Checking amps at the breaker.

mbcabinetmaker · Post by **mbcabinetmaker** » Sat Jul 25, 2009 9:03 pm

Thanks for the help guys. I will get the mfg of my meter tomorrow. I just don't remember. I have had it for several years and remember it costing around $100.00 when I bought it. I did check to make sure everything was tight in the panel box including grounds, neutrals and breakers.

JPG · Post by **JPG** » Sat Jul 25, 2009 9:38 pm

Clamp on ammeter IS the safest way to go. Does the one you are using have a sliding clamp on it? The loop over the conductor MUST be totally closed to complete the magnetic path(It measures current by observing the magnetic field around the conductor). The meter must be set to the proper range. It must be intended for AC use. Unless it is digital, no battery is needed. If digital, battery is necessary. Do the other functions(volt,resistance) work properly? Have the ends of the pole pieces(the loop joint) become rusted? Is it digital(or analog)? If analog, does it have a needle clamp? If so is the clamp 'released'?

BTW It clamps AROUND the conductor, not ON it!

Ed in Tampa · Post by **Ed in Tampa** » Sat Jul 25, 2009 11:39 pm

Yes the clamp goes around the wire not on it. The clamp ends must come together. You must have the meter set on the right scale, AC amperage, 10+ amps. Lastly you must have current running through the wires, the lights or whatever the load must be on or in use.

For meters with leads you can only measure current by placing the meter in series, this is dangerous with 110 and not advised. Besides most meters that require series connection usually have a max amperage of 10 Amps not enough for you test.

Sears does sell a clamp probe that can be used on any meter that has similar probe plugs. You plug it into the meter put the clamp around the wire in the circuit to be measured and set your meter on 10 amp scale. I believe the clamp is 10 to 1 reduction so 10 amp looks like 1 amp on the meter.

Careful 110 will bite you and if you bump the 220 you may find yourself jumping across the room. Whatever you do keep your left hand in you pocket. So you don't make a circuit through your right arm across you heart and out the left. Bad for hearts!

mikelst · Post by **mikelst** » Sun Jul 26, 2009 8:57 am

I haven't seen any one else mention it so I'll say that you should only have one wire inside the clamp. If you have more than one wire you will get false current or even zero readings as the current if not in phase can cancel each other.

There should be a specific setup for current reading, usually on a rotary dial switch it is divided into 5 areas.

Volts AC
Volts DC
OHMS
Amps AC (this may be marked Current or I instead)
Amps DC (this may be marked Current or I instead)

With the meter on,
insure you are set to the max setting on the AC Amps setting.
You should not need any leads with this function.

Clamp the wire coming out of the breaker you are checking and reduce the range to get the best reading possible.

If more than one wire is coming out of the breaker clamp them one at a time and add the results for total current.

This should get you the total current for the breaker.

mbcabinetmaker · Post by **mbcabinetmaker** » Sun Jul 26, 2009 11:22 am

Just got home from Church and went to the shop to try again. Clamped around the wire and nothing. I had the meter (by the way it is a Greenlee CMT-60) set to the A or amp setting. On a whelm while in this position I switched to the off position and then back to A. Results 12.5 amps. Now it works every time in the A position. Maybe it has some type of internal reset or something, but at least it is working. So with the amps well with in range of my # 12 wire and 20 amp breaker, and after checking all connections in the panel I will replace the breaker to see if it is faulty. If not it could be a connection in one of the lights. If so begins the needle in the haystack search. Thanks for your help guys.

beeg · Post by **beeg** » Sun Jul 26, 2009 12:14 pm

Have ya checked that the contacts on the breaker are clean? If nothing else reseat the breaker.

JPG · Post by **JPG** » Mon Jul 27, 2009 2:27 am

Re: More than one wire coming off the breaker. The currents in the conductors will be in phase(there is only one phase/polarity involved here). The total current passing through the breaker can be measured by clamping the meter around both(all) the conductors attached to the breaker(load side). You COULD also measure the current in each conductor separately.

As Beeg has suggested, pull the breaker out of the buss bar and reinsert it solidly! Watch what you touch. If possible, turn the main breaker off while reseating it.

dusty · Post by **dusty** » Mon Jul 27, 2009 6:20 am

Is it not a code violation to gang wires from a breaker?

JPG · Post by **JPG** » Mon Jul 27, 2009 9:08 am

dusty wrote:Is it not a code violation to gang wires from a breaker?

Usually! A down stream splice IS more usual!

dusty · Post by **dusty** » Mon Jul 27, 2009 10:58 am

JPG40504 wrote:Usually! A down stream splice IS more usual!

Are we talking about serving two or more circuits with the same breaker OR

are we talking about using two wires for the same feed (like two #14 is better than one #12).

Both seem like a NO NO to me.

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Checking amps at the breaker.

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