Conduit overheating

[bwyllie]

Going to look at a problem where a conduit is overheating, surface temp is 130 degrees. Don't have any readings or info on the feeder installation besides that it is a "long run" but can anybody offer suggestions as to things to look at?

Thanks

 

[480sparky]

130? F or 130? C?

 

[bwyllie]

Good question.

 

[480sparky]

The former doesn't worry me much. That latter may.

 

[76nemo]

Multiple circuits in the pipe?

 

[480sparky]

How close to the panel is this temp taken? If it's right above it, I'd look at the terminations. If it's in the middle of the run, something is seriously wrong.

Take an amp reading and see if the wire's even big enough for the load.

If you've got an IR camera or thermometer, be sure to take it along.

Let us know what you find out.

 

[don_resqcapt19]

60?C is 140?F, conductors fully loaded may operate at this tempeture and be code compliant. The only issue would be the energy that is wasted producing this heat.

 

[charlie b]

If this is a set of parallel conduits, check to see if all the phase A conductors are in one conduit, the phase B in another, etc.

 

[weressl]

If this is a set of parallel conduits, check to see if all the phase A conductors are in one conduit, the phase B in another, etc.

Or the grounded conductor is routed/not routed.

 

[bwyllie]

well I just visited the site and found that the electric unit is fed w/ 2/0 thhw-2 and run fully loaded at 133Amps. Temperature reading were approx 100 deg F to 115 deg F. Building engineer indicated temperature rises overtime to 130 deg F. They are concerned because of the heat generated on the conductors and conduit but I believe everything is operating properly as designed. thoughts?

 

[StephenSDH]

Does seem warm, but the wires are protected by the breakers thermal trip. If the breaker isn't tripping you should be fine, just losing money do to line losses. Sounds like a continuous duty application without bumped up cables. I would just let it ride, unless there where other negative side effects.

 

[weressl]

Does seem warm, but the wires are protected by the breakers thermal trip. If the breaker isn't tripping you should be fine, just losing money do to line losses. Sounds like a continuous duty application without bumped up cables. I would just let it ride, unless there where other negative side effects.

Unless it is a high resistance ground fault.

 

[tonyou812]

I would upsell them for bigger condutors. Why not if its a continuous duty application. Plus it will make them "feel" better about it.

 

[Mr. Wizard]

I've witnessed conduit getting hot like that. The reason we found was the lack of neutral. Well, it was there, but ran in another conduit (green helper fubar). It was a multiwire circuit powering mainly lights and computers. The conduit that contained "A" phase was very hot to the touch. But the problem I write about was total installation error. But you may want to check your neutral, as that was our problem.

 

[bwyllie]

Thanks for the suggestions, no neutral, straight three phase load.

 

[LarryFine]

Thanks for the suggestions, no neutral, straight three phase load.

The only two causes I can see would be too-small conductors or the conduit carrying a lot of current.

Of ocurse, it could be something weird like heat from the load being drawn through the conduit.

 

[don_resqcapt19]

2/0 is an 145 amp conductor in the 60?C column, a reading of 130?F (54.4?C) does not surprise me with a 133 amp load.

 

[broadgage]

As others suggest, this may be a compliant installation with the conductors expected to run that warm if heavily loaded.

It might be worth suggesting larger conductors to the customer though to reduce the losses, for which they are presumably paying.
Also the voltage drop in the present just adeqaute conductors may be causing problems elswhere.

If a branch circuit or feeder is going to be fully loaded throughout working hours, useing wire bigger than code requires can be justified by the energy saved.

 

[brian john]

Under sized conductors or overloaded.
Too many conductors in the conduit.
Inductive heating from mis-wired circuitry.

 

[bwyllie]

Of ocurse, it could be something weird like heat from the load being drawn through the conduit.

That is actually something that was discussed. The control panel that this feeder feeds is an enclosed control panel with no ventilation or fan and there was heat being generated in this panel.