MC branch circuit

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wireday

Senior Member
Location
New England
Occupation
Master electrician
Im installing a 20amp 120/208 three phase branch circuit. Its a commercial job. the length of the run is approx 37 feet the first 27 is coming from the panel up to a attic area where the plywood floor is screwed in place so i can support across on the joist.then it jumps out over a suspended ceiling the remaining ten feet. The branch circuit is terminating at a ceiling receptacle. I have a nice anchor plate with cut outs for receptacle. This plate will be supported at each corner with hang wire. there are two hang wires between the receptacle location and the joist. these are going to a troffer light.I plan to support the mc to them as well. the hang wires to the light are for electrical use only.
 
The wires supporting the light are just before the receptacle location,the receptacle will have a bought plate made for this purpose,and that will also be supported with a 4 hang wires one on each corner.the support wires on the light are 4 ft apart.
 
wireday said:
I have a nice anchor plate with cut outs for receptacle.
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Can you attach/bolt a 4 inch square box (for receptacles) to the anchor plate ? Or do you plan to use a box ?

Bat wing the MC to the ceiling wire, right?


What will you plug into the receptacles ?
 
wireday said:
The wires supporting the light are just before the receptacle location,the receptacle will have a bought plate made for this purpose,and that will also be supported with a 4 hang wires one on each corner.the support wires on the light are 4 ft apart.
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So if I read this correctly the light and box are supported independently of the grid. Cool.

Now what supports/secures the MC?
 
the mc would attach at each hang wire on the light, it would go from the joist about 3ft hit the first wire then 4 ft then about a foot to attach to one of the hang wires for the receptacle plate.
 
the plate has a spot for a single gang steel city box,the receptacle will have a large machine below it,its a production machine that a couple people will operate.the plug is a five prong,120/208
 
wireday said:
the mc would attach at each hang wire on the light, it would go from the joist about 3ft hit the first wire then 4 ft then about a foot to attach to one of the hang wires for the receptacle plate.
Click to expand...


Good. Also attach MC within 1 foot from the receptacle plate, or closer.
 
jumper said:
Okay,securing and support is within every 6', unless connected to a fixture, and independent of the grid, cool.

Cables are secure and supported 1' from the fixture, correct?
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My references for my questions:

300.11 Securing and Supporting.
(A) Secured in Place. Raceways, cable assemblies, boxes,
cabinets, and fittings shall be securely fastened in place.
Support wires that do not provide secure support shall not
be permitted as the sole support. Support wires and associated
fittings that provide secure support and that are installed
in addition to the ceiling grid support wires shall be
permitted as the sole support. Where independent support
wires are used, they shall be secured at both ends. Cables
and raceways shall not be supported by ceiling grids.

330.30 Securing and Supporting.
(A) General. Type MC cable shall be supported and secured
by staples, cable ties, straps, hangers, or similar fittings
or other approved means designed and installed so as
not to damage the cable
.
(B) Securing. Unless otherwise provided, cables shall be
secured at intervals not exceeding 1.8 m (6 ft). Cables containing
four or fewer conductors sized no larger than
10 AWG shall be secured within 300 mm (12 in.) of every
box, cabinet, fitting, or other cable termination.

(C) Supporting. Unless otherwise provided, cables shall
be supported at intervals not exceeding 1.8 m (6 ft).
Horizontal runs of Type MC cable installed in wooden
or metal framing members or similar supporting means
shall be considered supported and secured where such support
does not exceed 1.8-m (6-ft) intervals.
 
Also this is a 20amp three phase 120/208 with neutral. Usually all I see is mc for lighting over suspended ceilings. this is a receptacle for a machine.
 
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