sodium light on/off cycling

[mvafixit]

I do maintenance at a large complex.(11 building) Over the past few years we have started replacing our double 90w flood lights with Heath/Zenith SL-5676 high pressure sodium lights from Home Depot. Almost always we soon get an on/off cycling happening soon after but it seems to solve it by replacing the bulb. I have not seen any other reference from other people about this so I wonder if it something I am doing. I have one of those fixtures doing it again that went through that process about 1 1/2 years ago. We have had 150 w sodium lights last 5 years or so.
The fixtures are photocell activated and I wonder about that but we have had the same results in many locations where I am sure other lights aren't an issue. I taped over the cell once and had same results. The lights are on circuits with other flood and sodium lights with current ranging from 9 to 12 amps. All circuits are controlled by mechanical switching timers. The units has silver (or aluminum?) wire which I am marretting to a copper wire. I usually put on a paste to protect the contact. Any ideas.

[jnaas2]

Are they going on and off because the photo cell isnt located in the right area, and just curious but why are they on mechanical timers and also on a photo cell and whats the watt rating on the photo cell

[mvafixit]

answers

The fixture available at Home Depot comes with the photocell built in. I considered disabling it but that means opening the case and cutting the wire and rewiring. I don't know the rating of the photocell. It is built into it. We use the timer because all the outside lights of the building (breezeway and walking areas, and parking areas) are on these circuits. A few buildings we have rewired the walkway and parking areas to photocells for the circuit which I know could be a part of the problem if it was only those buildings.

[HayZee518]

check out the bulb itself. a lot of them are meant to be installed in [BASE UP or BASE DOWN] position. like the old mercury bulbs the firing pool of mercury is either base up or base down.

[596]

Having 2 photocells in series would cause some strange problems.

Heath Zenith is marginal brand, like so many things from HD.

Are you sure the voltage rating on the fixture matches what you have....meaning you are not putting a 240 volt fixture on 120, or vice versa? Some fixtures are multi-volt capable, and you have to wire that correctly according to the instructions.

[mvafixit]

thanks for the comments everyone

I think it is likely the problem is the bulb or the quality of the ballast.
I am sure the fixtures are only for 120v and there is only a black and white wire so I can't go far wrong. On two or three buildings there are photcells on the circuit as well as the built in one in the fixture and if they were the only ones with that problem I would suspect that. The fixture is self contained and the bulb can only be mounted in a hanging down position. I realize Home Depot doesn't necessarily mean the best quality but I thought Heath Zenith was a good brand name. I also felt the replacement bulbs were good but they seem to be having a shorter life than I expected. During the on times the bulbs glow very nicely but then go dark after 2 to 5 minutes. I therefore suspect the ballast but I would have thought others would have camplained about them also. This is why I wondered about our circuits or feedback from others with this problem. Thanks again.

[HayZee518]

mercury and high pressure sodium have an accessory installed at the factory called a "getter." when the tube is first fored up the getter vaporizes any extra gasses in the envelope. sometimes this getter creates a hot spot within the bulb which shortens it usuable life. you say the bulbs can only be mounted with the base up so look on the bulb shell it should say BU meaning base up.