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#85549 - 07/14/03 07:52 PM 3 ph GFI  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,306
I have used one of these
[Linked Image]
to protect a 3 phase motor, the gfi trips out the contactor's coil....

is it viable ?

~Steve


2017 / 2014 NEC & Related Books and Study Guides

#85550 - 07/14/03 08:37 PM Re: 3 ph GFI  
JBD  Offline
Member
Joined: Jul 2001
Posts: 599
WI, USA
I doubt that you could call this "personal" protection like that offered by a UL Class A GFCI. Note that the Leviton web page lists specific contactors that have been tested.

The UL testing for GFCI devices includes a time element. Exceptfor the listed devices, it is unlikely that your contactor contacts will break the arc and open the circuit fast enough to classify as Class A. But any protection is better than no protection.



[This message has been edited by JBD (edited 07-14-2003).]


#85551 - 07/14/03 09:31 PM Re: 3 ph GFI  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
Offhand, 5mA leakage/trip on a motor will probably send someone to the looney bin.


#85552 - 07/15/03 06:46 AM Re: 3 ph GFI  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,306
Quote
But any protection is better than no protection.


exactly my assumption...

the unit shown comes in a 'spa unit' with it's own contactor, the only alteration i've done was to stuff a third conductor thru the GFI.

it appears to be quite functional, listings aside, why is this frowned on?

what would make it inapplicable to 3 phase?


#85553 - 07/15/03 10:29 AM Re: 3 ph GFI  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
Sparky, the intent was not to imply 5mA protection is not permitted for such a load, but that after some aging, motors with enameled wire pounded into fishpaper-lined stator slots may produce excessive trips/leakage that could become frustrating to users/maintainers of the motor. {For this application, 208Y serving a GFCI-protected motor may be less problematic than 240∆.}


#85554 - 07/15/03 11:01 AM Re: 3 ph GFI  
C-H  Offline
Member
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden
I'm really confused. Where does the contactor come in?


#85555 - 07/15/03 03:13 PM Re: 3 ph GFI  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,306
hmmm,
i understand the 'leakage' part, i guess i've lucked out so far....

C-H,
the contactor is fed by a 3ph branch that goes thru the high-umph gfi's ct.

the coil is for the motor

the load side of the gfi would drop out the coil

that is, if i'm not simply chasing my tail here, fooling myself that it will function???


#85556 - 07/15/03 07:02 PM Re: 3 ph GFI  
US Coreman  Offline
Member
Joined: Mar 2003
Posts: 36
Illinois, USA
Ya' know, I'd like it better if they clearly stated that it was intended to be applied to a 3 phase load somewaht more clearly than: quote"Adds ground fault protection to heavy equipment powered through 3- or 4-wire circuits". Because if you go to look at the wiring diagrams, http://www.leviton.com/sections/prodinfo/newprod/npleadin.htm, you will see that they only list : 30 Amp GFCI Wiring Diagram 3 - 2 Phase Circuits (120/240V Relay, 3-Pole),beyond which the pther diagrams call out 120, 208/240, or 120/140 volt circuits. I believe that they also erroneously call it "2 phase". The part of the heading on the web page that calls out Only for 3- and 4-Wire Systems That Include Grounded Neutral, and also depicts it in the wiring diagram, would lead me to believe that it is not listed for your installation since a 3 phase motor does not employ the system neutral. Additionally, where would you obtain the 120v control circuit from.

The current donought would appear to be a zero equence type so while it might work in theory, it probably wouldnt be listed.

As an aside, last year or so, I tried to buy one of the Leviton spa packs that you mentioned, and that do exist in the catalog. I was told by Leviton that if I wanted to purchase a large quantity of them, they would build them, but they didn't notmallr do a onesy or twosey sale. So I complained to the Leviton salesman, and he GAVE me the sample he had in his trunk. It works well.

[This message has been edited by US Coreman (edited 07-15-2003).]


#85557 - 07/15/03 07:37 PM Re: 3 ph GFI  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,306
US Coreman,
why can't the gfi unit's 110v can simply be part of the 110v control circuit?

i do wish for clarity here also, because CMP-20's stance on pool gfi protection would seem to revolve around this very issue

listed or no, it is (as far as i can tell) funtional at this time

that is, unless there is something i've blatantly missed.

which is my inquiry here.......


#85558 - 07/16/03 07:39 AM Re: 3 ph GFI  
PCBelarge  Offline
Member
Joined: Jun 2003
Posts: 681
Dobbs Ferry, NY, USA
I don't understand why you would want or need to GFCI protect the control circuit?
Is that suppose to GFCI protect the motor?
Like US Coreman, I do not believe this to be listed for the application you are using it for.

Pierre


Pierre Belarge

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