Grounding

[EPC]

I was at a site that had new 120V ballast and lamps installed on a 208/120V utility connection. The owner is complaining that the electronic ballast are failing frequently (about 40 out of 416 in 6 months). At the incoming panel the neutral has a ground connection to the water pipe (Measured at 32 ohms). The phase current is about 150A, with about 10 amps in the neutral and near zero in the ground lead to the pipe. At the main panel I did not see a bare ground wire going to any of the feeders. In looking at a the lighting panel there was not any ground wire coming in or going to the lamps.

The building was installed in the early 1970's and may not have required the ground wire then. Since then the incoming utility transformer has been replaced and the area lights have new ballast and lamps (fixtures are the originals). When this type of rework is done, does the code require that the ground wire be added? The equipment ground is whatever the steel conduit provides. I do not know if the lack of a ground wire is part of the failure problem and I am grasping at straws to find a possible cause other than bad ballast.

 

[iwire]

The code does not require a grounding 'wire' even today.

The steel raceway is an acceptable grounding conductor.

 

[ron]

For a fluorescent fixture to work properly, it needs to be bonded well.
The steel raceway is an acceptable grounding conductor per NEC as a minimum. Is it good enough for operation, who knows?

This is from the Universal Ballast Website.
Appendix E: Grounding

Ballast cases and fixtures must always be grounded. The ballast case may be grounded to the fixture or otherwise connected to ground. It would be hazardous to make contact with an ungrounded fixture or ballast when in operation. Neglecting to properly ground the ballast and fixture may result in the failure of certain lamps to start.
If improper grounding is suspected, check for poor contact due to excessive paint on the fixture, loose mounting of the ballast or surface rust, which may be impeding electrical contact.
Starting Aid

For reliable starting, each lamp must be mounted within the following distances of a grounded metal fixture, or grounded metal strip running the entire length of the lamp.

• T12 Rapid Star: 1/2 ?
• T12 Slimline, 800ma or 1500ma Rapid Start: 1?
• T8 Rapid Start: 3/4 ?
• T8 Slimline: 1-1/4 ?

 

[iwire]

If the fixture is grounded at all, it is sufficient to make the lamps light.

 

[stew]

One other thing you may want to look at is if any of theses strings of fixtures are on mwbcs. My sense is yes and and I have found more than on instance where this problem killed ballasts prematurley. In one installation I found the loose nut in a j box which was the front end of the circuit. I hade been changing ballasts at this warehouse frequently and even had some fail quickly after installing. Found the neutral problem and corrected it and now my ballast replacement business there has dropped of to nothing alas. Oh well the customer is happy anyway and thinks I am a genius.(little does he know......)

 

[EPC]

Grounding

In 'STEW' reply what does 'mwbcs' stand for or mean?

 

[iwire]

One other thing you may want to look at is if any of theses strings of fixtures are on mwbcs. My sense is yes and and I have found more than on instance where this problem killed ballasts prematurley.

I am going to have to say that is simply untrue, no fact in that at all.

Perhaps there were incorrectly installed multi-wire branch circuit but a correctly installed multi-wire branch circuit will not kill ballasts.

 

[iwire]

In 'STEW' reply what does 'mwbcs' stand for or mean?

Multi-wire Branch Circuit

Branch Circuit, Multiwire. A branch circuit that consists
of two or more ungrounded conductors that have a voltage
between them, and a grounded conductor that has equal
voltage between it and each ungrounded conductor of the
circuit and that is connected to the neutral or grounded
conductor of the system.