I have two 175 watt HPS fixtures that have been out of service for a few years that I reinstalled today. Upon installation and powering up, both these units light up for a while then go off. They immediately relight for a while and go off again continuosley. The one unit will light for only about a minute or two. The other one however will light for a longer period of time, maybe 10 minutes then go off. These are both Hubbel fixtures. Anyone got an answer for this? Is the ballast causing this or what? I can't see both of them doing the same thing. They were working when they were taken out of service the first time. Thanks in advance for any thoughts.

Did you say 175 Watt HPS are you sure it is 150 watt unit ?

Anyhow change the bulb first { make sure they are correct wattage to match the ballast } that useally take care of it.

second thing is that do both luminarie have photocell on each unit? if so get new photocell on it.

Merci,Marc

My mistake, yes they are 150 watt HPS. No, neither one have a photo cell. They are hard wired.

change the bulbs first that useally take care the issue but just watch out on 150 watts verison there are two types of them one them is 55 volt and other one is 100 volt verison.

so check the ballast little more closer to see if it say " 150W/55V or 150W/100V

The other thing is the arc tube length the 100 volter have longer tube than 55v verison

Quick note here any 150 w med based bulb are 55 volt only but on mogual based bulbs it can go either way so pay attetion to this details.

Merci,Marc

Thanks Marc. I will check on that.

Regards,
Kevin

That seemed to take care of the issue by simply changing the bulbs.I have never seen that problem before as a bulb cycling like that. Thanks again, Marc

Kevin

Merlin.,

The HPS do have very typical action when the bulb get near end of the life they will cycle on / off due the arc voltage requirement.

over the time the arc voltage rise and when get to the point where the ballast can not able keep the arc on it will go out when cool off it will relit with high voltage starter.

There are few non cycling HPS on market so when they get near burn out useally what they will do is change colour itself going from orange to white-bleuish colour or complety disabled the bulb interally one of the two way.

Merci,Marc

This is also the way to determine when Metal Halide and Mercury Vapor require re-lamping. Extremely common at end-of-lamp life. I actually find it useful. When they don't cycle, but simply go out, it could also be the ballast or a power issue.

Well explained by Marc.