I was always under the impression that if you have a lamp out in a fixture than it is creating more of a strain on the ballast, or a greater strain on the other lamps that are still working. Is this true or am I making this up on my head?
Strain on lamp, yes and no. ballast, not usually.
Almost all standard T8 ballasts operates the lamps at 85-88% light output.
If you remove a lamp on a 4 lamp ballast, the remaining 3 lamps operate around 100%. (BF 1.0)
3 x 1.0 = 3
0.87 x 4 = 3.5
Suppose you're running 3 lamps (its permitted by ballast manufacturer in this case), but one of the lamp fails. Now, the remaining two lamps will probably operate 1.0+ BF.
Usually the lamp manufacturers permit up to 1.2 BF for high output application, but anything beyond voids lamp warranty.
Or total output is about 85%, not the hopeful 25% reduction, because some, but not all power gets allocated to remaining lamps.
If ballast maintains the same efficiency, you'll be getting 15% reduction in output. The reduction in power maybe greater or lesser than 15% depending on design.
You should specify PARALLEL lamp operations whenever you can. Programmed start is usually series, but parallel is available. Series means that if one lamp goes out, a string goes out.
The probability of one going out is greater than all three going out separately, so if one goes out whole string goes out. As such, series design significantly shortens group re-lamp interval.
As I mentioned, GE UltraMAX sells on holding same lamp ballast factor even when one or more lamp fails preventing lamp stress and improve the ability to fine tune by de-lamping.
Where did the OP say these were fluorescent fixtures? Did I miss something?
Everybody inferred it is for fluorescents and they are almost certainly right. If this were a DIY site this assumption might have less foundation.
Many ballasts support more than one lamp count configurations as per the official specifications, but the label on the ballasts don't necessarily tell you every possible approved usage.“OR” is one of those very tricky words.
Ballasts are sold to be installed as per the required lamp count not as a reflection of 2 or 3 lamps burning in a fixture at any one time, or one burning out.
Frankly it’s my general understanding that all fluorescent ballast are wired in Series.
Frankly my interest was sparked by the fact that the levels of the ballast factor of this new product was so low.
Z1, welcome to the forum!The manufacture of a fixture I installed told me that if I run one lamp in this two lamp fixture if could catch on fire. The fixture has two 13watt CFL's.
Can that be right?
The manufacture of a fixture I installed told me that if I run one lamp in this two lamp fixture if could catch on fire. The fixture has two 13watt CFL's.
Can that be right?