Outdoor light bypass

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mgookin

mgookin

Senior Member
Location
Fort Myers, FL
Occupation
Retired inspector, plans examiner & building official
This is for installation of a GPS enabled relay controller which effectively is a timer which never requires programming. The optimal installation is with a clear view of the horizon, although it does work inside an attic with wood trusses, plywood roof and asphalt shingles. It does not work under a steel pan roof atop bar joists. There are two valid reasons to have a bypass. First is to service bulbs & ballasts which may be on the circuit and second is to turn on the lights on Christmas day, for a parade, etc. This switch can be down at grade, in an electric room, etc. while the control is mounted up high. One existing customer has to send guys up ladders every time they have an event just to put a cup over the existing photocontrols. This bypass installed in his electric room will make him happy.

This creates a parallel condition when both the switch and the control are closed.

Any objections?

Thanks in advance.

Light Control bypass.JPG
 
mgookin said:
This is for installation of a GPS enabled relay controller which effectively is a timer which never requires programming. The optimal installation is with a clear view of the horizon, although it does work inside an attic with wood trusses, plywood roof and asphalt shingles. It does not work under a steel pan roof atop bar joists. There are two valid reasons to have a bypass. First is to service bulbs & ballasts which may be on the circuit and second is to turn on the lights on Christmas day, for a parade, etc. This switch can be down at grade, in an electric room, etc. while the control is mounted up high. One existing customer has to send guys up ladders every time they have an event just to put a cup over the existing photocontrols. This bypass installed in his electric room will make him happy.

This creates a parallel condition when both the switch and the control are closed.

Any objections?

Thanks in advance.

View attachment 9056
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We do that all the time on our exterior door lights. We use a photocell that turns the light on at dusk regardless of switch position. And the switch can turn the light on anytime.
We have never been questioned on it.
 
qcroanoke said:
We do that all the time on our exterior door lights. We use a photocell that turns the light on at dusk regardless of switch position. And the switch can turn the light on anytime.
We have never been questioned on it.
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Ah, but according to what iwire and kwired have been saying on this thread, this may be a violation of the NEC's rules regarding parallel conductors, since you will have parallel paths for current if the bypass switch and GPS controller are both turned on at the same time. Of course, that means just about every other bypass switch in existence would be in violation, too...

I'm not trying to start another debate about if this is or is not a violation, but I thought you ought to know it may be an issue with some AHJs (with others, not so much).
 
The issue I see is more with proper labels/placards. Someone could see the switch is off and be working on the lights, then the photocell turns them on.:rant: If this is not a dedicated circuit to the lights, then the breaker being turned off may not be an option, and a power on/off switch may be needed as well.

Another control issue, is what is going to keep someone from over riding the photocell and leaving the lights on permanently?
 
JDBrown said:
Ah, but according to what iwire and kwired have been saying on this thread, this may be a violation of the NEC's rules regarding parallel conductors, since you will have parallel paths for current if the bypass switch and GPS controller are both turned on at the same time. Of course, that means just about every other bypass switch in existence would be in violation, too...

I'm not trying to start another debate about if this is or is not a violation, but I thought you ought to know it may be an issue with some AHJs (with others, not so much).
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We have been doing this for the entire time I have been employed at my job. (29 years) a lot of our drawings go through a third party or state plans reviews.
Not once has it ever been questioned. And we draw the detail right there where anyone can see it.
 
qcroanoke said:
We have been doing this for the entire time I have been employed at my job. (29 years) a lot of our drawings go through a third party or state plans reviews.
Not once has it ever been questioned. And we draw the detail right there where anyone can see it.
Click to expand...
Please understand, I'm not trying to question the validity of the design--it's probably what I would do myself, actually. And I certainly won't contradict your first-hand experience. I was just pointing out to the OP that there may be some AHJs who will reject the design based on their interpretation of the Code's parallel conductor rules. They're probably few and far between (if indeed there are any), but if he's planning to market this solution nationwide he may want to be aware of the possibility.

One solution to this problem-that-will-probably-never-come-up would be to use a DPDT switch instead of a single-pole switch. The second pole could be set up to cut power to the GPS controller when the bypass is enabled, allowing it to double as a disconnect for the controller (though not for the light). If it's bad for the GPS controller to be disconnected from power, the DPDT switch could be set up to cut power after the GPS controller, so it would still function as a bypass switch, but the possible parallel path would be eliminated.
 
n1ist said:
The conductors aren't in parallel. The switches are wired in parallel.

/mike
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The way I would analyze it (based entirely on common sense, of course, which is very risky) is that if the two conductors always are energized or de-energized at the same time and connect the same points they are in parallel (making a ring branch circuit prohibited as parallel).
But if there are normal conditions which cause the current to follow exclusively one conductor or the other, even if there are other conditions that cause it to follow both, they are not in parallel.
 
Use a 3-way switch

Use a 3-way switch

Use a 3-way switch . similar as to a generator bypass switch

Put the Black screw to the load

one brass screw to the controller( normal operation)

the other brass screw to HOT ( bypass operation)

this method eliminates backfeeding the photocell/controller.

I will mount the switch horizontally And label with a magic marker/sharpie to avoid confusing normal people that would assume its a off switch.
 
JDBrown said:
Please understand, I'm not trying to question the validity of the design--it's probably what I would do myself, actually. And I certainly won't contradict your first-hand experience. I was just pointing out to the OP that there may be some AHJs who will reject the design based on their interpretation of the Code's parallel conductor rules. They're probably few and far between (if indeed there are any), but if he's planning to market this solution nationwide he may want to be aware of the possibility.
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Understood,
I noticed on your bio that you do a lot of airport design. The buildings we produce are used on a lot of federal property airports. (the orange and white ones) So I'm not used to laymen being in our shelters. If you are in our shelter you had better know what you are doing.
As you said if the right AHJ questioned the design shown I'm not so sure we could defend it as code compliant.
But we have never had to........ ;0)
 
kingpb said:
If sense was so common, more people would have it:lol:

And if you try to make it fool proof, along will come a bigger fool.
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I was watching NOVA (on PBS) the other day. A professor in the MIT Materials Lab was making a battery and he said it needed to be "cheaper than dirt" and "the only way I know how to make it cheaper than dirt is to make it from dirt" as he placed a scoop of dirt into a beaker.
 
mgookin said:
I was watching NOVA (on PBS) the other day. A professor in the MIT Materials Lab was making a battery and he said it needed to be "cheaper than dirt" and "the only way I know how to make it cheaper than dirt is to make it from dirt" as he placed a scoop of dirt into a beaker.
Click to expand...
Technically, that could at best make it as cheap as dirt. Cheaper than dirt would require all of the other components to be literally cheaper than dirt.
 
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