# Calculating Fluorescent Wattage/Amps usage when delamped



## Lighting Retro (Aug 1, 2009)

Here's an interesting scenario I do not have documentation on to answer:

A warehouse we visited had such burned out 8' 2Lamp T12 strip lights (75W lamps) that the ones that are on barely flicker. Most fixtures are delamped. However, all fixtures still have burning ballasts. All the ballasts are hot to the touch. A majority of the fixtures have been delamped, but all have ballasts. 

How does one calculate the juice being used for ballast only? We're running 240V in this scenario. The labels on the ballast say how many amps they draw, but that is in conjunction with the types of lamps. 

For instance, in front of me is a 2 Lamp 4' T12 ballast for either 34 or 40W lamps. 
(2)F40 T12 40 Watt = 0.73 amps
(2)F40 T12 34 Watt = 0.63 amps

This particular ballast is 120V. 

No mention of what the ballast would use on it's own. Any input? I like to be accurate on this, and I find no documentation.....Thanks.


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## 480sparky (Sep 20, 2007)

Are the ballasts rated for 240 volts? Some are strictly 120v, some are strictly 277, some only do both. And some don't care..... 120 to 277 or anything in between.

As for the amp draw, check with the manufacturer.


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## Lighting Retro (Aug 1, 2009)

480sparky said:


> Are the ballasts rated for 240 volts? Some are strictly 120v, some are strictly 277, some only do both. And some don't care..... 120 to 277 or anything in between.


I did not bring a lift to open the fixtures up, so I cannot be exact on that question. 

I will assume Universal voltage (120-277) or the most conservative of equations for usage stats to be safe. Better to underpromise/overdeliver, etc.


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## Toronto Sparky (Apr 12, 2009)

Bench test one with an amprobe.


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## Lighting Retro (Aug 1, 2009)

Toronto Sparky said:


> Bench test one with an amprobe.


Yeah, apparently I decided to "donate" my amp probe on an audit.  I need to pick up another, but was curious to know if anyone else knew the answer or had tested it.


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## dangilmore (Aug 27, 2009)

*Flouresents a thing of the past????*

Am I the olny electrician out there pushing the newest LED replacement tubes for existing Flouresent Light fixtures to our larger customers?????They are Twice as efficient as the T-8 bulbs and although they are still very expensive but I am sure they will eventually come down in cost ,they have an average life of 50,000-80,000 hrs.=Much,much longer life expectancy than normal t-8 bulbs,and cut power usage at least in half,we have a customer who owns multiple athletic clubs,he just bought his third one and that particular one club alone has a current MONTHLY power bill of $9500.00 a month!!!Yes you heard that right(Nine Thousand five hundred dollars a month)we should be able to cut that down considerably considering it currently has at least 50 "High Bay type lights,400 watts a piece" and hundreds of trougher type flouresent lights ect.,and we have found a company that actualy now carries New LED High bays that save 60%-80% power usage while still putting out almost the same amount of light with No UV light and little or No Heat,No ballasts to replace and we are told will last up to 17 years running 8 hrs a day,365 days a year!I think with the "Going Green thing" these New LED lights will be required in the distant future,You guys should really check them out to stay up on the game.They are not all the same though,so do your homework first,Some of the t-8 bulb type replacements for instance you just have to change the bulb,while other t-8 replacements you need to disconect the ballasts and rewire the fixtures according to thier specs ect.,and you need to check the actual amount of light they put out to see wich ones will fit your needs the best.Dont have a heart atack though when you see the price,you have to look at the cost savings over time in usage and see if its worth the change or not,Larger buildings,bigger savings,little buildings,smaller savings ect.Your local supply houses most likely will charge you three times as much for them because they dont carry them in stock yet,We found your best bet is to find them online and have them delivered ect.,Good Luck guys,like everything else they will come down in price over time.Oh by the way who was the idiot that decided we needed
'Tamper Proof GFCI outlets"and submitted it to the code?I meen really think about what a GFCI outlet is used for and then try and explain why it needs to be "Tamper Proof",I can understand the regular outlets being tamper proof somewhat but really,..GFCI Tamper Proof Outlets?????I personaly think it was the manufacturers so they could charge more for them,but thats my oppinion,what do i know?Oh and by the way they also make LED Flood bulbs and outdoor wallpacks now too,check them out!Have a good one guys and stay safe out there.,Dan Gilmore-Master Electrician/contractor,Portsmouth New Hampshire.


