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#58356 - 11/07/05 01:58 PM Backfed Photocell?
Redsy Offline
Member

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
A photocell will operate a lighting contactor. If I install a switch to bypass the photocell and energize the contactors coil, the bypass switchleg will also (back)feed into (red) photocell output leg.
Is this a concern?

Thanks.

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#58357 - 11/07/05 02:03 PM Re: Backfed Photocell?
Dnkldorf Offline
Member

Registered: 12/12/04
Posts: 1091
Loc: nowhere usa
Not for me....

It is the same phase, right?

Your not really backfeeding it, your applying the same phase on the red wire, as if the photo cell was operating properly.


Dnk.........

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#58358 - 11/07/05 02:06 PM Re: Backfed Photocell?
ShockMe77 Offline
Member

Registered: 06/11/05
Posts: 823
Loc: Rahway, New Jersey
Not if its on the same phase. I've wired motion detector lights like this in the past. When the light switch is on, obviously the lights are on. When the switch is off, the motion feature controls the light. I think what you are describing is the same thing.

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#58359 - 11/07/05 02:09 PM Re: Backfed Photocell?
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
I do not see any code issue with it.

However another option would be the use of a 3 way switch (SPDT)

Common to contactor coil.

One terminal from constant feed.

One terminal from red of the photo cell.

You end up with ON or AUTO with this set up and no back feed to the red of the cell.

Make sure the EGC is large enough.

Bob

[This message has been edited by iwire (edited 11-07-2005).]
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#58360 - 11/07/05 02:40 PM Re: Backfed Photocell?
Redsy Offline
Member

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
Thanks guys.

The phasing is OK.
I think I actually did this configuration once before, but I'm not sure.
My concern is damaging the photocell.

iwire,

EGC, what's a EGC?




[This message has been edited by Redsy (edited 11-07-2005).]

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#58361 - 11/07/05 05:44 PM Re: Backfed Photocell?
capt al Offline
Member

Registered: 06/20/04
Posts: 203
Loc: Norton, Ma USA
EGC = Equipment Grounding Conductor.

Al

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#58362 - 11/07/05 06:14 PM Re: Backfed Photocell?
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Not a problem. I usually do this very thing.

You are not "back feeding" the photocell. The photocell is nothing more than a switch. It does not draw any current.

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#58363 - 11/07/05 07:11 PM Re: Backfed Photocell?
Redsy Offline
Member

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
Thanks again guys.



[This message has been edited by Redsy (edited 11-07-2005).]

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#58364 - 11/07/05 07:56 PM Re: Backfed Photocell?
Larry Fine Offline
Member

Registered: 02/18/05
Posts: 684
Loc: Richmond, VA
Redsy, from what I understand, as long as the line (black) wire is hot, there's no harm in energizing the load (red) wire.
_________________________
Larry Fine
Fine Electric Co.
fineelectricco.com

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#58365 - 11/08/05 04:09 AM Re: Backfed Photocell?
Redsy Offline
Member

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
Larry,

The line won't ALWAYS be hot when the red is fed from the bypass. Only when the timers contacts are closed.

Thanks.

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