Has anyone ever seen this?

[kentirwin]

I replaced a "fisheye" style photocell (Tork 3002) on a wallpak fixture where I work a few months ago. It worked just fine, as I fully expected it to. A couple of weeks ago we had a thunderstorm with some nearby lightning strikes. I always come to work before daylight, partly to check all the site lights. The folowing morning that wallpak was out. Great. I'll see what's up in a little while. Sun came up, wallpak lit up and stayed on all day. Came back before dawn the next day and the wallpak was out. Sun came up and it lit! This photocell has religiously reverse operated ever since. The only thing I can think of is that ligtning somehow freaked it out. I have never seen this before. :roll:

 

[bphgravity]

Re: Has anyone ever seen this?

I'm not sure if I have ever seen one actually reverse its operation, but I do know these devices are very sensitive to diiferent stimulus. I believe most come with instructions to not focus the "eye" of the device directly towards the sun or it may not work correctly or be damaged by the intensity of the sun. I suppose if a near ligthning strike were to occur, the great intensity of the flash may indeed damge the sensor even if it is not exposed to a surge or transient.

 

[charlie tuna]

Re: Has anyone ever seen this?

kent,
i have never seen a photo cell reverse it's function, but i do believe they need to be over-rated to last! if the rated load of the photo cell is even close to the load of the fixture the life span of the cell is very short!

 

[charlie b]

Re: Has anyone ever seen this?

The photocell itself cannot "reverse" its function. It only has one: when light strikes it, it generates a voltage. The thing that reversed its function has to be the circuit that senses the photocell's voltage and takes a control action (e.g., opens a contact and turns off a light). That circuit might be built into the same case that holds the photocell, but that circuit is where you would have to look to find the problem.

 

[kentirwin]

Re: Has anyone ever seen this?

Charlie - At the moment I can't visualize what you mean exactly. The pcell controls only the wallpak fixture that it's mounted in. It wires just like a single pole switch in line between the incoming 277V circuit and the hot to the ballast. It also wires to the neutral of the circuit. Like I said, I'm not sure what you're trying to tell me but I've watched this thing for over two week and it most definitely operating in reverse order.

 

[charlie b]

Re: Has anyone ever seen this?

It's a question of language. To my mind, the word "photocell" refers only to the component that is struck by light and produces, by virtue of the "photoelectric effect," a voltage. I think you are using the word "photocell" to include both that component and the electronics that perform the on/off function. All I am saying is that the "thing that is struck by light" cannot be the component that has failed, and that is to blame for the symptoms you are describing. Some other component within this device has failed, not the "photocell" itself.

 

[stuart in mn]

Re: Has anyone ever seen this?

That is pretty odd. The Tork 3002 is just a little photocontrol device, with a photocell and an SPST switch, so there shouldn't be any way it could reverse its function. (if anyone is interested, this is the link to the Tork catalog page: http://www.tork.com/main4an2.htm

They're pretty durable devices, I've never seen much problem with them failing. On the plus side, they aren't that expensive to replace.

[ July 29, 2005, 02:23 PM: Message edited by: stuart in mn ]

 

[kentirwin]

Re: Has anyone ever seen this?

The photocell is all that controls the on/off function. Nothing else has been touched or manipulated in any way. It's function has very definitely reversed. I offer no explanation - that's why I started this thread. All I've done with pcells in the past has been to replace them. Supposedly they're desgined to fail closed. I also know from experience that this is not always true. It's not a big deal. I could replace it tomorrow and call it a day. I's the WHY that puzzles me.

 

[charlie b]

Re: Has anyone ever seen this?

OK. Here's a guess. You are electrician. This happened where you work. I'm guessing that you are not the only electrician who works there. Do you suppose that another electrician came in, saw the failed device, replaced it, but got the wiring backwards? Can you be sure that the one that is presently misbehaving is the same one you installed several months ago?

 

[physis]

Re: Has anyone ever seen this?

What Charlie was saying is that the photocell only changes resistance in responce to the light level and needs amplification and switching electronics to control the contacts. The electronics, probably the ampliying section, is what's gone goofy.

The 3002 has SPST contacts. It would be hard to wire that wrong. But I don't suppose impossible.

 

[kentirwin]

Re: Has anyone ever seen this?

I work in an unusual place. I AM the only electrician there. We have electrical process technicians that ONLY work on process equipment. As far as electricians - it's just me and the contactor personnel I call in. The ONLY one who works on site lighting is me. As far as wiring the pcell backwards - I haven't seen it done in a long time but (and I may be wrong) I don't believe it will work backwards. In fact I believe it won't change state at all if wired backwards. At any rate, it's not wired backwards. I wired it a few months ago and it worked fine until it became possessed. The truth is out there...

 

[jimwalker]

Re: Has anyone ever seen this?

Hold on to it.Never know when you might just need a reversed photocell.Like others i have never seen this happen.

 

[George Stolz]

Re: Has anyone ever seen this?

Originally posted by charlie b:
Do you suppose that another electrician came in, saw the failed device, replaced it, but got the wiring backwards?

Miswiring couldn't produce the effect he is describing, IMO.

That's pretty wild, Kent, but hey, stuff happens.

 

[physis]

Re: Has anyone ever seen this?

George that snake is most likely just some photoshop effort. What really amazes me is these jackalopes.



[ July 30, 2005, 02:28 PM: Message edited by: physis ]

 

[hurk27]

Re: Has anyone ever seen this?

don't believe it will work backwards. In fact I believe it won't change state at all if wired backwards. At any rate, it's not wired backwards

If a thermo type photo cell is connected in reverse Ie. line to load and load to line all it will do is cycle on and off all nite. If it is a relay type it will make a good stobe light.

A thermo photo cell's operation is simple there is a very small heater that is in series with the photo cell and load there is also a resistor that is in series with the photo cell. when there is power on and light hitting the photo cell the heater heats up and opens a bi-metal N/C contact, when it gets dark enough the photo cell lowers the amount of current to the heater through the resistor thus allowing it to cool and the bi-metal contacts close turning on the light. This photo cell would have to have been mis-wired in the factory to have it operate in reverse?

 

[George Stolz]

Re: Has anyone ever seen this?

Originally posted by physis:
George that snake is most likely just some photoshop effort. What really amazes me is these jackalopes.

You know, it is the "Official Mythical Creature" of Wyoming. No joke.

 

[iwire]

Re: Has anyone ever seen this?

Originally posted by georgestolz:

Originally posted by physis:
George that snake is most likely just some photoshop effort. What really amazes me is these jackalopes.

You know, it is the "Official Mythical Creature" of Wyoming. No joke.

A little board out there huh?

Here in RI there was a battle to become the official drink of RI.

It was between a frozen lemonade drink and a coffee milk. :roll:

 

[physis]

Re: Has anyone ever seen this?

It starts to get a little difficult to take an office seriously when they start having official jokes.

So the rabbi says to the.....................and here's the new tax code!

 

[kentirwin]

Re: Has anyone ever seen this?

Yesterday my supply house outside guy was here and I pointed across the street that seperates the engineering bldg. to the brightly burning wallpak controlled by the posessed pcell. He got on the phone and called the local Tork rep. Rep replies, "that's not possible". Rep then admits he's only a rep but will contact Tork engineers in Richmond (VA). I'll let ya know.

 

[physis]

Re: Has anyone ever seen this?

my supply house outside guy

Sooooo, is he a salesman or someone with knowledge?