Line voltage reading question

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Old 11-20-13, 08:17 AM
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Line voltage reading question

I borrowed a low impendence digital multimeter from a friend (gets rid of phantom voltage I am told).

I was testing it on some outlets. Let me say all devices are wired correctly and everything appears to be normal.

From hot to neutral I was reading 122v ac.
From hot to ground I was reading 122 and from screw on plate to hot I was reading 122.

From Neutral to ground I was getting a reading of less than 1. -- somehwere like .18.

My questions:

Is 122v AC on the high side of normal?

Is it abnormal I have miniscule (less than 1.) voltage on neutral to ground?

Again this meter eliminates phantom voltage.... is it possible the circuit I was testing it on is an Edison circuit and that is why there is miniscule voltage on neutral to ground or am I missing something something else?
 
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Old 11-20-13, 08:32 AM
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It is a bit high but within the normal range. Plus or minus 5% is the allowable range which is 114 - 126 volts though I think 123 or 124 is the highest I've ever seen. During peak summer usage I've seen it drop to 117 intermittently and hold at 118 during the hottest part of the day.
 
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Old 11-20-13, 08:34 AM
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Your readings sound normal. Line voltage is 120V + 10%, or 108 - 132V. 0.18V is so close to 0.0V as to be meaningless.

is it possible the circuit I was testing it on is an Edison circuit and...
IDK. What is "an Edison circuit"?
 
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Old 11-20-13, 08:43 AM
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"edison circuit" I had my friend clarify, he said thats slang, that he meant to say its that two circuits are sharing the white wire?

Anyway, I tried it again under some load. I put on a microwave on one circuit and tested neutral to ground on the other circuit of the "shared" situation. With the microwave running I was getting minimal again like .6 and then it would decrease when the microwave stopped.

As far as 122 being on the high end.... could that be an issue on my end or would that be determined by what the utility provides... other words, my problem or utility problem?
 
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Old 11-20-13, 08:51 AM
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"edison circuit" I had my friend clarify, he said thats slang, that he meant to say its that two circuits are sharing the white wire?
That's a multiwire branch circuit, or MWBC.

Anyway, I tried it again under some load. I put on a microwave on one circuit and tested neutral to ground on the other circuit of the "shared" situation. With the microwave running I was getting minimal again like .6 and then it would decrease when the microwave stopped.
That sounds normal for a MWBC when connected. Voltage readings, however, should be taken with the conductors disconnected from all loads and devices.

As far as 122 being on the high end.... could that be an issue on my end or would that be determined by what the utility provides... other words, my problem or utility problem?
What problem? The answer is still that
Originally Posted by Nashkat1
Line voltage is 120V + 10%, or 108 - 132V.
 
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Old 11-20-13, 09:01 AM
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The small voltage you are seeing is the resistance drop across the neutral wire when it is carrying a load. The length, gauge, and all connections between the load and the panel, where neutral and ground are connected together, determines that voltage. The readings you are getting are probably due to just the length of the run. With length and wire gauge that can be calculated.

A multiwire branch circuit actually decreases the voltage across the neutral when there are loads on opposite phases of the circuit, the current flows through the other hot instead of the neutral.

Bud
Nash, you are just faster than I am .
 

Last edited by Bud9051; 11-20-13 at 09:03 AM. Reason: excuse
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Old 11-20-13, 09:06 AM
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Thanks BUD9051!. Excellent reply. So because I was testing neutral to ground with loads applied is why I am seeing the miniscule voltage. When I have tested outlet before with my cheap multimeter (high impendence) I would never see anything neutral to ground, that is what threw me.

WIth the low impendence meter, I probably will always see the miniscule voltage then on neutral to ground because the meter puts a 3ma load on the circuit anyway. Is that correct thinking?


Originally Posted by Nashkat1

Line voltage is 120V + 10%, or 108 - 132V.

GOt it! Understand better now.
 
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