# DIALux - 25W T8 .ies adjustment



## qbarnes (Apr 7, 2015)

Hi y'all. Looking for an .ies file to model a 25W T8 setup has been pretty tough. The majority of fixtures automatically use a 32W T8 for their .ies file. My question:

If I know the fixture, is it accurate to manually adjust the lumen output w/in the luminaire settings in DIALux? (ie, from 2830 mean lumens for the 32W T8 to 2280 for the 25W T8)

Thanks


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## Electric_Light (Apr 6, 2010)

qbarnes said:


> Hi y'all. Looking for an .ies file to model a 25W T8 setup has been pretty tough. The majority of fixtures automatically use a 32W T8 for their .ies file. My question:
> 
> If I know the fixture, is it accurate to manually adjust the lumen output w/in the luminaire settings in DIALux? (ie, from 2830 mean lumens for the 32W T8 to 2280 for the 25W T8)
> 
> Thanks


Hey, 
I'm glad you're showing interest in this awesome technology rather than being fixated on LEDs. 

*T8 is an anomaly* as it's the only thing where the real world ballast factor and spec sheet ballast factor deviate significantly. Spec sheets assume 1.0, nearly always. I would use 2,000 to 2,115. This is assuming the more typical 0.88-0.9 BF, then the lamp's mean lumen depends on the type you use. The extra long life is a bit less. 

Some IES spec sheet uses 700 series lamps while some uses HPT8, so that's why you see 2700 lumens on some while 2950 on others. 

If you're using initial lumen value on the standard life 25W, it could be around 2,250 lumens. 

If you need a higher precision value, you need to use the values from the lamp datasheet and ballast factor for the specific ballast when spec sheet and calculation war could affect the bid award decision, but otherwise, I think 1800 on "L" ballast, and 2,100 on typical/N ballast is close enough. 

http://www.gelighting.com/LightingW..._4_Ecolux_25W_Lamp_SellSheet_tcm201-21073.pdf


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## randolph333 (Feb 10, 2015)

Does DIALux allow you to specify a lighting loss factor? A quick and dirty hack for this is to just divide lumen output of the 25w lamp by that of the 32w lamp and multiply your actual LLF by that. As EL says, for better precision, you have to consider the ballast factor.


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## Electric_Light (Apr 6, 2010)

25W lamps can have issues if used with older ballasts that don't have striation control or it's exposed to air draft. If the room is too chilly to walk around in t-shirt and shorts, it will need a breakage protection sleeve. Not the pre-coated stuff. You need the external tube not so much to protect from breakage, but to keep it warm. Else you will have terrible performance. 

28W/841 is roughly the same as F32T8/741 and has less nuisance/compatibility issues than 25W. 

They're both good in enclosed troffers or wrap arounds. Not so much in strips without a sleeve cover. 

When 25 or 28 can't be used, for garage and such due to low cold start requirements, you can use 32W 800 series (2950) or HPT8 32W (3100) on a "low" ballast". 
----
Anyways, for calculations, figure out the lamp lumens they gave in the ies.
Put the new in there and multiply by 0.88


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