Energy Saving Question

<...1) 40 W fluorescent lamps with Electronic chokes....>

The savings will be nil as the power consumption will be the same.

<...2) CFL lamps with equivalent lux...

...3) LED lamps with equivalent lux...>

The savings will be the difference in the power ratings, multiplied by the on-time of the lamp, multiplied by the value of the energy in each case, assuming the power is on a per-kWh tariff basis. The calculation will be different if the facility is on a peak demand tariff.

Are we talking about troffers?

1) why back to the old 40 watt T12. The newer F32T8 have about the same or higher Lux output.

2) CFL Compact Fluorescent Lamps will cost more in the long run cost of replacements is higher

3) LED will save power and long term relamping cost but initial purchase is high. Whether you will be saving depends on the price of power down the road.

ozzb has it right. A 40 watt fluorescent lamp with a magnetic ballast and starter consumes a total of about 46 watts per lamp due to losses in the ballast.

Since the 32 watt T8 lamps will fit inside the same sockets, you can use them instead of the T12 (40Watt) lamps. The fixture can be reused if the ballast is changed to match the 32 watt lamp. Then the total watts would be closer to 32 watts per lamp with about the same light output. You can access catalogs on line to compare specifications and color selections.

A CFL relamp project would likely be much more expensive considering the cost of new fixtures and the labor to mount and wire them.

LED lamps perform slightly better than fluorescent lamps but the initial cost is still high.

Your BEST choice is to install the new 28W lamps and ballasts-

If you change out the lens with a new dropped face milk-white, you can install 2 of the "high power" lamps and new ballast in a 4 lamp fixture with 66 watts compared to the old 184 watts and nearly the same NET light delivered.

OR you can install 4 of the low level lamps 87 watts vs. 184 watts with about the same light output (again with new lenses).

OR, if you don't want to change lenses, use the mid-range lamps at 98 watts vs 184 and the same light output.

These new lamps also have a 24,000 hour MINIMUM life, vs the 20,000 hour "half life" (50% of the lamps will have failed) of "normal" fluorescent lamps.

One other item- you did not say what type of fixture you currently have.

IF they are the "old" parabolic fixtures, you DEFINITELY want to change the lenses and get rid of the parabolics. Those fixtures keep about 45-50% of the light bouncing around in the fixture. By changing to the 2 high output lamps vs the current 4 lamps, OR 2 low power lamps vs the current 3, you will actually get MORE light out with significantly less incoming power.

T12 and T8 refer to diameters of lamp tubes.

Thus a T12 lamp has a diameter of twelve eighths of an inch, or 1-1/2 inches.

Typically, a narrower lamp is more energy-efficient. Since the T8 is eight eighths of an inch, or one inch in diameter, it is a more energy-efficient lighting mechanism than the T12.

T-8 lamps are available a variety of lengths, and they also come in either straight or U-shaped lamps.

The Mercury issue:

Top-quality T8 lamps function with reduced mercury, a potentially harmful substance used in many lighting fixtures.

Although recycling is still recommended after these lamps are spent, these lamps are generally more sustainable than T12s.

For lighting with no mercury content whatsoever, check out LED lighting.

The Benefits of Retrofitting from T8 to T12

Retrofitting lamps from T12 bulbs to T8 bulbs is cost-effective and easy to do

Transitioning from T12 to T8 usually costs about $20 per lamp, parts and labor included (a US figure) - $2 in general with 200+ systems.

Installing T8 bulbs usually results in a five to seven year payback period in a commercial setting

If you cannot upgrade all at once, upgrade as old T12 lamps burn out

In Europe T8 is almost the only fluorescent bulb and is used with the same ballasts on 220/240 volts. While first providing a starting voltage and then functioning as "ballast" the 32 Watts bulb works with the same efficiency, because of the higher voltage applied.

The ballast is different from the 120/60 Hz version. Does it work this way in the US too?

There is forth option also, which may be much more effective:

Instead of changing the lamps, think of putting the occupancy sensors with Light sensitive sensor built in. Lamps will be ON, only if person is there in the area and ambient light is not sufficient.

Besides, try to use maximum of natural light.

This may save maximum energy.

All the best to your energy saving efforts.

What is wrong with T5 lamps?

The OP might try hiring an engineer to design a system - sounds like an office manager is trying to be cheap.

