Want to upgrade to a 600w but concerned about the extra heat>>Look here

for the guy below:
The Jump from a 400watt hps to a 600watt will increase your grow rooms temps by 33%
becasue it transfers 33% more energy to the air per/sec


if your room is 80(f) with a 400w hps it will be 106(f) with a 600 watt hps



to find how much hotter any watt bulb is use this formula

(higher wattage) - (lower wattage) = diffrence in watts

(diffrence in watts) / (higher wattage)= %more watts

(Current temp X %more watts) +(Current temp) = (Temp with higher wattage)


the math below just proves that it is a linear trend


I came out with aprox... a 400 watt hps in a 16 square foot room will change the temp +.48294(F)/per hour

i understand that if i say that you would think the room heats up forever but it will stop because of ventilation.. i am only using these 2 points to figure out the % difference

so for a

400 watt = +.48294(f)/per hour
600 watt = +.72135(f)/ per houre

A 600 watt hps is 34% hotter

well i just lit up so im done with math... plus u would have to give me like 20 different data points to calculate the actual temp of your cab. so if you think your setup could handle a 34% increase in heat go for it....

if anyone is wondering how i did the math.

i started off with the watts (1 watt = 1 joule/sec) after that i have the energy to pluge into

q=mc(delta)T

q= energy = 400j/s
m= mass = 1.5g/per 16square foot room i had to use Pv=nrt to find that out
c= heat capacity of air= 1.012kj/kg
DeltaT= temp change and thats what i solved for

for the mass
pv=nrt

p = pressure= 1 atm
v= volume = 125 cubed meters
n= moles = solved to be = .052
r= constant.= 8.314
t= 25(C) room temp

mass = moles*atomic weight

atomic weight of air is 28.97g/mol

what the fuck .... that just makes things look confusing . You will have to use bigger extractor.

i wonder if you switched from a 400watt magnetic ballast to a 600 digital the percentage of heat would change

still good info

well i dont know if it would change the heat much but u would get more light& less heat from a more effecient ballast

just the ration of (heat:to:light) would change

energy in = energy out


the reason i decided to slove for the diffrence in energy is because people can make diffrent size cabs but the 600 watt hps will always put out 33% more energy per second

so , say your 400 watt hps puts out 100 joules/sec in the form of heat & 300 joules/sec in light

and if that 100 joules/sec heats your room up to 80(f)

a 600w hps would have the same ratio making 133 joules/sec and that will make your room 33% hotter


so take your current temp and at 33% to it

(temp)(.33)+(temp)= 600watt temp

magnetic ballasts do run hot. so it is also adding heat to the room.
i have never owned a digital ballast so i do not know how much cooler it would run, if any.
somone may chime in who have been through a magnetic to digital.

but again, very good info.

The Jump from a 400watt hps to a 600watt will increase your grow rooms temps by 34%
becasue it transfers 34% more energy to the air per/sec


if your room is 80(f) with a 400w hps it will be 107.29(f) with a 600 watt hps

Click to expand...

this is the worst analysis i have seen on riu. the (f) temperature of air is not directly related to the energy in the air. if it were, then zero degree (f) would have zero energy. it does not. that's what the kelvin scale is for.

my freind sorry i put a (f) in place of a (k) but the ratio is still the same


and after u find the ratio it dose not matter what unit of temp u use because it will still be 33% hotter when it evens out

thank you for noticeing that, but i solved for (kelvin) and because zero kelvin can not be reached the only idea why you think the formula is wrong is invalid.(haters)


oh and


Temperature is most defiantly related to how much energy is in an object or gas

What did u think temperature is a scale of

RyanTheRhino said:

The Jump from a 400watt hps to a 600watt will increase your grow rooms temps by 33%[/B][/FONT][/COLOR]
becasue it transfers 33% more energy to the air per/sec


if your room is 80(f) with a 400w hps it will be 106(f) with a 600 watt hps

Click to expand...

ok, let me try to say the same thing in smaller words. if the jump from a 600 watt light to a 400 watt light is 33%, what is the loss in temperature from 400 watts to nothing?

or, to try another way,the ratio in f is not the same as the ratio in k. k starts at appr. -273 c. a one degree change from 0 to 1 f is 100% increase while it is a 1/1.8/273/100 % change in k. get it yet? k is proportional to the thermal energy in something because it was designed to measure exactly that. f is a step child.

His math is horribly wrong... going from a 400 watt light to a 600 watt light may make a change of ALMOST 50% more heat emitted(he did the math reverse... it's not 33% more but 50% more). By following his retarded logic if your room temp is 80 degrees with a 400 watt light than it'll be 200 degrees with a 1000 watt.

Even if your room were absolute 0 Kelvins and adding a 400 watt light made it 200 Kelvins, a 600 watt light wouldn't make it 300 Kelvins because heat isn't linear anyway.

Also, wattage isn't a method of evaluating heat emissions... but it is close enough for all intents and purposes.

If your room is 70 degrees with no light on and adding a 400 watt bulb makes your room 80 degrees, than it is reasonable to expect a 600 watt light to make the room 85 degrees... however due to heat dissipation and the fact that heat isn't linear and dozens of other micro variables you can expect anywhere from 83-85 degrees.

