Heat felt in cables

Tosh · Oct 25, 2013

Hey folks looking for a second opinion on this one, was carrying out an eicr on an car dealership it department , all going well just the usuall cracked sockets blind grommets missing from things etc . Got to one board that feeds a lot of it computers and there was obvious heat from the DB cover before I removed it , there was heat in the RCBOs and associated cables that was easy noticed , I wouldn't have expected such heat as there's no load in the computers , any ideas on this one:bulb2:

Sintra · Oct 25, 2013

Did you check what current was being drawn by the different cables? 70 degrees is pretty warm

Tosh · Oct 25, 2013

No my van was a good bit away with the clamp meter in it, but didn't think there was enough computers there to warrent the heat output , was just wondering if any one else has had this in an it department

dan86 · Oct 25, 2013

TFM said:
there was heat in the RCBOs and associated cables that was easy noticed

heat damaged? did you do any tests? presumably you have finished the EICR. did you code it?

Tosh · Oct 25, 2013

No I have not tested the board as the person ordering the work is on holiday and I want clarification as too what is a limitation on the board as I cannot kill power to most circuits as the board feed offices that deal with it customer services etcNd there is also a board which just feeds the server equipment which I have meant to test but the place is open 24/7 so I want a method statement off the person ordering the work to tell me when I can issolate supies , it was only when removing the DB cover to do a dead test on a sub main circuit I felt the heat , was just looking for some advice

Sintra · Oct 25, 2013

TFM said:
No I have not tested the board as the person ordering the work is on holiday and I want clarification as too what is a limitation on the board as I cannot kill power to most circuits as the board feed offices that deal with it customer services etcNd there is also a board which just feeds the server equipment which I have meant to test but the place is open 24/7 so I want a method statement off the person ordering the work to tell me when I can issolate supies , it was only when removing the DB cover to do a dead test on a sub main circuit I felt the heat , was just looking for some advice

How did you do a dead test on the sub main without isolating the board.

Tosh · Oct 25, 2013

It was it was DB fed from the board that had the heat in I that is was testing . Ie a 63 amp 3 phase mcb feeding a DB that I was testing so i could issolate the DB that was fed via the DB which had heat in it

Lucien Nunes · Oct 25, 2013

The heat dissipated by an MCB or RCBO depends on how near its rating it is running. It is not just the total load that is of interest in DB self-heating but what size circuits and breakers are carrying it.

Engineer54 · Oct 25, 2013

I would also check the tightness of all the connections in the main distribution board. Oh, and when your next there, take your amp clamp with you. Totally pointless having test equipment if you're just going to leave it in the van!!

plugsandsparks · Oct 26, 2013

Reminds me of a small control panel I built for control of 5 radiant heaters, total capacity was 16.5KW, I mounted the thermostat to control the heaters inside the panel..... bad idea. The heat from just the cables and contactors raised the temp inside quite a lot really. Felt like a small heater in itself. Anyway, moved the thermostat to outside the panel after that. Point being when stuff is running at high current for periods it does generate heat. whether its a concern or not can only be done by testing against the limits of the equipment installed. I often come across warm equipment. I only get really concerned if I cannot keep my hand on it.