How do I hookup McDonnell & Miller Guard Dog RB-122 to Weil McLain CGI-5 Boiler
I have a Weil McLain CGI5 boiler. Previously I had a McDonnell & Miller Guard Dog RB-24 Low water cutoff (LWCO) hooked up to Weil McLain CGI-5 boiler. Since they are not sold anymore I bought a McDonnell & Miller Guard Dog RB-122. The wiring is a bit different. When I connect the 2 yellow controls from the RB-122 to the Yellow wiring (t-stat controls) on the WM control the T-stat is always on (calling for heat). I tried a different connection to the WM but ended up blowing the control module (fortunately it only cost me $70 from an Ebay seller to replace it instead of $150 & up from the local dealer). So to get my boiler to be controlled by my thermostats and not the RB-122 I have disconnected one of the RB-122 yellow cables. How should it be hooked up properly?
That is a 120v lwco, so you will have to wire it different, don't hook your t-stat to it at all, instead wire it to your service switch, high voltage..
Take the black wire from your incoming power after the boiler service switch and disconnect it, hook it to the black wire and one yellow wire, then hook the white to the white wire, and lastly hook the remaining yellow wire to the black wire that you disconnected from the service switch power... So the yellow wires just break that incoming power.... You can also just hook the yellows to the same test at wire so it breaks it and not feed the yellows 120 I believe..
I dont like using high voltage lwcos on gas boilers... Should have just bought a cheap 24v lwco...
This post was edited by an admin on March 5, 2013 6:31 PM.