Don't try estimating thermodynamics if you know nothing about basic physics. You claim to have degrees in mechanical engineering and chemistry... I smell BS. Otherwise, your university did you a horrible disservice by selling you a degree you have no right possessing.

well I am not sending a rocket to space here, it is an idea that works well in C & F. for the most part it is linear because the more watts you use it exponentially increases heat because the light is less efficient, but the more kinetic energy the gas has the longer it take for it to heat up which is also exponential, so I used the 2 to cancel each other out. The whole time this is happening the heat is also dissipating to the rest of the room eventually reaching an equilibrium point where it starts pouring out of your room, cab, shed whatever creating convection currents making it impossible to achieve a higher heat..... Unless you start putting more energy into the system faster which would be a higher wattage bulb in this case. Yes it is not perfect the many micro variables are negligible that is why they are called micro variables I am just looking for a generality not creating a new law.

I never used Kelvin in this idea I used joules the Kelvin’s canceled out when I was looking for a ratio in relation to energy

Stop reading out of the book and just try stuff u don’t know what could happen

And if u are so knowledgeable how would you precisely calculate this (with limited variables)

well you just saved me some cash. i was gunna buy a 600 watt hps, but i cant find any strains that will grow in 200F temps so now i'm stuck with my little 400

I run 4 600w in my room with a 250cfm fan goin 24/7...my room stays at a consistent 78 degrees.....I started on 400w ballasts/bulbs, but you gain a ton more lumens using a 6 to a 4. lumens < temp....you can always lower temps, you cant get more lumens.......600 < 400

LOL @ SixString, are you joking?

And I already showed a rough calculation... whatever the difference between no light and a wattage in relation to the higher wattage bulb. If a 400 watt light increases the room temp by 10 degrees then it is reasonable to assume a 600 will increase the room temp by another 5 or so degrees based on simple math and observation. You can't do accurate calculations while excluding microvariables or using exponents to cancel eachother out because they play a large part in the math. All we can do is make reasonable assumptions.

2 ^ 10 = 1024
2 + .05 ^ 10 = 1310

VERY different because of that fraction of a point(5%). The microvariables can become big variables.




You also can't simply use exponents to cancel out because they are exponential not linear and play a different part in equations.

4^4 - 2 ^ 4 = 240

I can't simply say "2^4 and 4^4 are equally exponential so they cancel each other out and make 2^4" because 16 is very different from 240



The point remains that the math is flawed and can only be reasonably guessed by observations with similar environments. No one here can do it unless you were to create a precise formula that takes into account every variable. The thickness, reflectivity, and materials used to make the grow room walls alone create huge differences in grow room temperature calculations, not counting starting temperature/light efficiency/spectrum/mass in the room/ventilation rate/humidity/altitude. In the end you're looking at a super computer to calculate the temperature. Just go off of the basic logic that others have observed and assume that a light with 50% more watts will increase the room by 50% more temperature than the original light increases.

I know exactly how to work this shit out in 4 easy steps -

1- buy 400w
2- buy 600w
3- measure temp with 400w
4- measure temp with 600w.
5- calculate difference.

And i aint even got a degree hahah

theres gotta be somones on this site who's done the switch and recorded the results

just gota stumble onto this thread

Unfortunately BuddaRoom and Smokinmayne... results vary based on your exact setup. The point of this in the first place was to save people buying 2 bulbs and knowing what they can get away with before they make the upgrade.

well Im not all educated or anything but I have a 600w quantum digital ballast that is dimmable. it will run at 300w,450w, and 600w. my room directly above the plants stays at 75f when its set on 450w when I turn it up to 600w it runs at 79f. so it only raised 4 degrees. granted my exaust fan runs more, its set up on a temp sensor speed controller that speeds up and slows down according to cooling requirements.

I've tested both in an airspace of: 750mmx1000mmx2400mm.

600w comes out considerably warmer, certainly not the 5 degree farenheit difference speculated, and more in line with the 33% calculation. I am sorry if you say his maths/physics is wrong, however using the same extraction, airspace and using 3 thermometer points recording temps my numbers are in line with what he is saying.

To explain, I am a first time grower, I bought a 600w lamp, set up my room, ran tests to get a setup that would be controllable with my airspace and had to step down to a 400w due to the temp issues.

I have the last 6 weeks (2 weeks of setup and testing, 4 weeks of growing) of temp data in csv format as I autodump all data, which gives me accurate reading on the performance against ambient of a 600w HPS, 400w HPS and 430w CFL (multiple lights). I don't have a physics degree to argue the point one way or the other, just experience with hard numbers in a very controlled situation.

The reason I say hard numbers is that my experience states that it is not possible to calculate temperature expectations based on energy output alone, since contributing factors (airspace, reflective distances, airflow restrictions, hotspots, external ambient temps.

My ACTUAL final figure, is that for an empty room, of this airspace, with an exterior air temp of 14c and airflow (which I don't have in CFM) of a 50w extraction fan running through a 100mm standard carbon filter I get the following results: 600w HPS 34c, 400w HPS29c,430w CFL 24c.

That is the temp that the overall, average air temp taken from 3 points around and below the light at expected canopy level during setup once temps had stabilised (takes around an hour for HPS to stabilise in the setup I have described above, as the CFLs put out much less heat they also stabilise quicker, like 20 mins).

Redeflect said:

Unfortunately BuddaRoom and Smokinmayne... results vary based on your exact setup. The point of this in the first place was to save people buying 2 bulbs and knowing what they can get away with before they make the upgrade.

Click to expand...

LOL you could put a 1000w cool hood in a 1mx1mx1m grow tent with the right extraction so what does it matter anyway ?!