Eight Foot Long Fluorescent Fitting. Calling All Old Sparks.

broadgage:

Many years ago, the common wattage of an 8 foot fluorescent lamp was 125 watts. Then in IIRC the 1970s a 100 watt 8 foot tube was introduced, intended to absorb about 100 watts in an existing fitting with an existing 125 watt ballast. The ACTUAL power absorbed by a 100 watt lamp on a 125 watt ballast varied a bit according to mains voltage, ambient temperature and component tolerances. It tended to average about 105 watts.


If you have a fitting with a 125 watt ballast, then either 100 watt or 125  watt lamps may be used without concern.


Later,  new 8 foot fittings were introduced with a ballast intended for the new 100 watt lamps. The ACTUAL wattage absorbed by a 100 watt lamp in one of these fittings also varied according to line voltage, temperature, and component tolerances, but tended to average about 95 watts.

If you have one of these slightly newer fittings intended for 100 watt lamps, then it wont reliably and correctly run a 125 watt lamp.

A 125 watt lamp on a 100 watt ballast MIGHT work under optimum conditions but might fail to start reliably at low temperatures or line voltage.

Thank you broadgage, I suspected that you would know the answer. I shall try to get more info and report back. The problem that I have found with old ballasts is that the electrical details printed on them can be burnt off due to the operational heat, and the details lost. If the old fitting is in the customer's house starting of the flu. should be o.k. If it is in an unheated garage problems may result in starting.


Z.

broadgage:

Many years ago, the common wattage of an 8 foot fluorescent lamp was 125 watts. Then in IIRC the 1970s a 100 watt 8 foot tube was introduced, intended to absorb about 100 watts in an existing fitting with an existing 125 watt ballast. The ACTUAL power absorbed by a 100 watt lamp on a 125 watt ballast varied a bit according to mains voltage, ambient temperature and component tolerances. It tended to average about 105 watts.


If you have a fitting with a 125 watt ballast, then either 100 watt or 125  watt lamps may be used without concern.


Later,  new 8 foot fittings were introduced with a ballast intended for the new 100 watt lamps. The ACTUAL wattage absorbed by a 100 watt lamp in one of these fittings also varied according to line voltage, temperature, and component tolerances, but tended to average about 95 watts.

If you have one of these slightly newer fittings intended for 100 watt lamps, then it wont reliably and correctly run a 125 watt lamp.

A 125 watt lamp on a 100 watt ballast MIGHT work under optimum conditions but might fail to start reliably at low temperatures or line voltage.

Thank you broadgage, I suspected that you would know the answer. I shall try to get more info and report back. The problem that I have found with old ballasts is that the electrical details printed on them can be burnt off due to the operational heat, and the details lost. If the old fitting is in the customer's house starting of the flu. should be o.k. If it is in an unheated garage problems may result in starting.


Z.