• We will be performing upgrades on the forums and server over the weekend. The forums may be unavailable multiple times for up to an hour each. Thank you for your patience and understanding as we work to make the forums even better.

GFCI vs RCD trip threshold-why?

Merry Christmas
Status
Not open for further replies.

mbrooke

Batteries Included
Location
United States
Occupation
Technician
NEMA & UL are north America standards, an ISO is global std.
the UL trip curve is not a device tested trip curve, its a performance curve to test against, etc. the device must perform at or better than the UL trip curve to be worthy of the GFCI UL stamp, etc.

Sounds good then. :thumbsup:
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
edit time was up

UL / NEMA are NA std's. an ISO would be better.

my HVAC unit had a failure, a possible fire hazard, UL said they did not certifiy the unit, Canadian CSA did. i submitted to CSA the issue and got nothing back. this issue could be affecting thousands of York made HVAC units.

basically, improper sizing of a relay. one relay pin basically vaporized off during the inrush amps at turn-on. i have since modified the ckt board, it now uses two hefty solid state relays to control the motor. the small relay is rated 10A, inrush amps at turn-on is around 30A !! the large relay was about max'd out, both were swapped to mosfet SSR's protected from flyback by big MOV's. even some of the wiring was bad, had to replace wiring inside the unit as well as the inadequate 14awg cap cord that was feeding the unit, its now hard wired using 12awg into a fused blade disco.

relays.jpg


DSC02574.jpg
DSC02575.jpg



DSC02581.jpg


burned_hot.jpg



But how would a GFCI have prevented that or a fire?
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
But how would a GFCI have prevented that or a fire?
i should have said in last post that nema/ul is US std stuff.
a GFI might have killed the juice as some amps went directly down to EGC when that relay pins melted off and hit the back panel. would that have been a worthwhile trip, likely not, but a trip would have removed power to a item that was in severe failure.

but, my point was, US gets products certified by CSA and then when there is a issue/claim you get no response and no US entity can help, different country and they dont care. with an ISO the certifying agency has more responsibility to respond. also, CSA has its std's, NEMA/UL has its std's, CE has its std's.......,,,,, too many "standards".

related to GFCI, you mentioned that other says 30mA is ok to protect people, UL has that # at 20mA or less, NEC says GFCI class-A only. so why all the diffs ??

All I have to say is: :roll::roll:
which means what? confused, intrigued, understand it ???
 
Last edited:

mbrooke

Batteries Included
Location
United States
Occupation
Technician
i should have said in last post that nema/ul is US std stuff.

but, my point was, US gets products certified by CSA and then when there is a issue/claim you get no response and no US entity can help, different country and they dont care. with an ISO the certifying agency has more responsibility to respond. also, CSA has its std's, NEMA/UL has its std's, CE has its std's.......,,,,, too many "standards".

related to GFCI, you mentioned that other says 30mA is ok to protect people, UL has that # at 20mA or less, NEC says GFCI class-A only. so why all the diffs ??

Two theories- tell me if I a may be correct:

1. The response time of UL GFCIs is slower at 5ma, faster at 20- 30ma RCDs trip slightly under 30ma... so what all is said and done it may be possible both have close response times?

2. Its possible that UL GFCIs take into account children.
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
Two theories- tell me if I a may be correct:

1. The response time of UL GFCIs is slower at 5ma, faster at 20- 30ma RCDs trip slightly under 30ma... so what all is said and done it may be possible both have close response times?

2. Its possible that UL GFCIs take into account children.
we have no actual GFCI trip times, all we have is a UL trip curve in order to get UL stamp. using UL curve only, yes, we can conclude that at 30mA it is required to trip faster.

A x time = joules

30x.5=15
6x5=30
dbl the energy at 6mA !! but 5x less amps. why? from experimental data, hence the UL curve developed.
note that the curve is exponential
in essence, GFI trips to keep the joules down, the mA # tells us what affects the body may experience, etc. recall that 1,000A for 0.00000001ms is not much energy.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
we have no actual GFCI trip times, all we have is a UL trip curve in order to get UL stamp. using UL curve only, yes, we can conclude that at 30mA it is required to trip faster.



Thus, be minimum standards only, 5ma UL and 30ma IEC would be about equal. Yes?








A x time = joules

30x.5=15
6x5=30
dbl the energy at 6mA !! but 5x less amps. why? from experimental data, hence the UL curve developed.
note that the curve is exponential
in essence, GFI trips to keep the joules down, the mA # tells us what affects the body may experience, etc. recall that 1,000A for 0.00000001ms is not much energy.

Does this also factor in watts? Id imagine 1,000amps at 1/10th of a volt would not be the same as 1,000 amps at 300 volts.
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
Thus, be minimum standards only, 5ma UL and 30ma IEC would be about equal. Yes?
Does this also factor in watts? Id imagine 1,000amps at 1/10th of a volt would not be the same as 1,000 amps at 300 volts.

since the UL curve has an edge between safe and not-safe zone, you might conclude that the edge from zero to 1A are "equal" in terms of safety, i just not sure why there is a linear region.
and yes, if you wish to convert to watts to compare at different voltages then do that, the voltage is common in my example so it just drops out, etc.
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
Does this also factor in watts? Id imagine 1,000amps at 1/10th of a volt would not be the same as 1,000 amps at 300 volts.
it also depends on the Power Factor of the body :lol:
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
since the UL curve has an edge between safe and not-safe zone, you might conclude that the edge from zero to 1A are "equal" in terms of safety, i just not sure why there is a linear region.
and yes, if you wish to convert to watts to compare at different voltages then do that, the voltage is common in my example so it just drops out, etc.

But you have to. Watts play a role. Remember that watts is work, so any internal heating of body tissue leads to cellular death.
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
But you have to. Watts play a role. Remember that watts is work, so any internal heating of body tissue leads to cellular death.

ok, then express it in VA with PF=1
 
I don't want to hijack a GFCI thread already in progress but I still want to ask. Why are GFCIs (RCDs) outside of North America set to trip at 30ma while GFCIs in the US are set to trip at 6ma? Isn't 30ma dangerous being past the let go threshold?

In Australia the government was concerned that nuisance tripping of the new fangled RCD's would put the public off the idea of using RCD's so they settled on 30mA as a compromise.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
In Australia the government was concerned that nuisance tripping of the new fangled RCD's would put the public off the idea of using RCD's so they settled on 30mA as a compromise.

This is a major eye opener. I do not deny that being true, but do you have any links (if they exist)? What was the compromise between?
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
In Australia the government was concerned that nuisance tripping of the new fangled RCD's would put the public off the idea of using RCD's so they settled on 30mA as a compromise.

many countries around the world use 30mA as the "norm/std".
i guess you are 5x safer in NA because the "norm/std" is 6mA ;)
or maybe you can argue that the folks at UL are just way smarter than rest of the world :lol::lol::lol:
 

iwire

Moderator
Staff member
Location
Massachusetts
many countries around the world use 30mA as the "norm/std".
i guess you are 5x safer in NA because the "norm/std" is 6mA ;)
or maybe you can argue that the folks at UL are just way smarter than rest of the world :lol::lol::lol:

You have a problem with 6mA protection that works?
 
Status
Not open for further replies.
Top