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## bobelectric (Feb 24, 2007)

Saw 4-foot t-8 lamps .Who wants spotty lighting that they produce? ( Adressing L.E.D. lamp replacement.)


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## Lighting Retro (Aug 1, 2009)

bobelectric said:


> Saw 4-foot t-8 lamps .Who wants spotty lighting that they produce?


what? T8 FAR outperforms T12. 

Are you using T5? They now make a Hi Lumen 28W T8, so there is virtually no use for T5 EXCEPT HO. Are it's rare to see adaptors for existing fixtures due to the different lengths. 

And for Mr. LED, the no heat thing is VERY misleading. Heat is a very big deal with LED, and you must be very careful when using them for Fluorescent replacements. There are all kinds of reports of poorly designed LED's that have failed in street lights and any enclosed fixtures. If you notice the design of well produced LED CFL or Incandescent replacements, you will note the fin design on the lamp for heat dissipation. 

This has been a major drawback for LED tubes so far. I have yet to have a manufacturer show us a solid product that is backed quite yet. All of them are no name companies that are saying their product will be around longer than they have been. I'm a little more conservative and will likely wait until one of the big guys comes out with a solid LED tube. 

And LED lasts 50,000 when it gives off white light. It has to be treated to be white, and it loses life off of its original 100k hours. To say 80,000 is a bit misleading, and no manufacturer dares to put that in writing. 

Just picked up an amp probe, so I'll test my ballast soon.


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## 480sparky (Sep 20, 2007)

Lighting Retro said:


> I did not bring a lift to open the fixtures up, so I cannot be exact on that question.
> 
> I will assume Universal voltage (120-277) or the most conservative of equations for usage stats to be safe. Better to underpromise/overdeliver, etc.


Be careful with the 120-277 designation. It may mean it takes 120 OR 277, not everything in between.


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## Lighting Retro (Aug 1, 2009)

480sparky said:


> Be careful with the 120-277 designation. It may mean it takes 120 OR 277, not everything in between.


Now that you mention that, I have never seen a 240V ballast. Did they ever make them? :blink:

Testing a 120V now....


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## McClary’s Electrical (Feb 21, 2009)

bobelectric said:


> Saw 4-foot t-8 lamps .Who wants spotty lighting that they produce?


 
What??,,,,t8's spotty??,,,someones confusing t8's for t12's.
Nothing spotty about a t8 after burn in


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## Lighting Retro (Aug 1, 2009)

Lighting Retro said:


> For instance, in front of me is a 2 Lamp 4' T12 ballast for either 34 or 40W lamps.
> (2)F40 T12 40 Watt = 0.73 amps
> (2)F40 T12 34 Watt = 0.63 amps
> 
> ...


Ok, I tested the above ballast and measured amp draw at 120V. It ran alternating between .24 and .25 amps, or 1/3 of what the fixture uses when lit. Very interesting. 

at least to me..... :whistling2:


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## Lighting Retro (Aug 1, 2009)

And for Mr. LED, if you are really sold on your LED lamps, I'd be interested in who you are buying them from via PM. Thanks.


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## s.kelly (Mar 20, 2009)

retro, fwiw... I am very interested in this type info. Have not yet taken the time to check out myself, but glad to see someone is.

Mr LED... I agree interesting concept, but I did some numbers on a community center I am working with to help reduce bills. Could not justify the expense... what I found were not cost effective unless I missed something.

Would also like to know if you have good experience with some mfg.


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## Lighting Retro (Aug 1, 2009)

s.kelly said:


> retro, fwiw... I am very interested in this type info. Have not yet taken the time to check out myself, but glad to see someone is.
> 
> Mr LED... I agree interesting concept, but I did some numbers on a community center I am working with to help reduce bills. Could not justify the expense... what I found were not cost effective unless I missed something.
> 
> Would also like to know if you have good experience with some mfg.


That also happened to be a newer magnetic ballast, rapid start Advance Mark III Energy Saver. I have a suspicion the older ones are worse. Actually looking forward to testing my next batch, but I just recycled all of the ones at the shop.


