Go Back   InterNACHI Inspection Forum > >

Notices

Electrical Inspections Contains discussions about electrical systems. This includes receptacles, panels, wiring, etc.

Reply
 
Thread Tools
  #16  
Old 11/9/09, 9:26 PM
Bob Elliott, 450.0002662's Avatar
Bob Elliott, 450.0002662 Bob Elliott, 450.0002662 is offline
Certified Professional Inspector (CPI) ®
 
Join Date: Aug 2006
Location: Chicago
Posts: 37,739
Default Re: GFCI on 2 wire systems



I thought I was an electrician .May explain my Einstein hair.
Reply With Quote
Find an InterNACHI certified Georgia Home Inspector (and anywhere else in North America)
  #17  
Old 11/9/09, 9:30 PM
Michael Larson's Avatar
Michael Larson Michael Larson is online now
Certified Professional Inspector (CPI)
 
Join Date: May 2006
Location: Hudson, WI including the Twin Cities of MN
Posts: 75,030
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by belliott View Post


I thought I was an electrician .May explain my Einstein hair.
I used to work with a maintence electrician that would wet two fingers and swipe at wire exposed wires to make sure they were dead.



As a Professional Home Inspector, I support the privacy of my clients.

You own your private information. I won't sell or give away yours, others do


www.InspectraPro.com
www.MinnesotaHomeInspector.biz

Michael Larson
Hudson, WI

Services provided in East MN and West WI

Call me


Reply With Quote
  #18  
Old 11/9/09, 9:40 PM
Bob Elliott, 450.0002662's Avatar
Bob Elliott, 450.0002662 Bob Elliott, 450.0002662 is offline
Certified Professional Inspector (CPI) ®
 
Join Date: Aug 2006
Location: Chicago
Posts: 37,739
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by mlarson View Post
I used to work with a maintence electrician that would wet two fingers and swipe at wire exposed wires to make sure they were dead.
No different from all the Gas company guys that used matches to check for leaks (OK I was guilty of that one too).

What drives me nuts is how many of the Electricians told me to work live or I was a sissy.

Other than getting scared, I ended up with many bloody knuckles from the kickback.
Reply With Quote
  #19  
Old 11/9/09, 11:10 PM
James E. Braun, CMI's Avatar
James E. Braun, CMI James E. Braun, CMI is online now
Certified Master Inspector
 
Join Date: Jan 2005
Location: Jefferson City, MO
Posts: 9,794
Default Re: GFCI on 2 wire systems

I have had 440 three phase throw me back when I was an industrial electrician. The flash and the loud pop is unreal. I accidentally bumped some dirt and it fell in the cabinet that I was testing a circuit in. I learned to knock the dust off the panel first before I opened it.
Also once my supervisor was hauled away to the hospital because some water was lying in an electrical panel when he opened the door. I heard the loud pop and I was a good 75 yards away.
Reply With Quote
  #20  
Old 11/10/09, 1:18 AM
Chuck Evans's Avatar
Chuck Evans Chuck Evans is online now
Certified Master Inspector ®
 
Join Date: Sep 2006
Location: Stagecoach, TX
Posts: 10,784
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by mlarson View Post
They prevent a fault current in excess of 5 mA from going through a person.

That is sufficient to prevent electrocution in most of the population.
I was referring to all of the other possibilities for electrical incidents e.g., miswired (line/load), malfunctioning, people getting shocked at switches, panels, dryer outlets, other devices, etc. People can come up with myriad ways in which to shock themselves. I just don't like to use absolute terms like "prevent" for these types of things, it can create a false sense of security for the unwitting.



