LED lighting in new buildings

[Electric-Light]

I actually trust the LED depreciation numbers more than the T8 numbers. Many of the LED estimates have turned out to be conservative as they get more data.

It sounds like you might have some doubts about T8 durability. Page 11 supports what I said earlier on RE80 T8 lumen maintenance.
http://www.pnnl.gov/main/publications/external/technical_reports/PNNL-22727.pdf

The unusually high performing LED is the Philips L-Prize, which was very expensive. It was about $50 for a 940 LM lamp and it was more of a publicity generating product than anything. Something unusual about this lamp is that phosphors are physically separate from the LEDs.

Solid state fluorescent lamps(LEDs) as well as normal FL lamps benefit by lower intensity operation to increase lumen maintenance and lumens per watt. In quest of lower production cost, some consumer LED lamps have actually come down in specs. CREE brand for example uses less than half the number of LED chips and drive them harder. This lowers the LPW as well as lumen maintenance. T5HOs and CFLs don't hold their lumens as well as T8 for the same reason.

Premium RE80 4' T8 lamp-ballast systems are 100-103 lumens per watt and the most important thing from here on is using a high efficiency fixture.

T5HO is a good choice for high-output applications like corridor or high-bay
You can get about 90 LPW delivered with premium efficiency fixtures.
Examples for 18-20K lumen per fixture range generally used to replace 400W MH

High efficiency...http://www.gelighting.com/LightingW...UltraStart_Watt-Miser_System_tcm201-22261.pdf

Or long life...
http://www.gelighting.com/LightingW...4_T5_Starcoat_Ecolux_XL_F54T5HO_SellSheet.pdf

In summary, fluorescent systems can provide a maintained output level in the 80-90 LPW range while LEDs speculated maintained performance can be 70-110 LPW, but in applications competing with linear T5HO and T8 lamps, cost per million lumens is far excessive. At common commercial and industrial utility rates, the simple payback can exceed ten years just for the fixture price difference. In the real world, proper adjustments should be made for time value of money which will extend the time or even eliminate the possibility of breaking even.

When I compared the prices on 100lm/W Philips LED retrofit kit vs 85 lm/W FLUORESCENT ES8 kit+2 HPT8 60,000 lamps, the LED was $17,000 more expensive per million lumen. This thread is about new buildings, but this cost gives a good general sense of what you might expect in cost difference between premium T8 vs LED fixtures. The LED option may turn out to be the Least Economic Design.

And the T8 numbers seem to be really dependent on starting intervals - put a T8 in a toilet room with an occupancy sensor and you either have to use a rapid start ballast which uses more power, or the lamp life will tank.

This was true years ago. Lamp cathodes were left on after start. The current NEMA Premium programmed start ballasts pre-heat, start and turn off the heaters, so they do not use more power.

There is also step dimming that dims down all the lamps instead of shutting off some lamps. This one can go back and forth between low and high modes without lamp life reduction or starting delay and less expensive than full range dimming.

Dollars per million lumens is a whole different subject.

All of those things above add up to $/ML. Many LED fixtures have bells and whistles to justify the higher cost as they're not able to come up with economical stripped down version.

 

[Fitzdrew516]

Now that LED lights are popular do you think designers of new construction will continue to use 277 lighting circuits?

Of course. I use them all the time when I design a lay out. If you have 480 why not? 277 is better for multiple reasons: More lights on a circuit, less voltage drop to worry about, smaller step down transformers, overall less opportunities for efficiency losses, etc. It's kinda like saying "now that motors are becoming more efficient do you think designers will continue to use 480v?"

-Drew

 

[majorminotaur]

Question, do they make 480 volt indoor LEDs other then Highbays?

Don't have a code book with me but I believe its against NEC to use higher than 277v on luminaires that are lower than a certain height (this might explain why some high bay 480v exist). Check section 410.

 

[mbrooke]

Don't have a code book with me but I believe its against NEC to use higher than 277v on luminaires that are lower than a certain height (this might explain why some high bay 480v exist). Check section 410.

Ok, that makes sense now, I hadn't thought of that :slaphead:

Found this in 210.6 Branch-Circuit Voltage Limitations. Is this the correct one?

(D) 600 Volts Between Conductors. Circuits exceeding
277 volts, nominal, to ground and not exceeding 600 volts,
nominal, between conductors shall be permitted to supply
the following:
(1) The auxiliary equipment of electric-discharge lamps
mounted in permanently installed luminaires where the
luminaires are mounted in accordance with one of the
following:
a. Not less than a height of 6.7 m (22 ft) on poles or
similar structures for the illumination of outdoor areas
such as highways, roads, bridges, athletic fields,
or parking lots
b. Not less than a height of 5.5 m (18 ft) on other
structures such as tunnels
Informational Note: See 410.137 for auxiliary equipment
limitations.

(2) Cord-and-plug-connected or permanently connected
utilization equipment other than luminaires
(3) Luminaires powered from direct-current systems where
the luminaire contains a listed, dc-rated ballast that provides
isolation between the dc power source and the
lamp circuit and protection from electric shock when
changing lamps.
Exception No. 1 to (B), (C), and (D): For lampholders of
infrared industrial heating appliances as provided in
422.14.
Exception No. 2 to (B), (C), and (D): For railway properties
as described in 110.19.

 

[kwired]

Ok, that makes sense now, I hadn't thought of that :slaphead:

Found this in 210.6 Branch-Circuit Voltage Limitations. Is this the correct one?

Doesn't restrict most 480 volt luminaires very much though. To get more then 277 volts to ground one must have a corner grounded delta system or two wire 480 volt system, otherwise most other sources capable of delivering 480 volts will have either 240 or 277 volts to ground and are within the requirements of that section.

 

[mbrooke]

Doesn't restrict most 480 volt luminaires very much though. To get more then 277 volts to ground one must have a corner grounded delta system or two wire 480 volt system, otherwise most other sources capable of delivering 480 volts will have either 240 or 277 volts to ground and are within the requirements of that section.

Ok, never mind. Read it wrong.

Is the choice of 277 simply a historical one or are 480 volt ballasts just more complex to make?

 

[kwired]

Ok, never mind. Read it wrong.

Is the choice of 277 simply a historical one or are 480 volt ballasts just more complex to make?

My guess is somewhat a supply/demand thing.

Lots of commercial applications demanding either 120 or 277 volts.

Most demand for 480 volts is in high bay industrial or roadway lighting - in places where 120 or 277 is not necessarily readily available and or the runs are long and they would simply prefer higher voltage anyway for voltage drop reasons.

 

[mbrooke]

Ok makes sense. But still for indoor lighting like a grocery store pulling one less conductor is a save.

 

[Fulthrotl]

Ok makes sense. But still for indoor lighting like a grocery store pulling one less conductor is a save.

the flexibility of a MWBC was, and remains pretty compelling. the other aspect is that
480 takes 2 pole breakers. three single pole breakers with a neutral will cover an awful
lot of light fixtures, and while you now need breaker ties, that wasn't always the case,
leading to lots of fun and merriment when you split a neutral that still had two circuits
being handled by it, above a t bar ceiling, in the dark.

 

[mbrooke]

the flexibility of a MWBC was, and remains pretty compelling. the other aspect is that
480 takes 2 pole breakers. three single pole breakers with a neutral will cover an awful
lot of light fixtures, and while you now need breaker ties, that wasn't always the case,
leading to lots of fun and merriment when you split a neutral that still had two circuits
being handled by it, above a t bar ceiling, in the dark.

Of course, but you can always dispense the neutral at 480 volts as done in parking lot lights. Around here nearly all of them are 480 volts. Done via 3 pole breaker.