multiple circuits from high rise building to roof

[tico17]

Hi,
question i have to run power for 30 air condenser on roof from each apartment. i have each individual conduit in electrical room up to the last floor from there i have to reach air conditioning racks on roof. can i just put a gutter before roof and install 4 1-1/2 conduits to roof and spread out or since they are from different apartments i wont be able to mix circuits in gutter box.

 

[hbiss]

Didn't we have this same question here about a year ago? Seems to be a popular thing in FL.

I see no problem mixing circuits in the gutter. Going to have to derate in those 1-1/2" runs.

-Hal

 

[tico17]

Didn't we have this same question here about a year ago? Seems to be a popular thing in FL.

I see no problem mixing circuits in the gutter. Going to have to derate in those 1-1/2" runs.

-Hal

Hall, yes i am going to derate them, but my question is if all circuits can be in a gutter even if they come from different apartments?.

 

[tank728]

A gutter is usually listed as a wireway and subject to article 376 (if I recall correctly) and it has its own derating chart. Verify with that chart.

30 condensing unit, means 60 current carrying conductors. That's a fair bit of derating. Now you know the physical layout of things and can determine current carrying conductors in a cross sectional area. That's going to ultimately determine the amount of derating. Perhaps order a long and skinny pull box and avoid the issue.
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​​​​To answer your question directly I see no reason why not. They are all branch circuits. I do not perform a lot of multi dwelling work though.

 

[kwired]

A gutter is usually listed as a wireway and subject to article 376 (if I recall correctly) and it has its own derating chart. Verify with that chart.

30 condensing unit, means 60 current carrying conductors. That's a fair bit of derating. Now you know the physical layout of things and can determine current carrying conductors in a cross sectional area. That's going to ultimately determine the amount of derating. Perhaps order a long and skinny pull box and avoid the issue.
​
​​​​To answer your question directly I see no reason why not. They are all branch circuits. I do not perform a lot of multi dwelling work though.

Hit the gutter at center and divert half conductors one way and half the other way and you maybe only have 30 current carrying conductors in any one cross section.

There is also a possibility of being able to apply 310.15(A)(2) exception in a situation like OP has.

 

[tico17]

Hit the gutter at center and divert half conductors one way and half the other way and you maybe only have 30 current carrying conductors in any one cross section.

There is also a possibility of being able to apply 310.15(A)(2) exception in a situation like OP has.

what i did but have not finish is that i ran one 1-1/2" to each roof rack on roof and the other end i was going to bring it to main gutter in 11th floor so that gutter will have 4 1-1/2" conduits plus all the other 3/4 that will go to each apt. so derating wont be as bad as it looks probably each conduit going on roof will have between 12 to 14 current carrying conductors.

 

[infinity]

Keep in mind that after derating your conductors only have to be large enough to meet the MCA of the unit not the OCPD size.