Electrical Panel Placement Question

[gklott]

Originally Posted by switz

Interesting detail, Airstream wires the "main" breaker backwards, with the hot shore power lead coming to the load side of the breaker. This allows them to use a much cheaper breaker box that does not have main power lugs with a dedicated main breaker like residential.

Some sealed circuit breakers, such as Eaton's CH branch breakers, can be back fed. Check to see if it is not marked "Line or Load".

However, when you backfeed a breaker as main, you have to use a hold down screw (and bracket) on the breaker. You also must install the insulating kit that prevents accidental contact with the supply screw terminals since they are always live when plugged into shore power.



As shown, our Airstream's new Eaton CH loadcenter has the hold-down bracket and screw required for the backfed 50A main. This limits your "main" breaker position to one of the top two locations. May be hard to see, but the 50A breaker has an insulating cover over the two 6 AWG feed screws.

We used the Eaton AFCI/GFCI combo breakers for all branch circuits, including the AC. They work well, and I highly recommend this for everyone doing a AC power renovation.

In your renovation, ensure that your grounded conductor (white wire) remains isolated from your grounding conductor (green wire) throughout your system.

73/gus

[switz]

The fine points of a screwed attached hold down fitting on the reverse fed breaker and an insulator over the hot wire connection are not part of the Airstream installations I have worked on. In fact the main is just a regular breaker like the others but is 30 amp rated.

[J. Morgan]

Originally Posted by switz

The fine points of a screwed attached hold down fitting on the reverse fed breaker and an insulator over the hot wire connection are not part of the Airstream installations I have worked on. In fact the main is just a regular breaker like the others but is 30 amp rated.

When working in my trailer breaker box(es), I unplug the trailer from shore power and turn the inverter off.

Crisis averted....

If a backfed breaker is the only practical means of disconnect I understand these requirements...

[gklott]

Originally Posted by J. Morgan

If a backfed breaker is the only practical means of disconnect I understand these requirements...

Securing the back fed main breaker is required in NEC section 408 for all load centers. Manufacturers all make these kits, called a retainer clip, retainer bracket, or retainer screw. This requirement is independent of having other disconnects. The retainer will be beneath the required dead-front cover.

When a normal branch circuit breaker is pulled (or falls) off the bus bar, the connection to the energized bus bar is broken. You are now holding an unenergized breaker.

When a back fed breaker is removed from the bus bar, the breaker remains energized (i.e., the little tabs on the breaker). You are now holding an energized circuit breaker that is no longer in the panel.



As shown, we have two back fed main breakers, and both have the Eaton retainer bracket. One main breaker is for the mid-street-side SmartPlug for normal 50A shore power. The other main breaker is for the front generator SmartPlug. We have the Eaton mechanical interlock dead front panel that prevents both breakers from being energized simultaneously.

The bottom two right slots contain the Eaton in-panel surge protector. All branch circuit breakers are Eaton type CH, AFCI/GFCI combo breakers.

73/gus

[gklott]

Originally Posted by switz

The fine points of a screwed attached hold down fitting on the reverse fed breaker and an insulator over the hot wire connection are not part of the Airstream installations I have worked on. In fact the main is just a regular breaker like the others but is 30 amp rated.

You describe the same poor quality work many forum members describe. We found all sorts of Airstream's don't-give-a-damn attitude issues throughout our trailer as we upgraded the AC and DC electrical systems.

73/gus

[A W Warn]

Originally Posted by gklott

You describe the same poor quality work many forum members describe. We found all sorts of Airstream's don't-give-a-damn attitude issues throughout our trailer as we upgraded the AC and DC electrical systems.

73/gus

It is NOT poor quality!
This method has been used successfully at least since the 1970's. If I was going to re-wire my trailer today, the back fed Square D QO breaker is exactly the way I would do it. IMO the QO panel back fed through a breaker is far superior to the combined 120/240v & 12v panels that are more common today.

[J. Morgan]

Originally Posted by gklott

Securing the back fed main breaker is required in NEC section 408 for all load centers. Manufacturers all make these kits, called a retainer clip, retainer bracket, or retainer screw. This requirement is independent of having other disconnects. The retainer will be beneath the required dead-front cover.

