ECN Forum Forums General Topics of the Trade General Discussion Area 100 W HPS fixture issue

I have a customer with a 100W HPS fixture on an outbuilding. The fixture is photoeye controlled. Almost everytime that a large load starts in the house (A/C, sewage ejector pump, ect.), the light shuts off and eventually comes back on.

The outbuilding and house are both on seperate loadcenters and feed from the same main panel at the meter. It appears to me that this is caused by voltage drop. Correct?? I even switch the fixture circuit to the opposite phase and it still does it. Could this be simply a photoeye problem, or utility service voltage drop???? Any suggestions?

Possibly the transformer is over loaded by other services. What's the incoming voltage at night? It tends to be a little lower in the evenings then the day

+1 with sparky, check the voltage in the evening, and look at the size of the transformer, and its load. Call the POCO and ask for someone to come out and look.

This is in a rural area, only service on this transformer. voltage. Under start-up surge from A/C or sewage pump, I saw it drop to 112 for about 1/2 second. I switched the fixture to the "higher" phase (121) and it still dropped out under surge.

Merlin:
Did you ck the voltage at the fixture, or the source panel?

Sure sounds like a Vd issue...at the fixture.

One side higher than the other would indicate possible loose neutral issue.

It's probably voltage drop, but try a new bulb to eliminate that before you spend a lot of money on it.

I agree with jdelvin that it could be a loose neutral. When A heavy load start on this service, does any lights on the premises get brighter?

I agree with the possible loose neutral situation also. As far as the transformer, My house is the only load on a 15 KVA pole pig, it is about 60 feet from the pole to my meter, every time my 4.5 ton AC compressor starts there is a noticible flicker in the lights. Put this same load on a 10 KVA pot and it could pull down enough to turn the light out. What kind of meter did you use to measure the voltage when AC started? Most DVOMs are not fast enough to catch the dip, so it is likely the reading you got was on its way back up before your meter settled down. Just my 2 cents.

Rewire your High Pressure Sodium fixture across 230 VAC instead of 120 VAC.

I'm presuming it has a CWA ( Constant Wattage Autoformer ) with multiple taps.

I also suspect that the wire gauge used to feed it needs 240 VAC.

You've made no mention of the distance to the outbuilding.

Check if the photo-eye can be replaced with a 230 VAC sensor, too.

Every time its voltage pulls low it changes its logical state -- which is the primary cause for the HPS to cut out.