Statement Evaluation

Status
Not open for further replies.
S

Steve V

Member
Location
Nashville, TN
Please evaluate a statement that an EE sent me.



Situation:

The Owner/GC sent me a Tenant Specification sheet and asked me to make sure we are providing the correct Electrical Service per this specification.

Tenant Requirements: " 1- 400 amp, 120/208v, 3 phase, 4w, panel w/ 400a 3 pole main breaker & 200a sub feed breaker and 1 - 225a MLO 120/208v 3P, 4W panel"

My Reply: "the requirements are not being meet. We have a 200a 277/480v 3P breaker feeding a 75kva transformer (with a max. amp of 208.2) feeding a 200a MLO panel"

EE Reply: "A 200 amp panel on 480/ 277 is equivalent to a 400 amp panel at 120/ 208."

Does this make sense to anyone?

Am I wrong?

Thank you.
 
If the goal is to have 400a at 208/120v, then a 200a sub-panel isn't gonna cut it.

The question is why have the 400a panel which then feeds a sub-panel? Is that important to the tenant? Very well could be; if it is, the 480v into a transformer doesn't comply.

As is often said here, more info is needed.
 
Haha, what the fire truck!
Ok then your good to go! Just send the EE statement to the GC/tenant with a note your Co. feels you are not being serviced and wait for the extra to roll in.
 
romex jockey said:
No

And i would ask s/he just what validates 'equivalent'

~RJ~
Click to expand...

If what they mean is that it can deliver the same amount of total power, they are right, but it still cannot handle more than 200A on each phase conductor regardless of the voltage. A little knowledge in a manager is a truly frustrating thing.
 
The specified design allows for 200 amps worth of load (at 120/208V) on the sub panel, in addition to 200 more amps worth of load on the upstream panel. The EE is correct in saying that 200 amps at the higher voltage is (essentially) equivalent to 400 amps (closer to 460) at the lower voltage. But the submitted design leaves out the ability to supply power to half of that equivalent 400 amps. You only get a 200 amp panel. You don't get the 400 amp panel that was specified.
 
At a basic level, I don’t see why 480/277 is being brought into the discussion at all on a 208/120 service. Was there a typo somewhere and the SERVICE is 400A at 480, then they want a 200A 208/120 sub panel fed from a transformer that was not mentioned in that original statement?
 
Jraef said:
At a basic level, I don’t see why 480/277 is being brought into the discussion at all on a 208/120 service. Was there a typo somewhere and the SERVICE is 400A at 480, then they want a 200A 208/120 sub panel fed from a transformer that was not mentioned in that original statement?
Click to expand...

I think you are looking at a situation where a building owner is trying to fill one of his empty spaces, like a strip mall or something similar.

The tenant says he needs 400A at 208/120V...the existing building service is 480/277V.

If the tenant has no need for 480/277, the simple solution would be to bring the 200A, 480V feeder to the space and supply a 112.5kVA transformer to a 400A, 208/120V panelboard.
 
Steve V said:
My Reply: "the requirements are not being meet. We have a 200a 277/480v 3P breaker feeding a 75kva transformer (with a max. amp of 208.2) feeding a 200a MLO panel"
Click to expand...

You cannot supply an MLO panel directly from the transformer (assuming its a 208/120V secondary to meet the conditions you mentioned.)
 
Jraef said:
At a basic level, I don’t see why 480/277 is being brought into the discussion at all on a 208/120 service. Was there a typo somewhere and the SERVICE is 400A at 480, then they want a 200A 208/120 sub panel fed from a transformer that was not mentioned in that original statement?
Click to expand...

I agree, I don't understand how anyone is giving answers to the OP. There is either a typo or a missing paragraph. I have no clue what is going on.
 
david luchini said:
I think you are looking at a situation where a building owner is trying to fill one of his empty spaces, like a strip mall or something similar.

The tenant says he needs 400A at 208/120V...the existing building service is 480/277V.

If the tenant has no need for 480/277, the simple solution would be to bring the 200A, 480V feeder to the space and supply a 112.5kVA transformer to a 400A, 208/120V panelboard.
Click to expand...
Huh. Somehow I must have missed the statement about having the 480V service... I was reading it from my phone at that time, I guess I just missed it (or it was edited after I posted that).

I agree. If the requirement was for 400A at 208V, you can't get that from a 75kVA transformer, so therein lies the problem.

By the way, you can't get 400A from a 112.5kVA either, it needs to be 150kVA minimum.
 
Status
Not open for further replies.
Top