When a normal branch circuit breaker is pulled (or falls) off the bus bar, the connection to the energized bus bar is broken. You are now holding an unenergized breaker.

When a back fed breaker is removed from the bus bar, the breaker remains energized (i.e., the little tabs on the breaker). You are now holding an energized circuit breaker that is no longer in the panel.



As shown, we have two back fed main breakers, and both have the Eaton retainer bracket. One main breaker is for the mid-street-side SmartPlug for normal 50A shore power. The other main breaker is for the front generator SmartPlug. We have the Eaton mechanical interlock dead front panel that prevents both breakers from being energized simultaneously.

The bottom two right slots contain the Eaton in-panel surge protector. All branch circuit breakers are Eaton type CH, AFCI/GFCI combo breakers.

73/gus

I use a separate breaker box for my two feeds, but all in all if I had used a backfed breaker it wouldn’t have mattered to me if I had used a holddown clamp or not because I wont take the cover off of the box if there is power being fed into it.

There is no need for that risk when the trailer itself is EASY to unplug from shore power and it’s EASY to turn the inverter off.

I get the hard requirement for residential installations, but not so much for a trailer.

That’s just my view, and the chances are about a million to one that any inspector would ever enter my trailer and give me grief about that.

[J. Morgan]

Originally Posted by gklott

Securing the back fed main breaker is required in NEC section 408 for all load centers. Manufacturers all make these kits, called a retainer clip, retainer bracket, or retainer screw. This requirement is independent of having other disconnects. The retainer will be beneath the required dead-front cover.

When a normal branch circuit breaker is pulled (or falls) off the bus bar, the connection to the energized bus bar is broken. You are now holding an unenergized breaker.

When a back fed breaker is removed from the bus bar, the breaker remains energized (i.e., the little tabs on the breaker). You are now holding an energized circuit breaker that is no longer in the panel.



As shown, we have two back fed main breakers, and both have the Eaton retainer bracket. One main breaker is for the mid-street-side SmartPlug for normal 50A shore power. The other main breaker is for the front generator SmartPlug. We have the Eaton mechanical interlock dead front panel that prevents both breakers from being energized simultaneously.

The bottom two right slots contain the Eaton in-panel surge protector. All branch circuit breakers are Eaton type CH, AFCI/GFCI combo breakers.

73/gus

I used a double throw double pole 30 amp switch to isolate me two inputs.

One position feeds shore power and the other feeds the inverter.

Previously I had three switched inputs, the two mentioned above and also a front mounted generator feed. I eliminated the gen feed because I figured I didn’t really need it, I can feed the generator through the regular shore power feed.

[gklott]

Originally Posted by A W Warn

It is NOT poor quality! This method has been used successfully at least since the 1970's. If I was going to re-wire my trailer today, the back fed Square D QO breaker is exactly the way I would do it. IMO the QO panel back fed through a breaker is far superior to the combined 120/240v & 12v panels that are more common today.

Am afraid you missed the point. Using a Square D QO backfed breaker is fine. Just like you, I also like having a separate AC panel rather than the combined panels in trailers. That's not the issue.

"408.36 (D) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel."

Square D makes exactly this retainer for your QO backfed breaker - PK2MB. You can get it at Home Depot. If you use the Square D QO breaker as you describe, would you follow Square D's installation instruction?

Why would anyone bypass an electrical safety item that costs less than $10 and takes 1 minute to install? When manufacturer's fail to install and to verify by inspection such a safety item, it's poor quality.

73/gus

[J. Morgan]

Originally Posted by gklott

Am afraid you missed the point. Using a Square D QO backfed breaker is fine. Just like you, I also like having a separate AC panel rather than the combined panels in trailers. That's not the issue.

"408.36 (D) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel."

Square D makes exactly this retainer for your QO backfed breaker - PK2MB. You can get it at Home Depot. If you use the Square D QO breaker as you describe, would you follow Square D's installation instruction?

Why would anyone bypass an electrical safety item that costs less than $10 and takes 1 minute to install? When manufacturer's fail to install and to verify by inspection such a safety item, it's poor quality.

73/gus

OR it means before working on the breaker box that power should be cut.