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## RePhase277 (Feb 5, 2008)

The "120 or 277" ballasts usually have three wires, a neutral, a 120 lead and 277 lead. The "120-277" ballasts have two wires.

If you know the manufacturer, they should be able to spec the unloaded draw. Otherwise, actually measuring one should do.


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## micromind (Aug 11, 2007)

If you're looking for watts drawn, be careful. Volts X amps does not equal watts. Power factor must be considered. 

The equation gets even more complex; even if you know the actual watts, if the POCO is billing VARS, then power factor becomes important. 

Simply removing lamps from a fluorescent fixture might result in very little cost savings.

Rob

P.S. I've seen magnetic ballasts with 240 volt input. They were for 2-F40T12s. The labels were green, if I remember. Been a long time though.


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## Lighting Retro (Aug 1, 2009)

micromind said:


> If you're looking for watts drawn, be careful. Volts X amps does not equal watts. Power factor must be considered.
> 
> The equation gets even more complex; even if you know the actual watts, if the POCO is billing VARS, then power factor becomes important.
> 
> ...


Good stuff. I remembered power factor but did not measure it. I have a power factor measurement tool if I remember right, but I'd essentially have to make everything into a 3 prong plug to get measurements, and I'm not sure I care to that extent. :laughing: I try to shoot low on all of our equations. I'm not counting the fixtures that do have lamps that are flickering and drawing full amps/watts, and I figure in this case that will more than make up for any power factor number I'm off. 

But your comment about it does make me wonder futher. Darnit, I might have to measure it all now. 

Thanks.


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## Toronto Sparky (Apr 12, 2009)

I for one do not like the light produced from LEDs.
They may be OK for a flashlight , but to live in that light will never work for me unless they improve the quality of light 1000%


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## Lighting Retro (Aug 1, 2009)

Toronto Sparky said:


> I for one do not like the light produced from LEDs.
> They may be OK for a flashlight , but to live in that light will never work for me unless they improve the quality of light 1000%


they do have all color temperatures now, and the stuff is improving

I see it replacing all CFL's in the next two years to three years, but the tubes are supposed to be pretty suspect still. 

I just saw a gas station with canopy lights converted to LED. Unfortunately it was during the day, but supposedly they are having good results with those. Just a matter of time....


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## macmikeman (Jan 23, 2007)

Lighting Retro said:


> Yeah, apparently I decided to "donate" my amp probe on an audit.  I need to pick up another, but was curious to know if anyone else knew the answer or had tested it.



I bought a very very very very accurate and high quality one at Northern Tools store in Ft. Myers a few years back for under 10 dollars in the discount bin.  True story. It is a backup for my Fluke now on the van.....


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## rexowner (Apr 12, 2008)

Toronto Sparky said:


> I for one do not like the light produced from LEDs.
> They may be OK for a flashlight , but to live in that light will never work for me unless they improve the quality of light 1000%


The quality of light has been improved.

The Cree lights I just installed have a CRI of 92, and a
Color Temp of 2700K (i.e. ~ same color temp as the 
incandescents we are conditioned to.) I had been
installing Halos since my supply house carried them, but
after one job with the Crees, the Cree appeated to 
be a superior product. (i didn't know about the Cree 
until someone on this forum told me about it on another
post.)

Fluorescents are the "Edsels" of lighting. CFL's, in 
particular, suck.

LEDs are not perfect -- IMO the color temp spectrum is
not perfect, but it is superior to fluorescents. There is
also the issue of them linearly declining in output over
time. I only have a few months installing these, so
time will tell -- I am not trying to be the salesman for
LEDs, but so far they look to be a good technology which
will improve over time.

One plus is that LEDs I've used are usually dimmable 
with standard dimmers, which is an improvement over
fluorescents.

In California, we have to install "high efficacy" lighting
by law. If anyone asks about recessed lights, my
recommedation is to install the Cree or Halo LED lights.

HTH.


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## bobelectric (Feb 24, 2007)

mcclary's electrical said:


> What??,,,,t8's spotty??,,,someones confusing t8's for t12's.
> Nothing spotty about a t8 after burn in


I meant the L.E.D. 4' t-8 lamps are annoying to look at,in use.


