No LOTO - 277 volt lighting controlled by photocell

[tom baker]

An electrical contactor was replacing exterior 277 volt wall packs, working on a manlift with out a harness.
He had not done a LOTO and was relying on the photocell being off. I got that job stopped.
Does anyone have any real life examples of why relying on a photocontrol is unsafe? And 277 V no less...

He was driving the manlift at high speed across the parking lot, someone pulled out in front of him, in the process of stopping he almost fell out of the basket.

 

[Cow]

How many more safety procedures does he have to break before you fire him?

I'm just curious?

Does he actually have to hit a car first or just get shocked...?

 

[hillbilly1]

He would already have been let go by us if we knew about it and he or she was one of our employees. See so many guys rely on the energy management systems to have the circuits off too. Very dangerous.

 

[cadpoint]

Why isn't it enough that this is a live circuit ?

What if the eye is wired behind the light instead of in front of the light ?

I saw a similar situation where on a Sunday afternoon a lift was servicing a sign for a busy strip mall, sitting right in the entrance, no cones, no flag man and one man free in to drive about in the crows nest.
:jawdrop:

 

[charlie b]

Does anyone have any real life examples of why relying on a photocontrol is unsafe?

No real life examples, but a simple reason none the less: If anything were to block the photosensor, it would allow power to be sent to the light fixture. It could be a bird flying by, a piece of paper or a leaf blowing in the wind, or (more likely) some motion of the worker himself. Talk about a candidate for the Darwin Award. How about this as a news item: "man killed by flying leaf."

 

[petersonra]

An electrical contactor was replacing exterior 277 volt wall packs, working on a manlift with out a harness.
He had not done a LOTO and was relying on the photocell being off. I got that job stopped.
Does anyone have any real life examples of why relying on a photocontrol is unsafe? And 277 V no less...

He was driving the manlift at high speed across the parking lot, someone pulled out in front of him, in the process of stopping he almost fell out of the basket.

It seems like he was violating all kinds of basic safety precautions.

He needs to be given a safety refresher course and some time off to think about it.

 

[hillbilly1]

if there was a temorary power loss, a lot of photocells will energize the load temporarily upon restoration of power.

 

[S'mise]

No real life examples, but a simple reason none the less: If anything were to block the photosensor, it would allow power to be sent to the light fixture. It could be a bird flying by, a piece of paper or a leaf blowing in the wind, or (more likely) some motion of the worker himself. Talk about a candidate for the Darwin Award. How about this as a news item: "man killed by flying leaf."

Most photoeyes will not do this, They have to have a darkened condition for at least 30 seconds before they switch. A more probable situation is the PE failing in the "on" condition.

 

[Cow]

if there was a temorary power loss, a lot of photocells will energize the load temporarily upon restoration of power.

That's what I was thinking too. Even somebody accidentally bumping the breaker off and then resetting it could possibly reenergize the lights just for a few seconds.

 

[kwired]

if there was a temorary power loss, a lot of photocells will energize the load temporarily upon restoration of power.

photo cells that operate by a relay likely will do this.

Photo cells that heat a bimetal strip which operates a contact will need time for the bimetal to cool before they will close the contact.

Still not a good reason to not turn off the supply however.

 

[hurk27]

photo cells that operate by a relay likely will do this.

Photo cells that heat a bimetal strip which operates a contact will need time for the bimetal to cool before they will close the contact.

Still not a good reason to not turn off the supply however.

Actually a thermo type photo cell will not only have the heater in series with the load, even when there is ambient light and it is off, it will turn on when all the loads or power is removed for a period time (1-5 mins.) even though the OP is about 277 volts its worth mentioning 240/480 volt photo cells do not disconnect both hot conductors, they are still three wire devices, so unless you have a contactor you will still have voltage at the fixture.

Ever change a bad lamp in a post light with the power still on, yes it will light till the photo cell heater turns it off again, most times we deal with multiple loads and this wont happen as the other loads will keep the PC off.

 

[TVH]

No LOT)- 277 volt lighting controlled by photocell.

No LOT)- 277 volt lighting controlled by photocell.

It appears your organization lacks a safety culture.

 

[tkb]

An electrical contactor was replacing exterior 277 volt wall packs, working on a manlift with out a harness.
He had not done a LOTO and was relying on the photocell being off. I got that job stopped.
Does anyone have any real life examples of why relying on a photocontrol is unsafe? And 277 V no less...

He was driving the manlift at high speed across the parking lot, someone pulled out in front of him, in the process of stopping he almost fell out of the basket.

Was it a scissor lift or a boom lift?

A scissor lift does not require a harness.

 

[pistolpigg]

It has been my experience that the best reason loto on anything with a photo cell is that you don't know if the photo cell is wired correctly if the line and load are crossed on some devices they will constantly click on and off but when dark the pc will bring the lights on as normal.