Distribution Enclosure Height Restrictions

[Simpuller]

I want to mount a splice enclosure (Distribution Panel) as shown in the image.
As I understand it as long as there are no manual operators in a panel then there's no height restriction.
Feel free to tell me what I shoud be calling this distribtion panel without operators.
The enclosure is 20in W x 38in H x 5.75in D.

Thanks for looking. Any help is appreciated.


https://drive.google.com/file/d/1-Drsg2e4xkSIz3oKbKjZTc933HTEV6en/view?usp=drive_link

 

[Elect117]

Access to the image requires permission.

The terminology used might be a little different than what I am used to. Splices are to be made in boxes, like gutters / wireways.

You are not supposed to make splices in a distribution panel where breakers are located. You can, if you follow the rules of 404.3(B) which points to 312.8.

There is a height requirement for any enclosure with any disconnect. See 404.8.

There is no height requirement for gutters, pull boxes, wireways, etc. I would note, however, if a feeder tap is made, then you will need to consider which tap rule and the distance required to install your OCPD to meet it.

 

[Simpuller]

Thanks. I just updated permissions on the image. The splice enclosure won't have any operators.
The wire gauge coming into the splice enclosure is 3/0 and both feeders are also 3/0.
The first sub is 4 feet away from the splice enclosure. The second will be 40 ft away.

 

[Elect117]

You should use 4/0 Cu for 225A main / subs. 3/0 is only good to 200A. Or install a 200A main. It is a violation of 240.4 (round up rule)

All feeders will require 4/0 or a tap rule.

 

[Simpuller]

90 degree Use-2 is 225 at 3/0. Unless my eyes decieve me.

 

[Elect117]

90 degree Use-2 is 225 at 3/0. Unless my eyes decieve me.

They do. See 110.14(C) and UL AALZ

They do not test or approve the use of 90°C ampacities where they are landed in panelboard, switchgear, bussing, breakers, fused disconnects, etc. The only approved use of that ampacity is in certain splices or mechanical lugs where not located in an enclosure. The rating is typically only used for the purposes of derating. Otherwise, you should use the 60°C for under 100A and 75°C for over 100A.

There are specific equipment (majority) that is rated 75°C at less than 100A but unless you specify it on the plan set and the contractor is purchasing the equipment, you should not use it. It is better off to go with the 60°C so the contractor can buy any equipment and it will still be compliant.

 

[Simpuller]

Many thanks. This is my home and shop and I am tackling a complete rewire on my own.
I really appreciate the input.
I have 400A available on the pole and to the mast.
I've been on the fence about going up to 400A because I don't need it now.
I know it looks goofy to have my Main disconnect outside be 225A and both my subs be 225A.
On the fence about increasing the main just for cost reasons since I don't forsee needing more than 225A.

 

[Elect117]

I would suggest talking this out with a a certified electrician.

Costs and lead times might help you narrow down the choice. You might be able to get a 400A rated disconnect and 225A breaker installed in it to reduce the cost impact of the initial install. That way if you ever need to you can upsize the subpanel runs later.

I would however suggest putting each feeder on their own breaker outside. So that one feeds the shop and the other feeds the home. For example, lets say you need to upgrade the shop but not your home, then you can isolate and upgrade that circuit without needing to rewire everything.

 

[Simpuller]

I certainly want to talk this out with a certified electrician.
In the old days when my father was building our house he made friends with the suppliers and they put him on the right track.
My local supplier got hot under the collar when I said i was using NM in a commercial red iron building.
Wasn't till the end of the converstation that he learned I was drywalling everything in at 1 hour rating.
I grew up with exposed emt everywhere in the house because it was an artist's loft.
I am determined not to have exposed emt.

There's nothing too complicated about this, but there are some strategy items I'm working through.
You've already corrected one error my supplier made on the 3/0.

I generally don't pull the trigger until vetted.
Thanks for your input.

 

[Simpuller]

I take it back. Supplier had a 200A breaker in the main breaker panel so 3/0 feeders to the subs would suffice.
Still looking at upping the amps though. I'm going to chart my loads to help me decide. Easy to overlook concurrent loads.
I'll probably end up running a 3" IMC mast with a LA400R main enclosure so at least i have the infrastructure to upgrade easily if needed.
If I run a trough below i can tap inside that to feed two sub breaker panels, whether that's breakered outside or change the inside subs to breaker subs.

