service confusion...

pharkusDecember 17, 2009

Alright. Neutral and ground are tied together at the first point of disconnection, and seperate thereafter.

Or so I thought.

What about mobile homes, with a breaker built into the meter base? I've been seeing 3-wire connection from said disconnect to the breaker box. Are all the ones I'm seeing illegal?

What about an apartment building? The place where I grew up, built in 1980, has, at the end of each building, six meters with main breakers built-in. 3-wire cables go from there to the breaker boxes in the apartments.

Fill me in.

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brickeyee

Mobile homes are built to their own standards, not the NEC.

HUD promulgates most of them.

    Bookmark   December 17, 2009 at 1:09PM
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pharkus

Fine. Was my apartment building also built to its own standards?

    Bookmark   December 18, 2009 at 3:19AM
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brickeyee

Buildings follow the NEC or whatever electric code was in effect when built or renovated.

Jurisdictions are free to adopt whatever standards they want, and change then as they see fit.

The code is far from a static thing, especially over many years.

    Bookmark   December 18, 2009 at 11:10AM
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pharkus

Alright, the code section that tells us to keep ground/neutral seperate after the first disconnect... was that in effect in 1980?

Assuming it was, what are the exceptions?

I'm not giving up on this. I have READ the explanation in a book before, but neglected it at the time as it didn't apply to what I was doing. Now I need/want to know and I'm not going away until I find out.

    Bookmark   December 18, 2009 at 6:44PM
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petey_racer

Mobile homes have always required a 4-wire feeder from the outside main.

If your apartment has no firewalls between the services and the apartment panels then a 4-wire feeder is/was also required.

    Bookmark   December 18, 2009 at 9:39PM
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brickeyee

"I have READ the explanation in a book before, but neglected it at the time as it didn't apply to what I was doing. Now I need/want to know and I'm not going away until I find out."

The full names for the conductors are the 'grounED' and 'groundING' conductors.

The groundED conductor is commonly called 'neutral' and carries current for 120 V loads.
It is the center tap of the pole transformer, and is tied to earth to make it 0 volts relative to the earth.
It returns all the current on a 120 V load (ignoring multiwire circuits) and is not needed for a 240 V load.

The groundING conductor (AKA 'ground' or 'safety ground') is NOT intended to ever carry current unless a fault occurs.
If you tie the groundED and groundING conductors together any place but a main panel you will have current flowing on both conductors during normal circuit operation.
The current splits between the two wires based on their impedance at 60 Hz.

This current can make anything connected to the groundING conductor have a voltage relative to earth from the voltage drop on the groundING conductor.

If you touch a well grounded water pipe (ir other solidly grounded point) and the supposed 'ground' that has current flowing (or anything attached to this ground) the voltage can cause a shock.

    Bookmark   December 19, 2009 at 11:19AM
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pharkus

If your apartment has no firewalls between the services and the apartment panels then a 4-wire feeder is/was also required.

Firewalls. I don't remember reading that, but the apartment did, in fact, have firewalls between the "box o' meters", as well as between each apartment, so I'll go with that.

What it boils down to, ultimately, is I need 4-wire in my current project and, thus, cannot make use of what's already there. :(

    Bookmark   December 19, 2009 at 12:01PM
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pharkus

HEY! WAIT A MINUTE!

I think part of it just popped back into my mind...

Subpanel in seperate building, no other metallic connections, ground rod on both ends... I think the book I read was counting the pole next to the mobile home as a seperate building, and the panel inside the MH as a subpanel.

    Bookmark   December 19, 2009 at 12:03PM
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petey_racer

A building separated by a firewall IS, or can be, two separate structures in the eyes of the code.

The thing is, a mobile home ALWAYS required a 4-wire feeder after the main disconnect on the pole. There was no old exception allowing a 3-wire feeder for mobile homes.
THIS is the reason a 4-wire circuit was ALWAYS required for ranges and dryers in mobile homes.

    Bookmark   December 19, 2009 at 4:44PM
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brickeyee

I will not do any work ion mobile himes or anything built under the HUD codes.

There are all sorts of low quality shortcuts allowed and made.

Splice are NOT required to be in boxes if 'approved devices' are used.

It is about the lowest quality stuff you have ever seen.

There are a lot of reasons that mobile homes decrease in value with age, unlike well maintained permanent structures.

    Bookmark   December 19, 2009 at 5:26PM
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fixizin

Well, if you think about it... you have a Federal Gov't that is thoroughly corrupt, demonstrably evil on many, MANY occasions, and obligated to service a staggering $2,000,000,000,000.00 in debt in just the coming 12 months... never mind "long term".

... so... we have a Power-Lusting, UNaccountable, cash-strapped entity, with a VESTED INTEREST in seeing that low-income people never reach an age, or state of illness, where they will be entitled to draw on the US Treasury, in any of its various forms (SS, VA, WIC, etc.)

... you could say HUD is just doing its part to "bump off" what Dickens called the "excess" population. =:O

    Bookmark   January 21, 2010 at 12:49AM
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brickeyee

"... you could say HUD is just doing its part to "bump off" what Dickens called the "excess" population."

Since mobile homes are not fixed structures, the NEC does NOT apply.

While most states now follow the NEC, for many years there was also a BOCA electrical code used in a number of states.

The mobile home makers wanted a single set of standards that they could follow.

HUD also wanted there to be SOME standard, so they adopted one for nationwide use.

Since mobile homes depreciate in value (and pretty quickly) there is no reason to hold them to as high a standard as fixed installations that may remain in use over 100 years.

HUD also wants to keep them affordable.

    Bookmark   January 21, 2010 at 10:14AM
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bus_driver

At one time, mobile home manufacturing was heavily concentrated in Elkhart, Indiana. Those units were shipped into many States. No way to build them to comply with every local code. While mobile home manufacturing is now more widely scattered geographically, having a Nationwide standard eases the problem of dealing with various codes. At this time, sales of new singlewide mobile homes is in sharp decline with many manufacturers no longer making them. The free market is reducing their numbers. Each revision of HUD codes brings HUD codes nearer to those for non-mobile housing. But transportability remains a necessity. I like the free market system.

    Bookmark   January 21, 2010 at 3:02PM
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