If an office has 4000 each 40 watt lamps would it not better be called a dungeon?

T5 lamps require a totally different fixture (with internal reflection/diffusion due to the high intensity light from the lamps0 so a significant cost and site disruption is involved.

Using a replacement T8 fits the same lamp holders in the same fixture, just a ballast change is required to maximize performance and extend lamp life.

Ballast life is typically 15 years or so, so changing these out (at worst) is just doing what will be required in a few years anyway and doing it as part of a defined, planned action rather than as a "one-of" sporadic event done 1000 times or more depending on number of fixtures.

On that same issue- typical "life" of most current F40/F34/F32 lamps is about 5 years, and lamp changes are sporadic and time-wasting (lamp change request entered into maintenance work list, getting ladders, locating new lamps, changing lamps, putting away ladders, etc.). By upgrading with new lamps and ballasts (and using the new 28 watt lamps) and assuming a typical 3,000 hour annual operating life (10 hour days plus some Saturdays) all will be running smooth for the next 8 years.

Assuming that lighting is about 40% of direct total electric usage- actually over 60% if you consider the energy usage of the A/C system (pumps, compressors, fans, etc.) then installing about 50% lower wattage lamps will cut your electric bill by about 55%-60%, depending on composition of the HVAC system. By the way, your HEATING bill might increase 10-15% due to less auxiliary heating from the lamps.

1) 40 W fluorescent lamps with Electronic chokes

By Using Electronic Chokes the Power factor will be improved enormously, As you said replacing 4000 lamps, it is 4000x40 = 160KW. if you have only a office area then it will be a good idea of doing such a change as cost is also a factor to be considered.

if the Place is part of a factory office then changing is not econmical as the Main switchgear might be having a Capacitor Bank taking care of the Power factor. And more over if you want to improve the P.F then option is yours as to change it to Electronic Chokes or not.

2) CFL lamps with equivalent lux

The lumens output for a 40W flouresecnt and 42W CFL is almost the same so there would be no advantage by changing it. only you will incurring high cost for the new fittings.

3) LED lamps with equivalent lux

your initial cost will be more and LED lamps for a office area of 250 lux is not a good option.

The Better options as said earlier in the previous posts are using flouresecent lamps with electronic ballasts and providing light sensors to control them if no occupancy is there.

1- Fl. lamps with magnatic chokes are x1.8 the declared wattage. you can save this amount with electronic choke plus noisless rapid start fl. lights.

2- CFL has a life cycle problem and replacement cost can be more due to frequent replacement.

3- LEDs are the talk of the day but initial cost is higher. I am sure if you are ready to invest initially you can save considerably in energy cost plus can be a green guy as an energy conservator.

I have no idea where the short life span of CFLs comes from. The lighting in my home consists of:

1) Fluorescent lamps

a) CFL

b) T5 tubes for light pools - electronic ballast dimmable

c) Circular fluorescents in some fixtures designed for that use

d) T8 tubes in cheaper fixtures - utility room & storage areas

2) Incandescent lamps in motion activated fixtures

3) LED night lamps

I have had zero problems with CFL life - haven't replaced even one the past three years. Cheap ones of anything from the bargain basket at the local big box are generally worth what you paid.

You can get varying guaranteed life periods for any new tube lamp - the longer life (up to 50 & 60,000 hours) are definitely more costly.

In another 5 years LEDs will be available at a far more attractive cost - maybe then I would use more.

Something I have read a little about are induction lamps - anyone know anything about them?

Lots of good ideas presented.

If you haven't already done so, you might try contacting a representative of your favorite fluorescent lamp manufacturer and ask him for a "system solution" for your conversion from T12 to T8. He will guide you through the cost savings calculations for the various systems mentioned.

The advantages of converting include a new ballast that has much less internal loss and lamps that come in standard wattages from 25 to 32 watts for a standard 4' T8. The different wattages come from the mixture of buffer gas consisting of argon and/or krypton. Lower wattage also means lower lumen.

The fixture can also suffer from poor performance if the reflecting surfaces are dirty or less reflective than a polished surface.

Note that high output lamps use more current and are somewhat less efficient in the numbers of lumens per watt you get. Use lumens to compare the amount of light you currently have. Your T12 catalog will list the typical lumen output rating for your current setting. Multiply the number of lumens times the number of lamps. That is what you will be replacing when you convert to any kind of lighting.