If I made the main breaker 400A then the feeders need to be sized for that. In that case having the subs mounted outside near the main makes sense for shorter runs of heavy gauge.
Your thoughts?
Don't be afraid to share advice. It's all on me to do it right. The job is permitted and legal. That's one of the nice things being in Missouri, I can do all my own work even on a commercial building. It just needs to be done right and pass inspection.

 

[Elect117]

I take it back. Supplier had a 200A breaker in the main breaker panel so 3/0 feeders to the subs would suffice.
Still looking at upping the amps though. I'm going to chart my loads to help me decide. Easy to overlook concurrent loads.
I'll probably end up running a 3" IMC mast with a LA400R main enclosure so at least i have the infrastructure to upgrade easily if needed.
If I run a trough below i can tap inside that to feed two sub breaker panels, whether that's breakered outside or change the inside subs to breaker subs.

You will have the tap rule if you want to reduce the size. I would put the gutter inside over the two panels with a main breaker to each panel. Indoor splices will have less risk to outdoor related decay like heat, dust, storms, critters, insects, etc.

There are a bunch of ways to cut a cake. It is too hard to describe all the ways you can or possible could complete the goal.

You are on the right track.

I would advise looking at possible parallel runs of aluminum or copper (only allowed to do parallel if it is 1/0 or larger) to reduce the wire size. Sometimes that can help reduce cost. Even if you have to use more conduits.

You can make a tap inside, right after the main, with a gutter above or below the panels. Just careful about the depth of the gutter being in the working space. Make splices with Polaris taps, and land in a panelboard with a main breaker or a simple fused disconnect switch and reduce the wire size to them based on their protection. See 240.21(B) for 25' tap rule. Then run that to where you need it.

I would advise against romex in a commerical enviroment, and probably suggest MC instead. It might even be easier to use since it has less restrictions and rules.

 

[Simpuller]

I know I'm not going to get much love trying to use romex, but it is code legal here under 5/8 type x.
It's commercial in name only and is more my home than anything...single occupancy and won't ever be more based on size and layout.
The inspector did give me the go ahead.
Anyway, I can be talked into MC, but it's much more expensive. I suppose peace of mind is worth something.
And, I do prefer stranded.

So the tap conductor length rule does affect my design.
One panel can be right near the tap trough but the other is 40ft away. So neither the 10' nor the 25' rule help me on the second panel.
So at mimumum I need to add an OCPD near the tap trough for the far away panel.
Ideally add two OCPDs for both panels and leave the subs lug only.
Which is I think what you were saying.

If I only had room for the extra panels.
Gotta get my lego hat on.
Appreciate the input very much.

 

[Simpuller]

Seems to me the simplest way to deal with this is to run a trough a near the first panel and splice there for the second panel 40ft away.
If I use the same gauge throughout then it's technically not a tap. It would just be a splice and y connection.
As far as I can tell the tap rules ony apply when you want to use a smaller gauge tap. Then the OCPD downstream of the tap and the tap conductor size determine the max current. If both legs of the Y connection are the same gauge as the feeder then the OC, GF, AF are all defined by the feeer and upstream OCPD so the 10' or 25' rules don't apply.
Am I seeing that right?

 

[Elect117]

You are correct.

The overall goal of a tap is to reasonably reduce the wire size. It is useful in a lot of situations but it might not be useful to you.

 

[Jraef]

I want to mount a splice enclosure (Distribution Panel) as shown in the image.
As I understand it as long as there are no manual operators in a panel then there's no height restriction.
Feel free to tell me what I shoud be calling this distribtion panel without operators.

A "distribution panel" is not a defined term, but makes me think of a circuit breaker panel. In the NEC, that term is used several times to MEAN a breaker panelboard, so I'd be careful using that for anything else. If it were a panelboard, any breaker operating handle cannot be higher than 6ft. 7in. from the finished floor.

If there is going to be nothing but wires and/or terminal blocks inside, it would be called a "junction box" or "splice box" and there are no height restrictions, but they must be left "accessible", which is a defined term, but not terribly onerous. It just means you don't need to alter the building to get access to it. But don't confuse that with the other defined term "readily accessible", which would preclude the use of a ladder to get to it. Junction/splice boxes are not required to be "readily accessible", just "accessible".