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Old 11-15-2011, 12:02 PM   #1
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Bad Circuit breaker?


I installed a generator interlock in my panel. all circuits work fine on utility power, on generator power I'm only getting voltage on every other circuit. I am assuming the 30amp 2 pole breaker for the interlock is damaged. Any ideas?

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Old 11-15-2011, 12:27 PM   #2
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Bad Circuit breaker?


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Originally Posted by mdaigs34 View Post
I installed a generator interlock in my panel. all circuits work fine on utility power, on generator power I'm only getting voltage on every other circuit. I am assuming the 30amp 2 pole breaker for the interlock is damaged. Any ideas?
Taking appropriate precautions measure the voltage drop across the switched-on CB. You should not see more than millivolts.

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Old 11-15-2011, 12:29 PM   #3
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Bad Circuit breaker?


Yeah your missing a phase somewhere. You can determine this using a volt meter and measuring across both legs coming off the generator. If you get 240 coming out of the gen at the point it attaches to the breaker then I would replace the breaker. If you do not get 240 at this point your problem is elsewhere.
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Old 11-15-2011, 01:31 PM   #4
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Bad Circuit breaker?


Quote:
Taking appropriate precautions measure the voltage drop across the switched-on CB. You should not see more than millivolts.
Measuring between a properly fed or wired two pole breaker you should see 240 volts, not millivolts.
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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
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Old 11-15-2011, 03:13 PM   #5
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Bad Circuit breaker?


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Originally Posted by Yoyizit View Post
Taking appropriate precautions measure the voltage drop across the switched-on CB. You should not see more than millivolts.
should read
Quote:
Originally Posted by Yoyizit View Post
Taking appropriate precautions measure the voltage drop across the closed contacts of each pole of the switched-on CB. You should not see more than millivolts.
My bad. It depends on what is meant by 'across.'

Traister wrote a handbook of electrical testing but did not live to see it go to print. IIRC, his numbers were
less than 30 mV for good contacts
and
more than 100 mV for bad contacts.
at rated current.
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