intermittent buzzing in electrical panel

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bbartmasse r

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Washington State
Hi All,

We do mainly small to medium sized residential PV systems. On occasion we get a customer who notices a buzzing sound in the main panel that comes and goes after the PV install.

In fact, it happens on my own, in my house. I never really cared much because the panel is nowhere near a bedroom.

I think it may happen in all our installs(no way to be positive of this) but its only a few who notice the sound.

Has anyone experienced this?

thanks
 
How often does it "come and go" and for what duration? I'm not meaning exact numbers, but is it often enough where you can camp and wait for it, and long enough where you can poke around while it's doing it?

This is especially nice that you can check it out on your own system. Grab a book and a chair.
 
Probably a bad breaker to bus stub connection

Probably a bad breaker to bus stub connection

while it is buzzing , use your thumb and "wiggle " each breaker.

If it starts or stops while buzzing ,then, it is usually that breaker or one adjacent to it.


Or..

Turn off the main and remove each breaker and look at the bus-stab connections for burnt ends,
Also . smell each breaker for that lovely"burnt Tuna flavoring"

and take a screwdriver and tighten all connections that are not live.

if it is the Main breaker ,or "live connection" then call an electrician.
 
[QUOTE

if it is the Main breaker ,or "live connection" then call an electrician.[/QUOTE]


I am an electrician.

the thing is, this has happened a number of times now on different locations. It sounds like a fly is in the panel for about 5-10 seconds

One customer we had, his panel was in his bedroom so it bothered him a lot. He changed the breaker out twice and it did not fix it. It is directly correlated to when the solar has been installed.

I do not think it has to do with the inverter because it happens at night as well.

My best guess is someone to do with the production meter.

thanks for any further suggestion.
 
AC current has magnetic fields that fluctuate at same rate as frequency of the supply. Anything that can be moved by such magnetic fields - including two conductors in a raceway that have such fields around them are subject to movement by the force of those fields. The higher the current level involved the more likely it is to create such a problem. An object that is trying to change direction 60 times a second will essentially "vibrate".

Now go to typical loads in a dwelling and often there are not that many constant loads or high level loads, and you only notice such problems when say an AC compressor unit or other larger motor load starts the rest of the time the magnetic fields are low enough there isn't too much noticeable effects. The goal with a solar install is to collect and distribute the unit's rating as much as possible so this sort of becomes a constant load at the units rating as long as there is sunlight to harvest.
 
bbartmasse r said:
if it is the Main breaker ,or "live connection" then call an electrician.
Click to expand...
I am an electrician.

the thing is, this has happened a number of times now on different locations. It sounds like a fly is in the panel for about 5-10 seconds

One customer we had, his panel was in his bedroom so it bothered him a lot. He changed the breaker out twice and it did not fix it. It is directly correlated to when the solar has been installed.

I do not think it has to do with the inverter because it happens at night as well.

My best guess is someone to do with the production meter.

thanks for any further suggestion.
Click to expand...
At night there is (of course) no current in the conductors associated with the PV system, and that includes the PV production meter if there is one. The fact that whatever is causing the buzz started when the PV was installed is, IMO, either a coincidence or due to some other wiring or breaker that was disturbed when the system was put in.
Click to expand...
 
ggunn said:
bbartmasse r said:
At night there is (of course) no current in the conductors associated with the PV system, and that includes the PV production meter if there is one. The fact that whatever is causing the buzz started when the PV was installed is, IMO, either a coincidence or due to some other wiring or breaker that was disturbed when the system was put in.
Click to expand...
I agree. May have first noticed after PV was installed, and that install may have disrupted something already there. I'd be seeing if this sound coincides with maybe HVAC starting (particularly a compressor unit) or something like that. If it does then you just need to figure out what component related to that is making the noise, maybe just loose fitting components within the breaker supplying that equipment - those magnetic forces are there from the day they get put into service, a component may take a long time to vibrate enough to wear away the plastic it is mounted into - then that allows even more movement and louder vibration noises.
Click to expand...
 
kwired said:
ggunn said:
I agree. May have first noticed after PV was installed, and that install may have disrupted something already there. I'd be seeing if this sound coincides with maybe HVAC starting (particularly a compressor unit) or something like that. If it does then you just need to figure out what component related to that is making the noise, maybe just loose fitting components within the breaker supplying that equipment - those magnetic forces are there from the day they get put into service, a component may take a long time to vibrate enough to wear away the plastic it is mounted into - then that allows even more movement and louder vibration noises.
Click to expand...

