GFCI minimum trip rating

[SiddMartin]

Does anyone know the minimum trip rating for personal protection on a GFCI? Is there a different min. trip rating for equipment protection? Can you get GFCI's with different trip ratings? (I beleive the standard is 6 ma), but can you get one that trips at 9 ma and is still legal?

 

[bphgravity]

4-6 mA. See the FPN to GFCI in Article 100 of the NEC.

 

[480sparky]

4-6ma is the only range acceptable for personnel protection.

 

[richxtlc]

Does anyone know the minimum trip rating for personal protection on a GFCI? Is there a different min. trip rating for equipment protection? Can you get GFCI's with different trip ratings? (I beleive the standard is 6 ma), but can you get one that trips at 9 ma and is still legal?

The equipment ground protection is designed to protect the equipment and not personnel. The ground fault setting depends on the size of the equipment and the circuit to which it is connected. These setting are usually high enough to kill a person.

 

[infinity]

I agree, Class A GFCI's trip between 4-6 ma. Older Class B GFCI's trip at a minimum of 20 ma and are not suitable for personal protection. GFPE protection used for protecting equipment will trip at 30 ma.

 

[jim dungar]

I agree, Class A GFCI's trip between 4-6 ma. Older Class B GFCI's trip at a minimum of 20 ma and are not suitable for personal protection. GFPE protection used for protecting equipment will trip at 30 ma.

I believe Class B GFCI's were for old pool lighting fixtures.

 

[wptski]

It may be 4-6ma but what's the allowable trip time? I don't have a link handy for one of those charts. You may be surprised at the lenght of the allowable trip times!

 

[480sparky]

It may be 4-6ma but what's the allowable trip time? I don't have a link handy for one of those charts. You may be surprised at the lenght of the allowable trip times!

According to P&Ss website, the trip time is 0.025 seconds nominal.

 

[infinity]

I believe Class B GFCI's were for old pool lighting fixtures.

That's correct. Dates back to the 70's I believe.

 

[wptski]

According to P&Ss website, the trip time is 0.025 seconds nominal.

The current and time are like two different things. I can't find one of those current vs time curves but somebody stated 6ma at 7.2 seconds which is what I'm getting at. I tested some P&S and Leviton a while back. The Leviton's trip time was over .1 seconds.

 

[480sparky]

The current and time are like two different things. I can't find one of those current vs time curves but somebody stated 6ma at 7.2 seconds which is what I'm getting at. I tested some P&S and Leviton a while back. The Leviton's trip time was over .1 seconds.

6ma will hold for 7.2 seconds?

 

[infinity]

According to this link Class A will trip at 6ma in 6/1000 of a second.

http://www.2d2c.com/gfci.php

 

[don_resqcapt19]

The UL Standard 943 for GFCIs says this in section 6.7.1.1

The maximum permitted time to trip in seconds is equal to the quantity (20/fault current in milliamps) raised to the 1.43 power.

The application of this formula would permit a 7 second trip time for a 5 mA ground fault. Many will trip quicker, but the standard specifies the maximum permitted trip time.

 

[wptski]

One can use a Ideal Suretest 61-165 to test GFCI trip time but I used a scope which actually showed the times to be a bit faster.

 

[brian john]

The equipment ground protection is designed to protect the equipment and not personnel. The ground fault setting depends on the size of the equipment and the circuit to which it is connected. These setting are usually high enough to kill a person.

The lowest setting I have seen on a GFP relay was 1 amp minimum and 10 amp maximum, GE relay in main switchboard subfeed CB in a hospital.

They also had some 10-100 amp and then the GE standard 100-1200.

Time delays were all the same for all relays Instantaneous-1.0 seconds.

In the 25 years I have worked at this facility we have never had a trip on any of these GFP protected relays and I tested all the relays and CBs 8 times in this 25 year period.

 

[gar]

090607-1314 EST

See the trip time curve on page 4 at
http://www.national.com/ds/LM/LM1851.pdf

.

 

[don_resqcapt19]

Gar,
They show the UL 943 time trip curve as a straight line, that is not correct.

 

[don_resqcapt19]

There is a nice chart on the second page of this document that shows the normal GFCI trip time, the maximum permitted trip time and the heart fibrillation threshold for normal adults.

 

[gar]

090607-1525 EST

don:

The National curve is plotted on log-log and the Leviton is log-linear.

The two curves for the UL limit look to be the same by checking the mid-point and the end points.

.

 

[don_resqcapt19]

I missed the log-log on the National plot.