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#198614 - 01/29/11 10:45 AM Grounding seperate bldg
crselectric Offline
Member
Registered: 09/24/06
Posts: 134
Loc: albany, ca
Old berkeley cottage has 2wire feed to garage. adl rod at garage and no 8 green to first splice box, rest of wire is bx with alum strip, no egc back to main, as it is old k&T in attic.
Client was getting shocked when using potters wheel in rainy weather, found a short from hot switch backwire lead to edge of metal box, read 2.45 ohms during dry weather with load unplugged. cleared after i rebuilt the switch box,

my Question is it required for safety to in stall a egc back to panel that feeds garage, I believe that there is no ground at panel, so would I run gec from rod to rod at main, If there is one? to clear future faults? this place has also been alteredto fit new appliances etc moved switches etc without proper wiring protection at KO's. min. gfci circ. gar and afci main house?
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#198618 - 01/29/11 12:06 PM Re: Grounding seperate bldg [Re: crselectric]
SJT Offline
Member
Registered: 07/24/02
Posts: 242
Loc: PATCHOGUE, N.Y.
Hello CRS,
Is this a detached garage, or attached to house? What is an adl rod? Possible, new feeder to garage needed.
SJT
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#198640 - 01/30/11 11:47 AM Re: Grounding seperate bldg [Re: crselectric]
crselectric Offline
Member
Registered: 09/24/06
Posts: 134
Loc: albany, ca
Detached bldg., some time earlier someone installed a ground rod at the sep. bldg #8 green and bonded the first j-box where the aerial wires come in. no bond between neutral and gr at garage, so fault would try to get back to house gec/rod. She was having shocks while running her electric potters wheel during rain season worse but a tingle when dry. so does there have to be a addtl short in equipment for her to recieve a shock I.e. bonded neutral in a electric wheel for the 2.5amps to get back to the return via the case. also the wheel has a 3wire plug so I assume its bonded to the local ground rod. could there be a current loop in garage equipment that I need to find? thanks chris
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#198646 - 01/30/11 01:38 PM Re: Grounding seperate bldg [Re: crselectric]
gfretwell Offline


Member
Registered: 07/20/04
Posts: 9066
Loc: Estero,Fl,usa
You still need the EGC going back to the house to clear a fault.
My guess is that you do actually have a ground fault now and that is why she is being shocked. I bet that wheel will trip a GFCI.
_________________________
Greg Fretwell
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#198652 - 01/30/11 05:43 PM Re: Grounding seperate bldg [Re: crselectric]
crselectric Offline
Member
Registered: 09/24/06
Posts: 134
Loc: albany, ca
In the repair I did I was not able to put the whole garage on a gfci circuit, I did clear a ground fault at the main wiring switchbox for the garage lights and some equipment but not the plug that the wheel was off of, but I did clear the live 110 off the metal boxes and bx wiring by changing the box so the switch wires were no longer touching the side of the box, definately removed the hazard, but not fully protected, am going to return but wasnt sure If I needed to add egc, or just get circuit on gfci Protection, So if I just put a gfci device in the first jbox and do I connject the garage ground rod to the device green without adding egc back to main, or try and sell her a new egc/circuit back to main, havent seen how conveluted it might be, chris
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#198653 - 01/30/11 05:48 PM Re: Grounding seperate bldg [Re: gfretwell]
SJT Offline
Member
Registered: 07/24/02
Posts: 242
Loc: PATCHOGUE, N.Y.
Are there only 2 wires feeding the garage now? Any water pipes or other metallic paths between Main House and garage?
Is there a small breaker panel in garage now?
SJT
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#198654 - 01/30/11 06:06 PM Re: Grounding seperate bldg [Re: crselectric]
crselectric Offline
Member
Registered: 09/24/06
Posts: 134
Loc: albany, ca
No garage panel just a 4x4 box with three no. 8's hot return and green from rod at bottom of wall, and then about 5 mc's going to other plugs around the room, and just a 2 wire going to plug below and lights (Now protected). So as it was the bx and metal boxes were sitting with voltage on them and i guess the earth path back to the main or pole wasnt good enough to allow too much current, do you think its relatively safe for a few days till I can get back out there, I didnt read any other shorts but could not do a exaustive search at that time, thanks chris
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#198667 - 01/31/11 05:44 AM Re: Grounding seperate bldg [Re: crselectric]
n1ist Offline
Member
Registered: 02/13/02
Posts: 176
Loc: Malden MA
If she is still getting shocked, there's still a ground fault somewhere that's energizing the case of the potter's wheel. Using a rubber mat under the wheel and chair may help prevent shocks until the problem is sorted out.

What size OCPD is feeding the #8 going to the shed?
/mike
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#198670 - 01/31/11 10:53 AM Re: Grounding seperate bldg [Re: crselectric]
SJT Offline
Member
Registered: 07/24/02
Posts: 242
Loc: PATCHOGUE, N.Y.
CRS,
The best defense to a shock would be to de-energize the circuit, until it can be resolved.
I would recommend establishing a grounding electrode at the garage, setting up a circuit breaker panel, and correcting the ground fault.
Sounds like the garage needs some attention to correct the violations that exist.
Good Day
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#198693 - 02/01/11 08:37 AM Re: Grounding seperate bldg [Re: crselectric]
gl53 Offline
New Member
Registered: 02/01/11
Posts: 4
Loc: Texas
I would look to see if the garage was originally wired with a california 3 way. It was common to run 3 wires to the garage from a 3 way switch which ran a light on a 3 way and a hot outlet. This was accomplished by using the travelers as the circuit and the 3 way switched the power relationship so the light had a same polarity for off concept.
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