by a CycleGard CG400 low-water cutoff, a very simple Honeywell thermostat, and a vaporstat.

The system seems to respond when I turn on the switch. The LWCO LEDs blink on and off for a moment. The supply voltage on the LWCO is 28 VAC. So far so good.

I tried bypassing controls individually by shorting their hot connections, first the thermostat, then the vaporstat. The system still won't start.

Which leaves me with the LWCO. How can I bypass that control to verify if that is the problem?

It looks like the LWCO control already has problems. I see the auto-test LED turn on every 20 minutes, but the low-water amber LED never turns on even if I drain the boiler well below the minimum. That may be a separate problem (a serious one I'd say) but I'd like to be able to turn on the heat at least for a couple of hours at a time, watching the water level just in case, until I get a replacement.

Thanks for any help.

Comments

  • mattmia2
    mattmia2 Member Posts: 10,819

    start with an ac voltmeter at the ignition control, see if there is 24vac in to it.

    does the boiler fire or try to fire when you cut the ac power for a minute or so and turn it back on?

    is it gas or oil?

    the lwco probe could be in a section that doesn't drain or could be covered in sludge or foam that is keeping it conducting.

  • 109A_5
    109A_5 Member Posts: 1,566
    edited December 1

    Hello gattu_marrudu,

    " Utica boiler " is kind of vague if we know the boiler's model there is a possibility we can find the wiring diagram on-line. Sounds like you have a multimeter, measuring across each device only some should normally have 24 VAC across them, the power source (the transformer), and the load typically the gas valve and/or ignition module, LWCO terminals 1 & 2, a Damper. If any of the control, limit or safety switches are open they will have 24 VAC across them and the normal load typically the gas valve and/or ignition module will be 0 VAC resulting in no heat.

    All wiring intact ?

    Is there a Damper ? If so does it open ?

    Is it a standing pilot or an Ignition Module ?

    Amber LED, sounds like there is a LWCO issue or a water level issue (see below).

    From the CG400 Instruction manual.

    image.png
    image.png

    https://hydrolevel.com/wp-content/uploads/2018/12/CG400-Instructions-web.pdf

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • HVACNUT
    HVACNUT Member Posts: 6,282
    edited December 1

    What model LWCO?

  • gattu_marrudu
    gattu_marrudu Member Posts: 26

    Thanks for all the comments so far. It's 48F in the house and my brain is slowly thawing…

    The LWCO is a cycleGard CW400. The boiler is a Utica PEG150EID with a UT 1003-600A ignition module. It's an intermittent ignition model. There is a damper, with the switch set on keep open. The unit looks relatively new (it came with the house) and all wiring looks intact. I haven't checked each point with a multimeter yet.

    I also read this other thread for the ignition module:

    https://forum.heatinghelp.com/discussion/157289/spark-ignition-series-1003-600a

    Below is the wiring diagram for the whole boiler:

    1733064679_screenshot.png
    1733065079_screenshot.png

    Orange and yellow going to the damper are in contact. Following the diagram, if I jump white and black in JP2 inside the LWCO I should effectively bypass it. I tried that but the furnace still won't start.

    There is no power to the ignition module (measured between PV and MV/PV). Does it mean that ignition is bad, or rather the LWCO is bad (as power is coming through the LWCO)?

    Since I'm on a tight timing I am tempted to replace both LWCO and ignition rather than waiting twice the delivery time from trial and error. But if any of you guys has a hint, I'd rather go for for a more accurate repair.

    I will do more tests while I wait for answers, and will get back if I find something interesting. Thanks.

  • gattu_marrudu
    gattu_marrudu Member Posts: 26
    https://forum.heatinghelp.com/discussion/comment/1823587#Comment_1823587

    It's a gas boiler. It won't even attempt to start. Normally the ignition buzzes for a few second (intermittent ignition) until the flame comes up, but as of yesterday, nothing happens.

  • gattu_marrudu
    gattu_marrudu Member Posts: 26

    Also:

    1733067049_screenshot.png

  • gattu_marrudu
    gattu_marrudu Member Posts: 26

    It's fixed. The culprit was the flame rollout switch that was open. I reset it and the furnace went right on. I didn't even know it existed before I looked at the schematics.

    That was hundreds of dollars saved and a lot of knowledge gained, for the price of one night sleeping rough :)

    By the way, as a reply to my own question, it looks like to bypass the low water cut-off without bypassing the other controls I need to pull the plug from J1, and jump the two extreme poles (red and black).

    Thanks for all the comments! And also, kudos to Utica for making a very useful and readable manual.

  • gattu_marrudu
    gattu_marrudu Member Posts: 26

    @mattmia2 Good call about the dirty probe giving false negatives. I will inspect that next. When I first inspected the boiler after buying the house, the gauge glass was stopped from top to bottom with a column of brown sludge. I would expect the probe to be in similar conditions by now.

  • mattmia2
    mattmia2 Member Posts: 10,819

    the rollout switch doesn't just open on its own. A tech or you need to figure out why there was rollout.

  • neilc
    neilc Member Posts: 2,837

    and get or have a couple CO Detectors w/ digital readouts, you can press a button and see low level CO before alarms sound

    known to beat dead horses

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