# 32w T8 to 25w T8



## nrp3 (Jan 24, 2009)

Has anybody done any large scale conversions of 32w to 25w conversions in office buildings? Either the 4ft or ubent bulbs, straight one for one bulb replacement. Was there any noticible light loss or flicker/striation? What brand?


----------



## DERITM (Apr 8, 2009)

We just finished a school retrofit 25W T8 from 32W. A change in ballasts was also required and these must have the letter "L" in the part number. If anything, the light output was better according to our light meter. After initial turn on (new multi voltage ballasts) no flikering or noise of any kind was observed. Worthwhile change.


----------



## nrp3 (Jan 24, 2009)

I was trying to avoid a ballast change. I was at a seminar put on by one of the major manufacturers and they felt as long as the ballast was within 10 years old (32w t8) that it should work. I like to try or test things out before selling them. I know one of my friends installed them in his shop a year or so ago and they didn't look quite right.


----------



## Electric_Light (Apr 6, 2010)

The Krypton filled 25W 48" T8 is susceptible to striation (visible moving rings or swirling effect inside the lamp) unless the ballast has anti-striation control (like GE UltraMAX or some Advance Philips Optanium). Other than, switching in a 25W in place of 32W doesn't guarantee 22% reduction on lamp power unlike replacing a 25W filament lamp in place of a 32W filament lamp on line voltage source. Ballast characteristics determine the actual power use.

See:
http://www.advance.philips.com/documents/uploads/literature/OptaniumBro_final2.pdf

Usually, 4' 25W lamps are made with the best RE80 phosphor available, so the output loss is minimal compared to lowest bid RE70 lamp (that cost like 98 cents a piece).

To see how much power you're saving, you need to have the system warm up to working temperature then measure the power usage of existing setup. Repeat the same with new setup, but you need to make sure the voltage at the time is close. (if old system was measured when voltage was 291v because it was warm and HVAC load was off, but when you measure the new system when the voltage is 263v because its hot and HVAC is running full load (or some other load), you're going to have a serious error in measurements. 

Today's all electronic ballast compensates for input voltage fluctuation and draws more amps when voltage goes down and vice versa, but older ballasts with passive power factor corrector do not. Those change in power usage (and light output) roughly proportional to voltage change from name plate rating. 

It's best to do side by side. Relamp a few fixtures on same circuit with 25W. Leave the same number of existing fixtures on same circuit with 32W. Compare the input current with a (true RMS) clamp meter. It's not ideal, but you can then multiply by line voltage to get approximate wattage since commercial use electronic ballasts are power factor corrected to be >0.90 and usually above 0.95. If you have a power analyzer, use it by all means

It's absolutely critical that you do the input power test along with the light meter test at the same time.


----------



## nrp3 (Jan 24, 2009)

I don't have a pq meter yet, the price i2 out of reach at this point. It is something I would like to have and I have been doing some reading about them. I have the book from ATP/Fluke. Ashamed to admit, but I hunt Ebay for deals on good used equipment. I don't have a light meter either. Most of my comparisons have just been with the eyeball and sure that you really need one to be able to compare apples to apples.

What they have is a mixture of single bulb strips 4 and 3 foot built into office furniture, 2 lamp ubent fixtures, and single bulb surface wraps in the common halls of apartment buildings.


----------



## Electric_Light (Apr 6, 2010)

nrp3 said:


> I don't have a pq meter yet, the price i2 out of reach at this point. It is something I would like to have and I have been doing some reading about them. I have the book from ATP/Fluke. Ashamed to admit, but I hunt Ebay for deals on good used equipment. I don't have a light meter either. Most of my comparisons have just been with the eyeball and sure that you really need one to be able to compare apples to apples.
> 
> What they have is a mixture of single bulb strips 4 and 3 foot built into office furniture, 2 lamp ubent fixtures, and single bulb surface wraps in the common halls of apartment buildings.


Can you even get the 25W U-Bent?


----------



## nrp3 (Jan 24, 2009)

This was put on by Philips and they claim to have a 25w ubent. I don't remember which one, but looking at the catalog, #FB32T8/TL841/6/EA/ALTO 25 Watt looks like one.


----------



## Electric_Light (Apr 6, 2010)

nrp3 said:


> This was put on by Philips and they claim to have a 25w ubent. I don't remember which one, but looking at the catalog, #FB32T8/TL841/6/EA/ALTO 25 Watt looks like one.


Must be new


----------



## kbsparky (Sep 20, 2007)

Electric_Light said:


> The Krypton filled 25W 48" T8 is susceptible to striation (visible moving rings or swirling effect inside the lamp).....


We call that the *Ghostbuster* effect. :blink: Looks like the output from those nuclear particle accelerators used in the movie. 

Simple remedy is remove the tube, reverse it, and reinstall it. Works every time for me .... :whistling2:


----------



## Electric_Light (Apr 6, 2010)

Here's my findings. Test environment at 75F in stand still air. 

Standard lamps respond much more to temperature rise than Krypton lamps. In bold is ballast spec sheet data, other values are measured.

Ballast used for test was a programmed rapid start Universal Lighting B332PUNVHP-A, designed to operate 2 or 3 lamps, operating 2 lamps at ballast factor of 0.99 as stated in sheet. 

Here's my measured [email protected] 

:
F48" T8 25W /841 Philips

50W enclosed 
52W open 
*50W* 

F32T8/841 32W Philips 
59W enclosed
68W open 
*64W*

http://www.unvlt.com/productLines/ap_sheets/ELFB/B332PUNVHP-A.pdf


Usually anything with a cover would be operating under enclosed conditions, so 50/59, a 15% reduction in power, not 25/32 = 22% reduction the simple lamp wattage values may suggest

This also only represents the performance with this ballast. Each ballast will handle 25W lamps differently, but one thing I've seen consistently is that standard lamps change in power consumption to a greater extent as a function of ambient.

Anyways, whatever testing you do, allow the system to warm up to normal operating conditions and light reading and input power should be taken at the same time.

Use the Kill-A-Watt power meter from Home Depot. It is the only device I know that performs fairly decently for such application compared to a lab equipment (which is a pain to setup, so I usually use the Kill-A-Watt for stuff like this). It is $30-40.


----------



## nrp3 (Jan 24, 2009)

I am curious, looking at that data sheet for the ballast, why does the power factor drop at 277v?


----------



## Lighting Retro (Aug 1, 2009)

nrp3 said:


> I am curious, looking at that data sheet for the ballast, why does the power factor drop at 277v?


power factor, or amp draw?


----------



## nrp3 (Jan 24, 2009)

Power factor. Although on closer inspection it says greater than, but seems to be less for 277.


----------

