buzzing 3 phase board

[Farmelectrics]

any idea why a 12way 3 phase board is buzzing supply cable is 4core 35mm there are no spare ways in db there is a mixture of 32amp rcbo 3 phase breakers lighting circuts etc tightened up all terminations done a load test on l1 l2 and l3 fluxtiuating readings as db supplys photo studio one thing i have noticedc is the db is not balanced very well

 

[george92]

We had this once when doing a pir turned out to be a central battery emergency lighting system wired up wrong and it backfeeding the board with a dc supply

 

[malcolmsanford]

Could be harmonics, are the phases coming through individual holes into a metal DB ? or is the entry slotted.

Are there any lighting relays in the board, they sometimes buzz, the same is there any contactors nearby that would transfer the sound into the board.

Are there any hotspots on the board ?

 

[stefan442]

Faulty main switch/breaker?

Turn each rcbo/mcb off one by one and see if the buzzing stops, lastly turn main switch off.

 

[QSGAZ]

Have you left your phone on top and someone is trying to ring you? hone:

 

[jumpin jax]

Or is there honey dripping out of the bottom by the incomer?

 

[Farmelectrics]

malc the entry is slotted and there is no contactors near by might try each breaker then main switch cheers lads

 

[Guest123]

A circuit operating close to the maximum rating of the protective device maybe...???

 

[Farmelectrics]

Lenny could well be the problem will get tong testers on individual circuits when all kit in photo studio is working had a similar problem in there large lighting circuit on 6amp breaker pulling 8.6amps

 

[Darkwood]

I bet you got dimmers on lighting somewhere???? switch dimmers off see if mcb stops buzzing, on the other hand if no dimmers then probably faulty mcb.

 

[rich.250]

A high inductive load can cause buzzing. what type CB's are there in the db?

 

[Farmelectrics]

Sounds like a faulty mcb or rcbo as Lenny said that's my plan of attack today will let you no

 

[nickblake]

if its possible without turning off any sensitive equipment switch each circuit off till the buzzing goes off , then check the load of that circuit ,and the Mcb rating ,also check the connections and make sure they are not loose

 

[rich.250]

Yeh could well be. Or a incorrect type. Good luck

 

[Farmelectrics]

dorman smith c type single phase and 3 phase

 

[Farmelectrics]

Couldn't solve problem as can't switch breakers off due to a busy photo studio tightened all connections still buzzing its a dorman smith board a right mess and not possible for me to clamp meter around cables from rcbo as lack of space plus didn't want to cause any tripping of breakers just have to put up with the buzzing for now