Lighting experts, interesting challenge, need some advice

[Joe Jensen]

I have a 20 by 30 garage that I use as a shop. Its has a finished ceiling at about 9 ft. 22 years ago I installed 9 used T12 four bulb commercial troffers flush in the ceiling. Lots of light, no issue there. I've since installed an air conditioner for the summer months here in Arizona. The AC is a 22 SEER mini split. The AC does fine in cooling the shop down but when I turn on the lights, tools, and dust collector it can't keep up. Might lights draw 14 amps at 120V. The AC is rated at 24,200 BTU. I assume that essentially all of the energy the the lights draw is converted to heat. Some in the ballast, the rest in the bulbs and then the light hits surfaces and heats them. The lights are drawing around 1600 watts which is 5500 BTUs. I would like to reduce the heat the lights introduce into the shop.

I would like to replace nine the old T12 four bulb 2 ft by 4 ft troffers with new high efficiency T8 two bulb troffers. Price isn't a super concern. This would reduce the number of bulbs by 1/2 and the new ballasts will be much more efficient. The holes are already in the ceiling for the existing troffers so I will be using the same locations.

Questions;
1) Will 18 four foot bulbs be too little light, should I chose three bulb fixtures?
2) What brand troffer should I buy?
3) What brand of bulbs, or does the efficiency change much?

[Roger Myers]

Joe,
No need to change the fixtures, simply change out the ballast. Put in new T8 electronic ballasts and I would stick with the same quntity of bulbs. If too much light and/or heat, you can put some on a dift. Circuit so you can switch on all or part. The sockets in the fixtures do not need to be changed for the T8 bulb.
The new ballasts will output less heat and will operate more efficiently.
Go with name brand on ballasts and bulbs... Any of the big three will be fine...having spent a career with Sylvania (now retird), I do have a bias...
The T12 to T8 retrofit is a common deal, and you can save by just doing the ballasts...

Roger

[Joe Jensen]

The current fixtures have two ballasts in each fixture. Would removing all, and just trying one ballast and two bulbs per fixture make sense to try, or are the new ballasts for 4 bulbs?

If the new bulbs are 32 watts each, I will be drawing 1152 watts if the ballasts are perfect efficiency. The Sylvania ballasts I read about claim 90% efficiency, so I would be drawing 1280 watts down from 1620 watts. I don't think that will make much difference in the heat load from lighting. thoughts?

[Scot wolf]

I'm seeing 9@ 112W each 1008watts total. That's running 4 32w t8's in each.

http://www.ballastshop.com/media/imp...-2030-R07a.pdf

[Barry Mabery]

Are the existing lights all one circuit or switch? If so, do you need them all on? You could wire them to two switch legs to help reduce the load. I agree with Scot - you should only pull about 1000 watts with all lights ON and less if you split them. By the way, we use the Advance Centium ballasts, as per Scot's link, in many of the lights we manufacture. They are very efficient and dependable. You could also, at slightly higher cost, wire some of the fixtures with 2 two lamp ballasts and put each ballast on separate switches for even greater control over the level of illumination and energy consumption.

[Roger Myers]

The current fixtures have two ballasts in each fixture. Would removing all, and just trying one ballast and two bulbs per fixture make sense to try, or are the new ballasts for 4 bulbs?

If the new bulbs are 32 watts each, I will be drawing 1152 watts if the ballasts are perfect efficiency. The Sylvania ballasts I read about claim 90% efficiency, so I would be drawing 1280 watts down from 1620 watts. I don't think that will make much difference in the heat load from lighting. thoughts?

Ballasts will run 4 lamps...so 1 ballast per fixture...

[Joe Jensen]

The current nine fixtures are all on one circuit today. Rewiring would be pretty difficult as I can't get at the space above them.

I currently have a LOT of light, but I'm used to it. I have 36 bulbs at 2200-2700 lumens each, maybe 80,000. According to the link at the sticky I need 50-100 lumens per sq ft and I have 600 sq ft. That says I need 30,000-60,000. If I do only 18 bulbs I will drop down to 50,000 lumens, which I'm sure will seem like a lot. Maybe I can try removing half the bulbs I have today to see what it's like with 40,000 lumens

[Jack Lindsey]

You raise some interesting points, Joe. My first question is why did you install troffers? They are seldom a good choice for a woodworking shop since they tend to collect a lot of dust which absorbs light and reduces the system efficiency. If you made the selection based on a particular need, fine, otherwise a more efficient fixture type might permit a reduction in the number of lamps. Typically I would expect the troffer to deliver about 20% less light to the workplane when compared to an open fixture. You stated that the existing system is 22 years old. Do you clean the fixtures on a regular basis by removing the lens and lamps and washing the painted surface? Even if you do I would expect some deterioration of the reflective qualities of the painted surface over 22 years. If this is the case you should seriously consider new fixtures, especially since the T12 lamps you currently use have been banned. If you want a simple solution just follow Roger's suggestion of reballasting and relamping the existing fixtures. If you want to pursue what might well be a far better solution then some work is required. First, I'd try to locate someone with a light meter who can take readings in your shop to see what lighting level you currently have. If you're satisfied with it then use the method described in my article to see how many new fixtures are needed. You may be able to reduce the number of lamps by 1/3 or 1/2, depending on the condition of existing lamps and fixtures. If you don't know anyone with a light meter (it has to be a photometer, not a photographers light meter) try calling your electric utility and see if they can help. The company I worked for provided meters for many of our energy conservation field reps and we measured lighting levels on a regular basis for our customers.

