T 5 lamps

[Jim W in Tampa]

Jim, the 54s are high output versions while the 28s are the standard T-5 wattage for that length. The pins are the same so IMO it is a real pain.

I service a facility that uses 100s of the 28 and 54 watt versions and the maintenance guys can never seem to install the right lamp size into the fixtures.

I double checked and the lamps say 28 temp #3500.Hopefully the reading is simply wrong but with the amount of power used to operate this building i dought it be noticed.

 

[weressl]

Bit confused on wattage of t5.They say 28 watts for the 4 footers.Have 40 of them installed 40 x 28 = 1120 watts but they are using almost 20 amps at 120 wich is 2400 watts.Am i missing something ?Ballast amps are 1 for 2 lamp fixture.

Use the ballast amperage listing for the SPECIFIC voltage AND tube size. Note that the T5/T/8/T12 ballast are not necessarily interchangeable. In other words you can't use a T8 tube on a ballast that lists only T12 tubes.

Remember the 80% circuit loading rule, eg. a 20A CB can only be loaded to 16A.

 

[weressl]

I did and my concern is the numbers just dont add up.So on the poco side that i get billed for does the 28 watts become real or is the ballast amps real cost ? If so they are no bargain.

It is the ballast/tube combination that needs to be evaluated. Ignore the Amps as you won't know the actual power factor of the individual ballast as it is often listed as "high power factor" or "better than 0.85 pf" ballast.

The ballast manufacturer will list on their detailed technical literature the actual wattage used by the ballast for each lamp-ballast combination. That is step one. Step two in determining the economy of the installation is looking at the lamp lumen output and dividing it by the watt consumed by the ballast. That will give you efficacy, the indicator of how much "light" you get for each watt consumed. Of course the higher, the better.

Some ballast manufacturers used to play tricks that would reduce the actual watts consumed per fixture BUT the light output was also reduced.

Tube life and CRI(color rendering index) is also important. A longer life may justify a slightly higher cost bulb and a higher CRI will "appear" to be brighter, it gives the sensation of having a better lighting for the same wattage.

 

[iwire]

Remember the 80% circuit loading rule, eg. a 20A CB can only be loaded to 16A.

That is not the entire story and leads people to believe that is what the NEC says.

Per the NEC a circuit can be loaded to 100% for periods not exceeding 3 continuous hours.