CFL vs linear fluorescents?

StaggeringGoat · Oct 5, 2011

I've got a 40x60 shop that currently only has ten 2xT8 fixtures for a blazing <24 lumens/sq ft. I need more lighting on a second switch...I'm used to >200 lumens/sq ft in my old shop.

This is a shop condo that I lease so I don't want to do anything too permanent or expensive. I was planning on adding more T8s until I'm happy but mounting them to the metal framing/ceiling is turning out to be trouble.

I've noticed that 19w 5000k CFLs are only about $2.50 each when ordered in bulk. I could buy like 30 of them and just use some cheap ceramic sockets and scatter them all over the shop instead.

Is there any reason why linear T8 type lighting would be better than CFLs lumen for lumen? The fixtures are more expensive, the tubes are more expensive, and they're harder to mount. They give more ceiling clearance but I've got 18' ceilings. T8s are slightly more efficient than CFLs, but that isn't much of a concern.

Charles (in GA) · Oct 5, 2011

Not sure how high they would be mounted. If more than 8-10 ft, I would consider some larger bulbs. I know, more expensive, but you get what you pay for.

THIS THREAD by veno, mounted 105w CFL's in porcelain sockets with reflectors, in a 40x50 steel building with the lights mounted ~14-15 ft off the floor.

Bigger bulbs equals fewer bulbs and fewer sockets and less wiring to run and secure.

Charles

mrb · Oct 5, 2011

remember, even 19w CFLs draw their current in spikes of over an amp. Dont go thinking youre going to put 75 of them on one circuit.

StaggeringGoat · Oct 5, 2011

mrb said:
remember, even 19w CFLs draw their current in spikes of over an amp. Dont go thinking youre going to put 75 of them on one circuit.

Can you elaborate on that? How many could a 20A circuit handle? 30 of them is only 570 watts.

mrb · Oct 5, 2011

StaggeringGoat said:
Can you elaborate on that? How many could a 20A circuit handle? 30 of them is only 570 watts.

do some research on power factor. CFLs have a very poor power factor, usually .4 to .7

I put a 13W CFL on a meter that is able to capture short bursts of current draw and that 13w cfl needed 1.2 amps. Realize this is reactive power that isnt billed for, but its current that is flowing in the circuit and needs to be accomodated.

The guy here with a bunch of 105w CFLs had his circuit breakers rattling from them being hammered with a 40 amp current spike 120 times a second....

StaggeringGoat · Oct 6, 2011

Charles (in GA) said:
THIS THREAD by veno, mounted 105w CFL's in porcelain sockets with reflectors, in a 40x50 steel building with the lights mounted ~14-15 ft off the floor.

Bigger bulbs equals fewer bulbs and fewer sockets and less wiring to run and secure.

I really like that setup. Do you think the reflectors really help much? I have a similar ceiling to that but it is completely white.

I was thinking about going with one of those splitters and using two CFLs per fixture, because 2x 19w is cheaper than a 42w. If I have a ton of CFLs I expect a few to die so it wouldn't be so bad to lose a $2.50 bulb, I'd be pissed if a 105w bulb died.

mrb said:
The guy here with a bunch of 105w CFLs had his circuit breakers rattling from them being hammered with a 40 amp current spike 120 times a second....

Hmmm...the ones posted above seem to work ok on a 15 amp circuit? How am I supposed to know how many 19w bulbs will work on a 20A breaker if I can't go by wattage?

I could really go nuts with the bulbs but now I'm not quite sure how to wire them? Say I start with 30x 19w CFLs or 570 watts. Will 12 gauge wire be sufficient? Could I use a larger breaker with the 12ga wire for the CFLs?

mrb · Oct 6, 2011

StaggeringGoat said:
I really like that setup. Do you think the reflectors really help much? I have a similar ceiling to that but it is completely white.

I was thinking about going with one of those splitters and using two CFLs per fixture, because 2x 19w is cheaper than a 42w. If I have a ton of CFLs I expect a few to die so it wouldn't be so bad to lose a $2.50 bulb, I'd be pissed if a 105w bulb died.

