MC Cable

Status
Not open for further replies.
D

dlducks

Member
Location
Ohio
I am working on a remodel job in a local hospital. We are replacing all the lighting and receptacle feeds in the patient rooms. The old wiring is in conduit.
The new installation is going back in in MC Cable. This is not a problem I know. I was told to just cut the existing conduit off and push the mc cable down into the existing conduit stubs and use this as a raceway without any kind a connector . My question is can I use the couduit as a raceway and can I even put the mc cable in the couduit?
 
First of all, since the conduit is only going to be sleeves now plane jane MC will not be allowed for any wiring in patient care areas, it will have to be HCFC or the new MC smart cable, (AC can be used for lighting above 7.5') see 517.13 and then 250.118

Now we have to go to 517.30(C)(3)c for the emergency circuits, this would only allow you to use flexible wiring methods in walls and ceilings that are "not otherwise accessible". It sounds as though you would have access to the conduit system so an inspector would/should tag the installation if there is some reasonable access to the spaces.

I don't understand why a flexible wiring method is being used in these conduits anyways, if the conduits go to the outlets and devices what would be the advantage of the cable?

Roger
 
The old ceilings are plaster, so the old lights and the conduit for the lights were solidly piped in just above the ceiling so they had to be removed. The cut off pipe is just for the ligth whips. The receptacle feeds are the required smart cable you stated and the mc is being used above the 7.5 level. So you are saying if the conduit system is accessable it can't be used as a sleve and if it isn't you can.
 
DL, welcome to the forum.

I would ask the AHJ for an opinion as to whether he/she considers the spaces to be accessible or not.

Back to the MC being used for the light fixtures above 7.5'. It is not allowed even in these areas of patient care areas. You do not need an insulated EGC for the fixtures but, the cable sheath will have to qualify as an EGC per 250.118

See 517.13(B) Exception No 2.

Roger
 
dlducks said:
I was told to just cut the existing conduit off and push the mc cable down into the existing conduit stubs and use this as a raceway without any kind a connector .
Click to expand...
Why not put a junction box atop the cut-off conduit stubs, and terminate the MC in the box with connectors?

You can even skip making joints in this box if you strip the MC long enough to reach the terminals in the panel.
 
Actually, Larry brings a point to the table that I missed, if the cable is not connected to the boxes or conduit with approved connectors, the required redundant grounding consisting of the cable sheath and the insulated conductor is non existent and therefor the installation is in violation regardless.

Roger
 
Roger, I came in late on this. Sorry. Would this also pertain to standard MC ran thru a raceway and not using standard connectors? I understand using the proper connectors with MCap and HCF.
 
Greg, if the raceway was a complete metalic raceway, standard MC (or any cable that had an insulated EGC in it) could be used with out connectors, but there would be no reason to use a cable assembly if this was the case.

Looking at 517.13 in it's entirety.

517.13 Grounding of Receptacles and Fixed Electric Equipment in Patient Care Areas

Wiring in patient care areas shall comply with 517.13(A) and 517.13(B).

(A) Wiring Methods All branch circuits serving patient care areas shall be provided with a ground path for fault current by installation in a metal raceway system, or a cable having a metallic armor or sheath assembly. The metal raceway system, or metallic cable armor, or sheath assembly shall itself qualify as an equipment grounding return path in accordance with 250.118.
Click to expand...

In order for the raceway or cable sheath to provide a low impedance fault clearing path, it would have to be installed continuous with propper connections at all points, this could not be acheived in the installation as described.

Now, looking at 517.13(B)


(B) Insulated Equipment Grounding Conductor The grounding terminals of all receptacles and all non–current-carrying conductive surfaces of fixed electric equipment likely to become energized that are subject to personal contact, operating at over 100 volts, shall be grounded by an insulated copper conductor. The equipment grounding conductor shall be sized in accordance with Table 250.122 and installed in metal raceways or as a part of listed cables having a metallic armor or sheath assembly with the branch-circuit conductors supplying these receptacles or fixed equipment.

Exception No. 1: Metal faceplates shall be permitted to be grounded by means of a metal mounting screw(s) securing the faceplate to a grounded outlet box or grounded wiring device.

Exception No. 2: Luminaires (light fixtures) more than 2.3 m (7 1/ 2 ft) above the floor and switches located outside of the patient vicinity shall not be required to be grounded by an insulated equipment grounding conductor.
Click to expand...

Connecting the EGC's of (A) and (B) in parallel is a must for redundacy as well as a lower impedance that only one of the EGC's would provide.

The metalic raceway or cable sheath is the primary ground in this application, this is the reason that (A) is required even for lighting fixtures above 7.5' even though the insulated conductor of (B) is not, meaning the metallic raceway or cable would need to be installed as though the insullated conductor doesn't exist or might fail.


Roger
 
Last edited:
With the smart cable though the casing is your redundent ground and you need to attach it to the box with the proper connector.

Sorry didn't see rogers post.
 
cowboy said:
With the smart cable though the casing is your redundant ground and you need to attach it to the box with the proper connector.
Click to expand...

Only if it has an insulted ground as well, not all smart cable has the insulated ground.

I am guessing cowboy knew this I just thought I would make that clear.
 
Iwire, I may have assumed that I was talking about the same thing. I was thinking of the green MC for use in patient care areas.

He was talking about patient care areas and since they require redundent grounding I wasn't sure how he was going to accomplish this running MC or AC through an existing flex conduit.
 
Status
Not open for further replies.
Top