MC in Dental Office

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jjc103

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Hi I'm new here but I was just wondering. I am wiring a small dental office. I know I must use a MC cable in the pstient procedure room in order to meet the requirements of a redundant grounding, but is it acceptable to use NM cable (romex) in the rest of the office. (waiting room, reception, hallways, file room, etc.).
Thank you
 
Remember NM cable cannot be run in suspended ceiling in your situation. That being said I would check with the local authorities and see how this building is classified. We cannot answer that question for you since it is dependent on the type of construction. Read art. 334.10 2005 NEC
 
jjc103 said:
Hi I'm new here but I was just wondering. I am wiring a small dental office. I know I must use a MC cable in the pstient procedure room in order to meet the requirements of a redundant grounding, but is it acceptable to use NM cable (romex) in the rest of the office. (waiting room, reception, hallways, file room, etc.).
Thank you
Click to expand...



Not all MC cable qualifies for installation for patient care areas.
The standard MC cable that has been installed for years is not suitable as a wiring method for patient care areas. Check out Article 330.


From the UL White Book:


METAL-CLAD CABLE (PJAZ)​


GENERAL​


This category covers Type MC metal-clad cable. It is rated for use up to​

2000 V, and Listed in sizes 18 AWG through 2000 kcmil for copper, 12 AWG
through 2000 kcmil for aluminum, or copper-clad aluminum, and employs
thermoset or thermoplastic insulated conductors. It is intended for installation
in accordance with Article 330 of ANSI/NFPA 70, ??National Electrical
Code?? (NEC).
The cable consists of one or more insulated conductors; one or more
grounding conductors (required for interlocked armor, as needed for smooth
or corrugated tube); one or more optional optical fiber members; and an
overall metal sheath. The metal sheath is an interlocked metal tape, a corrugated
metal tube, or a smooth metal tube. The metal sheath of singleconductor
cable is nonferrous. A nonmetallic jacket may be provided under
and/or over the metal sheath. Cable with metal armor, rated 5000 to 35,000
V is covered under Medium-voltage Cable (PITY) and is marked ??Type MV
or MC.??
Cable with interlocked armor that has been determined to be suitable for
use as a grounding means has interlocked aluminum armor in direct contact
with a single, full-sized, bare aluminum grounding/bonding conductor. This
cable is marked to indicate that the armor/grounding conductor combination
is suitable for ground. The equipment grounding conductor required
within all other cable with interlocked armor may be insulated or bare, may
be sectioned, and is located in the cable core but not in contact with the
armor. Any additional grounding conductors of either design have green
insulation. One insulated grounding conductor may be unmarked, one other
may have only a yellow stripe and the balance have surface markings that
indicate they are additional equipment grounding conductors or isolated
grounding conductors.
The sheath of the smooth or corrugated tube Type MC cable or a combination
of the sheath and a supplemental bare or unstriped green insulated
conductor is suitable for use as the ground path required for equipment
grounding . The supplemental grounding conductor may be sectioned.
When sectioned, all sections are identical. Each additional green insulated
grounding conductor has either a yellow stripe or a surface marking or both
to indicate that it is an additional equipment or isolated grounding conductor.
Additional grounding conductors, however marked, are not smaller
than the required grounding conductor.​

PRODUCT MARKINGS​


Information regarding temperature rating, voltage rating, cable and conductor​

Type and AWG size is shown either on a marker tape under the
armor or on the surface of a nonmetallic jacket, if used.
Copper-clad aluminum conductors are surface printed ??AL (CU-CLAD)??
or ??Cu-clad Al.?? Aluminum conductors are surface printed ??AL.??
Cable employing compact-stranded copper conductors is so identified
directly following the conductor size, wherever it appears (surface, tag, carton
or reel), by ??compact copper.?? The abbreviations ??CMPCT?? and ??CU??
may be used for compact and copper, respectively.
Tags, reels and cartons for products employing compact-stranded copper
conductors have the marking: ??Terminate with connectors identified for use
with compact-stranded copper conductors.??
For termination information, see Electrical Equipment for Use in Ordinary
Locations (AALZ).
Cable suitable for use in cable trays, direct sunlight or direct burial application
is so marked. Cable marked for direct burial is also considered
acceptable for encasement in concrete.
Cable marked ??Oil Resistant I?? or ??Oil Res I?? is suitable for exposure to
mineral oil at 60?C. Cable suitable for exposure to mineral oil at 75?C is
marked ??Oil Resistant II?? or ??Oil Res II.??
Cable containing one or more optical fiber members is marked ??MC-OF.??
Cable with a nonmetallic outer jacket that complies with the Limited
Smoke Test requirements specified in UL 1685, ??Vertical-Tray Fire-
Propagation and Smoke-Release Test for Electrical and Optical-Fiber
Cables,?? and all unjacketed metal-clad cable may be marked with the suffix
??LS.??
Cable with an interlocked armor that is intended as a ground path is
marked ??armor is grounding path component,?? and is provided with installation​
instructions.
 
