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LWCO on hydronic boiler

Jeff W_2
Jeff W_2 Member Posts: 57
in THE MAIN WALL
Has anyone used the McDonnell Miller Guard Dog (RB-24) LWCO on a Vitodens 100? If so...do you know which harness is compatible? Thanks in advance...

Comments

  • Paul48
    Paul48 Member Posts: 4,469
    FYI

    Regarding the ground wire http://www.weil-mclain.com/en/multimedia-library/pdf/weil-mclain-pdf/service-bulletins/SB0302.pdf
  • CMadatMe
    CMadatMe Member Posts: 3,086
    edited August 2012
    Why?

    Unless you have an inspector that hasn't a clue its just a Christmas ornament. Boiler will not fire unless you make the flow switch. . There should be a wiring diagram on the front panel of the PPM dependent on the application..Shouks be using a 120V LWCO and have it cut power at the junction box.

    There was an error rendering this rich post.

  • meplumber
    meplumber Member Posts: 678
    Concur with Chris

    A LWCO is not necessary on the Vitodens in most jurisdictions, except under certain conditions. Viessmann even has a letter and Third Party Listing information that has been accepted when we have used the Vitodens 200 in commercial/institutional installations.



    If you have to use one, I prefer the Hydrolevel 170. It simplifies the wiring, simply killing 120v to the boiler in the event of a low water condition.
  • Jeff W_2
    Jeff W_2 Member Posts: 57
    Thanks guys...

    I got the letter from my Viessmann rep...
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Unless you have an inspector that

    My installing contractor put a M&M RB-122-E LWCO on my W-M Ultra-3. It can be wired many different ways, but it is wired so that if it senses low water, it cuts all power to my boiler. (One circulator can continue to run though.)



    Now according to my installation manual, this is not needed in some jurisdictions because the controls (no flow control switch) detect low water if the water temperature of the boiler water goes up to fast, or if it gets too high. But my contractor says the inspectors around here insist on seeing a LWCO on the boiler, so they put one in. I see no harm in having both a belt and suspenders. If either one notices low water, better turn the thing off.



    Compared with the total cost of the boiler, indirect hot water heater, replacing baseboard, splitting system into two zones, etc., the cost of the LWCO cannot be much. I just looked it up. It costs about the same as a middle of the line thermostat on the Internet, anyway (not including installation, of course).
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