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crankcase 11-05-2012 06:21 PM

Suspect Electric boiler causing brownout
I have a 15KW boiler for radiant heat fed from panel thru a 60A and 30A 240V circuit. Also have the same size breakers at the boiler. Sometimes the boiler will make a low hum noise and sometimes it will hum with a louder noise, this when it is not heating. This has happened a few times and I cycle the breakers at the boiler and it stops. Yesterday my wife was in the house and heard clunk similar to cycling a double pole breaker ( I cycled one for her and had her confirm it sounded similar.) After she heard the noise half of the house had no power. I was outside, came in checked the panel and boiler and no breakers were tripped, but the boiler was buzzing. I could tell that the boiler was running because the temp gage and pipes were warm. I cycled the breakers at the boiler and the humming stopped and the boiler came back on to heat. I didn't know about the brownout on half the house until after I power cycled the boiler. The power must have been restored when I cycled the two breakers.

Almost seems like for some reason I lost phase A or B on some 120V circuits. I'm going to check all grounds and the contactor lugs and wires for discoloration and loose connections first.

FYI: this boiler can modulate or power 1-2-or 3 heating elements depending on an outside ambient temperature sensor. It is also wired thru a off peak CT meter.

crankcase 11-05-2012 08:36 PM

Ok I just got some more details from the wife. It appears that the story has changed. Has this ever happened to anyone else? New facts:

* Partial bottle of wine in fridge with plastic wrap and hair rubber band "cover"

* It was a power surge (not her) that flickered so fast that the clocks didn't even loose their time.

* It wasn't half the house, it was the plasma tv that turned off.

The noise she heard had to have been the contactors on the boiler opening up. Still going to look at the connections tonight but leaning towards a bad contactor for the humming noise.
I'll post any findings.

dmxtothemax 11-05-2012 10:34 PM

What are you on man ?

mpoulton 11-05-2012 11:53 PM

Sounds like normal contactor noise to me.

frenchelectrican 11-06-2012 01:41 AM


Originally Posted by mpoulton (Post 1045744)
Sounds like normal contactor noise to me.

It may be so but some of the contractors which I ran into simauir to the OP's situation some case they will use the receifer to change over to DC to quite down the buzzing noise plus the coil itself will be marked in DC instead of useal AC rating.

So if the recifier do go bad it will make the contractor buzzing pretty good and I keep couple spare one on hand which I get them once a while.


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