I was asked to install a new High Pressure Sodium fixture near an existing one. From the existing fixture I conduited 50 feet and set the new fixture. Both of these fixtures are controlled by a photo cell on the roof. The existing fixture was existing and old. It must have had a bad starter because it would go on and off at regular intervals. When I first installed the new fixture and tested it, the old and new fixture would "take turns" being on. I wasn't sure what was going on with that. I do know neither had their own photo cell.
Now two months later, the old fixture only blinks and the new one doesn't work. I tested the voltage at the new fixture (feed 120V) and at the socket (54V), so I think the transformer is shot.

Here is my question. I can see why the old fixture is not working (old), but could a problem with that fixture ruin the new fixture?

Let me know if I left out any important details.

Many thanks,
Byron

Hello Bwise;

From the descriptions you have given, it sounds like Lamp failure on both fixtures.
HPS Lamps will cycle on/off when they near the end of their "Life" - more frequently as age increases (age = operation hours).

These must be 150 Watt (or less) HPS Lamps with Medium bases - which would be appropriate from the 54 Volts measured at the Lamp Holder (Med. base socket). These Lamps are 55 Volt Lamps.
If the Lamps are Mogul Base, then the open circuit Voltage is kind of low, and a Ballast replacement may be required.

Be sure the Ignitor on the newer fixture is operational, by installing a known-working HPS Lamp of the same Wattage in the fixture and powering it up. If Lamp does not start, suspect Ignitor failure.
If you have an equivalent, known-working Ignitor, swap it out with the existing Ignitor in the fixture being tested, then power it up to verify Lamp starts.

One last thing - or two :
<OL TYPE=A>

[*] Verify correct wiring between Lamp, Ballast and Ignitor,

[*] If a PF Capacitor is used, verify it is connected on the "Input" side of the Reactor coil... where the 120 VAC circuit connects,

[*] Verify the Reactor's leads are connected to the correct "sides" - e.g. Input side to branch circuit "hot" wire.
</OL>

If you need wiring Schematic assistance, check the Technical Reference section of ECN for H.I.D. Ballast Schematics.

Let us know of the outcome - and most of all... Good Luck!

Scott 35

edited to fix a blunderful statement!

[This message has been edited by Scott35 (edited 03-15-2005).]