engineering evaluation

[flatlander]

Hello
A long time client of mine is looking to buy a building. It does not meet his electrical needs nor does any in the area he wants.
He is looking to upgrade his service to a 480v system. Is there a point where things jump into a new realm where additional space, clearances and such come into play that could hamper project?
600 am 480v277
Or 800 a
Or 1000a
1200a

Thanks

 

[ron]

Sections 110.26 and 110.34 have the working clearance tables that show required values to watch out for depending on the voltage

 

[ptonsparky]

A jump to. 1000 amp.adds GFP to.the service.

 

[drktmplr12]

Hello
A long time client of mine is looking to buy a building. It does not meet his electrical needs nor does any in the area he wants.
He is looking to upgrade his service to a 480v system. Is there a point where things jump into a new realm where additional space, clearances and such come into play that could hamper project?
600 am 480v277
Or 800 a
Or 1000a
1200a

Thanks

110.26 (C) requires that gear 1200 A or above, over 6 ft wide and with over-current devices, you must have egress (exit) on both sides of the equipment unless you either double the working space requirements of 110.25(A)(1) or provide "Continuous and unobstructed way of egress travel" . To be perfectly honest, I am not certain that a designer cares about Unobstructed Egress because there should be nothing permanent in front of electrical equipment either way. I believe this requirement points to more of owner's use such as storage boxes, or temporary tools/ladders/etc that would impede egress in an emergency.

It also requires that any exit within 25 ft from the nearest edge of the working space for 800A or above equipment must open in the direction of egress and be equipped with panic hardware.

My understanding is that the intent of having two exits (one on either side) it to be sure one is not trapped by fire coming from the front of the gear.

 

[charlie b]

The threshold for needing a second entrance and egress from the working space is now 1200 amps AND over 6 feet wide. That might impact the decision.

Also, a rule of thumb I have used in the past is that once you get to 750 KVA or higher (roughly 2000 amps at 120/208 volts), it becomes economically advantageous to go with a 480/277 backbone system. Below that, the cost savings from not needing any step-down transformers, not dealing with the energy losses associated with the transformers, and not having to install the additional 120/208 volt distribution panelboards tends to offset the costs of the larger size feeders that serve the branch panelboards.

 

[charlie b]

To be perfectly honest, I am not certain that a designer cares about Unobstructed Egress because there should be nothing permanent in front of electrical equipment either way. I believe this requirement points to more of owner's use such as storage boxes, or temporary tools/ladders/etc that would impede egress in an emergency.

I think there is more to it than that. A couple years ago I got into a (losing) argument with a plan reviewer on this issue. His interpretation was that "unobstructed" means (essentially) that if you are facing the equipment and need to escape from an event, you need to be able to walk backwards (or make a 180 degree turn and continue to walk directly forward) and thereby reach the door. Basically, he wanted me to move the equipment to the wall that is exactly opposite to the doorway. He believed that if you have to take a couple steps away from the equipment and then turn left or right to get to the door, you will have lost the advantage of an unobstructed exit.

 

[jim dungar]

He believed that if you have to take a couple steps away from the equipment and then turn left or right to get to the door, you will have lost the advantage of an unobstructed exit.

I don't think I have ever seen any electrical room, e-house, or walk-in switchgear enclosure built like this. Using this reasoning would require that all doorways be at least the same width as the electrical equipment, as anything less requires you to move to the right or left.

 

[Jraef]

What are his reasons for wanting 480V? What type of building is this? The reason I ask is because I have had 2 different people (with more money than sense) ask me about getting a 480V service to their HOUSE, because they mistakenly believe it will cost them less because the current will be lower.

Assuming this is a business and they truly need 480V for machinery, then you must assume that if he wants it and doesn't have it now, a LOT of his existing electrical gear in the building becomes useless. the small 120/240V (or 208V) branch stuff can be re-used after transformers are added, but all of the primary gear must be replaced. People don't understand that you can't use 240V rated gear on 480V and get floored by the cost to change the service voltage.

 

[flatlander]

What are his reasons for wanting 480V? What type of building is this? The reason I ask is because I have had 2 different people (with more money than sense) ask me about getting a 480V service to their HOUSE, because they mistakenly believe it will cost them less because the current will be lower.

Assuming this is a business and they truly need 480V for machinery, then you must assume that if he wants it and doesn't have it now, a LOT of his existing electrical gear in the building becomes useless. the small 120/240V (or 208V) branch stuff can be re-used after transformers are added, but all of the primary gear must be replaced. People don't understand that you can't use 240V rated gear on 480V and get floored by the cost to change the service voltage.

A jump to. 1000 amp.adds GFP to.the service.

Thanks for the great advice and feed back. This would be in an industrial park. I personally don't know the justification yet. I think it has to do with machinery. I am waiting on a list from them. They were looking to future proof their needs. I'm more inclined to look at other things like spare conduits and a lager footprint for additional gear for the future. I've seen things go unused so many times.