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Joined: Sep 2005
Posts: 99
T
Tripp Offline OP
Member
But Bob - tell me more about this bad neutral thing: why would one leg show high and the other low? Is that the only possible scenario?

Thanks in advance for elaborating.

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Joined: Jan 2003
Posts: 4,391
I
Moderator
Morning Trip, when you try to measure line to neutral on a feeder that lost the neutral connection the meter is not in parallel with the feeder. You actually are in series with part of the load on the circuit.

Here is one of Rogers drawings, it may help to explain the problem.

[Linked Image]

As the drawing is now if you place your meter leads between the neutral and the hot you will read 120 volts.

Leave you meter connected but 'disconnect' the neutral at the source, now what is the meter reading?

That would depend on the size of the load on each of the hots.

The meter could read anywhere from 0 volts to just short of 240 volts.

It will also if one side reads 25 volts high the other side will read 25 volts low.

Many times a lost neutral will end up releasing smoke from appliances that do not like an extra 50 or more volts. [Linked Image]

Sorry if I can not explain it well, perhaps Jon will step in.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Joined: Sep 2005
Posts: 99
T
Tripp Offline OP
Member
Thanks, Bob. I will have to save this post and the graphic to refer back to several times, I'm sure.

Joined: Mar 2005
Posts: 240
Member
ok guys i will set myself up for this one.
what if you reversed the connections at the 2 pole breaker(move the red wire from L1 to L2 and the black wire from L2 to L1) and then took a reading at the sub panel now you would have power on the leg that was zero and zero on the one that had power or perhaps like someone else said about loose connection at the 2 pole hence woolahh 240 appears.
just a thought good or bad?
h20

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