My Weil-McClain (model CGX) boiler is 10 yrs old, has 3 zones and performs well. Over the years I've replaced with no problem the circulator (leak problem) and a few balky zone valves. Recently I noticed the circulator running when the thermostats shouldn't have been demanding heat. Upon checking, I found all zone valves closed. So in looking for the problem, I tapped the relay switch that controls the burner and circulator, and found it was the probable source of the problem. I replaced this plug-in relay with a SIMILAR one and the system operates fine now. The problem is that the new relay hums loudly and annoyingly. The original relay, White-Rogers 91-112006-11000, 24v was a DPST switch and is apparently no longer available. The replacement, said to be correct by my supplier and equivalency tables on the web, is a Smart Elec SE90340 24 vac 2PDT, which fits the plug-in unit. Aside from the DPST/DPDT difference, the new relay has eight blades, whereas the original had six. After the first replacement relay was installed and worked OK, but hummed loudly, I exchanged it for another relay, but that hums also. Should add, the relay hums or buzzes only when boiler or circulator are ON; not when system is dormant. What now? Can I trust the replacement to work OK in my absence? Is the hum a symptom of a further problem, such as a bad transformer? Should I continue looking for an exact replacement of the original relay?
All clues to this vexing problem will be appreciated.

 

I feel fairly confident that you don't have to worry about the reliability of the new relay. I'm not sure why it makes noise but I'm sure what you hear is the 60 cycle hum of household electricity. If the relay was somehow incompatible with the control, it would probably not last more than a day or two. If the original replacement is not available, your only other choice would be to replace the whole control. I would not recommend that unless the noise is unreasonable.

Ken

 

Thanks, Ken. I think I can put up with the buzzing for now. Come springtime I won't be hearing it at all. Appreciate your comments. Paul