120V vs 480V lighting

[PhaseShift]

The majority of our plant is 480V lighting. We now need to run new lighting to a particular area of the plant. Because of the the infastrucure and cable that has already been installed to this area it may be easier to run 120V lighting. We will have 100W lights. Is there any disadvantge to running lighting at 120V assuming multi-tapped ballasts? I figure 100W is 100W so operating cost should be the same minus a small amount of losses.

The other option would be to pull 480V power in 120V control signal conduit. I have always been told this should be avoided. These runs are about 200-400ft.

Would it be better practice given these two options to go with 120V lighting, or mix 480V lighting in 120V control conduit?

 

[ron]

If the insulation for the 120V circuits is 600V rated, I see no problem mixing 120V and 480V circuits.

 

[ultramegabob]

Is there any disadvantge to running lighting at 120V assuming multi-tapped ballasts?

you will need more circuits at 120v for the same number of lights, material may wind up costing more. do you have plenty of breaker space available?

 

[Jraef]

... I figure 100W is 100W so operating cost should be the same minus a small amount of losses.

You are 100% correct on that point.If loading isn't an issue for you, there is no significant difference.

I for one do not like mixing 480V in the same conduit as 120V control signal conductors if it can be avoided. Nothing illegal about it if the insulation is OK, but it can cause problems on sensitive circuits. For example it's difficult to induce enough energy onto a 120V control wire to energize a PLC input. But if energized elsewhere, I have seen induced voltage from adjacent 480V lines under load be high enough to KEEP the PLC input high when it was supposed to go low.

 

[Jraef]

... I figure 100W is 100W so operating cost should be the same minus a small amount of losses.

You are 100% correct on that point.If loading isn't an issue for you, there s no difference.

I for one do not like mixing 480V in the same conduit as 120V control signal conductors if it can be avoided. Nothing illegal about it if the insulation is OK, but it can cause problems on sensitive circuits. For example it's difficult to induce enough energy onto a 120V control wire to energize a PLC input. But if energized elsewhere, I have seen induced voltage from adjacent 480V lines under load be high enough to KEEP the PLC input high when it was supposed to go low.

 

[Tevil]

(1) Is there any identification to distinguish between the 120v and 480v circuit when they are in the same conduit?
(2) Is the identification future proof, meaning that no one will/can make the mistake in the future to believe both circuits is 120v?
(3) Will the placement of this identification at all locations along the cable run, (Junction boxes, Pull boxes)?

 

[glene77is]

(1) Is there any identification to distinguish between the 120v and 480v circuit when they are in the same conduit?
(2) Is the identification future proof, meaning that no one will/can make the mistake in the future to believe both circuits is 120v?
(3) Will the placement of this identification at all locations along the cable run, (Junction boxes, Pull boxes)?

Tevil,
Excellent tip.
I have seen 120V and 277V lighting run in the same conduit, with no ID.
I have seen the 277 attached to the 120 lighting system. Burns ballasts.