Hello everyone !
I have some questions about the F25T12 25 watt.
I am incharge of lighting in a small store that has about 35 4ft double bulb fixtures mostly with high power factor rapid start ballasts. I use to use the Sylvania 40 watt work shop bulbs rated at 12,000 hours, simply because I like waching them burn out often .
 A few years ago I started using the Sylvania 25 watt bulbs. They seem to be the same brightness. I also seem to get about the same life out of them, maybe a little less.
My first question is why does it say "not for use on ballast marked E"? Which I believe is all most all High Power Factor ballasts.
Next question can using these bulbs cause any danger as far as possably a ballast fire?
When using these bulbs like this am I saving energy?

By the way, I have not been having problems with ballast failers or anything like that

Thank you
Great site BTW

I'm not an expert on these lamps, but from what I've noticed, they are essentially F40T12's designed to be used in low power factor residential "shop light" ballasts. These types of ballasts already operate lamps at about 25w. So, a regular F40 tube rated at 40w will actually be underdriven on an LPF shop light ballast. Therefore, you could use a cheaper 25w shoplight tube, with its cheaper halophosphate phosphor (same as the old F40 Shoplite or Cool White lamps) and those tubes would be driven appropriately by the LPF ballast. Rated life is about 12,000 hrs. Since the entire energy consumption of a shoplight using two of these lamps is less than a high power factor "commercial" fixture with F40T12's, the lamps aren't required to have better quality phosphors as "E" rated 40w lamps must.

Now, if you use the F25 lamps on a "commercial" HPF ballast, the rated lifetime is now 6000 hrs as the tubes are now overdriven. They should be about the same brightness as a standard 40w T12 lamp though.

I prefer to always use the full 40w lamps, particularly as they have CRI=70 and higher, but I haven't seen any problems due to using the cheaper "shoplight" lamps.

I agree with Alain....the F25T12 lamps are electrically the same as F40T12 as far as what the ballast sees but designed to operate at a lower current. At my work, I've installing both F40 and F25 (whichever is on sale at the hardware) and found they usually perform about the same (ACE brand made by GE). Early on, when shoplite bulbs first came out, they were very short lived, especially the Sylvanias, but later on they all seem to go longer before burn-out.

As far as ballast danger, the only thing to avoid is using 34w lamps in one of those low power factor ballast designed for two F25 or F40 lamps. 34w lamps perform differently than 25w or 40w four foot lamps and will make LPF (or NPF) ballasts run hotter.

The 25w shoplite is an E-Pact exemption for residential LPF ballast. I have used these in 24/7 applications and gotten as much as 35,000 hours of burn time on HPF ballast. The government does not want people using full wattage CWs., hence the tricky labeling.

Ya I found out that the F34T12 on LPF ballasts trips off the thermal protecter. Also makes a bad burning smell

The 25w lamps are electrically same as 40w lamps, but the electrodes are optimized for lower power.  Life is on HPS commercial ballasts is typically shorter due to the elecrodes are overheated.

The house I'm moving into, I just removed several F40T12/25 shop lamps from many of the fixtures.  They aren't that old but already have severe blackening, especially compared to similarly aged Ecolux lamps.

They're specifically designated for residential ballast and meant to be operated at 0.25A.  The standard 40W is the same as IEC specs, but this one isn't.

Specs as listed in ANSI C78

Lamp abbreviation 25W/48T12/RS
Nominal wattage 25 watts
Nominal overall length 48 in (1200 mm)
Bulb designation T12 (T38)
Base G13, Medium bipin
Circuit application Rapid start, Low power factor (Lag)
Ballast (Shoplight)

Arc wattage (W) 24.5
Approximately cathode wattage
(With 3.6 V on each cathode) (W) 1.5
Total wattage (W) 26.0
Voltage (V) 106
Current (A) 0.250