X ray in healthcare

[hhsting]

Please see sketch below. In medical outpatient clinic I have 208/120V three phase system voltage and x ray uses 240V single phase. So in order to provide that line side of panelboard is tapped with 200A circuit breaker. The circuit breaker then feeds the transformer 208V single phase to 240/120V single phase. The transformer secondary feeds shunt trip 100A enclosed circuit breaker. The Emergency Pull Off (EPO) switch is located next to the x ray shown below floor plan. When pushed according to control diagram below shuts the breaker off

The question I have is can the EPO shown below can it be X ray disconnecting means as mentioned in NEC 2017 Section 517.72 or does it need to be actual disconnect and EPO does not count? Does anyone know?

 

[Strathead]

Ask yourself, what would happen if, the 120 volt circuit feeding the EPO shunt trip circuit was deenergized. So, the answer is no you can't use the EPO as a disconnect.

 

[Fred B]

I don't know if a passively operating disconnect would count, such as having a disconnect that is contingent of a secondary sources operation such as the EPO/shunt trip system. I would say it would not meet the requirements. It would seem a positive direct disconnect would be required for this safety requirement. I've only installed one Xray, and it had an actual disconnect that broke both conductors located right at the technicians station.
The code section addressing the disconnecting means 517.72(A) states the disconnecting means shall be provided in the supply circuit.

 

[roger]

The EPO is not intended to be the disconnect, it is what it is, an "Emergency Off Switch" which will be operating a shunt trip in the disconnect.

Roger

 

[roger]

There will be manufacturers drawings with the xray machine that will be the actual installation drawings.

Roger

 

[petersonra]

Unless there's something special about the breaker that has the shunt trip installed on it, you can still open the breaker manually so I don't see why it can't be used as a disconnecting means. Maybe there is some special rule for healthcare equipment that requires otherwise.

I do not think that the EPO push button itself can be used as the disconnecting means, but I don't see why the circuit breaker it trips can't be used as the disconnecting means.

 

[Fred B]

Unless there's something special about the breaker that has the shunt trip installed on it, you can still open the breaker manually so I don't see why it can't be used as a disconnecting means. Maybe there is some special rule for healthcare equipment that requires otherwise.

517.72(B) "The disconnecting means shall be operable at a location readily accessible from the X-ray control."
That to me would say not if that breaker is not in same room and close proximity as the controls that the technician is operating. A runaway X-ray is critical to shut down in short order, seconds not minutes.

 

[roger]

Unless there's something special about the breaker that has the shunt trip installed on it, you can still open the breaker manually so I don't see why it can't be used as a disconnecting means.

The enclosed shunt trip breaker is the actual disconnect and will be installed with in site of the PDU or equipment it controls. The EPO will be located in an area that may be out of site from the machine (control booth for example) and is for the technician in case the need for shutting down the equipment is needed

In cases where the breaker is located in the control booth and meets the requirement of the disconnect location being in site of the equipment and being able to be operated by the technician EPO's might be omitted

Roger

 

[petersonra]

517.72(B) "The disconnecting means shall be operable at a location readily accessible from the X-ray control."
That to me would say not if that breaker is not in same room and close proximity as the controls that the technician is operating. A runaway X-ray is critical to shut down in short order, seconds not minutes.

Operable being the key word. The EPO button is the operating means and the cb is the disconnecting means. Or so it would seem to me.