Or it could be a long existing condition that the HO just happened to notice after the PV was installed. We have gotten that a few times where the HO is convinced that we "did something" in our installation process that caused some perceived problem where there is no connection whatsoever between what we installed and what he is seeing. We even once had a complaint from a guy who claimed that after we installed PV on his next door neighbor's house his lights flicker - even at night. We always check out these claims - even the neighbor's - but so far not one of them could be traced back to anything we did.
Click to expand...
 
ggunn said:
bbartmasse r said:
At night there is (of course) no current in the conductors associated with the PV system, and that includes the PV production meter if there is one. The fact that whatever is causing the buzz started when the PV was installed is, IMO, either a coincidence or due to some other wiring or breaker that was disturbed when the system was put in.
Click to expand...

There is no power flow at night, but there may be current flow due to the filter capacitors in the inverter. I monitor many PV systems with data acquisition using separate power meters and they usually show zero power at night but some AC current (0.3A on an SMA 10KW inverter is typical, higher currents on some Fronius). Real power is zero, but reactive power is present. If the residence has some non-linear AC loads, either highly inductive or high harmonics such as from dimmers, the inverter can draw reactive current and this may cause the buzzing.
If the circuit breaker is turned off when this happens and the buzzing does not stop, the problem is not due to the inverter.
Click to expand...
 
OP hasn't even verified the PV system is related to the problem, only that it was presumably noticed after the PV installation.

Sounds very possible that it is something that happens every time HVAC compressor starts up or something like that. PV install could have moved/disrupted something allowing it to move/vibrate more easily then before the PV install but the condition was always there. Just one possibility of many.
 
The reason I posed the question is because it has been noticed enough time directly after a PV install that it makes me believe it is associated with the PV.

3 different customers not including myself have noticed the same buzzing and described it in the same way. One of those three I heard myself and could confirm it was the same sound that comes from my panel.

The other two are in my opinion credible sources, one of them even works for our local utility.

The sound is elusive, when I hear it at my house I have only a few seconds to run over and investigate before it stops. The biggest loads I have in my house are a small water heater, small mini split heat pump (sound happened before I installed this), and a fridge.

Interesting that nobody has come across this. thanks
 
bbartmasse r said:
The reason I posed the question is because it has been noticed enough time directly after a PV install that it makes me believe it is associated with the PV.

3 different customers not including myself have noticed the same buzzing and described it in the same way. One of those three I heard myself and could confirm it was the same sound that comes from my panel.

The other two are in my opinion credible sources, one of them even works for our local utility.

The sound is elusive, when I hear it at my house I have only a few seconds to run over and investigate before it stops. The biggest loads I have in my house are a small water heater, small mini split heat pump (sound happened before I installed this), and a fridge.

Interesting that nobody has come across this. thanks
Click to expand...

Ok, fishing a bit here but maybe non true sinusoidal wave form from inverter output is contributing to that sound?
 
kwired said:
Ok, fishing a bit here but maybe non true sinusoidal wave form from inverter output is contributing to that sound?
Click to expand...

Seems to me it could even be the opposite; better quality wave from the inverter than utility. In either case I could see non-congruent waveforms perhaps leading to something. But personally I think the more likely explanation is just something getting disturbed or noticed due to work being done.
 
ramsy said:
Did you read the attached letter in post #5 ?

People have seen and diagnosed similar issues with SMA inverters & Siemens breakers.
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I saw that post and decided not to comment because a) it was not necessarily on topic, and b) seems implausible. There's no sensible reason why Seimens breakers should be susceptible to problems when other brands of breakers are not, and that's just one example of a detail that makes little sense. I for one, would need to a quantification of the word 'numerous' in that letter before taking it seriously. It could just be a bad run of breakers from the factory, and it happened to be a solar installer who uses SMA who reported the problem. We solar guys do tend to use a lot of quads because we deal with existing panels instead of planning out enough spaces for new installs.
 
jaggedben said:
I saw that post and decided not to comment because a) it was not necessarily on topic, and b) seems implausible. There's no sensible reason why Seimens breakers should be susceptible to problems when other brands of breakers are not, and that's just one example of a detail that makes little sense. I for one, would need to a quantification of the word 'numerous' in that letter before taking it seriously. It could just be a bad run of breakers from the factory, and it happened to be a solar installer who uses SMA who reported the problem. We solar guys do tend to use a lot of quads because we deal with existing panels instead of planning out enough spaces for new installs.
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How is that not related enough to at least consider there might be a problem with at least one of Siemens products? Even if it is just one bad production run of product?
 
As I said, not necessarily in topic. The OP said nothing about Siemens or SMA, and the letter about Siemens failures said nothing about buzzing. We should have more info to connect the two before discussing them in the same thread.
 
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