jjc103 said:
Hi I'm new here but I was just wondering. I am wiring a small dental office. I know I must use a MC cable in the pstient procedure room in order to meet the requirements of a redundant grounding, but is it acceptable to use NM cable (romex) in the rest of the office. (waiting room, reception, hallways, file room, etc.).
Thank you
Click to expand...

You're right. See 517.13 and 250.118. Also see the definition of Patient Care Area and the FPN below it in Article 517, 2005 NEC. Use "hospital grade" MC.
 
It depends on the type of construction of the building. If it is Type I or II, you can't use it. If it is Type III, IV or V, you can use it, but not in a suspended ceiling.
 
ryan_618 said:
It depends on the type of construction of the building. If it is Type I or II, you can't use it. If it is Type III, IV or V, you can use it, but not in a suspended ceiling.
Click to expand...

As I understand it
If it is type I or II construction by choice it is allowed

If it is required to be of type I or II then NM is not an option
 
M. D. said:
As I understand it
If it is type I or II construction by choice it is allowed

If it is required to be of type I or II then NM is not an option
Click to expand...

Correct. However, that is something that is difficult the average electrician (or electrical engineer) to determine. Type of construction is governed by several things. Allowable height and area, use and occupancy, separated vs. nonseparated uses, use of a sprinkler system, proximity to lot lines, the use of fire rated construction, these are all variables that come into play when determining type of construction.
 
jjc103 said:
is it acceptable to use NM cable (romex) in the rest of the office. (waiting room, reception, hallways, file room, etc.).
Thank you
Click to expand...
If that is what those areas can use by code, than yes. You usually only have to use the medical wiring in areas where patients are treated, while the rest of the office is treated as a normal office space. We have had to use the medicla wiring in sterilization areas before, but that is usually only if they are exposed as part of the means of egress.

Don't forget that you don't have to use GFCI receptacles in patient care areas with medical grade wiring.
 
MC in Dental Office

The long and short of it-hospital grade wire[HFC ] is required in the areas that are considered patient care areas--this means homeruns to the panel -NOT just up to a 1900 in the cieling and changing wiring methods at that point.Your exceptions are that if the cieling height where the fixtures are installed meet the exceptions requirements and you locate the associated lighting switches for these same "Luminaires" outside the patient care area/room you then do not have to use Hospital grade wire for the lighting and switches-you still must use it for all recpts in the patient care area.You do not have to use hospital grade recpts in the treatment rooms unless required by critical care area,or other addt'l health care facility rules.
GFI requirements are as usual[wet,sink,etc] unless addt'l ammendments are added.
Re; romex use-your safest bet when in doubt about the classification of a structure would be to ask a building dept official or fire marshall as to what designation this building will ultimately have. It is not under the purview of the electrical inspector to make that determination--he can only tell you the possibilities.
Lastly--most dentist,doctor,etc offices that I worked in generally had dropped cielings--that would exclude RX up there.So the question then becomes exactly how many different wiring methods do you really want to use in one project?The time spent in making the correct transitions at various points would seem labor intensive to the point of negating any savings from use of rx instead of MC.
But that is just one mans opinion.
 
mthead said:
So the question then becomes exactly how many different wiring methods do you really want to use in one project?The time spent in making the correct transitions at various points would seem labor intensive to the point of negating any savings from use of rx instead of MC.
But that is just one mans opinion.
Click to expand...


I agree that it can become confusing sometimes between the different locations/wiring methods.
That is why one generally sees just HFC most of the time.
 
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