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## McClary’s Electrical (Feb 21, 2009)

macmikeman said:


> ```
> I bought a very very very very accurate and high quality one at Northern Tools store in Ft. Myers a few years back
> ```
> for under 10 dollars in the discount bin.  True story. It is a backup for my Fluke now on the van.....


 
High quality at Northern??? I'd have to see that to believe it:no:


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## dangilmore (Aug 27, 2009)

*Led*

WOW....Dident think I would get so much negativity from Most of the Electricians here in regards to the new LED lights,but I am glad to know that some do like them,the ones that dont have either NO experience with them yet or are just ordering the wrong LED's,(dident do thier homework) Yes,some do work better than others and since they are fairly new to the market I am sure they will improve with time and the cost will come down as more companies start to manufacture them,in the meentime,I have had some good luck with them so far and will continue to push them where I can, try Checking out WWW.NORMANLEDS.COM. High Bay leds they sell actually come with a two year warranty for the guy who said they wont back them up,and you guys had better get with the program because these may be required in the not to distant future like it or not!!!Going green is starting to become more mandatory in some areas,In the meantime I will continue to make lots of money with this stuff installing it,while others sit at thier shops wondering why they have no work and they continue living in the last century,but what do I know,I am just a dumb electrical contractor who does a lot of work for the government,malls and other commercial buildings as well as for my Long term residential customers,I think they continue to use me because i keep doing my homework to keep them up to date on the latest tech ect.,and try to save them money where i can instead of just installing whatever the LOCAL supply house happens to have in stock ect.& then overcaharging them to install the CRAP and I dont seem to be as slow as some other contractors,I wonder why that is???Been in buisiness since 1986 and the apprentice who sat next to me in the apprenticeship classes happens to now be the senior editor for the National Electric Codebook,maybe you heard of it??so I would think I would have learned a little something in all that time in the field....But again what do i know???....:whistling2:"Live in the past,& stay in the past,look to the future and survive the recession",I know I will survive,will you? Dan G.


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## Lighting Retro (Aug 1, 2009)

if I didn't know better, I'd say you were selling LED's for those guys. It is good to hear someone with good results. I have a guy saying he'd give a 5 year warranty. Now that is worth looking at. 

The ONLY reason to look at LED because of the price is longevity of the product. That is the only way to justify ROI by taking into consideration relamp cycles. The issue is less with the 2 year warranty than the labor YOU have to eat if the product fails. As long as you have a solid company, you should be good to go. So far, I've yet to find one with a product that is cost effective to sell, but I'll look those guys up. Thanks for the tip brother. 

Good to know we have a long time pro on the board willing to share LED experience. Gracias.


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## Lighting Retro (Aug 1, 2009)

Wow. Ok, after being curious as to the question of how much the power factor would affect the actual draw of the ballast, I hooked up my Kill A Watt inline with the ballast to see what results it would yield. 

The same ballast shows a draw of .28 amps, a PF of .11 and is only pulling 3-4 Watts. That is a WHOLE lot different than I thought previously. Glad I didn't present that! 

The ballast also shows no sign of warming up at this time. I'll look for more numbers once I can test a failing/failed fixture with burned out lamp/lamps in it to see how that also affects numbers. I've been curious to know as well just how much a fixture draws when the lamps are connected, but appear to be burned out, flickering, etc.


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## Lighting Retro (Aug 1, 2009)

Also, this response came in from Phillips on the same question, but regarding an 8' strip on 277V



> Cynthia,
> 
> From Steve's note it looks like he has either 8' slimline or HO magnetic ballasts in these fixtures. For the fixtures where the power is on and there are no lamps, you can use as a rule of thumb that they are consuming *about 10-12 watts *of power. In the fixtures where there is still one lamp in the socket the power consumption will be higher but it would have to be measured. The reason the lamps are just flickering is because these ballast are rapid start series wired. One lamp will not operate properly with series wired ballast unlike an instant start paralleled wired ballast.
> 
> Roger



So there you have it from the pros.....


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## macmikeman (Jan 23, 2007)

mcclary's electrical said:


> High quality at Northern??? I'd have to see that to believe it:no:



Tongue in cheek.....:jester:


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