[Scot wolf]

I'm seeing 9@ 112W each 1008watts total. That's running 4 32w t8's in each.

http://www.ballastshop.com/media/imp...-2030-R07a.pdf

I don't understand why you don't think this solution is viable?? Your amp draw would be 63% of your current use by just reballasting and new blubs. If you clean everything while you're at it, it might be brighter than your current setup.

[Roger Myers]

Joe,
Jack's points are all valid and it really now comes down to a cost/benefit decision.
As we age, we all need more light, so I would hesitate to reduce your potential light....
You can simply reballast all fixtures and use only three bulbs per fixture.... Adding a fourth when/if you need it. This was a common practice among businesses to save energy costs in past years, before companies invested in smarter lighting controls....
You can of course meter the light output, but not sure that is necessary.
While I am sure you have some losses with the old fixtures, you have plenty of light, so why trash old fixtures and spend money on new, not to mention the time and labor, and disposal costs....

You can selectively adjust your lighting level by using some of the existing fixtures as 2 lamp, 3 lamp, or 4 lamp fixtures...

The T8's along with the new ballasts will be a pleasant surprise.... As to the heat load from the lighting...after you swap to T8's this issue will be much improved... Your existing T12’s are old inefficient magnetic ballasts....

No need to over think this, unless you have a lot of extra time and money... If you were struggling with low light output then you would need more work...

Roger

[Don Kondra]

I had 11 - 4' double fluorescent units in my shop, as the ballasts go I'm replacing them with CF bulbs.

No more fooling with ballasts, ends, tubes, etc.

Shop is 26' x 36' with 10' ceiling, this doesn't include the lights in the 10' x 10' spray booth.

The 45w bulbs I am using are the equivalent of 170w incandescent @ 2800 lumens and the bonus is they are 5500K.

They also run cool enough you can hold your hand on them...

http://www.alzodigital.com/online_st...t-daylight.htm

Just saying...

Cheers, Don

[Leo Graywacz]

Your lights aren't the only problem, you machines are too as you state. Reducing your lighting load is only going to help a little. If you have your DC ducted back into the shop there is a good heat source right there.

The only thing that is going to really work is upgrading your AC to something larger. If it is doing OK then you don't have an issue. Since you have an issue then you don't have enough cooling power.

What temps are you trying to keep your shop at?

I would be happy with 80F

[Joe Jensen]

Some answers.
1) Why troffers? 22 years ago I was younger and had less money and experience. I bought the troffers for $9 each with bulbs so the price was right. I cut 2ft by 4ft holes in the drywall ceiling and inset the troffers. They have doors and foam seals and after 22 years of WW there is very little dust inside. I don't quite understand why an open fixture is better than one with a door and seal but I'm just an electrical engineer and not a lighting expert.
2) I really wanted a larger AC. I had a 12 gauge 220 line where the mini split unit was to be installed. The panel is completely on the other side of the house. Installing a larger line would have required trenching 100 ft and going under the driveway. So I ended up buying the highest SEER 20amp AC I could get. I have a very well insulated attic over the garage and R19 garage doors but the sidewall on the west has no insulation. I am planning to have someone come out and foam in the cavities behind the drywall.
3) You are right about the machines. The AC is close to handling the hottest days. I start it in the morning when it's maybe 85-90 and it cools right down to 78. I'm good working until it gets to 108 or so. Then the temp will slowly climb and level out at around 84-85. I am hoping that by removing 800 watts or so, and insulating the side walls I can get close to enough. Life is compromise. Sadly I am moving to a 5HP dust collector from a 2HP so the lighting will probably not even make up for the collector, but the collector only runs a few minutes each hour.

I have pretty much decided to buy Sylvania Quicktronics ballasts and Sylvania Octron XPS 25 watt bulbs. They have almost the same lumens as my current T12, and they are 25 watts. Thoughts?...joe

[Leo Graywacz]

I have vented my 2 1/2HP cyclone collector outside. Three great results from that. No more filter, reduced noise by 10x and 90% of the heat generated by it goes outside.

Not sure what that will do in the winter. And with AC being harder to generate than heat venting outside may suck out to much cool air.

Arizona huh. HOT!!

[Joe Jensen]

I'm guessing that venting the DC outside would REALLY overwhelm my AZ based AC