Made a mistake in fluorescent lighting choice - HEAT!

[tmcdonal]

My garage is approximately 34’ x 22’, basically a four car garage, with two cars parked in front of two others. The garage is insulated and finished and I’ve been converting half of it into a climate controlled workshop area - 16’ x 22’. I’ve added a 12,000 BTU dual split A/C, a partition wall, and 12 T8 fluorescent fixtures (two 4’ bulbs each). I wired them on two light switches so I can have 6 or 12 fixtures on at a time (staggered lighting). I chose the fixtures mostly based on the ability to surface mount.

Fixtures:
http://www.contractorlighting.com/4ft-lamp-watt-fluorescent-double-channel-strip-120277-p-400.html
Bulbs:
https://www.1000bulbs.com/product/56690/F-32L359.html

This is an 8’ ceiling and it’s plenty bright, which I like. However, I’m in San Antonio, TX and we’re in regular 100 degree days right now. This weekend I was working in there and had the A/C set to 74 and it got down to 84 (independent thermometer). So I did a little experiment, where I left it at 74 and it got down to 73 overnight, then crept up to 77 during the day. I then set it at 80 degrees and it stayed at 79 all night and day. It was 100 degrees outside each day and all seemed reasonable.

Last night, I turned on the lights with the A/C set for 80, real reading of 79, and left the room for a couple of hours. Came back and it was 82 degrees. Used an infrared thermometer and found the fixtures were all reading at 100-105 degrees. The whole point of this shop was to have a cool place to work when you’re running the A/C 9 months of the year.

I’m ready to admit I made a horrible decision on these lights for this application. I’m looking for cooler lighting options. Although pricey, it looks like tube LED’s might be a good choice for retrofit - keeping the fixtures, ditching the ballast. However, I can find no information on heat output. I see some that have heat sinks in the back, so wondering if anyone knows how hot they run?

Was looking at:
https://www.1000bulbs.com/product/113554/PLT-30017.html as a possibility.

Alternately, any other lighting suggestions?

-Tom

 

[pattenp]

You are going to take a big lumen hit with the LED lamps. The LED is 1900LU vs. about 2800LU for the T8.

 

[Mustang51js]

What do you have above the garage, if it's an attic I would put in a attic fan. I can't see to many other options that will give off less heat

 

[04fivefour]

Do you have any fans to circulate air? Also Cree is making led tubes that look to be of high quality.

 

[tmcdonal]

It is an attic. I installed a solar attic fan, which helped quite a bit. This has been a slow progressing project over this Summer, heavily due to the heat.

I don't have any fans in there. Was thinking about adding a ceiling fan, but not sure I want to be circulating the heat from the ballasts.

I may order a couple of bulbs to see what it's like. I have a couple of extra fixtures I can experiment on. I like the current brightness, but truth be told, it is a bit of overkill. I have a friend who winces every time I turn on the lights as we enter.

-Tom

 

[pcpro15]

The LED's are nice, but are costly. Just know you will have to replace one side of the ends on your fixture if you use the bulbs you linked. I've installed some expensive LED's in a building before, but unless your willing to spend around 2g for your 12 fixtures, those are out of the question.

 

[Aceman]

I have a very hard time believing the little bit of heat coming off a handful of T8 strips is enough to overpower your air conditioner. I don't think your seeing the real issue here, that your AC unit is possibly undersized. I'm not a HVAC tech, so I'd have to leave that up to someone else to answer.

 

[pattenp]

Aceman, he's got T8's.

 

[Aceman]

Aceman, he's got T8's.

I must be dyslexic today, I'll edit my post.

 

[351cmach]

I have a very hard time believing the little bit of heat coming off a handful of T8 strips is enough to overpower your air conditioner. I don't think your seeing the real issue here, that your AC unit is possibly undersized. I'm not a HVAC tech, so I'd have to leave that up to someone else to answer.

My thoughts exactly

 

[ForceFed70]

If you spend a boatload of money for premium LED fixtures, you'll be able to buy fixtures that are 10% more efficient than T8.

In other words, you can reduce that heat output by 10%.

Your mistake wasn't with the lighting, it was with the AC design. 12,000BTU for a 4 car garage? That's not nearly enough. A professional would have recommended double that in your climate.

For the cost of the LED fixtures, you could buy a properly sized mini-split and actually fix your problem rather than wasting more money.

