I've never seen a house wired using Flexible Metal Conduit. Are you sure this isn't BX Armored Cable? Are the conductors similar to THHN or cloth & rubber?

 

There are a bunch of homes through Cali that are wired in steel FMC, done from the mid 60's up to the early 90's. They are using the FMC as the ground on these places.

 

Well first off, there's got to be an MBJ, some GE's, some GEC's proximal to the service.

@ndly, vintage wiring methods vary. You'll need to identify what you have for any of us to expand on them .

If in fact you've BX , you'll find 1000 yrs experience all over it @ ET

~CS~

 

In your receptacles, you're getting voltage between the hot wire and the box because the box is grounded by means of the metallic conduit back to the panel. If you have a main breaker panel serving as the first service disconnect means, then the panel should utilize the bonding jumper.

 

i thought FMC was a ground up to 6'.....? :001_huh:~CS~

 

They have a heck of a lot longer runs going than that. The worst part is that most of the installations I have seen have a good amount of rust and deterioration on them.....

 

older house grounging system

older house grounging system

here's some utube instructions on grunging

 

Its definetlty flex with THHN. There probably is a bonding jumper in there but like I said its kind of crowded in the panel. I was wondering where the ground was derived. Its just my curiosity.

 

It was a typo ****

 

Yes....A complete pain in the A**....but better than having to remove sheetrock!

A good flexible fish tape goes a long way....

 

Try a vacuum.

 

Well, that's more than i can say for all the bit & brace installs i reno

Those boys didn't drill 1/16" of wood more than they had to.....

~CS~

 

So..................I guess I get the same quality of explanations here as I do from 80% of JWs I have worked with. Nothin but wise cracks and subject changes. To those who gave me decent answers...thank you. And the rest, well

 

Dude, you have your answer, and you knew it all along.

The grounding is being performed via the conduits, albeit probably a poor ground in some locations. The panel/service is likely grounded to the main water supply and/or a ground rod.

 

Thanx switched. I was referring to the grunging link. No patience for smart alecs. Anyway I just never seen it before and thought it was strange. Seems like it would be unreliable.

 

Im the chillist bro out there. And yes I do understand NEC.

if that were true, you wouldn't have got your panties twisted up at all.

if you aren't going to proof read your posts, expect to be teased.

teach yourself how to use the ignore feature if you don't like it.

carry on.

 

Damn, apprentices be buy'n up castles on here. Congrats to you guys, i think.

 

Hello ppl. I recently bought a house built in the early 70s in great shape. Nothing wrong with the electrical in the house as far as problems go. Now I am curious to know how these older homes are grounded. I am a 3rd year apprentice inside wireman. Work commercial and industrial so I am familiar with grounding systems. Now the electrical was run with fmc and metal boxes. No grounding conductors at all. The boxes are grounded somehow because I read voltage from the ungrounded conductor to the box. My question is how was this accomplished? Are the conduits and boxes serving as the low impedence path back to the service? Is the main panel grounded? I did however notice on the service drop there are two cables coming into the meter and three coming out into the panel. One of which is landed into a neutral bus. Didnt see any bonding jumper in there although it was kinda crowded. Any insight would be helpful. Thanx

As a 3rd year apprentice you should be pretty handy with the NEC and understand it, your school should be teaching you the NEC grounding and bonding .

What you are talking about can be found in 250.118, 2014 NEC.....

250.118 Types of Equipment Grounding Conductors. The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:
(1) 
A copper, aluminum, or copper-clad aluminum conductor. This conductor shall be solid or stranded; insulated, covered, or bare; and in the form of a wire or a busbar of any shape.
(2) 
Rigid metal conduit.
(3) 
Intermediate metal conduit.
(4) 
Electrical metallic tubing.
(5) 
Listed flexible metal conduit meeting all the following conditions:
a. 
The conduit is terminated in listed fittings.
b. 
The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. 
The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground-fault current path does not exceed 1.8 m (6 ft).
d. 
If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed.
(6) 
Listed liquidtight flexible metal conduit meeting all the following conditions:
a. 
The conduit is terminated in listed fittings.
b. 
For metric designators 12 through 16 (trade sizes 3⁄8 through 1 /2), the circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. 
For metric designators 21 through 35 (trade sizes ¾ through 1¼), the circuit conductors contained in the conduit are protected by overcurrent devices rated not more than 60 amperes and there is no flexible metal conduit, flexible metallic tubing, or liquidtight flexible metal conduit in trade sizes metric designators 12 through 16 (trade sizes 3⁄8 through ½) in the ground-fault current path.
d. 
The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground-fault current path does not exceed 1.8 m (6 ft).
e. 
If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed.
(7) 
Flexible metallic tubing where the tubing is terminated in listed fittings and meeting the following conditions:
a. 
The circuit conductors contained in the tubing are protected by overcurrent devices rated at 20 amperes or less.
b. 
The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground-fault current path does not exceed 1.8 m (6 ft).
(8) 
Armor of Type AC cable as provided in 320.108.
(9) 
The copper sheath of mineral-insulated, metal-sheathed cable Type MI.
(10) 
Type MC cable that provides an effective ground-fault current path in accordance with one or more of the following:
a. 
It contains an insulated or uninsulated equipment grounding conductor in compliance with 250.118(1)
b. 
The combined metallic sheath and uninsulated equipment grounding/bonding conductor of interlocked metal tape–type MC cable that is listed and identified as an equipment grounding conductor
c. 
The metallic sheath or the combined metallic sheath and equipment grounding conductors of the smooth or corrugated tube-type MC cable that is listed and identified as an equipment grounding conductor
(11) 
Cable trays as permitted in 392.10 and 392.60.
(12) 
Cablebus framework as permitted in 370.60(1).
(13) 
Other listed electrically continuous metal raceways and listed auxiliary gutters.
(14) 
Surface metal raceways listed for grounding.
Informational Note:  For a definition of Effective Ground-Fault Current Path, see Article 100.

So..................I guess I get the same quality of explanations here as I do from 80% of JWs I have worked with. Nothin but wise cracks and subject changes. To those who gave me decent answers...thank you. And the rest, well

You are talking to electricians who are not at work, but are talking electrical work and having a little fun too, without all the fun you would not have gotten an answer at all because no one wold be hanging around here.

So chill out and have a little fun brother

 

Houses are cheap where I live.

 

Im the chillist bro out there. And yes I do understand NEC.

 

Do You?because I've been reading it 40 years an still don't get it.

If you read the code article I posted that should make it so You understand how the grounding works using metal raceways.

 

This is the best fish tape I have for using on flex or old underground conduits...
http://www.idealind.com/prodDetail.do?prodId=zoom-fish-tapes&div=5&l1=fishtapes&l2=zoom-fish-tapes

 

This is the best fish tape I have for using on flex or old underground conduits...
http://www.idealind.com/prodDetail.do?prodId=zoom-fish-tapes&div=5&l1=fishtapes&l2=zoom-fish-tapes

Nice, what did that go for?

 

.....

 

I've had it for about 12 years now....I imagine somewhere around $75?

 

Alot of cities by me were wired in fmc. Mudrings had a side clip that got in the way of gfci's👎. 6' rule was not in place back then.

 

Alot of cities by me were wired in fmc. Mudrings had a side clip that got in the way of gfci's?dc4e. 6' rule was not in place back then.

Yes much more than 6 ft runs in this house.

 

Seems mighty Chicago-ish, was this a local rule?

~CS~

 

I had the head inspector for one city recently tell me that I could ground a fixture on a 2 wire circuit by just attaching a pigtail from the metal box to the fixture ground wire. Problem solved!:blink:

 

I dont think it was either.