517.13, redundant ground

Status
Not open for further replies.

lile001

Senior Member
Location
Midwest
We are working in an MRI facility. The MRI manufacturer, Siemens, asks that all branch wiring within the RF shield be on isolation transformers, and be ungrounded two wire. NEC 517.13 requires that all wiring in a patient exam room (an MRI is a patient exam room) have redundant grounds, i.e. a metal sheath and an insulated ground wire.

How have people handled these requirements in the past?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
lile001 said:
We are working in an MRI facility. The MRI manufacturer, Siemens, asks that all branch wiring within the RF shield be on isolation transformers, and be ungrounded two wire. NEC 517.13 requires that all wiring in a patient exam room (an MRI is a patient exam room) have redundant grounds, i.e. a metal sheath and an insulated ground wire.

How have people handled these requirements in the past?

Is this really a patient exam room, or is it part of the equipment?
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
I would not call an MRI Roon a "Patient Exam Room." It is a test, in the same context that drawing blood is a test. But even further, the MRI is non-intrusive, in that there is no puncturing of the skin or insertion of any probe.
 

lile001

Senior Member
Location
Midwest
Exam room or not exam room

Exam room or not exam room

charlie b said:
I would not call an MRI Roon a "Patient Exam Room." It is a test, in the same context that drawing blood is a test. But even further, the MRI is non-intrusive, in that there is no puncturing of the skin or insertion of any probe.

This particular MRI is quite likely to have intrusive tests. They are doing psychological brain research, and they are likley to have all kinds of things hooked up to the patient while they do the MRI. Some of those things may connect the patient inadvertently to ground. I know they already plan to have eyeball trackers, and quite likely other things like skull electrodes. They intend to ask people all kinds of questions while scanning thier brains. Don't ask me how the skull electrodes can work inside such a heavy magnetic field, I just wire it up. But in this instance, the much-debated topic of whether an MRI is a patient exam room is moot - they ARE going to hook invasive diagnostic equipment up to the patient while doing an MRI, and some of that invasive equipment MAY be conductive, and WILL be connected to electrical power.
 
Status
Not open for further replies.
Top