Hmmm...the ones posted above seem to work ok on a 15 amp circuit? How am I supposed to know how many 19w bulbs will work on a 20A breaker if I can't go by wattage?

I could really go nuts with the bulbs but now I'm not quite sure how to wire them? Say I start with 30x 19w CFLs or 570 watts. Will 12 gauge wire be sufficient? Could I use a larger breaker with the 12ga wire for the CFLs?

here is a good read on the subject http://www.cliftonlaboratories.com/compact_fl.htm
"Although the average power consumed by the CFL is 21.2 watts, the peak current is 1.17 amperes. And, current is drawn only for 2.6 milliseconds for each half-cycle. At 60 Hz, a half-cycle is 8.33 ms, so the lamp's full required power is consumed over about 31% of the AC cycle."

no you cant put bigger breaker on #12 wire for lighting

When doing your lighting circuits, figure for around 1.25 amps per cfl bulb. Its because the CFL doesnt draw its power continuously like a regular bulb does. It draws its power in short high current spikes. One package for a 15W CFL says dont put more than 10 on a 20A circuit.

StaggeringGoat · Oct 6, 2011

Hmmmm....very interesting information. I take it T8s with electronic ballasts don't have the same problem?

I've only got one 20A circuit I can tap into for this, plus what's left of the main 20A lighting circuit that only has 640 watts already.

StaggeringGoat · Oct 6, 2011

I have a "kill-a-watt" meter that shows power factor, watts, and VA. I just hooked up a "15 watt" CFL and showed 17 watts of power consumption, but 30 VA and only .57 power factor.

Would it make sense to size the wiring/breaker based on the VA number as if it were watts?

mrb · Oct 6, 2011

StaggeringGoat said:
I have a "kill-a-watt" meter that shows power factor, watts, and VA. I just hooked up a "15 watt" CFL and showed 17 watts of power consumption, but 30 VA and only .57 power factor.

Would it make sense to size the wiring/breaker based on the VA number as if it were watts?

you need to size based on VA for the continuous load, but you still need to take into account the current spike unless you want your breakers rattling themselves to death. 20 bulbs probably wont be too bad but 60 would be an issue.

Charles (in GA) · Oct 6, 2011

I have a Ecosmart CFL, marked as 42 watt, .70 amp, in a floor lamp. The Kill-A-Watt says it is drawing 31 watts, 70.0 VA, .56 amps, with a power factor of .45. I'm showing 123.4 volts and 59.9 Hz. This bulb hasn't been used alot. I replaced a mogul based 3 way bulb (using an adapter) since I wasn't crazy about burning 300 watts when I turned it on.

Charles

StaggeringGoat · Oct 6, 2011

I tried one of my T8 fixtures with the kill-a-watt, 2 bulbs = 50 watts and .98 power factor with 51VA. (hey, that's more than 100% efficient :lol_hitti

)

Does anybody make CFLs that have a better power factor? Why are they so bad?

mrb · Oct 6, 2011

StaggeringGoat said:
Why are they so bad?

cost, and no room for the necessary caps and inductors.

remember with CFLs, power factor is only half of the issue. The other issue is the current spikes which a kill a watt isnt going to capture.

Here's another way to put it: a normal 10w lamp would draw 10 watts all the time. A CFL will draw 100 watts at a 1/10 duty cycle for an average of 10 watts. (these numbers are for example only) so you have to be able to supply it with its 100 watts....

im really suprised this issue isnt more widely publicised and discussed....

StaggeringGoat · Oct 6, 2011

mrb said:
A CFL will draw 100 watts at a 1/10 duty cycle for an average of 10 watts. (these numbers are for example only)

Yeah...that's what I'm understanding. Can't the wire be undersized though to account for the duty cycle?

Edit: would there be any way for me to correct the power factor with capacitors on a string of say 30 or more CFLs?

mrb · Oct 6, 2011

StaggeringGoat said:
Yeah...that's what I'm understanding. Can't the wire be undersized though to account for the duty cycle?

nope. cant undersize wire on lighting circuits.

mrb · Oct 6, 2011

StaggeringGoat said:
Yeah...that's what I'm understanding. Can't the wire be undersized though to account for the duty cycle?

