electrician question -flexible amp clamps around conduit

[Howard Sterndrive]

I am thinking of purchasing flexible amp probes for a 3 phase power analyzer.
If I have single runs inside metallic conduit, can I measure amps just wrapping around the conduit?

 

[bigdee]

Re: electrician question -flexible amp clamps around conduit

Whoaa!!!! you can't run single 3 phase conductors in seperate conduits unless you want to make a giant induction oven. I seen that done once, three 4" conduits running across the ceiling of a factory with each conduit carrying an individual phase. When the power was turned on the entire length of all three conduits turned cherry red and melted.

 

[Howard Sterndrive]

Re: electrician question -flexible amp clamps around conduit

something wasn't connected right there... or the conduit was steel? .. scary

both the feeds into our shop come in that way - three individual conduits - each carries 1 conductor to each of 3 individual 200A breakers
pretty sure it's aluminum so no inductive effects - not magnetic

Lots of 3 phase gen sets I have worked on run the legs in separate conduit to the lugs or to the breaker.

I just want to know if I will get an accurate reading. If I have to open panelling, I will just continue with the amp clamps I have.....jaws don't open wide enough to go around this conduit

 

[sschefer]

Re: electrician question -flexible amp clamps around conduit

something wasn't connected right there... haha.. scary

both the feeds into our shop come in that way - three individual conduits - each carries 1 conductor to each of 3 individual 200A breakers

Lots of 3 phase gen sets I have worked on run the legs in separate conduit to the lugs or to the breaker.

I just want to know if I will get an accurate reading. If I have to open panelling, I will just continue with the amp clamps I have.....jaws don't open wide enough to go around this conduit

I agree, inductance doesn't go any further than the conduit thats why it's used. Sounds like a bad earth (ground) in bigdee's experience.

You really need to read it at the box.

 

[bigdee]

Re: electrician question -flexible amp clamps around conduit

I agree, inductance doesn't go any further than the conduit thats why it's used. Sounds like a bad earth (ground) in bigdee's experience.

NEC prohibits service feeders to be run in separate conduits,ABC phases have to be run together ...long parallel runs in steel conduit with a separate phase in each conduit will create eddy currents and heat up the conduit on high ampacity loads. The grounding has nothing to do with it, in fact it is the grounding on BOTH end of the conduits that contribute to this phenomenon by creating a current loop.

 

[LongLine]

Re: electrician question -flexible amp clamps around conduit

Sparky has to remove a large wire so he uses his wrap around meter to test if the line is live or not. No reading, so he crabs his sawzall & has at it. 10 seconds later, after a melted sawzall, a gaint flash, and knocking out power to 4 buildings, he realizes it was a shielded cable.....oops... lucky he's still alive.

Un-related, but moral is - Please be careful with any wrap around.

Tom B.
(LongLine)

 

[joed]

Re: electrician question -flexible amp clamps around conduit

In response to the question. NO you can not measure it through the conduit. It needs be around the cable only.

 

[sschefer]

Re: electrician question -flexible amp clamps around conduit

In response to the question. NO you can not measure it through the conduit. It needs be around the cable only.

What I said, not sure how it got missinterpreted. Oh well.