ECN Forum Forums General Topics of the Trade General Discussion Area florescent lights working on 90 volts

I went to check some lights in a Pediatric Clinic. Normally just have to replace a ballast. This one had a dual-lite emergency ballast in it, with 2 hot feeds. Lights would not work on emergency ballast. The regular ballast feeds through the emergency ballast(bunch of wires). There was no diagram for the wiring on the emergency ballast, so before I did anything I took voltage readings on the 2 hot feeds feeding the ballast. I had around 115 volts on one, and only 90 volts on the other one. I traced the conduit a little in the hallway above the ceiling and find that the wire that only has 90 volts is feeding other lights in the hallway with regular ballast, and the lights are working:D I wouldn't think they would work on that low voltage, but obviously there's a bunch of them working on it. I'm suppose to go back on a Saturday and try to trace the problem. I'm thinking that this may be the reason the emergency ballast is not working. Either the low voltage has burned the ballast up or it just won't "kick in" with that low voltage. Plus I'm sure the low voltage is not good for the rest of the lights. Any thoughts on what would make the voltage be low? Loose neutral somewhere maybe? It's looks like it's going to be a job trying to find it. This place is pretty big. I'll probably have to check some j boxes at random, starting close to the panel. Thanks for your input...

sparkync:

The 'E' ballast has an internal battery that provides reduced illuination from 1 or possibly 2 fluorescent lamps in the fixture, and should be on a 'nite lite (24/7) circuit, usually with any exit or other egress lighting.

Are you sure you were not 'reading' the 90 volts on the output?? (From the battery component)

IMHO, these ballasts are a PITA, but you have to live with it. You could find the wiring schematic at 'Dual-lite' BUT you need the model # from the ballast.

John, no I took voltage before it ever got to the ballast and even with the ballast not hooked up. I went to another fixture that didn't have the emergency ballast in it, and got 90 volts. I pulled up the wiring diagram on dual-lite, and it don't show 2 hot feeds feeding the ballast, but it says there may be other diagrams. On the cover of the fixture, it says "Caution, this fixture is fed from 2 power sources". So now I'm a little confused. I put in 2 calls to Dual-lite, but haven't got a response yet. On the 90 volts problem, I even checked my meter again to make sure it wasn't messed up. I took a reading on an outlet nearby and found 120 volts, so I know my meters ok. Thanks for the reply anyway. Hopefully Dual-lite will call me today. Steve...

sparkync:
You may have to dig deeper. Can you locate the source of the 90 volts? There may be an 'emergency power source' located in the facility.

Is there any info on the 'e' ballast?

Look around by the panel(s).

sparkync;

The link below will take you to Dual-Lite's "Somewhat Common" Fluorescent Battery Backup Ballast Wiring Schematic (PDF File):

UFO-3AW

Schematics on the last page (page 4).

There are Two Ungrounded Leads for the Battery Backup Ballast: "Switched Power" and "Unswitched Power".

I have a few questions to ask...

1: The Voltage Measurements you posted, were these taken L-G (Line to Ground), or L-N (Line to Neutral)?

2: Is there a readable Voltage between the Two Ungrounded Conductors feeding the Ballast (at the Fixture)?

3: Which Circuit is feeding the Em. Battery Backup Ballast's "Unswitched Lead";
the "115 Volts" Circuit, or the "90 Volts" Circuit?

4: If you turn off the Switch(es) controlling the Lights on the effected Circuit, does the Voltage on the "Unswitched" Circuit at the Em. Ballast change?

5: What is the length of the Switched Circuit? (from Panelboard to Fixture you are Shooting Trouble at),

6: What is the FLA (Full Load Amperes) of the effected Circuit - measured at the Branch Circuit OCPD?

7: What is the Voltage between N-G (Neutral to Ground) at the Fixture with the Switched Fixtures:
a: ON,
b: OFF

The issue appears to be poor makeup in One or more Fixtures.
Could be Open Common Neutral, Fried Wirenut(s), incorrect connections at Fixture(s), Open Neutral to Panelboard - Grounded at One (or more) Fixtures...
Or maybe a Voltage Drop issue from too many Fixtures on same Circuit.

Will wait for your reply.

-- Scott

Scott, I can answer a few of your questions now. I don't have the answers to the other ones yet. Will probably know in the morning; that's when I'm going to trouble shoot it some more. #1. I took voltage reading from Line to ground and line to neutral. Got 90 volts on both ways.
#2. I took voltage reading between the two and got around 34 volts I think. # 3. I'm thinking the 115 volts is feeding the "unswitched lead" and the 90 volts is feeding the switched lead. I'll have to verify that tomorrow.
The other questions I'll find out tomorrow. If it IS the switched lead that is 90 volts, then I'll start my trouble shooting at the switch. Could be a switch going bad. I have thought about two many lights on the circuit. I took a quick look at the electrical prints the other day and noticed a bunch of light that seemed to be on the circuit, but didn't have time to verify it. Thanks a lot for your questions. It will give me some idea of where to start tomorrow. Steve..

If the circuit is dropping 30 volts at a switch, it should be easy to find. For example, a 10 amp load and a 30 volt drop across a device equals 300 watts. That's a lot of heat.

Maybe start with voltage readings at the panel. It sounds like a bigger problem than one circuit, perhaps a bad neutral coming into the building.

twh, I've already checked the voltage at the panel and everything seems alright. 120 volts leaving all the single pole breakers (no double poles are there. Thanks anyway.

I wish I could be there with a cup of coffee to watch. My last guess is that there is a UPS supplying power to one hot. Good luck!

Steve,

Good luck with the Troubleshooting!
Hope you find the problem(s) easily, and without too much searching.

Will be looking for your update.

-- Scott