Heat from lights

If 1 1000watt hps is suppose to put out 3500 btu… how many btu should I figure for 4 1000 watt hps in air cooled hoods with glass… 1 400 cfm fan per two lights… trying to figure ac size for 10x10 with 4 lights

You need an HVAC guy to help with calculating the heat load. @Countryboyjvd1971 might be around to help.


I can’t help you with the HVAC calculations (that will be a complicated one), but I will tell you - I use (1) 400 CFM 6" fan with my 1000 watt HID light and air cooled reflector. I’m pretty sure you are going to want one fan per light if you are planning on running them at full power.
Keep in mind for your HVAC calculations - you will probably want inlet fans as well, either on a temperature controlled switch or with a variable speed controller so you can boost the inlet air as needed.

2 lights per 400 cfm should be fine… the fans will be at the start of the whole air cooled ducting, blowing… i dont want fans down line having to work in the heat… and i’m thinking about a sealed room with an air conditioner… only “burp” exhaust at night when the humidity spikes. if the 4 lights require 14,000 btu of ac without air cooled reflectors…it should be significantly less with air cooled reflectors… try closing up your tent with 1000 watt normal reflector… gets real hot real quick… try it with air cooled reflectors, not nearly as hot… especially with insulating the outsides of the hoods. im just looking for a btu rating of a 1000 hps with an air cooled reflector.

Sorry for delay I am around should you need any assistance thanks for the tag @Myfriendis410

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so for a 10x10x80" tent… 4 air cooled 1000w hps (2 400CFM fans) how much btu should i figure for the lights when sizing my ac? if a 1000w light is 3500btu, how much is an air cooled light?

You can figure 12,000 btu of ac per 100 sqft.

The two fans you have are they attached to the air cooled hoods or what are you Using carbon filters

Can you post a picture of your set up so I can get a better feel for your set up

I work full time but will check back

Real quick sketch… think that’s all the heat sources. Ambient temp outside the room will fluctuate with the weather… no hotter than like 95 max. There will be 200 gallons of chilled water inside the room also… at 68° in 3” pipe.

Looking at the space and the way your havevthe lights rigged up I’d say 12-14000 btu should cover you since most of your heat load will be exhausted out threw the sealed fixtures

If you haven’t bought a exhaust fan set up for the room check into infinity fans on amazon then come with controllers and will speed up and slow down or turn off with demand lots of control and they are DC motors which are more efficient to run

That’s just one of many room so I will look into the infinity fans. So is the an adapter plug on the fans instead of the normal 120v plug… …I’ll see when I look…

is there a better way to set the room up to keep the heat down?

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A physical partition between the lights and the space above the lights will reduce heat load so long as that volume is vented away.

You want your fans pulling air out … not pushing air out… they will work more efficiently that way… :wink:
I run three 600 watt hps lights in 8 inch ducted xxxl hoods with one 8 inch 800cfm exhaust fan with no issues… plants can touch the glass with no issues… :wink:


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I thought you didn’t want to pull the heat through the fans… wears them out quicker… and I always heard to push when hooked up to lights… pull to exhaust the room…?

Nope … all wrong… not really that much heat when you factor in air movement… :wink:
Pushing heat will only heat up your room… those hoods are not air tight… :wink:
Also , your scrubber isn’t that efficient when controlling smell… :wink:
Have been in a shit load of grow rooms… I wont bull$hit you… :wink:


Good catch @peachfuzz I didn’t even notice that he was only using one fan
I thought he had a fan on both ends for the lights
One pulling one pushing
Which is what I would do to ensure a good draw
If you only using one fan def pull the air at exhaust end of run
@peachfuzz knows his stuff @Juco so you can trust his advice

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Ok… I’ll switch my fan to pull through the light and see if the temp drops from where it usually is. On the hoods… I sealed any air leaks and after putting the glass in I put masking tape around the edges to seal it… so the lights shouldn’t leak at all… and if pulling the air you will end up pulling the smell wherever it vents to if not totally sealed… trying not to blow my neighbors away with the smell!

On the scrubber you mean pulling the air through it works better? So just flip the fan around?

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Yes … pull the air out… :wink:



after moving my fan to the end of the duct and making it pull the air out my temp actually went up or stayed the same but there is more airflow… …is either one of these pics a good setup?

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Go with bottom set up
Do you have exhaust for tent as well of just the hoods
Are the hoods sealed or open