T8 vs T12 lighting savings

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dm9289

Industrial Maintenance Electrician
Location
Pennsylvania
Occupation
Industrial process repair/ maintenance Electrician
I work in a old plant where we are replacing about 300 t12 ballasts and 34w lamps with t8 retrofit ballasts and 32w t8 bulbs.

Is there any substancial energy savings in doing this? Especially since this involves buying new ballasts and bulbs and discarding and paying for removal of the old equipment.

What if any consequence is there in putting a t8 bulb in a t12 ballast and vice versa?
 
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gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
120123-2126 EST

dm9289:

Go to Home Depot and buy a Kill-A-Watt EZ, about $30.

Somehow get a light meter.

Setup an appropriate test setup to compare a new T8 fixture with one of your current fixtures.

It would be desirable to set up a Variac so you can maintain an approximately constant 120 V. If you do this I can provide further information.

The Kill-A-Watt EZ can measure V, I, W, VA, PF. You may need to allow the light to be on for a while, at least a few minutes, to establish a stable condition.

Your new fixtures (ballast is electronic and is not likely PF corrected) probably have a much worse PF than the magnetic ballast units. A large number of these might be a problem. Electronic ballast can not be PF corrected simply by a parallel capacitor.

Some uncontrolled measurements I just made.

Hardware store quality T8 with electronic ballast, 4'.
124.1 V, 0.77 A, 56.7 W, 96.2 VA, 0.58 PF

Several years old hardware store T12 with electronic ballast, 4'.
124.2 V, 0.74 A, 65.4 W, 92.0 VA, 0.71 PF

Magnetic ballast 8' Slimline, one fixture. About 40 to 50 years old, might have newer ballast.
123.7 V, 0.88 A, 99.1 W, 109.6 VA, 0.90 PF

Different 8' Slimline, about same age, but ballast age unknown.
123.6 V. 0.97 A, 114 W, 120 VA, 0.96 PF.

I think that the T8 and T12 bulb characteristics are sufficiently different that a T8 in a T12 fixture could be a problem. That may not be the case for a T12 in a new electronic ballast designed for a T8. Search the Internet on that question. I saw a discussion somewhere but I don't remember the details.

.
 
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