I looker at a job for boat dock and swim platform on small lake. he wants a 15 amp 120 volt gfci outlet on land next to the dock and wants it fed from a 20 amp gfci breaker in the barn . I know it will work . this sounds like a good idea . I never thought of this. what is your input ?
REDUNDANT GFCI
- Thread starter domnic
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fmtjfw
Senior Member
- Location
- Fairmont, WV, USA
Sounds good, the breaker protects the wiring to the receptable, but the recteptacle need not be a GFCI.
Good catch! Just you wire the GFCI at the barn properly, so a non-GFCI receptacle at the dock gets protected from ground aults.
I think he is saying from a life safety perspective redundant is good
in mining we use 5 layers
a neut gnd resistor, as low as 100 mA
Secondary on the main cb, small td of 0.1 to 0.2 sec
a pt across it to trip at 50%
a ct on it to trip at 40%
both trip the main
Primary on the branch ckt
gf relay tripping branch cb at 30%
a ground monitor, if continuity >3 ohm trip branch cb
in mining we use 5 layers
a neut gnd resistor, as low as 100 mA
Secondary on the main cb, small td of 0.1 to 0.2 sec
a pt across it to trip at 50%
a ct on it to trip at 40%
both trip the main
Primary on the branch ckt
gf relay tripping branch cb at 30%
a ground monitor, if continuity >3 ohm trip branch cb
mgookin
Senior Member
- Location
- Fort Myers, FL
x2
Its inexpensive, hurts nothing and of all examples of electrical overkill this is one that is not entirely unreasonable or "out there"- what if the gfci breaker gets moved or replaced w/ a standard for some reason (can you say trunkslammer)? Considering the location and circumstances, this 2nd layer of gfci is perfectly acceptable.
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Why spend some more when those loads are on the same feed? Knowing how to wire things is important. Do it like this:
Yes, I am aware of feeding reg recs with/thru gfci- but if the ho gets this explained to him and still wants it done his way w/ the redundant protection, then imo, just let it be- he's paying for it.
- Location
- Massachusetts
Did you honestly just explain to a forum of electrians how to wire a GFCI?
Your faith in our abilities is a bit lacking.
Yes, you can wire them that way and sometimes we do. But in the OPs case the customer asked for redundancy, a GFCI breaker feeding a GFCI receptacle. Given the failure rate of GFCIs and the number of electrical accidents that happen around the waterfront it does not sound like a bad waste of $15.00.
Beyond the OP many of our commercial kitchen customers will not accept what your diagram shows, they want a GFCI receptacle at each point of use.
MD84
Senior Member
- Location
- Stow, Ohio, USA
There is more than just redundancy here. The receptacle will offer higher sensitivity to cord connected loads. A good idea IMO.
- Location
- Massachusetts
A class A GFCI has the same trip requirements regardless of breaker or receptacle.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
I thought that 6ma was 6ma at every point in the series circuit.
More of a concern to me is that a fault will trip either one or both, making resetting more frustrating.
the person saved by the back-up really won't care about that
nor should they
If the fault is between the first and second will both trip?
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
I agree that a backup makes sense, especially given the failure rate of receptacle GFCIs and the lack of testing.
I do not agree that one type is more sensitive than the other.
I do not agree that one type is more sensitive than the other.
fmtjfw
Senior Member
- Location
- Fairmont, WV, USA
NO, GFCI's only look downstream.
kwired
Electron manager
- Location
- NE Nebraska
How long of a run between the two GFCI's?
The longer the run the more capacitive leakage you may have causing undesired tripping.
If you want "double protection" that is fine but don't put one of them at the beginning of a long run.
The longer the run the more capacitive leakage you may have causing undesired tripping.
If you want "double protection" that is fine but don't put one of them at the beginning of a long run.
mgookin
Senior Member
- Location
- Fort Myers, FL
.
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- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Unlike the arc signature detection part of AFCIs. The threshold current is downstream only.
kwired
Electron manager
- Location
- NE Nebraska
Sort of. Only thing they really care about is that current that goes out comes back on another monitored conductor, then there is also a signal injected that allows them to instantly trip on a neutral to ground fault even if no load current is otherwise present.
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