In fact if this is part of Airstream’s service procedure then the elimination of the clamp is a non issue.

An Airstream is not a structure, it’s a vehicle. All vehicles service facilities are bound to abide service procedures in much the same way as one of the first procedures to working on a vehicle is very often to disconnect the negative terminal from the battery.

An example might be where a person does some electrical work on their car and deploys the air bags by accident because the battery is left connected.

Who’s fault is that?

Beyond that, any electrician who has any cause to call himself an electrician is going to see a breaker marked “main” and know that this breaker is feeding power to the the trailer and it’s a shock hazard if it’s handled in a careless manner.

Poor quality because of the lack of a plastic clamp? Nah, just different than you see things.

[gklott]

Originally Posted by J. Morgan

Poor quality because of the lack of a plastic clamp? Nah, just different than you see things.

Yes, I see poor quality. Why? The trailer manufacturer or owner fails to follow:
- load center and breaker manufacturer's installation instructions, and
- best electrical safety practice in NEC 408.36 (D).

Design safe; build safe; operate safe; maintain safe = stay safe!

73/gus

[J. Morgan]

Originally Posted by gklott

Yes, I see poor quality. Why? The trailer manufacturer or owner fails to follow:

- load center and breaker manufacturer's installation instructions, and

- best electrical safety practice in NEC 408.36 (D).



Design safe; build safe; operate safe; maintain safe = stay safe!



73/gus

Like I said, unplug the trailer and no risk at all.

It’s not the same animal as a hot wire coming fresh from the meter base that is difficult and or illegal to disconnect.

It’s my understanding that trailer manufacturers are not bound by the NEC. Is that untrue?

[gklott]

Originally Posted by J. Morgan

It’s my understanding that trailer manufacturers are not bound by the NEC. Is that untrue?

Airstream (Thor) is a member of RVIA, and our trailers have the RVIA seal. From RVIA, "This seal communicates the manufacturers’ certification that it complies with the RV standards adopted by the Association."

The RVIA adopted safety standard for all travel trailers is NFPA 1192 - "Standard on Recreational Vehicles". From NFPA 1192:
"4.4 Electrical Requirements.
4.4.1 All electrical installations, systems, and equipment shall comply with Article 551, Parts I and III through VI, of NFPA 70.
4.4.2 All low-voltage electrical installations, systems, and equipment shall comply with ANSI/RVIA LV."

73/gus

[Al Zeppelin]

Under the (almost complete) bed platform she goes. Good day of framing yesterday.

[mythbuster88]

Originally Posted by Al Zeppelin

Under the (almost complete) bed platform she goes. Good day of framing yesterday.

Really nice!

[Al Zeppelin]

I have about three weeks to have her camping ready, and the neverending yet brief given her size tours I'm sure is to come. We're on the end of an interior peninsula, which looks like a huge open treeless field beside us with a bunch of campers on the outside looking in so it's going to be a fishbowl of sorts. The pressure is on. In the rear floor you can see the original electrical feed. Main feed to two fuses to aluminum cloth jacketed wiring feeding 9 outlets (which have been replaced). Also visible is the square plate on the floor where a single original bolt comes up through the floor attaching the floor to the frame.

[J. Morgan]

Originally Posted by Al Zeppelin

I have about three weeks to have her camping ready, and the neverending yet brief given her size tours I'm sure is to come. We're on the end of an interior peninsula, which looks like a huge open treeless field beside us with a bunch of campers on the outside looking in so it's going to be a fishbowl of sorts. The pressure is on.

I love building Airstreams.

[mythbuster88]

Originally Posted by Al Zeppelin

I have about three weeks to have her camping ready, and the neverending yet brief given her size tours I'm sure is to come. We're on the end of an interior peninsula, which looks like a huge open treeless field beside us with a bunch of campers on the outside looking in so it's going to be a fishbowl of sorts. The pressure is on. In the rear floor you can see the original electrical feed. Main feed to two fuses to aluminum cloth jacketed wiring feeding 9 outlets (which have been replaced). Also visible is the square plate on the floor where a single original bolt comes up through the floor attaching the floor to the frame.

Hard to imagine you can do it all in three weeks! Takes me forever to get anything done.