Bulb heat - Watts to Btu to Celsius Calculation

[Fuzzy Duck]

Been pondering over the above calculation to work out the average temperature a HPS/MH/HID may give off which we all know leads to heating the grow room up by X celsius/farenhiet.

Unfortunaly i'm not an maths expert so if any body with any knowledge on the matter could assist or point towards a correct answer would be greatly appriecated.

I have used these calculators so far...

Watts to Btu
Watts to BTU/hr conversion

Example - 400w = 1364 Btu per hour

Btu to Celsius
Convert Btu to celsius heat unit - Conversion of Measurement Units

Example - 1364 Btu = 757 celsius - that seems a lot to me & not sure how that figue is worked out yet might be some thing to do with btu per hour tho ?

So i divided 757 by 60 (60 minutes in a hour) to get an average temperature generated by a 400w bulb of 12 celsius - which i think might be a correct anwser ?

Thoughts, opinions & advice is all welcome



Whilst thinking about all of this some other dimension may play a part in working some other stuff out.

1. Cubic volume of grow area & bulb size may effect total temperatures as small area will heat up quicker than a larger area which may stay cooler on average ?

2. Extraction fan reducing heat by air flow so that might be CFM calculation over BTU ?

Prehaps i'm thinking to much right now... i'll figue it out tho eventually.

 

[Fuzzy Duck]

Mmm 17 days...

Prehaps maths 'n' medication don't mix to well.



Good thing i was not asking huow much a 600w bulb heats up cubic meter volume of grow area as well... lol

 

[HiTimes4Me]

lol I just found this post and I would like to know this as well as there was a bit of a discussion about it on one of 420fieds thread and TorturedSoul is also interested in this...maybe you should PM him the link to this thread....Actually I'll do it for you bro

 

[TorturedSoul]

Been pondering over the above calculation to work out the average temperature a HPS/MH/HID may give off which we all know leads to heating the grow room up by X celsius/farenhiet.

Unfortunaly i'm not an maths expert so if any body with any knowledge on the matter could assist or point towards a correct answer would be greatly appriecated.

I have used these calculators so far...

Watts to Btu
Watts to BTU/hr conversion

Example - 400w = 1364 Btu per hour

Thing about BTU is, it's a unit of energy measurement. It's most commonly (at least in North America) used in terms of describing heat gain/loss, but that's not its entire scope by far.

One watt is approximately equal to 3.41214 watts, yes, so your calculation for a 400-watt light (or at least one that is theoretically 100% efficient, using exlactly 400 watts) would be correct.

But, again, that's total energy - not just the heat involved. So out of that ~1364 BTU/hour, a fair amount of the total isn't turned into heat... it's turned into light (otherwise there would be no light... more-or-less). The fabled 100%-efficient light source would, of course produce no (again, more-or-less, probably more accurate to say "very little") heat since all the energy it consumed would be converted to light.

Uhh... That's why 400 watts' worth of CFLs, 400 watts' worth of MH, 400 watts' worth of HPS, 400 watts' worth of LED, 400 watts' worth of incandescent, 400 watts' worth of (et cetera) all produce different amounts of heat - and light. They all operate at varying degrees of efficiency, which just means that you get this much from this light type, a different amount for a different light type. With the difference between energy consumed (used) and light produced being turned into waste... heat.

One of those things that aren't often thought about by folks that start with a couple small CFLs "because they don't want the heat produced by a HPS" (lol) and then they end up with 400-watts' worth of CFLs and cannot understand why their grow room is hotter than their buddy's grow room that is lit by a 400-watt HPS (even though each individual small CFL's surface temperature tends to max out at around 159°F, much cooler than the 400-watt HPS' surface temperature). And, additionally, why their buddy's garden has produced more grams at harvest from the same electricity consumption (on average).

We can also take that as one of those "redneck indicators" to show that LED grow-light technology hasn't matured yet; being more efficient (producing less waste-heat per watt) means that they should be capable of producing significantly more grams per watt - and that doesn't always seem to be the case... yet.

Where's a smart person that majored in both practical electrical engineering(?) and applied physics when you need him/her, lol?

Like someone once said, take two sealed (and perfectly insulated) spaces of the same size, place a lit propane torch in one, and place a million lit candles in the other... and see which one gets too warm to party in first.