Chuck Evans (TREC #7657)
Level III Infraspection Institute Certified Infrared Thermographer (#8402)
HomeCert Houston Home Inspections & Thermal Inspections Find us on Facebook
The Woodlands Home Inspections
Magnolia TX Home Inspections & Thermography


Houston, TX
_______________________
Awards Committee Member

SUBMIT YOUR AWARD NOMINATIONS HERE

The InterNACHI Awards Committee is the final authority of issuance of any award the committee offers.
Reply With Quote
  #21  
Old 11/10/09, 9:10 AM
Michael Larson's Avatar
Michael Larson Michael Larson is online now
Certified Professional Inspector (CPI)
 
Join Date: May 2006
Location: Hudson, WI including the Twin Cities of MN
Posts: 75,030
Default Re: GFCI on 2 wire systems

I simply stated the facts.



As a Professional Home Inspector, I support the privacy of my clients.

You own your private information. I won't sell or give away yours, others do


www.InspectraPro.com
www.MinnesotaHomeInspector.biz

Michael Larson
Hudson, WI

Services provided in East MN and West WI

Call me


Reply With Quote
  #22  
Old 11/10/09, 12:20 PM
Ralph Brady's Avatar
Ralph Brady Ralph Brady is offline
Active Poster
 
Join Date: Feb 2007
Location: Eureka, CA
Posts: 619
Please Note: rbrady is a non-member guest and is in no way affiliated with InterNACHI or its members.
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by cevans View Post
I wouldn't say they prevent, but rather that they reduce the potential for someone to get shocked. People can always find ways to electrocute themselves.

Many older homes' electrical systems are not grounded, however, short of fully rewiring the house, GFCI can be an effective way of providing improved protection against shocks and maintain "code" compliance with three prong outlets (use the "no equipment ground" stickers).
Since you picked up on Michaels comment but not mine, I will repeat:
They DO NOT reduce the potential for electrical shocks.

Also, the only "improved protection" they provide is to reduce the risk of death by electrocution.
You can also maintain "code compliance" by using 2-prong receptacles.

Personally I only recommend GFCI's in an ungrounded system at the same places I would recommend them with a grounded system. I do add a comment that "addition of a grounding conductor will reduce the risk of less dangerous electrical shocks".
Reply With Quote
  #23  
Old 11/10/09, 12:42 PM
Michael Larson's Avatar
Michael Larson Michael Larson is online now
Certified Professional Inspector (CPI)
 
Join Date: May 2006
Location: Hudson, WI including the Twin Cities of MN
Posts: 75,030
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by rbrady View Post
Personally I only recommend GFCI's in an ungrounded system at the same places I would recommend them with a grounded system. I do add a comment that "addition of a grounding conductor will reduce the risk of less dangerous electrical shocks".
Agreed



As a Professional Home Inspector, I support the privacy of my clients.

You own your private information. I won't sell or give away yours, others do


www.InspectraPro.com
www.MinnesotaHomeInspector.biz

Michael Larson
Hudson, WI

Services provided in East MN and West WI

Call me


Reply With Quote
  #24  
Old 11/10/09, 2:04 PM
George P. Wells, CMI's Avatar
George P. Wells, CMI George P. Wells, CMI is offline
Certified Master Inspector
 
Join Date: Oct 2004
Location: Michigan
Posts: 1,121
Send a message via Skype™ to gwells
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by rbrady View Post
From what I have heard, at least 220 will knock you off, unlike 110 which just makes your muscles hold tighter.
That is false.



Forensic Electrical Consultant
EE, Licensed Master Electrician/Electrical Contractor



BestInspectors.Net
By Inspectors, For Inspectors

Inspection Report Software
& Business Coaching


Since 1992
Reply With Quote
  #25  
Old 11/10/09, 2:49 PM
George P. Wells, CMI's Avatar
George P. Wells, CMI George P. Wells, CMI is offline
Certified Master Inspector
 
Join Date: Oct 2004
Location: Michigan
Posts: 1,121
Send a message via Skype™ to gwells
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by thowell View Post
Looking for some help on clarification. My understanding is a GFCI will prevent elec shock in a 2 wire system. I have seen them in bathrooms and kitchens. The part that trips me up is, a 2 wire system is still not grounded. That should be a safety concern, but not unsafe with a GFCI installed. (correct?)
Second part of question, in a home with 2 wire outlets why couldn't a person put GFCIs in all the locations? Like the living room for example. I was ask this question the other day. The occupants would be protected, correct?
Thanks folks.
Tim, without getting into a long detailed explanation (which most would probably find boring anyway), let me dispel one common misunderstanding. Two-wire systems are grounded. It is because they are grounded that GFCIs work on them.

