Nuetral and ground continuity.

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green2012

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highland park, il
I went over this a few times and wiring looks good. This is a pipe and wire installation. I piped from the main panel to the exterior of a home and mounted a spa disconnect. Pulled 2 hots, a neutral, and a ground. When I finished landing all the wires in the disconnect, I started testing for any unwanted continuity before I turned on the breakers. I tested positive continuity between neutral and ground conductors. Is this normal? The main panel nuetral is bonded to the box. I know Im suppose to get continuity between neutral and ground at the main panel and all the ground wires can land on the neutral bar at this panel. Is this why Im reading continuity at the disconnect?
 
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Volta

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Location
Columbus, Ohio
Yup, sure is. As you have essentially stated, the grounded and grounding conductors are connected at the service disconnect. In fact, you want the lowest resistance reading you can get between them. For a more comprehensive test, you could remove one or the other at the source and should read many millions of ohms.
 
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green2012

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Location
highland park, il
It leads me to ask a dumb question though. If a nuetral wire nut came off in a grounded metal box, would it trip the breaker if they made contact? And how about this scenerio, If the spa installer mixes up the neutral and ground wire and lands them in reverse. Then the ground ( that lands directly on the disconnect metal enclosure ) would become the neutral. All metal pipe leading back to the panel would have neutral current? This wouldnt pop the breaker either? Why doesnt this pose electricution hazard? I guess Ive always wondered why I can touch the neutral bar in the panel and not get juiced.
 
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GoldDigger

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green2012 said:
It leads me to ask a dumb question though. If a nuetral wire nut came off in a grounded metal box, would it trip the breaker if they made contact? And how about this scenerio, If the spa installer mixes up the neutral and ground wire and lands them in reverse. Then the ground ( that lands directly on the disconnect metal enclosure ) would become the neutral. All metal pipe leading back to the panel would have neutral current? This wouldnt pop the breaker either? Why doesnt this pose electricution hazard? I guess Ive always wondered why I can touch the neutral bar in the panel and not get juiced.
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In this and other expense cases, the neutral wire is carrying current, but is at voltage very close to ground. Because of the bond at the main panel, if the neutral touches a grounded metal object some current will flow back to the secondary of the service transformer through the ground path rather than the neutralBut the voltage difference will be so low that the will not be a dangerous spark.
 
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Volta

Senior Member
Location
Columbus, Ohio
And the resistance of your dry skin is generally high enough that very little current will pass across it. But as the resistance decreases, say, by cutting your finger on the corner of that grounded conductor bar, more current will be able to flow. The further 'downstream' from the service disconnect, the more likely that there will be a difference between the grounded conductor and real or equipment ground.
 
Little Bill

Little Bill

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green2012 said:
I went over this a few times and wiring looks good. This is a pipe and wire installation. I piped from the main panel to the exterior of a home and mounted a spa disconnect. Pulled 2 hots, a neutral, and a ground. When I finished landing all the wires in the disconnect, I started testing for any unwanted continuity before I turned on the breakers. I tested positive continuity between neutral and ground conductors. Is this normal? The main panel nuetral is bonded to the box. I know Im suppose to get continuity between neutral and ground at the main panel and all the ground wires can land on the neutral bar at this panel. Is this why Im reading continuity at the disconnect?
Click to expand...

green2012 said:
It leads me to ask a dumb question though. If a nuetral wire nut came off in a grounded metal box, would it trip the breaker if they made contact? And how about this scenerio, If the spa installer mixes up the neutral and ground wire and lands them in reverse. Then the ground ( that lands directly on the disconnect metal enclosure ) would become the neutral. All metal pipe leading back to the panel would have neutral current? This wouldnt pop the breaker either? Why doesnt this pose electricution hazard? I guess Ive always wondered why I can touch the neutral bar in the panel and not get juiced.
Click to expand...

Just a side note: All the packaged spas I have connected, the instructions say to use nonmetallic pipe to the disconnect.
 
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green2012

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Location
highland park, il
We cant use non metalic pipe in chicago. All internal pipe has to be metal. The only time we use pvc is when we are putting it under ground, and even then I prefer to use rigid conduit.
 
iwire

iwire

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Massachusetts
green2012 said:
We cant use non metalic pipe in chicago. All internal pipe has to be metal. The only time we use pvc is when we are putting it under ground, and even then I prefer to use rigid conduit.
Click to expand...

Metal conduit under ground is even more nuts than EMT in wood framed homes. :D
 
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