BtW, in the (possibly) useless trivia category, I read earlier that burning your average wooden match releases approximately one BTU of energy (as heat).

British thermal unit - Wikipedia, the free encyclopedia

I wish I still had half as many functioning brain cells as I once did. (At least I have enough remaining to know that it wasn't cannabis that did them in lol .)

Oh, and I used the qualifier "more-or-less" above because what I stated fails to take into account that some portion of the illumination which a light-source produces might be in IR/near-IR, some might be absorbed by other objects and turned into heat, et cetera. But that tends to complicate things somewhat....

 

[Fuzzy Duck]

Cheers for the replys gents


The question at hand does appear more complex than i first imagined, i'll ask a couple of friends who like lots of big maths equations & see what we can come up with.

 

[kushgrower26]

the bulbs dont hurt the plant being that close to them

 

[HiTimes4Me]

the bulbs dont hurt the plant being that close to them

I'm confused about this post...the op's question is how much heat an HiD bulb puts off...in general...not how close is too close or will it hurt plants or anything of that nature...and btw yes bulbs can kill plants...burn plants...bleach plants...we all appreciate your input but its best to stick with the thread topic

 

[wheat berry]

you might email hps or mh manufactures and get the answer you want.


if you simply want to determine the extraction fan size needed, the following formula might be of some help.

cfm=3.16xwatts/Tdiff........ for F

cfm=1.6xwatts/T diff......for celsius

to calculate how much airflow I need?
Several pieces of information are needed:
The amount of heat to dissipate or “get rid of”, in watts;
The allowable temperature rise in Celsius or Fahrenheit; and
The derived factor of 1.76 for Celsius and 3.16 for Fahrenheit.


With that, the formulas are:
Airflow(CFM) =1.76 X Watts divided by allowable temperature rise in Celsius (Delta T).
Airflow(CFM) =3.16 X Watts divided by allowable temperature rise in Fahrenheit (Delta T.)


T(max) = Maximum Allowable Temp in Cab

T(inlet) = Ambient Temp being sucked in through your intake, be that passive or active. Use the greatest possible maximum this could be.

Calculate T(diff):

T(diff) = T(max) - T(inlet)


i'm kind of medicated so i must go now

 

[MadMike1337]

Been pondering over the above calculation to work out the average temperature a HPS/MH/HID may give off which we all know leads to heating the grow room up by X celsius/farenhiet.

Unfortunaly i'm not an maths expert so if any body with any knowledge on the matter could assist or point towards a correct answer would be greatly appriecated.

I have used these calculators so far...

Watts to Btu
Watts to BTU/hr conversion

Example - 400w = 1364 Btu per hour

Btu to Celsius
Convert Btu to celsius heat unit - Conversion of Measurement Units

Example - 1364 Btu = 757 celsius - that seems a lot to me & not sure how that figue is worked out yet might be some thing to do with btu per hour tho ?

So i divided 757 by 60 (60 minutes in a hour) to get an average temperature generated by a 400w bulb of 12 celsius - which i think might be a correct anwser ?

Thoughts, opinions & advice is all welcome



Whilst thinking about all of this some other dimension may play a part in working some other stuff out.

1. Cubic volume of grow area & bulb size may effect total temperatures as small area will heat up quicker than a larger area which may stay cooler on average ?

2. Extraction fan reducing heat by air flow so that might be CFM calculation over BTU ?

Prehaps i'm thinking to much right now... i'll figue it out tho eventually.

I hope this is helpful:
1000 Watt HPS Bulb puts off: ~3600 BTU
600 Watt HPS Bulb puts off: ~2060 BTU
400 Watt HPS Bulb puts off ~1360 BTU

This is heat energy only in addition to the light produced by the lamp.

What the BTU tells you is how much heat has to be dealt with per hour of use. BTU is a rate of heat transfer, nothing more.
A 400 watt lamp puts 1360 BTU into the environment for every hour it is on.

Your heat removal has to be sufficient to remove the heat from the bulb, the humidity from the air, and any heat from other equipment in the space.

 

[o2much4me]

Great thread thanks to everyone !

