MC vs. running pipe for commercial job

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I am bidding a job and the spec calls for 4 250 KCM aluminum conductors (plus #6 Grnd) in 2 1/2" pipe or MC cable with rubber sheath (we use TECK cable a lot in Canada with is MC with a rubber sheath on the outside).

The complete run is through a building (school) running approximately 200 ft going through 4 cinder block support walls (core drill required). From the electrical room to the end of the run there will be approximately 6 90 deg turns and several changes in elevation (offsets will be required). About 110' of the run is through ceiling space with a tile ceiling (2x4 ceiling tiles) with some areas being quite tight with the other stuff run in the ceiling (eg. plumbing, data, power, etc.). The remainder of the run is surface mounted (about 30' on one end at the electrical room, and 60' on the other end going to the 3 phase 120/208 sub-panel. I have attached a drawing of the run and you will notice the area in the tiled ceiling is outlined in a yellow box (the cable run is the red arrows).

The 4C 250KCM MC cable itself has an outside diameter of approx 2.4" and 200 ft of MC weighs around 500 lbs.

My thinking is that because of the size and the weight of the MC cable and the fact that we probably cannot run from one end to the other and will probably have to start somewhere in the middle.

I would rather use the MC because normally the labour to run + the materials is a lot less than piping + materials.

To avoid damage to the ceiling tiles and T-bar frame I think I would have to use pulley blocks setup every 10 ft or so to keep the heavy MC off the T-bar frame.

Does anyone have experience running MC cable in this type of situation? Is is feasible or should I plan to use pipe?

Thanks in advance.

Attila
 

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rambojoe

Senior Member
Location
phoenix az
Occupation
Wireman
is the t-bar ceiling a plenum? (ceiling space as a duct..) I don't think you could have any non metallic coating on the mc if so.
schlepping that size multi conductor feeder would be very labor intensive. wouldn't the pipe be cheaper? looks like you got the job after the window for underground! I couldn't find if either teck cables are plenum rated...
 
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Fulthrotl

~Autocorrect is My Worst Enema.~
The 4C 250KCM MC cable itself has an outside diameter of approx 2.4" and 200 ft of MC weighs around 500 lbs.

My thinking is that because of the size and the weight of the MC cable and the fact that we probably cannot run from one end to the other and will probably have to start somewhere in the middle.

I would rather use the MC because normally the labour to run + the materials is a lot less than piping + materials.

To avoid damage to the ceiling tiles and T-bar frame I think I would have to use pulley blocks setup every 10 ft or so to keep the heavy MC off the T-bar frame.

Does anyone have experience running MC cable in this type of situation? Is is feasible or should I plan to use pipe?

Thanks in advance.

Attila

just being honest, it's gonna be hard not to trash a t bar ceiling putting in MC cable.
let's say you pull from the middle, both ways.... the second half of that, when you
have to get the MC up into the ceiling, is probably not going to turn out well.

you might as well take down the t bar in that area and put it up again later,
as opposed to remove and replace it after the crap gets bent out of it.

i was on a crew pulling 500 MCM MC under a computer floor, to feed PDU's.
150' to 250' runs, iirc. so, like pulling above a ceiling grid, but easier, you
could stand there on the floor, and fit it in.

i'd use pipe, if it were me, based on that experience. not a fun week.
there were six of us horsing that crap in.
 
MC vs Pipe

MC vs Pipe

Thanks for the replies.

The engineer specified TECK cable or pipe so either would be acceptable in the ceiling space.

Can't run underground as suggested in one reply.

I think pipe is the way to go as recommended as it will be unfeasible to take down t-bar and replace. Either way it will be a tough one.

Thanks again.
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
I am bidding a job and the spec calls for 4 250 KCM aluminum conductors (plus #6 Grnd) in 2 1/2" pipe or MC cable with rubber sheath (we use TECK cable a lot in Canada with is MC with a rubber sheath on the outside).

The complete run is through a building (school) running approximately 200 ft going through 4 cinder block support walls (core drill required). From the electrical room to the end of the run there will be approximately 6 90 deg turns and several changes in elevation (offsets will be required). About 110' of the run is through ceiling space with a tile ceiling (2x4 ceiling tiles) with some areas being quite tight with the other stuff run in the ceiling (eg. plumbing, data, power, etc.). The remainder of the run is surface mounted (about 30' on one end at the electrical room, and 60' on the other end going to the 3 phase 120/208 sub-panel. I have attached a drawing of the run and you will notice the area in the tiled ceiling is outlined in a yellow box (the cable run is the red arrows).

The 4C 250KCM MC cable itself has an outside diameter of approx 2.4" and 200 ft of MC weighs around 500 lbs.

My thinking is that because of the size and the weight of the MC cable and the fact that we probably cannot run from one end to the other and will probably have to start somewhere in the middle.

I would rather use the MC because normally the labour to run + the materials is a lot less than piping + materials.

To avoid damage to the ceiling tiles and T-bar frame I think I would have to use pulley blocks setup every 10 ft or so to keep the heavy MC off the T-bar frame.

Does anyone have experience running MC cable in this type of situation? Is is feasible or should I plan to use pipe?

Thanks in advance.

Attila

I think your weight is off. Southwire 250 weighs about 165 pounds per 100 feet without coating, with coating shouldn't be that much more. I would think twice about using it instead of pipe and wire. Take a little time to plan every section. Regarding the T-bar area, it isn't that hard to pop a few T's out. Or since you have to strap it somehow anyway, and it sounds like you are necessarily going up against the ceiling, use trapeze and pull across it.
 

iwire

Moderator
Staff member
Location
Massachusetts
This may or may not be an issue for the OP in Canada but for us under the NEC in most cases parallel MC runs will result in a EGC size violation.
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
This may or may not be an issue for the OP in Canada but for us under the NEC in most cases parallel MC runs will result in a EGC size violation.

Southwire offers standard MC with upsized grounds expressly for this purpose. Also, with about a 3 week lead time, you can get any size and conductor configuration of MC you want with factory minimum. So that is only an issue of planning, not code. FYI:)
 

iwire

Moderator
Staff member
Location
Massachusetts
Southwire offers standard MC with upsized grounds expressly for this purpose. Also, with about a 3 week lead time, you can get any size and conductor configuration of MC you want with factory minimum. So that is only an issue of planning, not code. FYI:)

I am aware there are ways to deal with it, that was why you can see the words 'most cases' in my post. :)

Many are unaware this EGC issue at all and it could be a very costly mistake to correct.
 

growler

Senior Member
Location
Atlanta,GA
Many are unaware this EGC issue at all and it could be a very costly mistake to correct.

Yes, the solution to the problem may be simple enough before you run the cable but not so easy once the cable is run.

I think your comment was a good one as this could end up being a very costly mistake and if he's already aware of it then he will know you mean well.
 
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