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Discussion Starter · #1 ·
Hey All,

We have a recent application of our that is a "wet" environment and we wanted to protect the machine with GFCI protection. The only problem is that not all the devices on the machine use a neutral (same are 208v 2 phase). I think this may cause a problem because the 3 phase GFCI breaker takes the 3 hot legs and sees if it matches the N leg, if I am correct. Thoughts?
 

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The term GFCI is supposed to be specific to a Class A ground fault circuit interrupter, intended for PERSONNEL protection by tripping at no more than 6mA of current flowing to ground. The requirements calling for that are mostly plug-in applications like kitchens, bathrooms and outdoor receptacles, not for hard wired equipment (with a few exceptions such as spas / swimming pools, and carnivals / circuses). So because of that, you will rarely find 3 phase devices that offer GFCI protection.

When you buy a 3 phase breaker with "Ground Fault" protection, that is usually not a GFCI level device, it is GFP (Ground Fault Protection), or otherwise referred to as "EQUIPMENT" Ground Fault Protection. The trip levels they provide are MUCH higher than what would be allowed in a Class A device; 30mA at best, often 100mA, somtimes, as in Service Entrance breakers 1000A and up, a percentage of the trip rating, as in 5-30%! In most of those devices, they use a much simpler "Residual Current Detection" scheme in which the breaker simply looks at the 3 phases (for 3 phase only loads) or the 3 phases + Neutral if there are single phase loads, and watches for any amount of current in excess of the trip level flowing in that does not return on another phase or the Neutral. Those are NOT intended to protect people from electrocution.

There is no section in the NEC (other than those mentioned above) that will require GFCI level protection for hard wired equipment, even in wet areas. The grey areas tend to be where there is 3 phase PLUG-IN equipment used in normally wet areas, not just where things get hosed down at night when everything is off, but where people are standing in water as they work on machinery, such as fish processing plants. I have seen some AHJs require GFCIs in that circumstance, it throws everyone into a tizzy when it happens.

So if you really want to provide Class A GFCI protection levels, it is hard (if not impossible, haven't looked in a while) to find that in a 3 phase breaker. There are UL listed devices that can be added to a circuit to provide sensing for Class A protection, then are connected to a breaker with a "Shunt Trip" coil installed. They are very expensive, meaning you REALLY have to need it or want it. Bender Systems is the most widely known of those.

Be careful by the way, the rules outside of the US and Canada are different, IEC rules on personnel protection include the 30mA devices, so they are often sold that way, but people here are unaware that they do not meet our standards.
 

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JRaef said:
The term GFCI is supposed to be specific to a Class A ground fault circuit interrupter, intended for PERSONNEL protection by tripping at no more than 6mA of current flowing to ground. The requirements calling for that are mostly plug-in applications like kitchens, bathrooms and outdoor receptacles, not for hard wired equipment (with a few exceptions such as spas / swimming pools, and carnivals / circuses). So because of that, you will rarely find 3 phase devices that offer GFCI protection. When you buy a 3 phase breaker with "Ground Fault" protection, that is usually not a GFCI level device, it is GFP (Ground Fault Protection), or otherwise referred to as "EQUIPMENT" Ground Fault Protection. The trip levels they provide are MUCH higher than what would be allowed in a Class A device; 30mA at best, often 100mA, somtimes, as in Service Entrance breakers 1000A and up, a percentage of the trip rating, as in 5-30%! In most of those devices, they use a much simpler "Residual Current Detection" scheme in which the breaker simply looks at the 3 phases (for 3 phase only loads) or the 3 phases + Neutral if there are single phase loads, and watches for any amount of current in excess of the trip level flowing in that does not return on another phase or the Neutral. Those are NOT intended to protect people from electrocution. There is no section in the NEC (other than those mentioned above) that will require GFCI level protection for hard wired equipment, even in wet areas. The grey areas tend to be where there is 3 phase PLUG-IN equipment used in normally wet areas, not just where things get hosed down at night when everything is off, but where people are standing in water as they work on machinery, such as fish processing plants. I have seen some AHJs require GFCIs in that circumstance, it throws everyone into a tizzy when it happens. So if you really want to provide Class A GFCI protection levels, it is hard (if not impossible, haven't looked in a while) to find that in a 3 phase breaker. There are UL listed devices that can be added to a circuit to provide sensing for Class A protection, then are connected to a breaker with a "Shunt Trip" coil installed. They are very expensive, meaning you REALLY have to need it or want it. Bender Systems is the most widely known of those. Be careful by the way, the rules outside of the US and Canada are different, IEC rules on personnel protection include the 30mA devices, so they are often sold that way, but people here are unaware that they do not meet our standards.
iGard is another.
 

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Discussion Starter · #4 ·
Thanks for the reply! It is in fact a RCD, with a 30mA tripping point, but my question is if it will always be tripping if I have an unbalanced load. IE we have a 2 phase device (L1 and L2) that does not use a neutral, but we also have devices that do use neutrals. We have located an Allen Bradley model that we would likely be using.
 
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