Shipping Container Converted to Mobile Field Office

[DBoone]

If you (or someone) is feeding a 125A panel with more than a 125A feeder than that is a violation to begin with. You can't feed another panel with more than the rating of the panel. You can feed the same or less but not more.

Yes that's right. I don't like not knowing how power will be provided on these big jobsites.

So my original idea was just land incoming power on the Main Lugs outside. Feed the inside panel from a 60 amp breaker. That leaves 2 spaces still available outside for future add on.

As as far as the separate structure having a main disconnect in one motion of the hand someone could turn off every breaker (4 spaces)

After reading the reply from Ben it sounds like he suggests I need to install a breaker with a hold down kit outside. Label it Main and then anybody that has a clue will know to back feed it with the incoming power. Then install another breaker to feed inside.

If I need the back-fed Main then sounds like a better design for me would be to exchange my 4/8 loadcenter for an 8/16 and use a 100 or 125 amp breaker for my Main. Then I can feed inside with my 60 and still have some space for future additions such as a service receptacle on the exterior.

 

[jaggedben]

See if I understand you correctly. We need a disconnect to our structure by code so instead of landing incoming power on the main lugs and then having a 60amp breaker installed which we run our feeder off of that breaker to the inside panel, you say I should install a 60 amp breaker outside with a hold down kit and label it MAIN. Incoming power would obviously land there and we have OCP to protect our panel and to serve as main disconnect.

Then below that, in the last 2 breaker slots install another 60 amp breaker and run our feeder off of that.

I think you are getting what I'm saying.

I'm suggesting you do it this way because you've expressed concern about not knowing who will be running power to these and how they will do it. For that reason I suggest that you have a place to land on an overcurrent device. That way your work is protected from damage if someone hooks it up to a feeder that doesn't protect the panelboard properly. A 60A breaker installed with a hold down would be one option. An alternative would be to put a 60A fused disconnect outside and a panel inside. That might be a little more expensive but the hookup might be even more 'obvious' to whoever hooks does it.

On the 'obviously' part of things, I should probably pull back a bit on that. Whatever you decide, I would make an instruction sheet for how you expect these to be powered. I get the impression you are making a number of these and trying to develop a standard approach.

 

[DBoone]

I think you are getting what I'm saying.

I'm suggesting you do it this way because you've expressed concern about not knowing who will be running power to these and how they will do it. For that reason I suggest that you have a place to land on an overcurrent device. That way your work is protected from damage if someone hooks it up to a feeder that doesn't protect the panelboard properly. A 60A breaker installed with a hold down would be one option. An alternative would be to put a 60A fused disconnect outside and a panel inside. That might be a little more expensive but the hookup might be even more 'obvious' to whoever hooks does it.

On the 'obviously' part of things, I should probably pull back a bit on that. Whatever you decide, I would make an instruction sheet for how you expect these to be powered. I get the impression you are making a number of these and trying to develop a standard approach.

Ben I appreciate very much the help on developing a good set up for this because as you have suggested, I'm not sure who or how power will be provided to it once its on a jobsite.

I like your suggestion that we eliminate that concern providing a breaker to bring the incoming power to. Protect our equipment no matter what is on the line side. So I will go with the Main breaker with hold down kit and will post instructions somewhere obvious that explains to land incoming power on the breaker provided. Even though it will be labeled "MAIN" I will still explain it for the next person.

Now to the design part of it. If I keep what I have then I will hav a 60 for my main and then a 60 for my feeder. I will be out of spaces outside.

Im thinking now I want to switch the outside panel with an 8 space and use a 100 or 125 amp breaker for my Main, have my 60 for the feeder and still have 4 spaces avail either for anything in the future, such as a receptacle on the exterior.

How does that design sound.

This is the only one we are doing as of right now but I want it to be right and have a good design so that's why I have had those questions.

 

[jumper]

Jumper, did not forget you.

Had a minor medical issue to address. Ben and you are on right track.

Will post later, gotta rest.

Need exterior gear rated for 100A, but realistically 60A service with a 5000W or more genny set up, 30A inlet with double throw switch, suse rated, is sufficient.

HVAC is 2P 15A, add six 20A 1P circuits, 60A feeder is good.

Derek

 

[DBoone]

Jumper, did not forget you.

Had a minor medical issue to address. Ben and you are on right track.

Will post later, gotta rest.

Need exterior gear rated for 100A, but realistically 60A service with a 5000W or more genny set up, 30A inlet with double throw switch, suse rated, is sufficient.

HVAC is 2P 15A, add six 20A 1P circuits, 60A feeder is good.

Derek

Hope all is well. Had a feeling something happened when I saw you had no activity on the forum lately.

 

[DBoone]

I don't see anything wrong with just using what I have and let the incoming power land on the main lugs. There are only four slots outside. All power can be disconnected easily with one swipe of the hand.

Like I said before, the only problem I see, and it would be practically impossible based on the projected load inside the office, would be we have our 60 amp double pole breaker feeding into the office and then if someone installed a double pole breaker of 70 amps or larger, and both the 60 amp and the 70+ amp breaker were loaded to the max at the same time, AND if the OCPD feeding our office trailer from the jobsite temp power was larger than 125 amps....then we COULD have an overload on our equipment outside.

