GFP too sensitive

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I agree that GFP is a good idea BUT if it cannot be properly coordinated with other devices, it is a poor option. In POCO high-voltage work, we often use a ground trip that is 50% of the phase trip
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It can be coordinated with the majority of OCPS in a building and a GFP at 408/277 solidly grounded system beats the heck of the devastation of an arcing ground fault.
 
brian john said:
1. Because the average construction electrician has no idea what to do with GFP.
2. Because the average electrical EC avoids testing and proper setup during construction.
3. Because the average electrical engineer avoids the issue at all cost.

So it is left to the end user to do something they usually do one of three things.

Pull the control fuses, shut it down.
Randomly pick a setting, based on lets try this.
Hire a firm to resolve the issue.
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I always throw it into the EEs lap nice and early in every job and I fax all paperwork to disolve myself of any liability. I am constantly amazed at how many electricians have no clue what to do with this all it seems to do is piss off the contractors so I never even involve them unless they ask. Sq D pisses me off when they turn them all to min setting at shipping.
 
quogueelectric said:
Sq D pisses me off when they turn them all to min setting at shipping.
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Why don't you just change them to what you think they should be? If you don't want the responsibility, then why would the manufacturer?
 
jim dungar said:
Why don't you just change them to what you think they should be? If you don't want the responsibility, then why would the manufacturer?
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Because it is the engineers job who designed the job to select the setting and for some reason they never want to do thier job and give you the settings unless you beg for them. Secondly the jobs are usually bought out as a package price and this should be included in the price. It is NOT the electricians job to design the system we are installers not designers. This is why the EEs get the big bucks and not us poor old broke electricians.
 
IMO I believe shipping them at minimum is a reasonable approach.

One it limits any liability from possible damage at higher settings (see law suits in other thread)
Two, during construction when everyone and his brother is swinging metal in and around panels that are open, partial open or covered in cardboard, it minimizes damage to distribution equipment and possible the swingers.
Three if shipped at maximum settings and the engineer wants it set lower the manufacture has exceeded what a designer specs, more liability issues.
 
quogueelectric said:
Because it is the engineers job who designed the job to select the setting and for some reason they never want to do their job and give you the settings unless you beg for them. Secondly the jobs are usually bought out as a package price and this should be included in the price. It is NOT the electricians job to design the system we are installers not designers. This is why the EEs get the big bucks and not us poor old broke electricians.
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Actually as I understand it you can not do an accurate coordination study until the EC installs all the conductors and provides the actual feeder lengths to the EE to complete the study.

That being the case it is not possible to ship the equipment 'pre-set'
 
Having discussed this issue at great length with manufactures, they want no part of this discussion, it is not their issue/concern. They make a product that meets applicable standards/codes and after that it is someone else's to take on.


IMO setting a GFP without a coordination study is fairly basic, but something we avoid, because I barely received a high school diploma much less a sheep skin and qualifying license to perform such studies. BUT like most things I do have an opinion that resolves the majority of so called "Nuisance Trips".

The often refered to nuisance trip IMO are actually a device serving it's intended function in many cases. To me a nuisance trip is a GFP that trips at 50 amps when the setting was to be 500 amps. I have seen this mismatched Relay and Current Sensor and also defective sensors and/or relays.
 
quogueelectric said:
Because it is the engineers job who designed the job to select the setting and for some reason they never want to do thier job and give you the settings unless you beg for them. Secondly the jobs are usually bought out as a package price and this should be included in the price. It is NOT the electricians job to design the system we are installers not designers. This is why the EEs get the big bucks and not us poor old broke electricians.
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Yes it is the SYSTEM designers job. Too often the EC has a design and build job, but he doesn't want to pay for design engineering so he asks the SALES engineer from the manufacturer instead to simply chose equipment. Selecting equipment is not the same as designing the complete electrical system. The sales guys know nothing about the operations of the facility, the intended loading, the desires of management etc.

