line to ground continuity

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Old 07-27-06, 01:25 PM
dh4
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line to ground continuity

Should there ever be continuity from line to ground? 15 amp fuses do not blow and circuits work yet with fuse out while replacing an outlet and testing the wires I had continuity to ground on both the white grounded wire and the black line.
Going back to the fuse box(240/30amp) servicing the floor of this old building and removing the fuses I could get continuity to ground on both poles(line). Should'nt this short?
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Old 07-27-06, 01:46 PM
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one reason you can read continuity; if you have anything plugged into that circuit or a light on that circuit,(either would have to be actually turned on) there is continuity between hot and neutral/ground.

as an example;You could possibly be reading from the hot, which is also part of a lighting circuit, through a light bulb to neutral/ground.

a motor and an incandescent light bulb and other things are effectively "shorts" in a sense. Hot and neutral are connected within these appliances. That is why they run/work
 
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Old 07-27-06, 02:17 PM
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Thanks! That clears things up for me.
Can I pose another one??
While coming in one day wet with rain I held the ground floor metal door open with one hand while with the other hand grapped the metal stair banister and received a nice shock. On testing, I discovered the door was carrying 40 volts!
On further testing, I got readings of 35v on the metal window frames set in the brick up on the third floor. This is in the rear of the building, as you move towards the front(45')
the voltage dissipates.
Aside from the obvious danger, I am baffled as to the source and apparent non-effect on the buildings circuits.
Thanks again
 
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Old 07-27-06, 02:32 PM
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Ok. Now that we know there are other problems we need to look at other things as well. The continuity reading you get could also be an actual unintended short circuit.

You may have a chafed wire grounding out to the metal in your house. Sometimes, if the resistance is high enough, it will not make the breaker trip (or fuse blow) but you willl get a shock. There could be many reasons to have this problem though.

As well, you may not have an adequately grounded and bonded electrical service.

That is where I would start.

Your neutral must be bonded to a grounding system as specified in the Nat'l Electrical Code. Also, all metal that is subject to the possibility of becoming energized must also be bonded to the grounding system. This will prevent a difference of potential (voltage) between two conductors.

Now for a fuse to blow, it must be subjected to a current flow inexcess of its rating. If there is a high resistance in the short circuit, there will not neccessarily be enough current flow to pop the fuse.
 
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Old 07-27-06, 03:07 PM
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Thanks, I will take your advice.
What amazes me is how this current leak that does not blow a fuse can be enough to migrate up 3-12' stories through masonry to energize window frames on the top floor! Perhaps it is the staircase that is energized and delivering the migrating voltage to the rear of the building?
By the way this forum is great...
Many Thanks
 
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Old 07-27-06, 03:39 PM
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Originally Posted by nap
Now for a fuse to blow, it must be subjected to a current flow inexcess of its rating. If there is a high resistance in the short circuit, there will not neccessarily be enough current flow to pop the fuse.
Or from hesat generated from a loose wire hooked up to a circuit breaker or fuse, or a bad contact between the fuse socket and fuse or breaker connectors to the buss.

My 20A water heater breaker kept tripping on me and I amp tested it and it was okay. Only to find out the screw holding the wire to the circuit breaker was just loose enough to cause a heat situation that I could not visibly see or smell (I saw no arcing nor heard any sizzle sounds). And the screw was not even all THAT loose. Just some. Ever since I tightened it, I have had no more tripping breaker, while before this, it was every day....for months.
 
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Old 07-27-06, 04:20 PM
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I've been trying to diagnose a lighting system problem with line voltage mushroom lighting around a pool. They wouldn't trip a regular breaker, but did on GFCI. Decided to pull up one of the lights, and the do-do that installed them used UF feeder cable, with compression fittings and electrical tape!! Direct buried connections with tape. Duh! Now I have to dig up 14 of them. Obviously the current is leaking, but not enough to trip a breaker. And around a pool, too!!
 
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