 

[wyliesdiesels]

I agree with the others on the size of the a/C unit. While the BTUs may be enough, its not centralized so its not gonna circulate very well!

 

[msgross]

Throw in a window air conditioner to battle the 100 degree days...

 

[Charles (in GA)]

Flo lights generate heat, no way about it. Doesn't matter which size (T12, T8, etc) they all do, electronic or magnetic ballast, doesn't matter. You have marginal A/C for the conditions.

Directly above the ballast on my T5HO fixture, 156°F

On top of the fixture, away from the ballast, just the bulb heat coming thru from beneath. 105°F

 

[Freejack]

Measuring the temp of the fixture tells you nothing relative to your A/C load. It's not the temp of the fixture you need to be worried about, it's the watts. The temperature of the lamp is just a measure of how well or how poorly the lamp housing can transfer heat into it's surroundings. Rather its the total watts of electricity that is convertered to heat energy that contributes to the cooling load.

This is just an example (with somewhat made-up numbers): The T8 bulbs are generaly 32 watts, so, that's 64 watts. So lets say the fixture draws around 1.2 amps at 120V, that means it is using 100 watts of power, 64 watts are produced as light (not exactly true as there is likely some heat loss in the bulb too), so 36 watts are produced as heat energy. In reality, its probably closer to 50 watts of heat energy, so for every flourescent fixture, it would be approximate to having a 60 watt incandessent bulb.

It's unlikely that that small amount of wattage is contributing significantly to your heat load.

Jake

 

[tmcdonal]

Your mistake wasn't with the lighting, it was with the AC design. 12,000BTU for a 4 car garage? That's not nearly enough.

I would agree, but that's not the space I'm cooling. I probably shouldn't have mentioned the four car garage, but the space I'm cooling is 16' x 22' = 352 sq. ft.

The A/C is able to maintain 79 degrees with it being 100+ degrees outside. However, with the lights on, it creeps up to 82 degrees. There's basically 12 little space heaters attached to the ceiling putting out 100-105 degrees each, so yes, the lights are affecting this.

My question was if somebody knew how much heat is generated by the tube LEDs or any cooler options. I searched and haven't seen this addressed.

This might just be something I have to live with in August and September here. However, I've ordered two tube LED bulbs and will follow up with the findings after I try them out.

-Tom

 

[Freejack]

You can calculate that based on the input watts, assumming same lumien output.

And again, just because it is hot does not mean it is transfering a lot of heat load into the environment. Those twelve fixtures are probably producting less than a total of 500 watts or 1200 btu/hr. LEDs may cut that in half, but it is a lot of expense for just an few hundred BTU improvement.

How many windows and or doors do you have?

Jake

 

[tmcdonal]

Zero windows, one double 6' door. The green and yellow rectangles represent the lights.



-Tom

 

[PushnFords]

I'm going to watch this thread...just bought the exact same bulbs....

 

[tmcdonal]

I'm going to watch this thread...just bought the exact same bulbs....

The Fluorescent or LED ones? It's the heat from the ballast I'm seeing on the infrared thermo.

-Tom

 

[Falcon67]

I'll try to shoot my fixtures tonight. I have 13 total and never noticed a heat issue. I have no trouble keeping 28x24 worth of space in the 70s with eight 8' 4 bulb T8 fixtures running, cooled by an older Samsung 10K window unit.

 

[wyliesdiesels]

Measuring the temp of the fixture tells you nothing relative to your A/C load. It's not the temp of the fixture you need to be worried about, it's the watts. The temperature of the lamp is just a measure of how well or how poorly the lamp housing can transfer heat into it's surroundings. Rather its the total watts of electricity that is convertered to heat energy that contributes to the cooling load.

This is just an example (with somewhat made-up numbers): The T8 bulbs are generaly 32 watts, so, that's 64 watts. So lets say the fixture draws around 1.2 amps at 120V, that means it is using 100 watts of power, 64 watts are produced as light (not exactly true as there is likely some heat loss in the bulb too), so 36 watts are produced as heat energy. In reality, its probably closer to 50 watts of heat energy, so for every flourescent fixture, it would be approximate to having a 60 watt incandessent bulb.

It's unlikely that that small amount of wattage is contributing significantly to your heat load.

