Garage Shock

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Penta

Member
I have a client who gets shocked while working on the table saw in his garage. The garage is fed with 14-2 UF with no ground wire and then split off to lights and receptacles via BX. If I sink 2 ground rods and ground the boxes will this help or am I missing something?
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Welcome to the forum.:)

Is this a detached garage?

When was this wired?

Driving ground rods and connecting them to the boxes will not eliminate the shock hazard.

Chris
 

Receptive

Member
There is some improper wiring going on somewhere. Have you checked all of the connections to make sure there are no line to case or neutral to case connections?
 

hurk27

Senior Member
I have a client who gets shocked while working on the table saw in his garage. The garage is fed with 14-2 UF with no ground wire and then split off to lights and receptacles via BX. If I sink 2 ground rods and ground the boxes will this help or am I missing something?

Yes you are missing something:

No low impedance ground fault path back to source. Ground rods can not safely provide for this, the resistance of Earth is to high.

GFCI's, the receptacles should be GFCI's at least it will open the circuit when a ground fault did happen.

Possibly a miss-wired cord or receptacle, or circuit, that is energizing the grounding of the table saw.;)
 

carlos cainas

Member
Location
Tampa
first you are overloading the circuit with table saw and lights tide together,you always have issues when you overload a circuit,run new circuits for table saw and one for the lights with proper ground from the panel.easy fixs.
 

hurk27

Senior Member
I want to add that this sounds like the house or garage has the old cloth covered wiring, for the most part in this old wiring the neutral can't be identified from the hot, then someone comes along and connects a new circuit to it, with backward polarity, then someone adds a 3 prong receptacle and boot legs the neutral from what they think is a neutral, but in reality is a hot, so when a 3-wire appliance is connected to this plug, the case and frame is now connected to the hot.

The best way to check for this is to run an extension cord, from a known properly wired and tested receptacle, and use it as a reference to see which wire are hot, and which wire is neutral, then if a boot legged neutral is found remove it, and install a GCFI receptacle.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
The best way to check for this is to run an extension cord, from a known properly wired and tested receptacle, and use it as a reference to see which wire are hot, and which wire is neutral, ...
Ah, Grasshopper, you have learned well. ;)


I would recommend a solenoid-type tester, not a regular voltmeter.
 

mcclary's electrical

Senior Member
Location
VA
http://www.youtube.com/watch?v=EQiMr5Xm2sU
I have a client who gets shocked while working on the table saw in his garage. The garage is fed with 14-2 UF with no ground wire and then split off to lights and receptacles via BX. If I sink 2 ground rods and ground the boxes will this help or am I missing something?


Once you watch this, come back and tell us if you still feel comfortable trying to fix this yourself!:mad::mad::mad:
 

hurk27

Senior Member
You're absolutely right. That dates farther back than my joining the site.

I started doing it back when I was a helper, and showed it to the guys I worked under.

ya know someting, I cant remember when I first joined this site:confused:

I was thinking it was in "99" or "2000" just not sure, I know we went through at least 4 forum formats. the one in "2003" was the one that shows us old timers all joining on the same date lol:roll:

Had allot of fun here, and met some really great people, as well as learned so much about code, and the laws that surround the building industry:D
 

hurk27

Senior Member
Could the table saw be the problem?

PS remember when we had member #'s? mine was 68.

At least you can remember you member # lol

sure the saw cord, table wiring could be a part of the problem, but we have to look at all the problems, as a whole, and only testing will tell the truth as to what is happening.

A shock hazard is a great concern for any electrician, and once you have knowledge of this, you should not stop until you found it, of course it will depend upon who's paying the bill, but, at least testing should be done as described above.
 

Penta

Member
Welcome to the forum.:)

Is this a detached garage?

When was this wired?

Driving ground rods and connecting them to the boxes will not eliminate the shock hazard.

Chris

It is a detached garage. It's not just the table saw that shocks, there is also a steel work table that provides a tingle.

Also I went from hot to garage door track and got 119volts. Aside from running a new circuit to the garage is there anything else I can do?
 

rcarroll

Senior Member
It is a detached garage. It's not just the table saw that shocks, there is also a steel work table that provides a tingle.

Also I went from hot to garage door track and got 119volts. Aside from running a new circuit to the garage is there anything else I can do?

How much time do you want to spend troubleshooting? Personally, I would try to convince your customer to install a new circuit or feeder to the garage. It may be faster, cheaper & safer. JMHO.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
It is a detached garage. It's not just the table saw that shocks, there is also a steel work table that provides a tingle.

Also I went from hot to garage door track and got 119volts. Aside from running a new circuit to the garage is there anything else I can do?

There has been a ground fault somewhere in the garage and since there is no EGC the metallic parts are now energized.

Where this is a detached garage, is there any other grounded metallic paths from this building to the main building such as a metal water pipe etc...?

If there are no other grounded paths between the 2 buildings then I would recommend bonding the neutral at the building disconnecting means in accordance with 250.32(B)(2) (2005 NEC) or 250.32(B) exception. Then, if it is possible, run an EGC from the detached garages disconnecting means to the rest of the garage wiring.

Chris
 
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