That is a lot of what-ifs. So someone tell me, can I just use what I have outside, land temp power on main lugs and take up two breaker spaces for my feeder and leave two open for future expansion.

I'm going to bond N and G outside because I don't know if temp power will be 3 wire or 4 wire.

 

[DBoone]

Need some help with the fine print

Outdoor Loadcenter: " Suitable for use as Service Equipment when not more than six Main disconnecting means are provided and when not used as a lighting and appliance branch circuit panel board OR when used with intregel Main breaker.....sum of breakers not to exceed Main rating.

** does that mean since I have lighting loads inside I am required to have a Main breaker? I cannot find Article 408-14 in my 2011 NEC.

Also the last sentence, does that mean the sum of breakers, including my backfed Main, cannot exceed the rating of my equipment, 125 amps? (That wouldn't make much sense to me)


Indoor Load Center: "..... single pole circuit breakers with a single handle are not permitted for use in a two wire circuit connected to a three wire system."

 

[jaggedben]

..
** does that mean since I have lighting loads inside I am required to have a Main breaker?

Yes. See next comment.

I cannot find Article 408-14 in my 2011 NEC.

I think it was removed from the code a few years ago but unfortunately you still see that on panelboards. I suppose it's debateable whether you still have to follow it just because it's in the panel instructions.

Also the last sentence, does that mean the sum of breakers, including my backfed Main, cannot exceed the rating of my equipment, 125 amps? (That wouldn't make much sense to me)

I think that only applies if you don't have a main breaker.

 

[DBoone]

Yes. See next comment.



I think it was removed from the code a few years ago but unfortunately you still see that on panelboards. I suppose it's debateable whether you still have to follow it just because it's in the panel instructions.




I think that only applies if you don't have a main breaker.

Based on our discussion I guess this is my conclusion and someone correct me if I am totally off base:

Based on Information on Panel Label


1) My outdoor loadcenter can be used as service equipment because:

A) I have 6 or less breaker handles
B) 408.14 has been removed from the code
C) Because I comply with the first two then I do not need the main breaker

2) As Service Equipment, the sum of the breaker ratings must not exceed the main rating, in my case 125 amps. This makes it impossible to overload the equipment.


**. If I see this correctly then it doesn't matter what is upstream of our service equipment, whether its a feeder and OCPD capable of handling 400 amps or one capable of handling only 40 amps, as long as the sum of our breakers do not exceed our panel rating we are good to go.

 

[DBoone]

Here is my main mental block I'm having...I keep wanting to worry about everything upstream of my equipment/office. I know my stuff will be safe and protected but my mind keeps going back to the protection of wires and equipment upstream.

I guess I shouldn't worry about that. That is on someone else.

 

[jumper]

Here is my main mental block I'm having...I keep wanting to worry about everything upstream of my equipment/office. I know my stuff will be safe and protected but my mind keeps going back to the protection of wires and equipment upstream.

I guess I shouldn't worry about that. That is on someone else.

Sorry, so late.

How far have installed the equipment?

Basically what you have is an unlisted office trailor, so the inside panel should have a main.

Power to the unit technically should be supplied by a disco within 30’, but since that may not happen, I go with a genny set up on the outside. That way you know there is a disco.

You need an outside receptacle, it is a small unit soone should be sufficient.

One outlet box for a light outside the door.

You will need todo the required testing, documentation, and labeling.

 

[jaggedben]

Hmmm...

I may have misled you.

We don't know that your panel is being used as service equipment. It's only service equipment if connected directly to the utility. I suppose it's conceivable that your units could be connected either directly to the utility, or only to a feeder from a service that's elsewhere. If the panel is not used as service equipment then the rules on that label don't apply. But if it is, then they do.

Either way, I still recommend providing a single OCPD to land on because then you are less obligated to worry about what someone else does upstream. I think it's less about what you're allowed and more about what is smart to do given your project.

 

[DBoone]

Sorry, so late.

How far have installed the equipment?

Basically what you have is an unlisted office trailor, so the inside panel should have a main.

Power to the unit technically should be supplied by a disco within 30’, but since that may not happen, I go with a genny set up on the outside. That way you know there is a disco.

You need an outside receptacle, it is a small unit soone should be sufficient.

One outlet box for a light outside the door.

You will need todo the required testing, documentation, and labeling.

Jumper thanks for info, and hope you are doing well, but at this stage that ain't gonna be able to happen. I can backfeed a Main outside, then feed inside but no Main inside. I guess I just don't see the need for the Main inside.

 

[DBoone]

Hmmm...

I may have misled you.

We don't know that your panel is being used as service equipment. It's only service equipment if connected directly to the utility. I suppose it's conceivable that your units could be connected either directly to the utility, or only to a feeder from a service that's elsewhere. If the panel is not used as service equipment then the rules on that label don't apply. But if it is, then they do.

