Help on determining need for GFCI

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vsab

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Hauppauge, NY, USA
Hello,

We are building a piece of outdoor equipment that will be enclosed in a metal industrial cabinet.
We have a 220V loadcenter attached to the cabinet to supply the power for the equipment.
The supplied power is three wires, Hot-Hot-Ground.
The loadcenter has several 220V GFCI Schneider Electric QO breakers we put in as a safety measure.
One of these breakers is used exclusively to power an APC UPS, which we used to provide the power to our electronics equipment (computer, data acquisition electronics, sensors, etc.).
All of our equipment is DC powered, we use commercial power supplies to convert the AC to DC.
the only AC equipment is an air blower, which is on it's own branch with a GFCI breaker.
The cabinet and all of the equipment is grounded.
There are no external outlets.
We have a problem with the UPS, it is tripping the GFCI breaker when the UPS output power is off (battery discharged or intentionally disable output power).
We contacted APC and were told that the UPS exhibits leakage currents as a result of the common mode filters present within the UPS and the equipment connected to it.

We are now questioning ourselves about the need to have the GFCI breaker for the UPS, or just replace it with a regular breaker.
I've been reading the electric code and could not find a definitive answer.
I'm hoping to gain insight from your comments. Thank you.
 
The general need for GFCI protection covers receptacles. If the UPS is hard-wired, you should be able to eliminate the GFCI.
 
vsab said:
Hello,

We are building a piece of outdoor equipment that will be enclosed in a metal industrial cabinet.
We have a 220V loadcenter attached to the cabinet to supply the power for the equipment.
The supplied power is three wires, Hot-Hot-Ground.
The loadcenter has several 220V GFCI Schneider Electric QO breakers we put in as a safety measure.
One of these breakers is used exclusively to power an APC UPS, which we used to provide the power to our electronics equipment (computer, data acquisition electronics, sensors, etc.).
All of our equipment is DC powered, we use commercial power supplies to convert the AC to DC.
the only AC equipment is an air blower, which is on it's own branch with a GFCI breaker.
The cabinet and all of the equipment is grounded.
There are no external outlets.
We have a problem with the UPS, it is tripping the GFCI breaker when the UPS output power is off (battery discharged or intentionally disable output power).
We contacted APC and were told that the UPS exhibits leakage currents as a result of the common mode filters present within the UPS and the equipment connected to it.

We are now questioning ourselves about the need to have the GFCI breaker for the UPS, or just replace it with a regular breaker.
I've been reading the electric code and could not find a definitive answer.
I'm hoping to gain insight from your comments. Thank you.
Click to expand...

You are saying your power supply is hot, hot, ground. That is not 120/240 but rather 240 volt. Or did you mean you have hot, hot, neutral?
 
If all of the equipment is DC powered, why not use batteries on the DC buss instead of an AC UPS then a rectifier? I don't think you need the GFCI for the UPS.

As an alternative.... APC is owned by Schneider and the GFCI is made by Schneider... let them work it out :D.
 
I don't see a need for the GFCI receptacle for the UPS as long as it's locked within the cabinet and not intended for any other use. You certainly don't need one for the fan.

-Hal
 
Thanks for all the replies!
Yes, I contacted APC and let them know that we are using products from the same parent company..... paraphrasing, they replied "it is what it is"...

We have 2 phases 127AC each, so across both phases we have 220VAC.
the lines coming from the main panel inside the building are Hot-Hot and ground.

The UPS is hard-wired into the loadcenter, the individual electronics equipment (Computer, monitor, data acquisition, etc.) are plugged into the UPS outlets. the UPS has two banks of four outlets.

From your replies, I gather that the GFCI breaker for the UPS is not needed. We tend to believe the same, since all the equipment powered by the UPS is contained within the metal cabinet.

We initially planned to use GFCI breakers on all branches, just to have an extra layer of safety.

Hal responded that we shouldn't need one even for the blower. The blower is 5 HP. since it is also outside and exposed to rain, etc. shouldn't a GFCI be necessary to protect anybody that touches the blower in the event the blower frame gets electrified?

Thanks,
Victor
 
vsab said:
Hal responded that we shouldn't need one even for the blower. The blower is 5 HP. since it is also outside and exposed to rain, etc. shouldn't a GFCI be necessary to protect anybody that touches the blower in the event the blower frame gets electrified?

Thanks,
Victor
Click to expand...

The blower frame shouldn't get energized if it's properly grounded.

Think of a typical AC unit. If there is anything a person is likely to touch it's the AC unit. People don't think twice about touching it and yet it's fed by 240V which is nothing more than two 120V circuits measured to ground. No requirement for ground fault protection.
 
Hi Growler,

Yes, all is grounded through a ground wire to the main panel, and also via a ground rod at the metal cabinet.

So, you're saying since residential AC units don't need GFCI protection, our outdoor chassis should not need either?

Isn't the general thought of a GFCI to be able to prevent shock if the ground wire is somehow compromised (i.e. severed)?
 
The ground would have to be opened. One side of the line would have to fault to the frame. Person would have to be in contact with conductive grounded material while touching the equipment. Not saying this can't happen, you can also win the lottery.

You're an engineer I take it. Stop over thinking this and over engineering.

-Hal
 
vsab said:
Isn't the general thought of a GFCI to be able to prevent shock if the ground wire is somehow compromised (i.e. severed)?
Click to expand...

GFCI’s are typically only required for personnel protection; like cord-and-plug use devices. Or if you’re sitting in a body of water that has contact with electrical equipment.

We don’t GFCI protect outdoor lighting, or other hard-wired equipment.


Sent from my iPhone using Tapatalk
 
vsab said:
Isn't the general thought of a GFCI to be able to prevent shock if the ground wire is somehow compromised (i.e. severed)?
Click to expand...
Correct, and the general rules in 210.8 (other than boat hoists and the household diswasher) all involve use of receptacle outlets. Potential for compromised EGC's is a factor in why the areas mentioned here got put here. Until 2017 NEC most of what was there only involved 15 and 20 amp 120 volt receptacles - those are the ones you see the most missing EGC pins on cord caps. No EGC to plugged in equipment means higher potential of no low resistance path to carry fault current and open OCPD, possible leaving equipment frame energized and subjecting users to shock risks.
 
hbiss said:
The ground would have to be opened. One side of the line would have to fault to the frame. Person would have to be in contact with conductive grounded material while touching the equipment. Not saying this can't happen, you can also win the lottery.

You're an engineer I take it. Stop over thinking this and over engineering.

-Hal
Click to expand...

Ha! good one. thanks!
 
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