Remember, You don't get what you don't pay for. If you want coordination settings, other than minimum, just make sure to ask for them as a separate line item on your equipment bill of material.
 
Coordination

Coordination

brian john said:
It can be coordinated with the majority of OCPS in a building and a GFP at 408/277 solidly grounded system beats the heck of the devastation of an arcing ground fault.
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A GFP on a 480Y/277V system that feeds no single-pole breakers and line-neutral loads can be set low and reliably used to reducing the hazard of arcing faults. However, if the facility has 277V lighting loads fed from 20A breakers, the GFP needs to be set above the trip behavior of the 20A CB to avoid nuisance trips. Worse yet is where even larger line-neutral loads/CBs exist.

If the GFP has tap settings of 0.2-0.8, unless the GFP breaker has a large sensor relative to the branch CB, coordination can be difficult to achieve. An study by an "engineer" is needed.
 
beanland said:
However, if the facility has 277V lighting loads fed from 20A breakers, the GFP needs to be set above the trip behavior of the 20A CB to avoid nuisance trips. Worse yet is where even larger line-neutral loads/CBs exist.

If the GFP has tap settings of 0.2-0.8, unless the GFP breaker has a large sensor relative to the branch CB, coordination can be difficult to achieve. An study by an "engineer" is needed.
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Exactly my point!!
 
jim dungar said:
Yes it is the SYSTEM designers job. Too often the EC has a design and build job, but he doesn't want to pay for design engineering so he asks the SALES engineer from the manufacturer instead to simply chose equipment. Selecting equipment is not the same as designing the complete electrical system. The sales guys know nothing about the operations of the facility, the intended loading, the desires of management etc.

Remember, You don't get what you don't pay for. If you want coordination settings, other than minimum, just make sure to ask for them as a separate line item on your equipment bill of material.
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On all jobs of this magnitude there is a set of blueprints from which the job is bid. There is an electrical section of these prints drawn up and designed by an EE who works for the architectural firm that drew up the prints.

We do not just wing it and design large distribution sytems for the customers on our own.
I think I will just put a generic 480v/3ph 2000 amp gear over there and figure out the small details later that just doesnt happen.
The engineering firm that designed the job on the blueprints should finish their job that they got paid for and pick the propper settings.
 
quogueelectric said:
We do not just wing it and design large distribution sytems for the customers on our own.
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This is a relatively common practice in Wisconsin where we have designer licenses as well as PE's.
 
brother said:
Exactly my point!!
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No kidding, we got that,:smile: but you just can't go cranking it up.

beanland said:
If the GFP has tap settings of 0.2-0.8, unless the GFP breaker has a large sensor relative to the branch CB, coordination can be difficult to achieve. An study by an "engineer" is needed
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The place you work for will have to pay an EE to do the study and then you can get what your after.
 
Originally Posted by beanland
If the GFP has tap settings of 0.2-0.8, unless the GFP breaker has a large sensor relative to the branch CB, coordination can be difficult to achieve. An study by an "engineer" is needed


I do not follow this at all. So a 4000 amp CB has a .8 setting how does this comply with the NEC and what does the sensor size have to do with this?

Typical settings are 100-1200 amps or take a 4000 amp CB, 5%-30% but this varies from manufacture to manufacture some use letters that coordinate to preset amperage's depending on frame and rating plug. Some use numbers following the same logic, others use percentages
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Just curious if anyone know of a diplomatic way to tell 'others' that it is not legal (code)/or wise to have a 800 amp gfp FEEDER for the panel trip BEFORE a 20 amp branch circuit breaker(with out ground fault) when you short the hot to ground on the 20 amp branch circuit (light fixture)??? Even though a gfp is more sensitive, the 20 amp branch still should trip before it does!!
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I got a good laugh out of this. This just happened yesterday on a SqD 800 amp MDP (Main dist Breaker) for lighting. A mechanic was connecting a circuit tracer to a lighting (277v) circuit and accidentily grounded. Dropped out 4 floors of lights.................
 
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