Loosing too many VHO Ballasts

[jrannis]

I was tempted to post this under the "lightning and power quality" topic like many people do, but I know better.

I went by a customers shop late yesterday to drop off some paperwork.
The building is just about 10 years old.
The shop area with 20' ceilings and a loft, has about 25 or so 2 lamp VHO fixtures.
The customer is loosing about 10 ballasts per year.
I checked a spare ballast, it is good for one or two F96T12VHO lamps
I looked at several fixtures and found one that had just turned off due to the internal thermal overload in the ballast.
I observed two new lamps in the fixture, F96T12VHO and a new, but very hot ballast in the fixture.
The fixture is mounted on bar joists and has plenty of ventilation.
The ballasts are rated for "outdoor"
The lamps turn dark at the ends after a short time in service.

Question:
I remember servicing VHO fixtures many years ago and didn't think that their was anything special about them. Some would even be date stamped 20 or 25 years old.
The customer has been buying both the lamps and ballasts at Grainger. I saw the box the lamps came in and looked at a ballast he had new in the box. They match.
What am I missing?

 

[jrannis]

I thought someone would have a quick and simple answer.

Any thoughts at all guys?
Im stumped on this one.

 

[ronmath]

Early blackening on ends of lamp usually indicates high or low voltage. Voltage should be within the ballast rating. Loose contacts with lamp holders. Make sure the lamps are securely seated in lampholders. Possibly a poor or cheap ballast. Another possiblity would be excessive on/off switching. I might recommend replacing these fixtures with a fluorescent high bay fixture with T8 lamps as the VHO lamps and ballasts have never been very reliable from my experience.

 

[jrannis]

Early blackening on ends of lamp usually indicates high or low voltage. Voltage should be within the ballast rating. Loose contacts with lamp holders. Make sure the lamps are securely seated in lampholders. Possibly a poor or cheap ballast. Another possiblity would be excessive on/off switching. I might recommend replacing these fixtures with a fluorescent high bay fixture with T8 lamps as the VHO lamps and ballasts have never been very reliable from my experience.

Much thanks,
I agree, I mentioned that the outrageous price he must be paying for the lamps and ballasts at Grainger would more than pay for the T8 fixtures.
each one of the VHOs are 1500s

 

[Dr.Sparks]

Voltage out of tolerance, loose/worn tombstones, high ambient temperatures, or possibly THD. Are there large motor loads in the facility?

 

[jrannis]

Mostly storage. I didnt see any equipment there.

 

[steve66]

My best guess would be high temp., or low voltage.

If the voltage is a little low, the ballast will compensate by driving more current to keep the power the same. More current will mean more heat.

Did you measure the voltage at any of the fixtures?

Any chance they are on a multiwire branch circuit?

 

[jrannis]

The place is not that big, I doubt they could have a VD problem.
Thanks for the heads up.
If an electrician didn't replace the ballasts, who knows what's going on.

 

[glene77is]

... possibly THD.
Are there large motor loads in the facility?

Interesting thought. :smile:
Turn On/Off spikes getting to the VHO tubes?