Damage caused by electrical shock is a function of time and current. Humans are particularly vulnerable to electric current. The challenge to manufacturers of GFCI devices is to limit current to a where it cannot seriously injure a person but do not deenergize circuits that should not be deenergized. Some loads (specifically, reactive loads) are more difficult than others.

GFCI receptacles have come a long way since the early GFCI devices still, they should not be used on circuits that have heavy motor loads because they could trip when we don't want them to trip. It would be a good idea, for example, not to put a refrigerator on a GFCI receptacle.

It is worth noting that false tripping problems only arise with reactive loads (motors, capacitors, etc). Resistive loads (heating elements, etc) do not cause false tripping (unless, of course, the appliance has malfunctioned).



Forensic Electrical Consultant
EE, Licensed Master Electrician/Electrical Contractor



BestInspectors.Net
By Inspectors, For Inspectors

Inspection Report Software
& Business Coaching


Since 1992
Reply With Quote
  #26  
Old 11/10/09, 8:23 PM
Larry F. Rollins Larry F. Rollins is offline
Certified Professional Inspector (CPI)
 
Join Date: Oct 2008
Location: Nashville, Tn
Posts: 162
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by rbrady View Post
Have you ever tripped a GFCI with your body (across two fingers doesn't count)? I don't recommend trying it, but would be interested in hearing if anyone has.

From what I have heard, at least 220 will knock you off, unlike 110 which just makes your muscles hold tighter.

While in electricians school(many moons ago) one instructor took an entire class to prove that a AAA battery could potentially kill a person. The technique involved two pieces of wire, two needles and a soldering iron. {you figure it out} He showed where if a needle was stuck in each arm(into a vein) and the battery applied, enough current would flow to stop the heart. As I remember, and it has been many years, .1 milliamp will stop the heart.
Both 220 and 110 will "tend" to throw you off since they are AC voltages. It is DC voltages that will lock you on. Granted 220vac will do a much better job of throwing you off than 110vac will. The rule of thumb is Low voltage AC and Hi voltage DC are the most dangerous.
My largest shock was aboard a submarine where I took a "shot" from the back of my upper arm to my sweaty hand through a pinhole leak in a pair of heavy rubber gloves. It was 440 vac, 400 cycle. Came to about 10 feet away and couldn't use my arm for awhile. The burns hurt like hell. The only long term affect was a very strong desire to never do it again!
Reply With Quote
  #27  
Old 11/10/09, 9:26 PM
Ralph Brady's Avatar
Ralph Brady Ralph Brady is offline
Active Poster
 
Join Date: Feb 2007
Location: Eureka, CA
Posts: 619
Please Note: rbrady is a non-member guest and is in no way affiliated with InterNACHI or its members.
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by gwells View Post
let me dispel one common misunderstanding. Two-wire systems are grounded.
I think most everyone understands that the neutral wire is the 'grounded conductor', and as such is grounded, even in a 2-wire system. It's kind of a given, that when we discuss un-grounded systems, we are refering to the lack of a 'grounding conductor'.

One thing that I think most people don't realize is that grounding the system acutally increases the risk of shock. If both conductors were isolated from ground, you would have to make contact with both sides (positive & negative) to get a shock - earth ground would not be the negative side. Grounding is used to stabilize the voltage.
Reply With Quote
  #28  
Old 11/10/09, 9:55 PM
Jim Port Jim Port is online now
Unmoderated Guest
 
Join Date: Jul 2007
Location: Maryland
Posts: 2,683
Please Note: Jim Port is a non-member guest and is in no way affiliated with InterNACHI or its members.
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by gwells View Post
GFCI receptacles have come a long way since the early GFCI devices still, they should not be used on circuits that have heavy motor loads because they could trip when we don't want them to trip. It would be a good idea, for example, not to put a refrigerator on a GFCI receptacle.

