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How hot can conductors get before Its a problem? #174553 02/08/08 12:28 AM
Joined: May 2001
Posts: 376
F
frank Offline OP
Member

Last night while adding circuits to a 200a panel i found that someone had fed a second panel by terminating the feeders on the main lugs of the first panel.The feeders to the second panel are smaller and warm to the touch.I didn't have time find the distrobution breaker to check It's size.I asked around and was told that just because the wires are warm dosen't mean it's a problem.I'll have to check it with the IR gun tommorow.thanks

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Re: How hot can conductors get before Its a proble [Re: frank] #174557 02/08/08 02:59 AM
Joined: Jul 2002
Posts: 8,346
Trumpy Offline
Member
Originally Posted by frank

Last night while adding circuits to a 200a panel i found that someone had fed a second panel by terminating the feeders on the main lugs of the first panel.The feeders to the second panel are smaller and warm to the touch.I didn't have time find the distrobution breaker to check It's size.I asked around and was told that just because the wires are warm dosen't mean it's a problem.I'll have to check it with the IR gun tommorow.thanks

You are telling us that you found conductor insulation hot enough to the touch and did not investigate further?
That to me alone, would ring alarm bells.
You'd better hope that them wires don't get any hotter, this is how building fires start.
It is not a IR gun you need, it is a clamp meter.
Having said that I would have cut the supply to that place before things got much worse.

Re: How hot can conductors get before Its a proble [Re: Trumpy] #174566 02/08/08 10:08 AM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
Member
Mike has a good point ... the temp you feel at one point may be quite a bit different at another point in the run.

The source of the problem could very well be that improper connection at the start of the circuit.

IR guns have their uses ... but they are no substitute to proper installation. Shoving two wires into a single lug is a pretty basic error.

Otherwise ... to answer your question ... you start running into trouble at 75C ... even if the wires have a higher rating on their particular insulation. Why? Because the places where the wires terminate are often only rated at 75C.

Re: How hot can conductors get before Its a proble [Re: renosteinke] #174570 02/08/08 11:06 AM
Joined: Jun 2007
Posts: 301
J
JValdes Offline
Member
Move the sub panel feeders to a breaker that is the right size for the wire and the main in the sub. It's possible the doubling up on the wires under the lugs have come loose. There should not be more than one conductor in each lug unless the lug is rated for two conductors. You have no overcurrent protection on the feeder. And if you don't have a main in the sub you could be in real trouble. That means no protection at all. Hot wires are the result of two things, overcurrent or loose connections. This should be addressed today.

Re: How hot can conductors get before Its a proble [Re: JValdes] #174574 02/08/08 11:59 AM
Joined: Jul 2004
Posts: 9,543
G
gfretwell Offline
Member
You have bigger problems than simply the listing of the lug and possibly undersized feeder conductors. If these are really stabbed into the line side of the service disconnect these are SERVICE conductors. That opens a whole big can of worms.


Greg Fretwell
Re: How hot can conductors get before Its a problem? [Re: frank] #174588 02/08/08 03:59 PM
Joined: Jul 2002
Posts: 717
M
macmikeman Offline
Member
Originally Posted by frank

Last night while adding circuits to a 200a panel i found that someone had fed a second panel by terminating the feeders on the main lugs of the first panel.The feeders to the second panel are smaller and warm to the touch.I didn't have time find the distrobution breaker to check It's size.I asked around and was told that just because the wires are warm dosen't mean it's a problem.I'll have to check it with the IR gun tommorow.thanks


I second all the above comments, and would like to take the time to add:
Hello Frank, I have something in common with you, I was born in your little burg across the river from motor city in the Hotel Deux. Went to elementary school at St. Thomas in Riverside. The internet makes for a small planet.

Re: How hot can conductors get before Its a problem? [Re: macmikeman] #174662 02/10/08 09:15 PM
Joined: May 2001
Posts: 376
F
frank Offline OP
Member
I should have explained the situation better This is a hospital that it currently under construction.The work has not been released to us yet so I can't touch it.The EE and project coordinator were both notified as soon as it was found and this is where my involvment ends.The conductors were so tight i couldn't get the clampon near them without a pry bar.The reason i asked was that someone said the conductors were designed for the load and can operate worm.Ive never heard of such an animal except for mineral insulated firewire.And this isn't MI
thanks

Re: How hot can conductors get before Its a problem? [Re: frank] #174663 02/10/08 09:33 PM
Joined: May 2001
Posts: 376
F
frank Offline OP
Member
Macmikeman It's -10F here with a foot of snow and Windsor/Detroit is in bad shape because of the auto sector.Most of the machine tool is gone and Im hearing the big have dropped the starting wage from 36 to 19 an hour for skilled trades.Windsor lost 8000 jobs in 07 from plant closure and FORD just closed the Nemac engine plant on friday.Glad to hear you made it out alive.
good luck

Re: How hot can conductors get before Its a problem? [Re: frank] #174672 02/11/08 11:32 AM
Joined: Mar 2005
Posts: 1,213
S
SteveFehr Offline
Member
"Warm" is one thing. All wires generate heat, and it's perfectly normal- after all, they're designed to work up to 75-90C in the worst-case scenario. If all the other wires in the box have no-load, it may only seem bad by comparison. "Hot" under normal operating conditions is quite altogether something different. Abnormal heat in this wire could indicate a problem- poor connection or undersized wire, for instance. If you think it's an issue, I'd get the prybar the clamp a meter on there ASAP to verify it's simply due to loading on the circuit. Can you access the far end of the circuit?

If this is a branch circuit supplying a fixed design load close to the NEC ampacity of the wire and temps are only slightly elevated above ambient, I wouldn't worry about it. But if by "warm" you mean "I burned my hand", then you may have a problem.


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