Checking Mains with Multimeter

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  #1  
Old 02-21-14, 05:24 AM
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Checking Mains with Multimeter

Just wanted to check before doing something stupid with my multimeter.

To check incoming power from the main service in my panel.

I would touch one probe to the neutral screw on the neutral lug. And the other probe then to the screw on one hot leg. 120.

Then repeat the process on the other leg for 120. Or one probe on the screw to one leg to the other screw on the other leg 240

The same idea would be used to check the main breaker using the breaker screws and the main lug screw on the neutral?

Also how do I check the mains hot to ground. and neutral to ground? (or is neutral to ground the same thing in the main panel?)

Thanks,
 
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Old 02-21-14, 06:28 AM
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As long as the meter is set for the correct voltage range and has the correct safety rating your process is correct.

Neutral to ground should be zero in the service panel.
 
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Old 02-21-14, 06:49 AM
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Checking hot leg to neutral is checking ground right? Or do I check hot leg to the metal enclosure since the two are bonded?
 
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Old 02-21-14, 08:22 AM
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Checking hot leg to neutral is checking ground right? Or do I check hot leg to the metal enclosure since the two are bonded?
Since the neutral is bonded to ground, hot leg to neutral and hot leg to the panel box should give the same reading, probably about 120 volts. One hot leg to the other hot leg should give you about 240 volts.
 
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Old 02-23-14, 06:06 AM
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And if I was tightening a circuit breakers screws, or replacing one, is it best to turn off the breaker and then tighten when its still attached to the busbar or should I be torqueing with the breaker in my hand?

And if tightening screws on the neutral bus, why is it alright to do so with the power on? Or should I turn off the main?
 
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Old 02-23-14, 08:17 AM
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It is always safer to work with the power off in the panel.

I would tighten the screws with the breaker turned off, but installed.
 
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Old 02-23-14, 11:21 AM
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I would tighten the screws with the breaker turned off, but installed.
So would I, but you are a pro. For a beginning DIYer it might be safer to hold the breaker in one hand to tighten the terminal, then install the breaker.
 
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