Radiology equipment - Who designs what

[anbm]

I have a question for folks who work for in MEP field. For radiology equipment (MRI, CT, NUC Med, etc), we typically show electrical feeder from our panel to xray main disconnect as well as providing power to the room lighting and all accessories support as called out per radiology equipment vendor drawings.

EC will need to refer to radiology installation drawing, details and do the all installation requirement.


We (MEP engineer) is not supposed to design all conduits, boxes, supports between parts, controls that work with the xray machine. This will be the responsibility of radiology manufacturer and designed by them, is it correct?

 

[VUGear]

If I understand your post, then yes that is correct; the engineer typically specifies the feed to the main disconnect for the imaging equipment, as well as specifying the room lighting and convenience outlets around the room, while the equipment manufacturer's shop drawing calls out the boxes, floor duct, wall duct and conduit they need for both the power downstream of the equipment's main disconnect to the x-ray generator for instance and their low-voltage cabling (as well as the cabling itself in some cases). It's rare these days to see the engineer duplicate that shop drawing information on his/her drawings. Note that many equipment manufacturers also dictate what kind of disconnect is installed in the room for their equipment, so the engineer isn't specifying that item either.

 

[line_noise]

My experience has been mostly similar to what has been posted already, 99% of the time that is how it goes down and there are no issues. However, I have never been able to satisfy myself that is what code has intended, nor does every AHJ intepret this the same way.

Issues I have encountered:

How is compliance with NEC 517.78 (C) handled?

Most installations have a power distribution unit with an isolation transformer, how do we evaluate compliance for grounding of a separately derived system since we have no knowledge of the secondary conductors or OCPD?

If the design of certain elements is "up to the Radiology equipment manufacturer", then how is it that they are not submitting their own sealed plans, and getting their own permit? If everything is submitted as part of a single document package / permit, aren't the engineer of record and the electrician taking all responsibility for the safety of the design and installation?

 

[steve66]

I typically duplicate their info onto our drawings, adding our items like convience outlets.

The jobs just always seem to go smoothly that way, and it seems any possible problems pop up during design instead of construction.

 

[VUGear]

How is compliance with NEC 517.78 (C) handled?

Usually the EOR covers the equipotential grounding in a performance spec, and the inspector relies on the test reports provided by the contractor, although in Florida for instance the state inspector will spot check the grounding personally.

 

[line_noise]

Usually the EOR covers the equipotential grounding in a performance spec, and the inspector relies on the test reports provided by the contractor, although in Florida for instance the state inspector will spot check the grounding personally.

Most of the equipotential grounding requirements I have seen, do not address fault current path, as required by 517.13(A) referenced in 517.78 (C). Therefore, an evaluation of the individual cables furnished by the radiology equipment vendor needs to be performed, and this information seems to be rarely (if ever) available from the manufacturer.

I don't doubt that these systems all seem to be adequately safe, as they are used by millions of people every year and I haven't heard of incidents, but I still am unable to close the gap and say that they are fully compliant with the NEC.

 

[steve66]

Most of the equipotential grounding requirements I have seen, do not address fault current path, as required by 517.13(A) referenced in 517.78 (C). Therefore, an evaluation of the individual cables furnished by the radiology equipment vendor needs to be performed, and this information seems to be rarely (if ever) available from the manufacturer.

I don't doubt that these systems all seem to be adequately safe, as they are used by millions of people every year and I haven't heard of incidents, but I still am unable to close the gap and say that they are fully compliant with the NEC.

517.13(A) refers to branch circuits. IMO, this doesn't cover equipment wiring past its point of connection.

Its up to the people who design and install and start up this equipment to be sure its a safe installation.

In most cases, the safety of the equipment is guarenteed by the deep pockets of the companies that make and install this equipment. (At least for big ticket items like MRI's and CT's.)

Steve