Edit: would there be any way for me to correct the power factor with capacitors on a string of say 30 or more CFLs?

quick answer is no.

ddawg16 · Oct 7, 2011

mrb....dude....come on....your better than that...

I have a lot of issues with your 'deductions'.

Yes, in the example you presented, Clifton labs did measure the 1.17 Amps....AT THE BULB.....but in the real world, when you factor in the RC of the total home wiring, the load center is not going to see anywhere near that kind of peak.....in fact, I think you would be hard pressed to see much of anything at the load center.

Factor in the isolation the step down transformer provides....it really becomes a non issue.

Case in point.....how come signal transmission over the power lines is limited to such low freq? Because of the freq resp of the step down transformers and the RC component of the home wiring....

Another point....ever look at the noise from an electronic ballast for a T5 or T8? No better than a CFL.

Love how people b!tch about mecury in CFL's...but seem to forget that tubes have it as well..

Now...getting back on topic.....

I have 16 recessed cans in the ground floor of my garage. All with 23W CFL's. I have plenty of light and I like the fact that I have so many options on color and wattage.

Tubes have a fixed wattage. The only thing you can change is color....but with CFL's....I have plenty of wattage options...as well as color.

mrb · Oct 8, 2011

ddawg16 said:
mrb....dude....come on....your better than that...

I have a lot of issues with your 'deductions'.

Yes, in the example you presented, Clifton labs did measure the 1.17 Amps....AT THE BULB.....but in the real world, when you factor in the RC of the total home wiring, the load center is not going to see anywhere near that kind of peak.....in fact, I think you would be hard pressed to see much of anything at the load center.

Factor in the isolation the step down transformer provides....it really becomes a non issue.

Case in point.....how come signal transmission over the power lines is limited to such low freq? Because of the freq resp of the step down transformers and the RC component of the home wiring....

Another point....ever look at the noise from an electronic ballast for a T5 or T8? No better than a CFL.

Love how people b!tch about mecury in CFL's...but seem to forget that tubes have it as well..

Now...getting back on topic.....

I have 16 recessed cans in the ground floor of my garage. All with 23W CFL's. I have plenty of light and I like the fact that I have so many options on color and wattage.

Tubes have a fixed wattage. The only thing you can change is color....but with CFL's....I have plenty of wattage options...as well as color.

im not talking about electrical noise (these days with switching power supplies in everything, noise is a given). im talking about the current spikes. Sure a couple CFLs on a circuit with other loads wont matter, but you cant go putting 40 or 50 CFLs on one circuit even if its only 1150 watts for 50x 23w lamps. Your average power consumption would be around 1150 watts but your peak load on the circuit would be closer to 60 amps. I have a box from a CFL that says not to put more than 12 or 15 -i forget the exact number on one circuit. Load a circuit up like that and you will hear the magnetic trip element in the breaker chattering.

As far as a T8 ballast, i dont know as I havent tested one myself but I think the load would be a little more linear than a CFL. More room and money for more caps and inductors.

StaggeringGoat · Oct 21, 2011

Alright, I got a bunch of CFLs and tried to test them on a circuit tonight, all I could come up with is 15 sockets for 23w CFLs. That's only 345 watts on a 20 amp circuit, which worked fine. Then I turned on a 1500w heater to load the circuit, so about 1845 watts total.

After a few minutes the breaker did get warm and then pop, even though I was using less than the 2400 watts it should provide. Is it normal for breakers to feel warm to the touch when heavily used? Are the CFLs heating it up?

mrb · Oct 21, 2011

the breaker tripped because you were presenting it with about 40 amps (CFLs, 15 x 1.2A = 27.6; heater, 1500 / 120 = 12.5A) it took longer to trip at that current level than say 40 amps of heaters because the current draw from the CFLs is pulsed not continuous like a heater so it took a few min for heat to build up in the thermal trip element on the breaker and trip.

edit: 20 amp circuit can supply 1920 watts continuously for an unlimited period of time without breaker tripping. Your breaker was hot because it was overloaded.

CFL vs linear fluorescents?

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