Pullbox splicing enough space?

Status
Not open for further replies.
Tainted

Tainted

Senior Member
Location
New York
Occupation
Engineer (PE)
I'm putting in empty wireways that will intercept empty 3ft x 3ft x 3ft pullbox for electricians to make splices and transition to MC cable.

This pullbox will be used to feed 30 apartments with MC cables.

For worst case scenario, is a 3ft x 3ft x 3 ft pullbox big enough to make (90) 3/0 wire splices? I'm sure this will require those polaris to make the splices

If you're curious how I got 90, it's 3 conductors per apartment, so 30 apartments totals 90 conductors to splice.
 
I thought MC cable had labelled inner conductors, so if the conduit/tube/wireway run is short enough, you could just strip off enough of the jacket, terminate the jacket to the box, and pull the conductors the rest of the way, with no splice.

Cheers, Wayne
 
Avoid splice? Use FMC instead of MC Cable? Then you can just pull in the wire without splices. Only addition would be the EGC that then must be pulled.
Personally I wouldn't want to be the service electrician and have to dig through a 3ft x 3ft x 3ft pull box to locate 1 of 90 splices that might be bad. And 30 Iive circuits in there. If you really like the idea of a splice box I would suggest a larger but shallow box such
That could end up looking like this but bigger and potentially worse:
1709031836171.jpeg
 
EMT to MC transitions are common in high rise apartment buildings. Risers come up from the service room and transition to MC down the hallways to each apartment. MC is used because often the number of bends in the MC cable is more than 360° so FMC is not an option. Besides that pulling long runs of #3/0 in FMC isn't fun.

As long as the conduits are in line with their respective MC cables your box is probably large enough. I would spec all barrel crimp connectors with cold shrinks for the transitions since they require far less room and make for a neater installation.
 
I don't think you will be able to get the cover on if you have 90 splice with conductors that large in there. Even if you do, should one of your first made up splices go bad, you likely need to take many others apart to get to it to repair/replace it.
 
kwired said:
I don't think you will be able to get the cover on if you have 90 splice with conductors that large in there. Even if you do, should one of your first made up splices go bad, you likely need to take many others apart to get to it to repair/replace it.
Click to expand...
Which is why you don't use Polaris style connectors and crimp each splice. Crimps are only slightly larger than the conductors.
 
infinity said:
Which is why you don't use Polaris style connectors and crimp each splice. Crimps are only slightly larger than the conductors.
Click to expand...
Which crimps?
kwired said:
I don't think you will be able to get the cover on if you have 90 splice with conductors that large in there. Even if you do, should one of your first made up splices go bad, you likely need to take many others apart to get to it to repair/replace it.
Click to expand...
good point... what size box you think I would need?
Fred B said:
Avoid splice? Use FMC instead of MC Cable? Then you can just pull in the wire without splices. Only addition would be the EGC that then must be pulled.
Personally I wouldn't want to be the service electrician and have to dig through a 3ft x 3ft x 3ft pull box to locate 1 of 90 splices that might be bad. And 30 Iive circuits in there. If you really like the idea of a splice box I would suggest a larger but shallow box such
That could end up looking like this but bigger and potentially worse:
View attachment 2570298
Click to expand...
you cannot use FMC to fish through shafts without supporting. At least with MC cable there is an exception where the cable does not have to be supported if fished through inaccessible places
 
Tainted said:
you cannot use FMC to fish through shafts without supporting. At least with MC cable there is an exception where the cable does not have to be supported if fished through inaccessible places
Click to expand...
Given those two choices you want to use MC cable if possible.
 
Tainted said:
Which crimps?
Click to expand...
Something like this:
bbcu040-copper-splice-blue.webp
 
infinity said:
Which is why you don't use Polaris style connectors and crimp each splice. Crimps are only slightly larger than the conductors.
Click to expand...
can probably make some difference whether you are passing straight through or making turn in the box as well.

Equipment grounding conductors will all need tied together and to the enclosure, where if there were no splices at all they also can pass through uncut.
 
Fred B said:
To me most times I've needed to consider pipe to flexable, it would mean stipping a lot of MC vs just pulling THHN into some flex.
Click to expand...
Certainly depends on the details. If it's a long MC run with maybe 40, 50, 60 feet of EMT, then that is no big deal to strip and probably worth avoiding splicing. Flipped around with short flex run, maybe individual conductors is the way to go.
 
electrofelon said:
Certainly depends on the details. If it's a long MC run with maybe 40, 50, 60 feet of EMT, then that is no big deal to strip and probably worth avoiding splicing. Flipped around with short flex run, maybe individual conductors is the way to go.
Click to expand...
Don't know if the Large MC pulls off easier than Small, but had to one time try to strip off 20 ft of MC #10 and it fought me the entire way. Then the next pull I went with EMT to Flex and pulled in #10 THHN and it was way easier. At least from my perspective, so since then have only pulled into flex rather than try to strip MC.
 
Fred B said:
Don't know if the Large MC pulls off easier than Small, but had to one time try to strip off 20 ft of MC #10 and it fought me the entire way. Then the next pull I went with EMT to Flex and pulled in #10 THHN and it was way easier. At least from my perspective, so since then have only pulled into flex rather than try to strip MC.
Click to expand...
I use AL MC feeder cable quite often (usually 1/0-250 sizes). And the stuff I get strips super easy. Just slice the armor with a sawzall and you can pull of, I don't know probably 30 feet at a time no problem.
 
Status
Not open for further replies.
Top