Jake

Just an FYI, not that it matters much, but your math is wrong. 1.2a @ 120v is 144w NOT 100w. Approx .8a x 120v would be 100w...

 

[sublimate]

This is just an example (with somewhat made-up numbers): The T8 bulbs are generaly 32 watts, so, that's 64 watts. So lets say the fixture draws around 1.2 amps at 120V, that means it is using 100 watts of power, 64 watts are produced as light (not exactly true as there is likely some heat loss in the bulb too), so 36 watts are produced as heat energy. In reality, its probably closer to 50 watts of heat energy, so for every flourescent fixture, it would be approximate to having a 60 watt incandessent bulb.

It's unlikely that that small amount of wattage is contributing significantly to your heat load.

Jake

Actually, unless the light is going out the window it all turns into heat as well as soon as it's absorbed by a surface.

So all 144 watts (1.2 amps x 120v) becomes heat. Multiple that by 12 fixtures and you have 1,728 watts of heat, or almost 6,000 BTUs/ hour (similar to a portable space heater:
http://www.northerntool.com/shop/to...laces+electric-heaters+electric-space-heaters ).

Lighting heat loads can certainly be significant.

 

[Freejack]

Yep, that is a very good point, but to the OP question, changing to LED's (assuming similar lumien output) would not reduce the radient heat from lighting, just the excess heat generated that is not producing light, which is what the OP was measuring with his temp gauge.

And that brings up a very good point, maybe putting the lights on two circuits and running half as many fixtures during the hot part of the day would help.

Just an FYI, not that it matters much, but your math is wrong. 1.2a @ 120v is 144w NOT 100w. Approx .8a x 120v would be 100w...

Doh! I was just trying to get to round wattage number to work with since I had to pull the amp number out of the air as none of the fixture data I could find on line listed amp draw (which seems odd if you are trying to size a lighting circuit). Criss crossed the numbers when I was calculating in my head!

Jake

 

[tmcdonal]

And that brings up a very good point, maybe putting the lights on two circuits and running half as many fixtures during the hot part of the day would help.

They are divided in half on two switches. Half on gives me sufficient light, not quite as bright as I prefer, but has seemed to help on the heat. I've also ordered two of the tube LED bulbs that do not use the fixture's ballast. It'll be a week or so, but I'll follow up with light output and temperature readings.

-Tom

 

[pcpro15]

They are divided in half on two switches. Half on gives me sufficient light, not quite as bright as I prefer, but has seemed to help on the heat. I've also ordered two of the tube LED bulbs that do not use the fixture's ballast. It'll be a week or so, but I'll follow up with light output and temperature readings.

-Tom

In reference to my previous post. Please make sure you buy non shunted ends to rewire your current fixture for use with LEDS if you did not already.

 

[JoeFin]

OK Guys -

First you take the Watts of Lighting - convert the Watts to BTU and start from there. That is just what is required to remove the heat generated from the lighting.

No big surprise there ...

THEN - you can calc depending on Degree Days, Insulation factor, and Square Footage

NOW - you have the number of BTU required to condition the space

 

[jvitez]

Hold on a minute there Baba Looey! You said you garage is insulated and finished. How much insulation is in the walls? And much more importantly, how much is in the attic?

 

[tmcdonal]

In reference to my previous post. Please make sure you buy non shunted ends to rewire your current fixture for use with LEDS if you did not already.

Sorry I didn't acknowledge it earlier. Yes, I read up on the proper wiring. Also, for anyone else considering, one end of the bulb has a label. That's the end that you attach to the electrical side.

The two bulbs just arrived. I've got a bit of car maintenance before a cross country trip in a couple of weeks. Not sure I'll get the lights tested before then, but I will follow-up when I try them out.

-Tom

 

[tmcdonal]

Hold on a minute there Baba Looey! You said you garage is insulated and finished. How much insulation is in the walls? And much more importantly, how much is in the attic?

I'll have to check it out to verify. I do remember after moving in, that I was very pleasantly surprised on the depth of the blown in insulation.

-Tom

 

[knobby]

A formula that has worked well for me to calculate the BTU load for lighting is 3500 BTU per 1000W
The inspiration for this was derived from manufactures BTU ratings of electric heaters (they all seem to spec out at 3500BTU per 1000W)
This appears to be consistent whether using incandescent, HID, LED or florescent FWIW

 

[Highbeam]

LEDs get hot too. Your money spent on the LED conversion is money wasted.

