Electrical Supervisor

Status
Not open for further replies.
D

ddouglas

Member
I have a three story office building and I am wanting to find the watts per square foot of each floor. If I know the amperage
(800A) and voltage (480V) of my switchgear, can I find the total wattage of the gear then divide by three (floors) to find the watts per floor then divide that by the footage of each floor or would I have to use the total ratings of the panels on each floor, power and lighting panels?
 
Last edited:
I'm not sure I understand your question. Are you asking how many watts per square foot are available from the service? If so it is voltsXampsX1.732/square footage for a 3 phase service.

If you can be clearer, I'm sure someone can help.

Jim T
 
Don't you usually do it the other way...
Calculate the sq. ft needs then size the gear?
 
celtic said:
Don't you usually do it the other way...
Calculate the sq. ft needs then size the gear?
Click to expand...
wE HAVE AN EXISTING BUILDING THAT WE ARE TRYING TO FIND A TRUE NUMBER, AS CLOSE AS POSSIBLE, OF POWER PER FOOT.
 
jtester said:
I'm not sure I understand your question. Are you asking how many watts per square foot are available from the service? If so it is voltsXampsX1.732/square footage for a 3 phase service.

If you can be clearer, I'm sure someone can help.

Jim T
Click to expand...
I REWROTE THE QUESTION TO INCLUDE MORE INFO THANKS
 
The equation I posted will give you true VA/sq.ft. of power available. I read your second post and am still a bit confused. You'll have to forgive me, on a good day I'm a bit confused. What are you planning to do with this number?

Jim T
 
The nameplate on the gear may say 800A for the bus amps but it may not be fed with 800A wire. If it has a main CB or fused switch then you're probably OK to assume 800A. NOW, how much is fed to each floor is still unknown. Don't assume that they are all the same size. (Maybe you intend to modify feeders...)

Now you only know that capacity of the service for non-continuous loading. If you want to know the available capacity for continuous loads, take the 800A x 80%, =640A unless the main is 100% rated. So the VA capacity for continuous loads is 640 x sqrt (3) x 208V. This gives you the service capacity in VA so you can calculate VA per sq ft.
 
looks like this depends on what you're goinig to use the numbers for.

if you are going for consumption, I'd say that installing a kWHr meter is best

adding panel ratings per floor may not actually give you an accurate picture, unless every breaker is utilized to its capacity by the installed loads.
 
Status
Not open for further replies.
Top