ECN Forum Forums General Topics of the Trade General Discussion Area photocell requirement for metal halide ballasts

thanks for the info from everyone .. I'm sorry for my confusion in the original post. We are using quad tap ballasts at 208V. I can only hope that the electrical contractor is actually checking the correct tap is being used. At 30', we have no easy way to do this ourselves. The original installer was a large electrical contractor co. that the general contractor had used as a sub. They keep saying they've never had this type of problem on any other job. So much for that. We'll try someone else.

One last question ... just how much life should you expect from these types of ballasts? and bulbs?

Ballasts seem to have no set 'average.' Some seem to die after a year; another put in, right next to it, on the same circuit, will last over a decade.

If I were to try to guess at a pattern, I'd look back at one job I maintain .... 13 years, 18 ballasts like yours, and I've had to replace two.

Bulbs seem to last 2-3 years.

Thanks - again - electre! Not having a photocell box handy, I wasn't sure just how close this installation was to the capacity of the photocell.

I assumed these things were triac based, the ones I have used were. There are no "contacts" to burn. At that point there is really no advantage to a 2 pole device since they all leak some current. The voltage on the lamp (to ground) won't be full line voltage but it won't be zero either.
In the equipment I have worked on with solid state switching they don't even bother switching all legs on a l/l load. Single phase gets one device and 3p gets 2.
Triac switches don't really like 3 phase since there is no real "zero crossing" but they do work. Typically they use something several times the actual current.

All I asked was is there a wiring diaghram of how to wire in a 120v photo cell to a 100w metal halide ballast.
I have 3 seperate lights that need a ballast. Each light has a bad or broken photo cell.
Just draw something that works.

Assuming the PC has 2 wires, it goes in series with the ungrounded conductor. Just be sure it is ballast rated.

Most photocells I have seen have three wires. 1 Active in, 2 Switched load out and 3 Neutral connection. Ensure that they are inductive rated and can handle the load. Most PC are rated for 4 to 8 Amps.