Ground fault relay settings
- Thread starter shead
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brian john
Senior Member
- Location
- Leesburg, VA
Re: Ground fault relay settings
Normally the GFP settings should be supplied as part of the coordination study.
During construction we normally recommend minimum settings 100 amps and instantaneous, for minimumizing damage to the equipment due to worker error.
There are some rules of thumb for GFP settings but the liability is immense and is only a stop gap measure. A current setting of 20 to 30 percent of the overcurrent device and time delay of .1 second or faster.
Settings at or below 300 amps are prone to nuisance tripping (in office buildings) as the majority of the CB's are 20 and 30 amp CB's. and settings noted above falls within the instantaneous setting for molded case CB's
BUT I STRESS THE LIABILITY ISSUE WHEN RANDOMNLY SETTING THE GF relay.
Normally the GFP settings should be supplied as part of the coordination study.
During construction we normally recommend minimum settings 100 amps and instantaneous, for minimumizing damage to the equipment due to worker error.
There are some rules of thumb for GFP settings but the liability is immense and is only a stop gap measure. A current setting of 20 to 30 percent of the overcurrent device and time delay of .1 second or faster.
Settings at or below 300 amps are prone to nuisance tripping (in office buildings) as the majority of the CB's are 20 and 30 amp CB's. and settings noted above falls within the instantaneous setting for molded case CB's
BUT I STRESS THE LIABILITY ISSUE WHEN RANDOMNLY SETTING THE GF relay.
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