GFCI trip rating

[megloff11x]

The GFCI was developed with a 5-6mA trip in the home because the tests showed that the "orphans and grad students and nursing home volunteers" subjected to shock testing had a worst case let go current of 5-6mA. The worst case group was small children.

They do make GFCI devices with a 30mA trip, which is more in the "healthy adult" group's let go current level.

With GFCI devices being mandated in many industrial settings, where children are verboten, is there consideration to allow a higher trip rating there? Much sensitive electrical equipment, whether listed and well tested or not, will nuisance trip 5-6mA GFCI devices. In one of our labs we started with GFCI breakers in the panel. They tripped immediately, and we had to change to GFCI outlets, which only trip occasionally.

I don't have my 2008 Code book here and can't remember if it says anything on the trip rating.

To me it seems silly to render a facility unusable to protect a group (children) who will never be present. You can say buy better equipment that won't trip a GFCI, but with who's checkbook?

Matt

 

[iwire]

The 30 ma devices are not for people protection they are for equipment protection and are GFP devices not GFCIs.

For protection of personnel the GFCI must trip between 4 mA and 6 mA.

See Article 100 for Ground-Fault Circuit Interrupter and Ground-Fault protection of Equipment.

 

[iwire]

The GFCI was developed with a 5-6mA trip in the home because the tests showed that the "orphans and grad students and nursing home volunteers" subjected to shock testing had a worst case let go current of 5-6mA. The worst case group was small children.

Matt, I have never heard anything at all like that, can you tell us where you read or heard that?

I have heard that 4 to 6 mA was found to be 'OK' for healthy adults and that may be to high for children and the elderly.

 

[megloff11x]

Mistake on my part.

I had my numbers from Dalziel's paper from the wrong percentile able to let go. He has 9mA for men and 6mA for women, and "so far it has been impossible to obtain reliable values for children; they just cry at the higher values."

They'd never be able to do this research today... The pictures of people being shocked while standing on a plate and holding a rod are amazing. Of course we used to test nukes and chemical weapons on soldiers back then too, and allowed people with long term syphyllus go untreated and watch what happens.

It looks like we'll have to live with nuisance trips and see if we can figure out and mitigate.

Matt

 

[iwire]

It looks like we'll have to live with nuisance trips and see if we can figure out and mitigate.

Matt

You may already be doing this but try to have equipment bought that can be hardwired or is not 125 volt.

Where you stuck with GFCIs put one at each point of use so only one or two pieces of equipment will be on one GFCI.

 

[celtic]

The 4 - 6mA rating is based on the "average" let go ...some healthy adults may not respond well to a 10mA blast.
One has to remember all the variables that enter the electrocution equation.

Recently, I read IAEI/Soares' book on grounding [I live in the fast lane]...I wondered how they determined the let go from a group of children and how/why their wasn't rioting in the streets [PETC anyone?] over this...must have been performed quite some time ago.

 

[megloff11x]

Most of it is 115VAC 60Hz. It's a lab. The different experiments require different powered equipment.

I feel silly for having misread the article and looking at the averages rather than the "almost 100%" can let go numbers.

Matt

 

[iwire]

[I live in the fast lane]...

I can relate. :smile:

I stumbled on this and have been reading it


NSTS 1988 News Reference Manual

 

[megloff11x]

The 4 - 6mA rating is based on the "average" let go ...some healthy adults may not respond well to a 10mA blast.
One has to remember all the variables that enter the electrocution equation.

Recently, I read IAEI/Soares' book on grounding [I live in the fast lane]...I wondered how they determined the let go from a group of children and how/why their wasn't rioting in the streets [PETC anyone?] over this...must have been performed quite some time ago.

I think back then orphanages would do this kind of thing to raise funds. It looks like the article was published in 1972 but the research was likely done many years before.

If we must, I'd prefer to use convicted felons and crooked politicians for guinea pigs.

Matt

 

[celtic]

I can relate. :smile:

I stumbled on this and have been reading it


NSTS 1988 News Reference Manual

I'm getting geared up to dive into 400 some odd pages of hilarity here:

ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ............

 

[celtic]

If we must, I'd prefer to use ... crooked politicians for guinea pigs.

Then there would be no more politicians

 

[nafis]

good luck , are you take in the PMP test . if yes i have some prescription to pass the test , i have taken yhe course few months ago .