Redundant ground in Dental Office

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KWH

Senior Member
How would you guys install a circuit for a dental chair, this will require a floor box in the slab @ ground level. I am thinking RMC or is there another option. I have seen pvc installed with MC pulled thru conduit but would'nt this be considered a wet location also is there a pvc box that will accept RMC.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
I use IMC for this. There is MC for wet locations, see 330.10(A)(11). Dental chair templates give you a pretty large target, so IMC right into the bottom of a box works well for me.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
Yes, IMC / RMC for power. Many chairs also require an additional PVC conduit for control wiring.

It is smart to ask them if they want extra lines or pvc conduit from head to foot. After concrete it gets costly and high pressure sales men will talk them into extras.
Only did one and was in rigid with comp. fittings. Far from a fun job and best be carefull not to miss anything like x ray buttons.
 

roger

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Location
Fl
Occupation
Retired Electrician
we did many dental offices and always run PVC stubbed thru floor and a 4 square box mounted to floor in access panel of chair.

So, that being the case you were not in compliance with article 517.13(A)

Roger
 

roger

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Location
Fl
Occupation
Retired Electrician
Depends on what they run inside that PVC. If MC with the redundant ground its OK. He did not tell us what about the floor, if the PVC is not in the ground he is fine.

Jim, if the PVC is run to and terminated to a 4"square box in the chair, the metallic sheath of the cable (which can not be standard MC) run inside this PVC could not be terminated with an approved connector to the same 4" square box.

Roger
 

220/221

Senior Member
Location
AZ
I hate using rigid for anything, but during the first and only dental office I wired (about 7 years ago) I could find no other legal way to do it.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
Jim, if the PVC is run to and terminated to a 4"square box in the chair, the metallic sheath of the cable (which can not be standard MC) run inside this PVC could not be terminated with an approved connector to the same 4" square box.

Roger
The PVC would only be a sleeve for the MC, so yes can put mc fittings on it and i know it must be MC rated as redundant. Not say perfect way to go but might be easier and cheaper
 

slick 50

Senior Member
The PVC would only be a sleeve for the MC, so yes can put mc fittings on it and i know it must be MC rated as redundant. Not say perfect way to go but might be easier and cheaper

Jim - You hit the nail on the head there. PVC was simply a sleeve, usually about 5 feet long from chair and stubbed into wall. 1" pipe cult flush with concrete and MC connector to 4" sqaure.
 

roger

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Location
Fl
Occupation
Retired Electrician
Jim - You hit the nail on the head there. PVC was simply a sleeve, usually about 5 feet long from chair and stubbed into wall. 1" pipe cult flush with concrete and MC connector to 4" sqaure.

That's not what you said in post #5, and as Bob said, you were still in violation with the MC.

Roger
 

KWH

Senior Member
The pvc is underground (direct contact with earth )

The pvc is underground (direct contact with earth )

This is a slab install @ grade level

Thanks
 
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