GFCI Confusion - Electrical - DIY Chatroom Home Improvement Forum
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools
Display Modes
Old 01-18-2010, 03:41 PM   #1
Member
 
Bigplanz's Avatar
 
Join Date: Apr 2009
Location: Louisville KY
Posts: 1,666
Rewards Points: 2,492
Default

GFCI confusion


I have a GFCI circuit in the basement. One of the downstream receptacles had a cracked plastic face plate, so I decided to replace it with a metal one. When I took the cracked face plate off, one of my fingers brushed a hot brass screw and I got shocked. Yet, the leak to ground did not trip the GFCI. I pushed the GFCI test button and it tripped. I tested the receptacle that shocked me with a GFCI receptacle tester and it glowed double green. When I pushed the test button, it tripped, just like it's supposed to. Yet, it didn't trip when I grounded it by brushing against the hot screw. WTF?!?!?
Bigplanz is online now   Reply With Quote
Sponsored Links
Advertisement
 
Old 01-18-2010, 03:59 PM   #2
the Musigician
 
DangerMouse's Avatar
 
Join Date: Jul 2008
Location: I'm right here!
Posts: 10,404
Rewards Points: 2,000
Default


you got shocked BEFORE it was protecting?

DM
__________________
[SIGPIC][/SIGPIC]Click here to see some of my original magic tricks and trick boxes!
DangerMouse is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 01-18-2010, 04:06 PM   #3
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000
Default


Make sure it is off the LOAD side of the GFCI & not the LINE side



Scuba_Dave is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 01-18-2010, 04:38 PM   #4
Tool Geek
 
PaliBob's Avatar
 
Join Date: Jun 2008
Location: Pacific Palisades CA
Posts: 2,590
Rewards Points: 2,160
Default


Quote:
Originally Posted by Scuba_Dave View Post
Make sure it is off the LOAD side of the GFCI & not the LINE side
Big tested the outlet in question with a GFCI Tester and it tripped the upstream GFCI so there is no Line/Load mix-up.

The shock was most likely from a very low level current that could take up to several seconds to trip the GFCI.


http://ecmweb.com/mag/electric_think_gfci/
.
Attached Thumbnails
GFCI confusion-gfci-shock.jpg  
__________________
Disclaimer
& Stay Safe
.....Bob Lavery
PaliBob is offline   Reply With Quote
Old 01-18-2010, 04:46 PM   #5
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 7,828
Rewards Points: 2,006
Default


A GFI is NOT intended to prevent shocks. It is intended to prevent electrocution.
Speedy Petey is offline   Reply With Quote
Old 01-18-2010, 05:04 PM   #6
Inspector/Instructor
 
codeone's Avatar
 
Join Date: Dec 2009
Location: NC
Posts: 369
Rewards Points: 250
Default


Quote:
Originally Posted by Speedy Petey View Post
A GFI is NOT intended to prevent shocks. It is intended to prevent electrocution.
Agree totally!
codeone is offline   Reply With Quote
Old 01-18-2010, 05:28 PM   #7
Member
 
Bigplanz's Avatar
 
Join Date: Apr 2009
Location: Louisville KY
Posts: 1,666
Rewards Points: 2,492
Default


Quote:
Originally Posted by Speedy Petey View Post
A GFI is NOT intended to prevent shocks. It is intended to prevent electrocution.
Yes, I know, thank you. However, it should trip at a threshold so low that if one felt a shock it would be almost imperceptible. This felt like any other 120V shock I have ever gotten. Made me jerk my hand away and go "Ow!"
Bigplanz is online now   Reply With Quote
Old 01-18-2010, 05:36 PM   #8
Too Short? Cut it Again!
 
