X ray disconnect

Probably not as a disconnect for a service tech to work on the equipment. That said the little bit of this kind of work I have done they always spec'd a EPO button that controlled shunt coil to a shunt trip breaker for the servicing disconnect. LOTO rules would still require you to verify it is open and then lock out the breaker whether you used the EPO to open it or not.
 
A control button is never a disconnect, even one that operates a shunt trip breaker. A disconnect is a device that directly opens the circuit conductors. The code section you cited requires a disconnect. You cannot use an emergency stop button or other control device to comply with that section.
 
don_resqcapt19 said:
A control button is never a disconnect, even one that operates a shunt trip breaker. A disconnect is a device that directly opens the circuit conductors. The code section you cited requires a disconnect. You cannot use an emergency stop button or other control device to comply with that section.
Click to expand...
Don;
Is there any provision for e-stop that would count? There's a lot of equipment where just pulling a disconnect is
rude. But given a few microseconds or tenths of a seconds, the equipment can shut down cleanly and shed load without sparking or whatever.
 
Understand the purpose of an e-stop. It's used as an emergency shut down by operators to quickly shut down the equipment if they encounter an abnormal or dangerous condition. It (or they) is usually located in a conspicuous location. An e-stop can be made to operate by the manufacturer however necessary for a quick and safe shutdown of the equipment and the protection of personnel and property. That doesn't necessarily mean removing all power.

A disconnect is used to remove all power from the equipment. It is not necessarily easily or quickly operable by the equipment operators or even in a location where they would want to go during an emergency. Killing power might also not be friendly to the equipment. (Think computer control) It is intended mainly for service of the equipment.

-Hal
 
brycenesbitt said:
Don;
Is there any provision for e-stop that would count? There's a lot of equipment where just pulling a disconnect is
rude. But given a few microseconds or tenths of a seconds, the equipment can shut down cleanly and shed load without sparking or whatever.
Click to expand...
If it ultimately ends up controlling the shunt coil to a shunt trip breaker there is nothing wrong with using it to open the breaker. But if you follow most any safety policy you still need to verify the power is off and lock the breaker if you turned it off for the reason of working on the equipment.
 
brycenesbitt said:
Don;
Is there any provision for e-stop that would count? There's a lot of equipment where just pulling a disconnect is
rude. But given a few microseconds or tenths of a seconds, the equipment can shut down cleanly and shed load without sparking or whatever.
Click to expand...
If the requirement is for a disconnect, there is no place where a control device can substitute for the required disconnect. However is it common to use both. The disconnect is for lockout tag out when working on the equipment and the control device is for normal or emergency shutdown.
 
don_resqcapt19 said:
A control button is never a disconnect, even one that operates a shunt trip breaker. A disconnect is a device that directly opens the circuit conductors. The code section you cited requires a disconnect. You cannot use an emergency stop button or other control device to comply with that section.

If the requirement is for a disconnect, there is no place where a control device can substitute for the required disconnect. However is it common to use both. The disconnect is for lockout tag out when working on the equipment and the control device is for normal or emergency shutdown.
Click to expand...
So lets's say I had a big red button for "safe shutdown" initiates a clean shutdown situation: saving state, turning off motors or loads, reducing spark potential... but it also triggers a timeout. Two seconds after the big red button is pushed it will activate the shut coil no matter what.

Is there a way to build that, under the NEC? A combination e-Stop and disconnect?
Or a shunt breaker with a touch sensor: the moment it's touched it initiates e-Stop, faster than a human hand could yank the breaker handles.


Where in the code is use of control button for a disconnect precluded?

Article 100 Disconnecting Means" reads "A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply. (CMP-1)".
Then "Article 100 switching device" further defines isolating switches.
Article 110.25 defines "Lockable disconnecting means". And 230.85 is all about marking.
 
brycenesbitt said:
So lets's say I had a big red button for "safe shutdown" initiates a clean shutdown situation: saving state, turning off motors or loads, reducing spark potential... but it also triggers a timeout. Two seconds after the big red button is pushed it will activate the shut coil no matter what.

