Thermal image question

[marcram]

I typically inspect commercial roofs and industrial equipment etc... but a realtor asked me to check a sub panel in a condo for her that was already inspected once before. Anyhow, I found that the neutral coming from the main was pretty hot (105 degrees) and this was with no load on the panel. Just wondering for my own personal knowledge what things might cause this condition. Thanks...

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[Marc]

Would this be a 120/208 panel (2 legs of a 3 phase SE) or a 120/240? The bus on the lower right...is that a ground bus? By 'no load' do you mean that all branch/feeder breakers are in the 'off' position or is it just that the appliances are not being used?

Marc

[marcram]

Hey Marc,

1) 120/240

2) All of the appliances etc... were off, not used - vacant residence

3)You are correct, that is a grounded bus at the bottom right corner

The grounding conductors are on the other side, seperated as typical

[Marc]

Hey Marc,

1) 120/240

2) All of the appliances etc... were off, not used - vacant residence

3)You are correct, that is a grounded bus at the bottom right corner

The grounding conductors are on the other side, seperated as typical

I can't figure it, assuming you've got your facts right. I do see what appears to be 4 incoming conductors into that panel suggesting 3 phase service. The incoming neutral and 7 branch circuit neutrals on the right side are all carrying a heavy current...in an uninhabited condo. I assumed it's a condo dwelling unit, not an office, with no inverter or electronic equipment including florescent light fixtures with electronic ballasts that would generate harmonics.

Sorry Marcram,

Marc

[Jim Katen]

I typically inspect commercial roofs and industrial equipment etc... but a realtor asked me to check a sub panel in a condo for her that was already inspected once before. Anyhow, I found that the neutral coming from the main was pretty hot (105 degrees) and this was with no load on the panel. Just wondering for my own personal knowledge what things might cause this condition. Thanks...

I wouldn't characterize 105 degrees as "pretty hot." More like slightly warm.

The pattern in your image was caused by a high-impedance connection -- probably not tightened to spec.

Something in there was using electricity or it wouldn't be heating up.

- Jim Katen, Oregon

[marcram]

Thanks Jim

[David Meiland]

According to the scale in your image, the hot spot looks to be 98 or less. How do you get 105? There is definitely current flowing. Curious as to why the owner asked for the inspection, and what might be discovered without any loads?

FWIW, there are several very good posters on electrical equipment issues at irtalk.com