ELECTRICAL ROOM LAYOUT ACCORDING TO NEC 110.26

[PE (always learning)]

Hope everyone is doing well,

I wanted to get a second pair of eyes on an electrical room that I'm laying out that has a 4000 amp switchboard (MSB). I just want to verify that this electrical room isn't causing any violations and that I'm not missing anything required from NEC 110.26. For instance, I have egress doors on opposite ends of the electrical room. Do these need to be right across from each other? I would think as long as the panels don't obstruct the egress path then I should be fine. Also, I have a panel L1 that could potentially open up into the south egress door, I'm wondering if this should be moved. Electrical room image is attached, any advice is always appreciated.

Best Regards

 

[Tainted]

If you double the clearance of MSB, you may get away with 1 door. What's the KVA of the transformer T1? Ensure panic hardware is installed

 

[drktmplr12]

Hope everyone is doing well,

I wanted to get a second pair of eyes on an electrical room that I'm laying out that has a 4000 amp switchboard (MSB). I just want to verify that this electrical room isn't causing any violations and that I'm not missing anything required from NEC 110.26. For instance, I have egress doors on opposite ends of the electrical room. Do these need to be right across from each other? I would think as long as the panels don't obstruct the egress path then I should be fine. Also, I have a panel L1 that could potentially open up into the south egress door, I'm wondering if this should be moved. Electrical room image is attached, any advice is always appreciated.

Best Regards

If this is an academic exercise you are good. With respect to egress doors. The thought is if there is a fire/hazard in the switchboard, it might block escape and so someone will need an alternate path. Your door placement appears to achieve this. I don't see any clearance issues.

If this is going to be built-

• I would slide the switchboard 18 inches from the right wall, provided L1 has 42" in front. This gives you space on the right side wall to locate 18" deep equipment.
• The transformer does not require working clearances, can even be located on support rack overhead the panelboard(s) it serves (not ideal, but also not unusual for commercial buildings)
• Also, slide the north door left about 15 inches, same reasoning.
• Be sure the switchboard can get in and out the main door. Height is usually the restriction since switchboards typically are shipped in sections. A standard pedestrian door is only 84 inches high. a switchboard is ~90 inches, plus electricians typically bring them in on rollers or a pallet. An 8-foot door should be safe.

 

[kwired]

If this is an academic exercise you are good. With respect to egress doors. The thought is if there is a fire/hazard in the switchboard, it might block escape and so someone will need an alternate path. Your door placement appears to achieve this. I don't see any clearance issues.

If this is going to be built-

• I would slide the switchboard 18 inches from the right wall, provided L1 has 42" in front. This gives you space on the right side wall to locate 18" deep equipment.
• The transformer does not require working clearances, can even be located on support rack overhead the panelboard(s) it serves (not ideal, but also not unusual for commercial buildings)
• Also, slide the north door left about 15 inches, same reasoning.
• Be sure the switchboard can get in and out the main door. Height is usually the restriction since switchboards typically are shipped in sections. A standard pedestrian door is only 84 inches high. a switchboard is ~90 inches, plus electricians typically bring them in on rollers or a pallet. An 8-foot door should be safe.

Aren't many switchboards set in place then the room built around them, or at least one wall not finished until the switchboard brought in?

If you need to replace switchboard that is someone else's problem in say 50 years.

 

[drktmplr12]

Aren't many switchboards set in place then the room built around them, or at least one wall not finished until the switchboard brought in?

If you need to replace switchboard that is someone else's problem in say 50 years.

I hear you, designer preference. Why not just install an 8-foot door to the exterior? It's minimal expense relative to the building.

that said, switchboards from SQD are out 10 months from approval so you might not be getting them before the walls are in.

 

[kwired]

I hear you, designer preference. Why not just install an 8-foot door to the exterior? It's minimal expense relative to the building.

that said, switchboards from SQD are out 10 months from approval so you might not be getting them before the walls are in.

Is that more of a current issue or always been a long wait?

Seen switchboards in interior rooms before. Service conductors underground until they emerge into switchboard is still considered outside the building

 

[steve66]

IMO the transformer needs clearance. The clearance required may be different for a transformer installed up in the air, but it still needs clearance.
I thought there was a paragraph that addressed that, but I can't find it right now.

I would make sure there is a door large enough to get a switchboard section through, especially if the walls are block. Like a 3-6 or 4-0 door. But IMO an 8' door isn't really necessary.

 

[drktmplr12]

Is that more of a current issue or always been a long wait?

Seen switchboards in interior rooms before. Service conductors underground until they emerge into switchboard is still considered outside the building

more current. We've seen closer to 12-16 weeks from approval for standard switchboards, pre-pandemic.

 

[drktmplr12]

IMO the transformer needs clearance. The clearance required may be different for a transformer installed up in the air, but it still needs clearance.
I thought there was a paragraph that addressed that, but I can't find it right now.

I would make sure there is a door large enough to get a switchboard section through, especially if the walls are block. Like a 3-6 or 4-0 door. But IMO an 8' door isn't really necessary.

the transformer has no serviceable parts. it does not require working clearances. Only space for ventilation.

that said, best to keep them on the floor or else someone will be cursing you under their breath one day.

i meant 8' high, not wide-apologies that this wasn't clear.

 

[steve66]

the transformer has no serviceable parts. it does not require working clearances. Only space for ventilation.

All electrical equipment requires sufficient working space per 110.32. That paragraph doesn't really specify a specific depth, so "sufficient space" is kind of arbitrary. But you certainly wouldn't be allowed to put anything right in front of the transformer.

The other question is does it require the space listed in table 110.34(A). This has been debated to the point of being pointless to debate again, but many people feel transformers require maintenance (like voltage testing and thermography) that requires the working space depth listed in 110.34(A).

 

[PE (always learning)]

Thanks everyone for the responses, very informational and I'm going through them right now