Either way, I still recommend providing a single OCPD to land on because then you are less obligated to worry about what someone else does upstream. I think it's less about what you're allowed and more about what is smart to do given your project.

Exactly. May or may not end up being Service equipment. I'm still going to bond N&G outside just in case it's a 3 wire feed to trailer.

I will get a 125 amp, 8 space panel rated for outside and backfeed a 125 or 100 amp breaker. Feed inside with a 60 and maybe stick a 20 amp outside for a receptacle.

And what section covers GES for this set up.

Thank you everyone

 

[jumper]

Jumper thanks for info, and hope you are doing well, but at this stage that ain't gonna be able to happen. I can backfeed a Main outside, then feed inside but no Main inside. I guess I just don't see the need for the Main inside.

No inside main may be problematic, but it may fly.

Okay, so inside is 8 space panel, 4 wire feed.

Outside is mlo with 60A main with hold down kit and 60A breaker to inside?

What about light and rec I mentioned?

 

[jumper]

Exactly. May or may not end up being Service equipment. I'm still going to bond N&G outside just in case it's a 3 wire feed to trailer.

I will get a 125 amp, 8 space panel rated for outside and backfeed a 125 or 100 amp breaker. Feed inside with a 60 and maybe stick a 20 amp outside for a receptacle.

And what section covers GES for this set up.

Thank you everyone

GES is 250.32.

Outside panel should not be set up as service.

 

[DBoone]

No inside main may be problematic, but it may fly.

Okay, so inside is 8 space panel, 4 wire feed.

Outside is mlo with 60A main with hold down kit and 60A breaker to inside?

What about light and rec I mentioned?

Inside is 8 space panel and I just called supplier and got them to order me an 8 space for outside.

Outside I am going to install a 100 or 125 amp breaker with hold down kit and backfeed it to serve as my Main outside.

Feed inside from a 60 amp breaker with 4 wires

*** at this stage I still have 4 spaces available outside

Feed an exterior receptacle from a 20 amp breaker

*** now I still have 3 spaces available outside for expansion



I do not have an exterior light.

I can separate N & G outside, float neutral, and install seperate ground bar if that's what you say I need to do. I just hope if it's a 3 wire feed to the trailer the installer doesn't just land the neutral and call it a day. Never know with some folks around here.

 

[jumper]

Inside is 8 space panel and I just called supplier and got them to order me an 8 space for outside.

Outside I am going to install a 100 or 125 amp breaker with hold down kit and backfeed it to serve as my Main outside.

Feed inside from a 60 amp breaker with 4 wires

*** at this stage I still have 4 spaces available outside

Feed an exterior receptacle from a 20 amp breaker

*** now I still have 3 spaces available outside for expansion



I do not have an exterior light.

I can separate N & G outside, float neutral, and install seperate ground bar if that's what you say I need to do. I just hope if it's a 3 wire feed to the trailer the installer doesn't just land the neutral and call it a day. Never know with some folks around here.

That will work. Next unit get a MB panel inside.

So, outside has 3 extra spaces. Good, exterior lights and maybe gen set up later.

You set up panel with n-g separate. Clearly label that a 60A OCPD protected 4W feeder is required.

You can only plan for so much.

What are the dimensions of the unit?

 

[DBoone]

That will work. Next unit get a MB panel inside.

So, outside has 3 extra spaces. Good, exterior lights and maybe gen set up later.

You set up panel with n-g separate. Clearly label that a 60A OCPD protected 4W feeder is required.

You can only plan for so much.

What are the dimensions of the unit?

Office dimensions are 8'x 20'

Remember I will have a 100 or 125 amp breaker installed outside with the hold down kit. The reason I want a backfed Main that is larger than 60 amps outside is I want to be able to take full, or close to full, advantage of my equipment's capacity.

If I have a 60 amp Main and then a 60 amp feeder, then IF my feeder was fully loaded I would have no room left for other loads.

If I use the larger Main then I could have a fully loaded feeder and still have capacity to handle other loads, all the while my equipment is still protected.



With that being said I am a little confused about your stating I should require a 60 amp feeder.

Could I post a label stating a requirement for a 4-wire feeder with OCPD no greater than my Main breaker ( 100/125 amp- whichever I end up using)

 

[jumper]

Office dimensions are 8'x 20'

Remember I will have a 100 or 125 amp breaker installed outside with the hold down kit. The reason I want a backfed Main that is larger than 60 amps outside is I want to be able to take full, or close to full, advantage of my equipment's capacity.

If I have a 60 amp Main and then a 60 amp feeder, then IF my feeder was fully loaded I would have no room left for other loads.

If I use the larger Main then I could have a fully loaded feeder and still have capacity to handle other loads, all the while my equipment is still protected.



With that being said I am a little confused about your stating I should require a 60 amp feeder.

Could I post a label stating a requirement for a 4-wire feeder with OCPD no greater than my Main breaker ( 100/125 amp- whichever I end up using)

Yes, if main breaker is 100 or 125 the feeder can match.

I would not really be too concerned about future loads. It is a small unit and HVAC is already being installed. Future loads can be served by whatever source is feeding the unit.