Loud buzzing from main breaker

Andy J.

Andy J.

Doin’ it LIVE
Joined
Nov 5, 2005
Location
Winston
HELP! Yesterday I replaced my 13 year old standard leaky hot water heater with a 27kW electric tank-less hot water heater. I have a 225 amp Siemens panel and ran 3 lines of 8/2 to 3 new 40amp 240V breakers, per the water heater instructions. I put one of the 40amp breakers on the left bar and 2 on the right bar.

When the system turns on, I get a loud buzzing from the main breaker. I have gotten bad breakers from the store before, so I cycled them on/off individually and ran the system in an attempt to isolate one, but was unsuccessful in identifying a particular 40amp breaker as bad. I also made sure that the other high-amp appliances weren't on at the time.

Is it possible that my main breaker is 'bad', but it never showed up due to low amp draw? I'm going to go check all my connections again and re-seat the new breakers just to be sure, but I doubt that is the problem(?). I have to go out of town tomorrow morning for work, so I need to get this figured out TODAY.
 
Doing some additional digging and found a Rheem TSM that states a 9kw heater should use 8 ga wire and a 50 amp breaker. The manual that came with the heater said a 40 amp breaker. Maybe what I'm seeing is those 40 amp breakers are maxed out and about to trip.

edit to add: its a 27kw heater with 3 elements, so 9kw each. Its hard to pinpoint the buzzing to a particular breaker, since its all in a metal box. I thought it sounded louder at the main, but maybe not...
 
How does this thing split the load across the 3 breakers? Is it literally 3 independent elements that run in parallel?
 
Andy J. said:
Doing some additional digging and found a Rheem TSM that states a 9kw heater should use 8 ga wire and a 50 amp breaker. The manual that came with the heater said a 40 amp breaker. Maybe what I'm seeing is those 40 amp breakers are maxed out and about to trip.

edit to add: its a 27kw heater with 3 elements, so 9kw each. Its hard to pinpoint the buzzing to a particular breaker, since its all in a metal box. I thought it sounded louder at the main, but maybe not...
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well 9k / 225 is exactly 40. If they really do run full bore, then you're right on the limit...

Per this chart, seems to be that should be #6 and 50A breakers.
https://groverelectric.com/assets/downloads/howto/08_How to Calculate Breaker Wire Size & Wattage.pdf
 
Touch the face of the breakers with a screwdriver or something hard and feel for the buzzing to definitively locate it.

Even if they are about to trip they shouldn't be buzzing.

I hate Siemens. Monumental pieces of shit and I refuse to buy them.

Not helpful to your situation but we have multiple Sullair air compressors at work, one has exhibited ongoing nuisance tripping. We replaced overloads, contractors, rebuilt the blowers, and even replaced the Siemens feeder breakers. This compressor motor kept tripping although it passed every test we put it through. I finally ordered an Eaton breaker in a Siemens bucket to put in the Motor Control Center and it hasn't tripped since.

Anything Siemens is a piece of shit.
 
I swapped out the 40s for 50s - no change. Can’t feel the breaker buzzing either. Tested it both with my hand directly and with a screwdriver.

I confirmed all the connections are good.

I had it running on 110 degrees, all three breakers, then flipped one breaker off and it stopped buzzing. Left the one breaker off and turned up the heat to 135 degrees and the buzzing returned.
 
What you are hearing is ..."normal"...not really but you probably arent going to get rid of it.
I suspect it has to do with how Siemens mounts their thermal strips in their breakers. Their expansion allows them to contact the inside of the case under heavy load and the buzz is the harmonic vibration...I'd bet you a nickel its at a resonance frequency of right around 60hz if you go buy a decibel meter.

Its the main that is humming. (its possibly the main bus bar, but Im betting internal to the main breaker - its a "thing" with Siemens resi breaker line)
The reason it doesnt when you flip one breaker off is you are reducing the total load on the main breaker. The reason it never did it before is because your old water heater didnt pull as many amps.

Its also why you power bill will be higher and why I never recommend a tankless electric heater.
 
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13bullets said:
Touch the face of the breakers with a screwdriver or something hard and feel for the buzzing to definitively locate it.

Even if they are about to trip they shouldn't be buzzing.

I hate Siemens. Monumental pieces of shit and I refuse to buy them.

Not helpful to your situation but we have multiple Sullair air compressors at work, one has exhibited ongoing nuisance tripping. We replaced overloads, contractors, rebuilt the blowers, and even replaced the Siemens feeder breakers. This compressor motor kept tripping although it passed every test we put it through. I finally ordered an Eaton breaker in a Siemens bucket to put in the Motor Control Center and it hasn't tripped since.

Anything Siemens is a piece of shit.
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Word. I don't buy Siemens motors any more. The bearings are junk. I've got 30yr old Westinghouse and GE motors still going strong on factory bearings while at the same time I've burned up or had bearings going out on 2yr old Siemens motors. Here lately I've been using Brook Compton. My motor shop started carrying them a few years ago and they are cheaper and seem to last. I haven't toasted one yet.
 
awheelterd said:
Word. I don't buy Siemens motors any more. The bearings are junk. I've got 30yr old Westinghouse and GE motors still going strong on factory bearings while at the same time I've burned up or had bearings going out on 2yr old Siemens motors. Here lately I've been using Brook Compton. My motor shop started carrying them a few years ago and they are cheaper and seem to last. I haven't toasted one yet.
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I don't really get to pick brands as I often have to take what's available in a certain time frame and make it work. I work for the utility in a generating plant and we try to just replace like for like, because once a system's installed, what else can you really do economically. We had a 150 horse Wye-Delta Siemens motor go out on one of these Sullair compressors once and the report came back non-repairable. It was an urgent repair and the only suitable replacement on the east coast was a 6 lead TECO-Westinghouse. I had three different quotes from three different suppliers, including Sullair themselves, that all had the nameplate info and they all quoted this same exact motor. We bought it, overnighted it out of PA, was on our dock by 10am the next morning. Maintenance gets it installed, the electricians go to wire it up, and everyone that didn't already know learned that day that 6 lead does not equal wye-delta. The damn thing had two 1s, two 2s, and two 3s, designed for across the line starting only. We had to call our motor shop to drive down from WV that day, pick it up, take it to their shop, re-lead it 1-6, and drive it back to us the next day. What a cluster-fuck.

Total thread derail, and not even really Siemens related. Anyhow...there's something that happened.
 
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