It is worth noting that false tripping problems only arise with reactive loads (motors, capacitors, etc). Resistive loads (heating elements, etc) do not cause false tripping (unless, of course, the appliance has malfunctioned).
If motor loads are causing a GFI to trip the appliance is leaking current in excess of the allowable UL amount. For example a sump pump motor under the UL standard is only allowed to leak a small fraction of the 4-6mA that a Class A GFI would trip at. I cannot find the exact leakage allowed.

As a side note refrigerators in a commercial kitchen are REQUIRED to be GFI protected.

I would ask which is better, a refrigerator with a tripped GFIand spoiled food or a faulty refrigerator with a fault and a dead person?
Reply With Quote
Find an InterNACHI certified Georgia Home Inspector (and anywhere else in North America)
  #29  
Old 11/10/09, 9:57 PM
John Shishilla's Avatar
John Shishilla John Shishilla is offline
Certified Master Inspector
 
Join Date: Jul 2008
Location: Melbourne, FL
Posts: 6,470
Default Re: GFCI on 2 wire systems


Those of you that try to predict when an electric current will, hurt, make you hold on, make you let go kill or seriously injure you are doing a disservice to those that are looking for answers.

It takes VERY little current to kill a person under the right circumstances A/C or D/C. If you must have a specific answer it is less than a milli amp. It can not be predicted with any degree of accuracy, to try is reckless.

I will step off the soap box now.



https://www.facebook.com/groups/Flor...ceinspections/


Visit the InterNACHI Awards page

John Shishilla
State of Fl Home Inspector #21
Certified Residential Contractor CRC1330745
Mold Assessor MRSA 1544



Serving all of Melbourne, Palm Bay, Cocoa, Rockledge, Viera, Satellite Beach, Indian Harbor Beach, Vero, Vero Beach and surrounding areas.

Honor Construction Inspection Service
www.honorconstruction.com

321-327-2950

Reply With Quote
  #30  
Old 11/10/09, 10:02 PM
Michael Larson's Avatar
Michael Larson Michael Larson is online now
Certified Professional Inspector (CPI)
 
Join Date: May 2006
Location: Hudson, WI including the Twin Cities of MN
Posts: 75,030
Default Re: GFCI on 2 wire systems

Quote:
Originally Posted by jshishilla View Post

Those of you that try to predict when an electric current will, hurt, make you hold on, make you let go kill or seriously injure you are doing a disservice to those that are looking for answers.

It takes VERY little current to kill a person under the right circumstances A/C or D/C. If you must have a specific answer it is less than a milli amp. It can not be predicted with any degree of accuracy, to try is reckless.

I will step off the soap box now.
As I said earlier 5 mA is non lethal in a normal person.

Hospital requirements are much lower for patient care areas. The limits are on the order of 100 microAmps allowable leakage current and 10 microAmps in certain areas without gong into more detail than is needed here.



As a Professional Home Inspector, I support the privacy of my clients.

You own your private information. I won't sell or give away yours, others do


www.InspectraPro.com
www.MinnesotaHomeInspector.biz

Michael Larson
Hudson, WI

Services provided in East MN and West WI

Call me


Reply With Quote
Reply

Thread Tools

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Emergency Lighting (commercial) mcyr Electrical Inspections 26 6/20/14 11:00 PM
"UFER" Ground? see last paragraph. jtedesco1 Electrical Inspections 19 8/23/11 4:56 PM
What's this video worth? jtedesco1 Inspection Education & Training 5 4/18/08 10:24 AM
Nice Report on AL Wire Terminations - Enjoy pabernathy Electrical Inspections 0 7/2/07 1:35 PM
PIC of State Rep and sponsor of new NACHI H.I. Bill in NH. gromicko Miscellaneous Discussion for Inspectors 53 8/30/06 6:58 PM

All times are GMT -4. The time now is 5:25 PM.
no new posts