Ringing Noise in Electric Panel - Solved

[akflyrod2]

After returning to the dock from a long trip I could hear a weird ringing/buzzing sound in the electric panel. My husband's hearing range couldn't detect it. After co-ordinating with me on the panel front listening and him on the back he found that vibration must have jiggled a wire slightly loose on the AC master breaker. (power was appropriately shut off during exercise) After tightening it up the noise stopped.

Oddly then I was working on painting the door frame outside and had my head down near the shore power connection and could hear the same kind of ringing sound. Again, we found the shore power connector needed to be pushed in harder. For some reason the keeper ring threads didn't catch. So, 'm not sure if this could have been dangerous or not but the noise was irritating anyway.

 

[Comodave]

Any loose electrical connection can be potentially dangerous due to resistance which causes heat which can cause a fire.

 

[rgano]

My guess is that the connections were also warmer than they should have been. Might I suggest going over all your connections in the panel and elsewhere with an infrared thermometer. After noting the warmer connections, shut down power and tighten them. Then retighten every connection in the boat for good measure because it's an old boat.

 

[akflyrod2]

Thank you both for the reply! We will definitely check out the rest.

 

[rwidman]

If one wire was loose, I would suggest turning off the power and checking the rest. You might also want to remove the one that you tightened and check for any corrosion or sines of arcing on the wire and the contact and clean them with a very mild abrasive like emery cloth (a nail board might work), then spray with electrical contact cleaner and re-attach.

As for the power inlet on the boat, these can be problematic. Make sure the plug is in all the way and turned as far as it will go, then tighten the threaded ring.

These connections can also benefit from cleaning as above. In addition, buy some "dielectric grease" and occasionally apply it to the prongs of your shore power cord. Just wipe it on, don't put a gob on it.

 

[STB]

In addition to the advice already given, and not having personally heard the noise to know what it is, I would advise to replace the affected breaker(s).

Breakers commonly use an internal electromagnet to trip the breaker. It is in series with the load, so as the current drawn by the load goes up, the current going through itngoes uo, and the magnetic force it exerts on the physical elements goes up. If there is enough current, it moves the latch and trips the breaker. This can happen instantly with a large current.

Chronically running a circuit near its limit, or frequently going over the limit can heat the coil and degrade it over time, both physically and electrically. Shod this occur, it might not trip when it should and you might hear a buzz when the lights should be out.

For the curious, most common breakers also include a bimetallic element, i.e.a strip composed one one side by one metal and on the other side by another metal. The metals change length differently as temperature changes. As the metal heats up from current, the difference in the way the two metals react cause it to change shape, releasing the latch. This metal strip and the associated mechanical parts can also be damaged over time (but im not sure that they'd buzz).

The magnetic part if the breaker provides instant protection from super high currents. The thermal part allows a combination of time and load to cause the trip as the LOAD causes the heating over time, allowing for short surges, within reason, as things start up, etc.

At any rate, when Inhear about a buzzing breaker...I like to suggest that both the cause of the buzz and the breaker be replaced. The buzz might well be it trying to trip, but not tripping (even if at a lower current than it should), and even if the breaker trips under some circumstances (because it could be tripping earlier or later than it should, or because it could be, for example, a thermal trip when a magnetic trip should already have happened, etc).

 

[rwidman]

In addition to the advice already given, and not having personally heard the noise to know what it is, I would advise to replace the affected breaker(s).

Breakers commonly use an internal electromagnet to trip the breaker. It is in series with the load, so as the current drawn by the load goes up, the current going through itngoes uo, and the magnetic force it exerts on the physical elements goes up. If there is enough current, it moves the latch and trips the breaker. This can happen instantly with a large current.

Chronically running a circuit near its limit, or frequently going over the limit can heat the coil and degrade it over time, both physically and electrically. Shod this occur, it might not trip when it should and you might hear a buzz when the lights should be out.

For the curious, most common breakers also include a bimetallic element, i.e.a strip composed one one side by one metal and on the other side by another metal. The metals change length differently as temperature changes. As the metal heats up from current, the difference in the way the two metals react cause it to change shape, releasing the latch. This metal strip and the associated mechanical parts can also be damaged over time (but im not sure that they'd buzz).

The magnetic part if the breaker provides instant protection from super high currents. The thermal part allows a combination of time and load to cause the trip as the LOAD causes the heating over time, allowing for short surges, within reason, as things start up, etc.

At any rate, when Inhear about a buzzing breaker...I like to suggest that both the cause of the buzz and the breaker be replaced. The buzz might well be it trying to trip, but not tripping (even if at a lower current than it should), and even if the breaker trips under some circumstances (because it could be tripping earlier or later than it should, or because it could be, for example, a thermal trip when a magnetic trip should already have happened, etc).

This is a good explanation and good advice.

 

[diver dave]

Noise at a connection point might be actual arcing. Resistors are quiet. I dont believe there are any magnetic parts at the shore power connecter to react to a magnetic field and start shaking.
You may have dodged a bullet.

 

[STB]

Noise at a connection point might be actual arcing. Resistors are quiet. I dont believe there are any magnetic parts at the shore power connecter to react to a magnetic field and start shaking.
You may have dodged a bullet.

I agree with you about arcing being the most likely cause of a buzzing sound at a shore power connection given that it was relieved by pushing it in.

Most shore power pedestals do have thermal-electric breakers which can buzz. A little might be normal, a lot likely wouldn't be. But, in any case, I 100% agree with you that this shore power thing doesn't sound like that.

 

[FF]

"Then retighten every connection in the boat for good measure because it's an old boat."

A long term solution is to clean each connection and place a star washer under the nut.

Electrical connections do not have to be overloaded to warm up many will get warm during normal operation.

This expands the connectors , which then return to size after the load is off.

The star washer produces force that keeps the contacts together.

A good rainy day project as a box of 100 is usually under $5.00 and the results are "forever".

 

[akflyrod2]

This is all great advice. Thank you. We have lots of rainy days here to get it done! :lol:

 

[FWT]

"Then retighten every connection in the boat for good measure because it's an old boat."

A long term solution is to clean each connection and place a star washer under the nut.

Electrical connections do not have to be overloaded to warm up many will get warm during normal operation.

This expands the connectors , which then return to size after the load is off.

The star washer produces force that keeps the contacts together.

A good rainy day project as a box of 100 is usually under $5.00 and the results are "forever".

GREAT tip. Thanks.

Seeing lots of styles of star washers. What do you like?

https://duckduckgo.com/?q=star+washer&t=chromentp&atb=v178-1&iax=images&ia=images

 

[diver dave]

I like external star in stainless.

 

[FWT]

I like external star in stainless.

Thanks

 

[FF]

Seeing lots of styles of star washers. What do you like?

The brass or copper ones that are tinned electrically match the terminal ends.

The washer is part of the electric current flow and SS stinks as a conductor compared to copper.

 

[diver dave]

Yeah, SS around 42x specific resistivity of Cu. Washer must be placed directly under the bolt/screw head on something like a breaker with tapped holes.
On a copper based system, phosphor bronze makes good lockwashers, at about 2x resistivity of Cu. But i dont see reasons to put even those innthe path of electrons.

I just finished installing some lightning down conductors on the boat, at the chainplates. Talk about materials, SS, tin, aluminum, and copper at those connections. Hopefully, the no-ox will keep the galvanics at bay.