multi-floor feeder design

[randy263]

I'm looking at upgrading an old 4 floor building, where the upgrade will mean virtually installing all new service and feeders to each floor. Each floor will be used for different purposes, and those purposes have not yet been fully defined. But as a rough estimate, 200A per floor seems reasonable starting place.

So my question is: Is it better to run home run 200A feeders to each floor with a 200A disconnect for each at the first floor (and an 800A main), or to run a single 800A feeder to the top and tap at each floor with a 200A subpanel/OCD? (or a hybrid, say two 400A feeders)?

The tap seems flexible for future. I'm not sure which is most economical. If a tap is used, can the tap be done with split-bolt connectors in a box at each floor or are lugs required?

 

[iwire]

Randy, there is so much to condiser and we have no idea what you are looking at.

How many sq ft are each floor?

You said

200A per floor seems reasonable starting place.

200A 120/240?

200A 208Y/120?

200A 480Y/277?


You went on to say

200A feeders to each floor with a 200A disconnect for each at the first floor (and an 800A main)

Just because you have four 200 amp feeders does not mean you have to have an 800 amp main.

Now that said, if it was me based on the very little info I have I would be thinking one dedicated feeder per floor.

What are you doing about metering?

 

[randy263]

Thanks for the reply. For what it is worth, there are about 2000 sq ft. per floor, this would be 120/240, and at least one floor will contain a residential apartment. I am presently working on better floor power estimates. But I think it is more of a general question on feeder design--I've seen examples of both with no clear explanation of why an engineer might choose one over the other.

How would you size the main breaker and service if less than the sum of the connected feeder capacities? You are right that it will never be that all the feeders are at full load at the same time. But also the idea is to avoid saving pennies now that will cost dollars later.