Daisy Chained GFCI Protection

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infinity

infinity

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I went to a safety orientation today for a new job site and the site safety supervisor stated that you cannot plug a GFCI cord set into a GFCI protected circuit (or daisy chain them together) because they "won't work properly". Where did this myth come from? :slaphead:
 
They cancel each other out, didn't you know? :D

It probably came from the same place that says if you hit two hammers together they'll explode... :slaphead:
 
infinity said:
I went to a safety orientation today for a new job site and the site safety supervisor stated that you cannot plug a GFCI cord set into a GFCI protected circuit (or daisy chain them together) because they "won't work properly". Where did this myth come from? :slaphead:
Click to expand...

This is what happens when people who are completely ignorant of electrical principles start teaching about electrical principles.
 
Double GFCI exists in most bathrooms with modern hairdryers plugged in. GFCI receptacle, GFCI plug, works fine. The same probably exists to a lesser extent with newer window unit ACs with similar plugs.

eta: we've removed GFCI receptacles from GFCI breakers so that the HO only has to look one place for a trip. No idea where the myth comes from, never heard it before now.
 
I can tell you EXACTLY where it probably came from. When I started as an apprentice in 1975, GFCIs were still relatively new. In training sessions on how to properly use them, this subject was raised by the GFCI manufacturers as a possible safety risk. It's not because there is anything that interferes with them working though.

The issue is, if you have a GFCI circuit breaker, and it is feeding a GFCI receptacle, and you get a ground fault on something fed from that receptacle, you will not know which one tripped. That then can set up a situation where you know that it tripped, but ASSUME that it was the receptacle, push the reset, and it doesn't work. So you then assume that the electric edger you had plugged into it is defective and start messing with it. Meanwhile, your wife can't use her hair dryer because it was on the same GFCI breaker, so she goes out in the garage and flips the breaker back on and your fingers get cut off. I'm using this because it was the exact cartoon they used to illustrate the issue.

Since then other code sections have changed and it's unlikely that the outdoor receptacle is fed off of the same GFCI breaker going to a bathroom. But like a lot of things, it starts out with some reasonable concept and over time, morphs into something different.
 
Jraef said:
I can tell you EXACTLY where it probably came from. When I started as an apprentice in 1975, GFCIs were still relatively new. In training sessions on how to properly use them, this subject was raised by the GFCI manufacturers as a possible safety risk. It's not because there is anything that interferes with them working though.

The issue is, if you have a GFCI circuit breaker, and it is feeding a GFCI receptacle, and you get a ground fault on something fed from that receptacle, you will not know which one tripped. That then can set up a situation where you know that it tripped, but ASSUME that it was the receptacle, push the reset, and it doesn't work. So you then assume that the electric edger you had plugged into it is defective and start messing with it. Meanwhile, your wife can't use her hair dryer because it was on the same GFCI breaker, so she goes out in the garage and flips the breaker back on and your fingers get cut off. I'm using this because it was the exact cartoon they used to illustrate the issue.

Since then other code sections have changed and it's unlikely that the outdoor receptacle is fed off of the same GFCI breaker going to a bathroom. But like a lot of things, it starts out with some reasonable concept and over time, morphs into something different.
Click to expand...

Pretty far-fetched now but I suppose it made sense then. my wag would have been the breaker trips, you figure it's the receptacle, start to replace, and someone resets the tripped breaker while your hands are in the wiring...
 
And it can get really complicated when someone wires several GFCIs downstream from each other, some of which aren't even in the same room. Just try to tell someone which one to reset first.
 
Fnewman said:
And it can get really complicated when someone wires several GFCIs downstream from each other, some of which aren't even in the same room. Just try to tell someone which one to reset first.
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Really simple: If it won't reset when you try, it is not the first one you need to reset, so keep looking. :lol:
 
GoldDigger said:
Really simple: If it won't reset when you try, it is not the first one you need to reset, so keep looking. :lol:
Click to expand...
i agree and can generally find them pretty easily myself; however, homeowners sometimes have trouble finding them all because some are put in strange places (inside linen closets, under sinks, etc.) for example.
 
Non electricians (and some electricians) don't get it at all. Many don't know why we need that "test/reset" feature on the receptacle because "there already is a breaker in the panel" that will trip if something is wrong.

You can explain until you are blue in the face that they are not providing the same sort of protection and it won't matter.
 
Behind basement toilet for macerating pump unit was a great lesson years ago.. GFCI feeding vanity receptacle and light. 2 hours to find.

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I learned yesterday that there are people on this planet who believe "The Martian", starring Matt Damon, is based on a true story. No level of stupid surprises me.


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infinity said:
I went to a safety orientation today for a new job site and the site safety supervisor stated that you cannot plug a GFCI cord set into a GFCI protected circuit (or daisy chain them together) because they "won't work properly". Where did this myth come from? :slaphead:
Click to expand...

From the early days of OSHA-mandated GFCI protection on job sites. GFCI receptacles and GFCI cord sets just did not get along.
 
480sparky said:
From the early days of OSHA-mandated GFCI protection on job sites. GFCI receptacles and GFCI cord sets just did not get along.
Click to expand...

But this is 2017 you think that the old way of thinking would be long gone by now. :)
 
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brantmacga said:
I learned yesterday that there are people on this planet who believe "The Martian", starring Matt Damon, is based on a true story. No level of stupid surprises me.
Click to expand...

Conversely, there are people who are unaware that Titanic was a real event... (Well excluding the part about Jack and Rose)

Some of the 120V EV charge cords (EVSEs) recommend against using a GFCI outlet since the EVSE itself acts as a GFCI. Guess everybody that parks their car outside is hosed... (I haven't had any issues in 4.5 years)
 
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480sparky said:
Yes, up until '93 or '96 or so. But I still run across old-timers who don't protect all c'top receps, just those within 6' of the sink.
Click to expand...

Not quite the same thing as claiming daisy chained GFCI's won't play well together.

I do think six foot from the sink should have been left as the rule all along, and the more recent dishwasher GFCI requirement was just about criminal as to why it is required.
 
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