Is it safe to say that when a ballast is blackened (burnt like) or leaking a black tar like substance that it is no good any more and needs replacement. I have noticed that when the ballast looks like that they still work, but do they work less efficiently?
If any ballast shows leakage of more that say a drop of tar where the wires enter, or if it appears that the label is burnt (not just yellowed) then it should be considered bad. My experience has been that ignoring those signs will eventually result in a total meltdown with lots of smelly smoke!! I've seen this happen even with "P" rated ballasts!
For those not familiar, "P" rated ballasts have a built-in thermal protector which is supposed to kill the input power before it completely burns up. But a fire is still possible if any of the following happen:
1) The fixture is left on and cycles on and off from the protector. It will still build up lots of heat, and possibly causing: 2) Failure of the thermal protector [contacts weld closed] or: 3) On 240v ballasts, some thermal protectors open only one of the incoming lines. If the ballast has a short to ground, current can still flow from the other hot leg and smoke it. (Haven't seen 277 ballasts fail like this, IIRC 277 is a phase-to-grounded[neutral] voltage.)
In short, if it looks bad, change it!! Cheap insurance against possible violent failure.
[edited for spelling]
[This message has been edited by mxslick (edited 12-01-2004).]
Sorry, I missed the efficiency question in my first post.
Based on the fact that the leakage usually indicates excessive temperature mainly caused by some internal fault, it very likely that the ballast is inefficient and drawing more than rated current. You could check actual current draw against the marked rating, assuming the label is still readable.
Such a ballast would tend to cause me greater concerns than how efficient it is.
I hve a question how old do balast have to be to have PCBS? and I have an old T12 fixture from the 50-60's buzzz that ballast goes but it still works and I like the look of the fixture but if the ballast goes will that old one have pcbs in it?
Theres always enough room in the junction box.You just need a bigger hammer