Join Date: Sep 2009
Posts: 9,634
Rewards Points: 2,000
Default


You sure the two are on the same circuit?
user1007 is offline   Reply With Quote
Old 01-18-2010, 05:45 PM   #9
Just call me Andrew
 
Join Date: Mar 2009
Location: Albany, NY
Posts: 2,271
Rewards Points: 1,032
Default


He knows that outlet is protected since it tripped with the tester.
__________________
Andrew

secutanudu is offline   Reply With Quote
Old 01-18-2010, 06:05 PM   #10
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 7,828
Rewards Points: 2,006
Default


Quote:
Originally Posted by Bigplanz View Post
However, it should trip at a threshold so low that if one felt a shock it would be almost imperceptible.
Absolutely not. A shock is a shock. It depends on how well you are "grounded" and how much current feeds through you. You "feel" the voltage, not the current.
If you are not grounded very well then you will not get much voltage. Similar to voltage drop.
Current flow trips the GFI. The GFI trips if it measures 5-6mA of current imbalance between the hot and neutral (or hot and hot). This 5-6mA can be leaking many places, including through your finger. It will trip in a very short time period, so it is completely feasible that you will get a very painful shock but not for nearly enough time to kill you.
Speedy Petey is offline   Reply With Quote
Old 01-18-2010, 06:53 PM   #11
Member
 
Join Date: Nov 2009
Location: Downriver Michigan
Posts: 86
Rewards Points: 75
Default


I'll be the devils advocate here

1. You were working hot. The safest practice would have been to shut the breaker off prior to work. Thus no chance of a shock.

2. GFCI and other safety devices must be designed to prevent injury/death BUT avoid nuisance tripping. Many old (and even new) pieces of electrical equipment (usually things with large motors) will trip a GFCI. If GFCIs were designed to a more stringent set of parameters there would be even MORE nuisance trips.
DownRiverGuy is offline   Reply With Quote
Old 01-18-2010, 06:53 PM   #12
Member
 
Bigplanz's Avatar
 
Join Date: Apr 2009
Location: Louisville KY
Posts: 1,666
Rewards Points: 2,492
Default


Quote:
Originally Posted by Speedy Petey View Post
Absolutely not. A shock is a shock. It depends on how well you are "grounded" and how much current feeds through you. You "feel" the voltage, not the current.
If you are not grounded very well then you will not get much voltage. Similar to voltage drop.
Current flow trips the GFI. The GFI trips if it measures 5-6mA of current imbalance between the hot and neutral (or hot and hot). This 5-6mA can be leaking many places, including through your finger. It will trip in a very short time period, so it is completely feasible that you will get a very painful shock but not for nearly enough time to kill you.
It appears from this article that one 'feels' the current, rather than the voltage. However, Table 2 of this article indicates that one registers a shock at 1.8 mA so I guess I got zapped at below a 5 mA level.

http://www.highvoltageconnection.com...kQuestions.htm
Bigplanz is online now   Reply With Quote
Old 01-18-2010, 07:19 PM   #13
Tool Geek
 
PaliBob's Avatar
 
Join Date: Jun 2008
Location: Pacific Palisades CA
Posts: 2,590
Rewards Points: 2,160
Default


BIG p, Thanks for posting the 'Shock' link.
I Bookmarked it
__________________
Disclaimer
& Stay Safe
.....Bob Lavery
PaliBob is offline   Reply With Quote
Old 01-18-2010, 07:54 PM   #14
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 7,828
Rewards Points: 2,006
Default


Quote:
Originally Posted by Bigplanz View Post
It appears from this article that one 'feels' the current, rather than the voltage. However, Table 2 of this article indicates that one registers a shock at 1.8 mA so I guess I got zapped at below a 5 mA level.

http://www.highvoltageconnection.com...kQuestions.htm
I guess you could say it is a combination of the two. It HAS to be. One is nothing without the other.

I just always laugh when someone throws out that old line "It's the amps that get you".
Speedy Petey is offline   Reply With Quote
Old 01-18-2010, 08:08 PM   #15
Member
 
Join Date: May 2009
Location: Brooklyn, New York (NYC)
Posts: 1,124
Rewards Points: 500
Question


Quote:
Originally Posted by Speedy Petey View Post
A GFI is NOT intended to prevent shocks. It is intended to prevent electrocution.
As a matter of fact it states so in the insert that comes along with the GFCI receptacle, That "You might feel a shock even if the receptacle will trip"!!
spark plug is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Freezer tripping GFCI davidclements Appliances 58 07-03-2015 05:46 AM
Gfci Circuit howard.wheaton Electrical 10 01-29-2009 05:14 PM
new gfci on new circuit pops rtoni Electrical 39 11-15-2008 10:18 AM
GFCI Question Mdbuilder Electrical 6 06-19-2008 03:15 PM
GFCI questions 5circles Electrical 4 11-05-2007 08:24 PM




Top of Page | View New Posts