Should have spent that money on a bigger ac unit.

 

[Travinsky]

Sorry, Thread highjack, will post elsewhere

 

[cybrdyke]

In reference to my previous post. Please make sure you buy non shunted ends to rewire your current fixture for use with LEDS if you did not already.

For that kind of lamp, yes. But there's new ones out there now that are simple plug and play LED tubes. The ballast stays in. The new LED tubes are either 14.5 watts or 16.5 watts, depending on which lumen output you choose. The 14.5 are 1600 delivered lumens, about the same as a 28w T8. The 16.5 are 2100 delivered lumens, a little brighter than a 32w T8. Seeing as how the ballast stays in, with the reduced wattage of these lamps, it is now working alot less hard to drive the lamps, hence it runs cooler and will last longer.
No fixture re-wiring or worry about sockets, but the ballast must be an instant start. These products are fairly new, so probably weren't out yet when you were doing your research.

 

[soob]

That A/C is undersized, no doubt about it. You're not going to make up for it by the small increase in efficiency from LED bulbs (assuming there is any efficiency to be gained compared to T8s, which are very efficient to begin with).

You shouldn't be cooling the garage all day anyway, unless you're planning to use it all day. Small A/Cs sized to keep the house cool by running constantly are for living space.

Bite the bullet and upgrade to a much larger a/c that can cool the room down quickly for when you're using it.

 

[aggie91]

from my AC background, your 12,000 btu unit is marginal in San Antonio for 352 SQFT since you have so many lights in the small space. The lights add heat load to the room and most of the heat is coming from the ballast. Have you tested it like you described with only half the lights on? I would have put at least a 16,000-18,000 btu system for that many T8 lights.

 

[pcpro15]

For that kind of lamp, yes. But there's new ones out there now that are simple plug and play LED tubes. The ballast stays in. The new LED tubes are either 14.5 watts or 16.5 watts, depending on which lumen output you choose. The 14.5 are 1600 delivered lumens, about the same as a 28w T8. The 16.5 are 2100 delivered lumens, a little brighter than a 32w T8. Seeing as how the ballast stays in, with the reduced wattage of these lamps, it is now working alot less hard to drive the lamps, hence it runs cooler and will last longer.
No fixture re-wiring or worry about sockets, but the ballast must be an instant start. These products are fairly new, so probably weren't out yet when you were doing your research.

I have also installed LEDS that do not need to replace the tombstones, but you do replace the ballast with a DC driver that has pigtails to the bulbs. This saves a lot of installation time.

That said, I am unaware of a company who keeps the ballast when converting to LED (which I'm sure a made in china product does exist). Ease of installation would be excellent if you are keeping the ballast, but it kind of defeats the purpose of going to LED does it not? (energy reduction) If you have some documentation on these, I would love to see it for fun.

 

[cybrdyke]

I have also installed LEDS that do not need to replace the tombstones, but you do replace the ballast with a DC driver that has pigtails to the bulbs. This saves a lot of installation time.Called "external driver" technology, these do exist, but the extra cost of the driver and time in swapping it out with the ballast has prevented this from becoming a popular trend.

That said, I am unaware of a company who keeps the ballast when converting to LED (which I'm sure a made in china product does exist). Ease of installation would be excellent if you are keeping the ballast, but it kind of defeats the purpose of going to LED does it not? (energy reduction) If you have some documentation on these, I would love to see it for fun.This "instant fit" technology is new. Not many have seen it yet. It was first offered by Philips and now others have followed suit. The ballast in a fluorescent circuit is not the main energy culprit. The lamps are. These instant fit lamps only use 16 watts each (including ballast). Since the load on the ballast is greatly reduced, it will run cooler. This technology has really taken off. They're pretty cool.

Hope this helps.
http://download.p4c.philips.com/l4bt/4/406662/led_t8_instantfit_lamp_406662_ffs_aen.pdf
CD

 

[cybrdyke]

As a side note, for those of you with T5HO lamps...that lamp runs considerably hotter than a standard T8 lamp. If you have a bunch of these in a small space, the difference is very noticeable.
CD

 

[pcpro15]

Hope this helps.
http://download.p4c.philips.com/l4bt/4/406662/led_t8_instantfit_lamp_406662_ffs_aen.pdf
CD

Thank you for the follow up