LED vs Air Cooled for BTU’s

So I have older air cooled hoods with glass and push a lot of air through them to cool them down. 5600 watts in total 2-1000’s and 6-600’s, all air cooled. I’m looking to moving to 5,550 watts of Full Spectrum Bar style LED Gavita/ ThinkGrow/ GrowersChoice/etc style lights. NOT the blurple lights. I’m looking for guidance or input from people who know, what this will do to BTU’s for cooling switching from the Air Cooled to LED. Right now I have a main 18,000 BTU’s for cooling and a stand by 6,000 that kicks in when thresholds are broken (mainly summer use). The room is sealed and Co2 is used. Right now Temps max out in the warmest summer months around 80 with use of both AC’s. Any detailed knowledge, input, guidance, perhaps a calculator, is very appreciated.

Thanks for Reading!

I don't know what percent of heat remains in the room from your HID setup. You would have to take your best educated guess.
The drivers vs ballasts will essentially be the same amount of heat.
Good LEDs are about 35% efficient.
5.5 x 0.65 x 3400 So you will have about 12K BTU going into the air.

7CardBud said:

I don't know what percent of heat remains in the room from your HID setup. You would have to take your best educated guess.
The drivers vs ballasts will essentially be the same amount of heat.
Good LEDs are about 35% efficient.
5.5 x 0.65 x 3400 So you will have about 12K BTU going into the air.

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You raise a very good point and I haven’t tried to calculate remaining heat at all from the current HID’s nor do I know an equation to do so. Also now that I think about it, it’s important I mention these are only 6” ducted air hoods not 8”, a long span to cover this length of run, all 1 continuous length maybe 30-35 feet. Run a total of about 1200 CFM through it between 3 fans spread out.

If you have room you could cut holes in some rubbermaid bins and use them as extraction vents. LEDs produce mostly convective heat so you might be able to exhaust a good amount of heat if you get right on top of them.

Your gonna have a hard time figuring that one out without trial i would say. You'll find that the led heat sits and rises from the lights, rather than radiates at the plants. I've tended to blow the heat down to encourage mixing and raise ambient temperature.

My approach would be to grab one of the units your looking at and switching out one of the hps. Run it in the room and see how things change. Assuming your in the northern hemisphere and the weather is cooling down, now would be a good time to experiment with it as you won't be depending on the limits of your AC.

1 W = 3.41 btu/hr

are drivers outside the room?

I can tell you first hand that a 460W Inda-Gro induction fixture contributed more heat to the grow space than a 1000W HPS in an air-cooled hood.
You could always improve the ducting so it's not pushing through so many hoods in each row?

Some of the info here may help with your guestimations:

lazaah said:

Your gonna have a hard time figuring that one out without trial i would say. You'll find that the led heat sits and rises from the lights, rather than radiates at the plants. I've tended to blow the heat down to encourage mixing and raise ambient temperature.

My approach would be to grab one of the units your looking at and switching out one of the hps. Run it in the room and see how things change. Assuming your in the northern hemisphere and the weather is cooling down, now would be a good time to experiment with it as you won't be depending on the limits of your AC.

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Blow air down and exhaust out the bottom of the tent?

I took out the glass in my hps hood. Mounted a 1/8” aluminum plate. Mounted my cob pin heat sink and drivers inside. Hood cooled led. Works so good I need to dump the warm air back in sometimes if the year.

The big difference is infrared. HPS puts out a LOT of infrared and LED almost none. This means you actually require warmer canopy temperatures to achieve optimal growth under LED. So some of the energy savings come from powering the lighting and cooling less watts but a big savings in cooling is also due to the need for temps set at say 84F instead of 79F.

Watts are watts when it comes to heat. The fact that your HID’s are air cooled means you are removing a good portion of the heat your producing, but LED’s don’t require as low ambient room temps. I would say they would about equal out in terms of BTU’s required to cool.

One of the benefits of LED’s is that you can cover the same square footage with less wattage. For instance HID typically is ~50w per sq ft, so your 5600w would adequately cover 112 sq ft. With LED you could adequately cover that same 112 sq ft. with 3360-4480w further reducing your cooling requirements.

NukaKola said:

Watts are watts when it comes to heat. The fact that your HID’s are air cooled means you are removing a good portion of the heat your producing, but LED’s don’t require as low ambient room temps. I would say they would about equal out in terms of BTU’s required to cool.

One of the benefits of LED’s is that you can cover the same square footage with less wattage. For instance HID typically is ~50w per sq ft, so your 5600w would adequately cover 112 sq ft. With LED you could adequately cover that same 112 sq ft. with 3360-4480w further reducing your cooling requirements.

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A watt isn't just a watt when it comes to heat. Some lights make more heat and less light while others make more light and less heat. Also an HPS has a ton of infrared light and that warms all surfaces it hits, thus more heat.

I will add that this is why so many HPS lights get a "5000 btu/hr" or even higher estimate for heat output. I think the "california rule" for DE HPS calls for something like 5500 btu/hr for a 1kW DE light. Thats more than 3.412 BTU/hr per watt, and it's legit due to the heat created by the IR light.

LED lights run more efficiently, making more light per watt input and they don't pump out a massive load of IR, if I remember correctly something like 60% of the light output from a HPS is in the infrared spectrum, not very efficient at making visible light.