Is there a way to build that, under the NEC? A combination e-Stop and disconnect?
Or a shunt breaker with a touch sensor: the moment it's touched it initiates e-Stop, faster than a human hand could yank the breaker handles.


Where in the code is use of control button for a disconnect precluded?

Article 100 Disconnecting Means" reads "A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply. (CMP-1)".
Then "Article 100 switching device" further defines isolating switches.
Article 110.25 defines "Lockable disconnecting means". And 230.85 is all about marking.
Click to expand...
As mentioned E-stop is for controls. This may get more into other regulations besides NEC as to how rapidly it must shut down once the E-stop is pressed. Otherwise yes a simple delay timer between the E-stop button and shunt coil or whatever other controls are needed for a programmed shutdown process could be placed in the control circuit with a final order of operations to energize the shunt coil. I wouldn't think there is much to most x-ray machines to shut down in an orderly fashion though. Maybe if there is moving patient exam table or something of that nature that also gets shut down, though that may be more common for more advanced medical imaging like CT or MRI machines.
 
brycenesbitt said:
So lets's say I had a big red button for "safe shutdown" initiates a clean shutdown situation: saving state, turning off motors or loads, reducing spark potential... but it also triggers a timeout. Two seconds after the big red button is pushed it will activate the shut coil no matter what.

Is there a way to build that, under the NEC? A combination e-Stop and disconnect?
Or a shunt breaker with a touch sensor: the moment it's touched it initiates e-Stop, faster than a human hand could yank the breaker handles.


Where in the code is use of control button for a disconnect precluded?

Article 100 Disconnecting Means" reads "A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply. (CMP-1)".
Then "Article 100 switching device" further defines isolating switches.
Article 110.25 defines "Lockable disconnecting means". And 230.85 is all about marking.
Click to expand...
Because the disconnect itself must open the circuit conductors.
You can use the E-stop, as long as there is a physical way to operate, and in most cases, lockout, the actual disconnect.
 
don_resqcapt19 said:
Because the disconnect itself must open the circuit conductors.
You can use the E-stop, as long as there is a physical way to operate, and in most cases, lockout, the actual disconnect.
Click to expand...
To be precise, where does that come into the code?

Article 100 Disconnecting Means" reads "A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply. (CMP-1)".

So if my disconnect consists of five parts spread over three cabinets that ultimately result in the conductors being disconnected, is there still a problem? Is there a requirement that a disconnect be unitary and if so where?
 
The device itself must physically open the conductors. Some large equipment has more that one device to open multiple sets of conductors and that is where the group of devices comes in.
However you can install it any way you want to, but I would hang a big red tag on it, as would most inspectors that I know.
 
hhsting said:
NEC 2017 Article 517.72
Click to expand...
Refer to the definitions for "readily accessible".

Being "readily accessible from the control location" is not the same thing as being "located in the control room."

As long as people in the control room have ready access, without the restrictions listed, the disconnect could be located almost anywhere.
 
What everyone else is saying. I think of this as the disconnect is an approved device. Whatever you "rig" is not approved, and can not be considered reliable withought required terts. So, it might be possible to have it tested and meet requirement. That is rarely a cost time effective option.

Note that I rarely work in the electrical world, abut that is how the engineering would would consider, say for a product large or custom installation, say of a mfg robot where a EM off switch would be present. If it is a large installation that will be inspected and tested anyway it might be an option but I think the manual disconnect will be present even if it can be perated remotely . . . IE you probably cant get around the basic requirment unless there is a good reason, say to large to operate?

Oh, my wife is a veterinarian. We have a 200A disconnected at our X-Ray machine. It literally take up 1/4 of the wall :) The electrician didn't understand the requirement . . . very well . . .
 
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