Ground Fault Breaker - advice needed...

[TexasFlood]

I am to build an electrical panel for a mobile unit which is to be powered
by 110VAC / 60 Hz (1 phase, 1 neutral and ground).
The unit is equipped with medium heating elements and have a max. current of
20A which is connected through a Hubble connector.

To protect from ground fault I wish to build the panel with a ground fault
breaker included.

According to European rules both the phase and the neutral have to be
disconnected in case of a ground fault.
Also the trig limit for protecting personell is 30mA current.

- What Ground Fault Breaker should I use. I would prefer one from Allen
Bradley but can't seem to find one that
disconnects the neutral line also.
- Is it mandatory that the neutral have to be diconnected also according to
US rules ?

- Also as far as I know US rules say that the trig limit for protecting
personell have to be 5mA - is this true ?

Sincerely


TF

 

[SQLit]

| I am to build an electrical panel for a mobile unit which is to be powered
| by 110VAC / 60 Hz (1 phase, 1 neutral and ground).
| The unit is equipped with medium heating elements and have a max. current of
| 20A which is connected through a Hubble connector.
|
| To protect from ground fault I wish to build the panel with a ground fault
| breaker included.
|
| According to European rules both the phase and the neutral have to be
| disconnected in case of a ground fault.
| Also the trig limit for protecting personell is 30mA current.
|
| - What Ground Fault Breaker should I use. I would prefer one from Allen
| Bradley but can't seem to find one that
| disconnects the neutral line also.
| - Is it mandatory that the neutral have to be diconnected also according to
| US rules ?

US rules do not require disconnection of the neutral. IMHO, they should,
but in actual fact they don't. Typical GFCI breakers do not have this
capability, but most GFCI receptacles these days do.

I am not sure about the "rules" but I know for a fact that the GFCI breakers
for residential DO open the neutral as well as the hot.

http://www.ab.com/industrialcontrol...load_protection/circuit_breakers/1492-MC.html

I found this page.

I was aware of AB making medium voltage stuff, never molded case circuit
breakers... Learned something new today...

 

[Roy Q.T.]

The Great Outdorrs.
Sound like a nice job to do.

Build Up the panel with the GFI Breaker of your choice, if memory serves
me right the neutral and hot are wired into the Breaker you have nothing
to worry about but to terminate it with nice workmanship using every
terminating item & the proper tools for a job well done, with no
scratches or marrs on the plastics & metals and Raintight Enclosures,
Fittings & Covers. spend,spend,spend };-) I do when I have to. ®oy

 

[John Gilmer]

There's no textual indication that these breakers interrupt the neutral.

The 120 volt units that stand alone (with or without duplex outlet included
in the unit) definitely do disconnect the neutral (likely because they want
to "protect" against wiring errors whereby neutral and hot are reversed.
If you don't believe me, you can take one apart and see for yourself. If
you have one in service, you can "test" trip it and see if there is
continuity between neutral and ground.

There is nothing to stop you from separating the overload protection from
the ground fault protection. The total cost may be less and since GFCI
units sometimes fail, it will be cheaper in the long run to separate the
functions.

 

[John Gilmer]

|
|>
|> There's no textual indication that these breakers interrupt the neutral.
|
| The 120 volt units that stand alone (with or without duplex outlet included
| in the unit) definitely do disconnect the neutral (likely because they want
| to "protect" against wiring errors whereby neutral and hot are reversed.
| If you don't believe me, you can take one apart and see for yourself. If
| you have one in service, you can "test" trip it and see if there is
| continuity between neutral and ground.

Are you referring to the dead front GFCI receptacles? Yes, I do know those
will disconnect the neutral. But these do not also do overcurrent protection.
I do not refer to these devices as "breaker".

Nor do I. But combined with a "real" beaker they will offer protection.
If the guy wants to make his design truly idiot proof and relatively cheap,
he can combine a cheap two pole breaker and a cheap two pole GFCI. A high
current ground fault would likely destroy the GFCI but maybe the breaker
would clear it in time.

When someone says "breaker", I think of typically a molded case circuit
breaker ranging from small 3/4 inch distribution panel breakers to big
15 inch industrial main breakers. These breakers all have separate
"contact chamber" for each pole in which there is a mechanism intended
to be capable of interrupting high fault currents. In order to be able
to nterrupt the neutral, and additional such "contact chamber" is needed.
The illustrated breaker was one with 2 such sections. In theory that
could be used to interrupt the neutral with hot 1 pole. But there may
be issues in the design that would preclude this unintended usage.

Well, using a "real" two pole breaker (including the type that has screw
terminals for both line and load and intended for stand alone use) and a
GFCI would provide near idiot proof safety.

| There is nothing to stop you from separating the overload protection from
| the ground fault protection. The total cost may be less and since GFCI
| units sometimes fail, it will be cheaper in the long run to separate the
| functions.

So how would you do this for a 3-wire shared-neutral circuit with the
requirement that the entire circuit be interrupted on any cause that
would interrupt any part of it? A 2-pole panel breaker won't do it.
A dead-front receptacle-style GFCI won't do it. The "hack" I came up
with is to use a 2-pole GFCI breaker followed by a 3-pole N/O contactor
with a 240 volt coil powered from the 2 hots.

That wasn't the problem the OP states. He said 120 volts. If you "hack"
you have to take apart the GFCI and pass the neutral conductor through the
sensing/injection toroids.
http://ka9wgn.ham.org/ |

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[TexasFlood]

I am sorry not to respond earlier on your replies (all of you)
I have had a network crash which "imobilized" me...

I have managed to scan the installation instructions on the Allen Bradley GF
breaker that I allready got.
I don't know how I can show this to you.....

On the front of this Allen Bradley GF breaker it says :

1492-MCEA220

2 POLE 20 AMP
120/240 VAC 60 HZ
10 kAIC
30mA Trip sensitivity

As mentioned ealier, I think that this one is a 2 poled GF breaker which
have to be used in a 2 phased application.
The neutral is only passing through (to enable measuring of the returning
current for the trip circuitry)

Maybe I should just get a 1 poled GF breaker and then accept not to have the
neutral disconnected...

I am a little confused when you talk tech.
It would really help to see the wiring illustrated on a schematic if
possible.

thanks again for the replies

TF