 

[aaw0701]

I have a quick question I am a first time poster and hope I am posting in the right thread here. I live in Michigan and the summer is rapidly approaching upon us. The dimensions of my flower room is 20x42 roughly 900 square feet and I am running 36 1000 watt lights 12 hours a day. I am using the Radiant 8" Air Cooled Reflector Unit have an complex ventilation/fan system running to keep the lights cool.

My question is how many BTU's of ac would i need or can get by with?

 

[MadMike1337]

I have a quick question I am a first time poster and hope I am posting in the right thread here. I live in Michigan and the summer is rapidly approaching upon us. The dimensions of my flower room is 20x42 roughly 900 square feet and I am running 36 1000 watt lights 12 hours a day. I am using the Radiant 8" Air Cooled Reflector Unit have an complex ventilation/fan system running to keep the lights cool.

My question is how many BTU's of ac would i need or can get by with?

I don't know if you got the right thread, but I will answer anyways. There is some margin for error in my calcuations, but that's probably in your favor.

36 1000 watt bulbs put off about a total of 144,000 BTU, or 12 Tons of heat.

36 1000 watt digital ballasts put off about 90,000 BTU, or 7.5 Tons.

36 1000 watt cap & coil ballasts will produce about 126,000 BTU or 10.5 Tons

Dehumidifying with AC in 900 Square Feet: 25,000 BTU or 2.25 Tons

There are a LOT of variables that I don't know the answers to:
- Do the lights exhaust out of the room?
- Are the ballasts in the grow space?
- What style of A/C do you plan to use?
- How are you controlling humidity?

I can give a better answer with those bits of info. Assuming the ballasts are in the room and that you are going to dehumidify with the Air Conditioner:

Easy answer: Between 20 Tons (240,000 BTU) with Digital Ballasts and 30 Tons with Cap & Coil Ballasts.
If you have Dehumidifiers in the room, then you will need more A/C.

Hope this helps!

MM

 

[aaw0701]

Thanks you Mad Mike for taking the time to answer. Here are the questions you are looking for:

There are a LOT of variables that I don't know the answers to:
- Do the lights exhaust out of the room? YES
- Are the ballasts in the grow space? NO
- What style of A/C do you plan to use? I am thinking about those mini ductless slpit systems
- How are you controlling humidity? We don't have much humidity but we have a humidity now, this is something that will come up later.

 

[MadMike1337]

Thanks you Mad Mike for taking the time to answer. Here are the questions you are looking for:

There are a LOT of variables that I don't know the answers to:
- Do the lights exhaust out of the room? YES
- Are the ballasts in the grow space? NO
- What style of A/C do you plan to use? I am thinking about those mini ductless slpit systems
- How are you controlling humidity? We don't have much humidity but we have a humidity now, this is something that will come up later.

You will be able to get away from most of the heat removal I listed above since you duct the heat from the lights out of the room. Seems to me that a 4 or 5 ton unit will do just fine for you as far as heat control and humidity removal. IMO, with a big room, some extra AC is a good thing, but if the AC is too powerful, it will cool the room too fast and make humidity go crazy.

 

[aaw0701]

Thank you Mr. MadMike1337 for your time I will start with a 4 ton or (2/2TON Ductless Mini Splits) and go from there.

 

[cedarnoir1]

MadMike, I'm curious about something. Well, a couple of things actually. I'm not familiar with BTUs being equivalent to or related to tons. I'm also used to seeing AC units rated in just BTUs. I've never seen them rated in tons, ever. I don't think that it's correct that energy is equivalent to weight. I mean, yes, you can convert mass to energy (E=mc^2, thank you Dr. Einstein), but you need the c^2 units (m^2/s^2) to make the units work out right, so even that isn't a straight conversion. Mass isn't the same as Weight, which a ton is measurement of. But I digress... So when you say ton, are you talking about 2000 pounds or something else? It must be another kind of ton that I'm not familiar with. Anyway, what I wonder is, if a 1000 W HPS light puts off 3600 BTU/h, what percent of that is heat and what percent is light, would you guess? I also have to question the ratio of heat given off by a digital ballast compared to a 1000 W HPS bulb. That much heat from the ballast relative to the bulb just seems too high to me, intuitively. I mean, it just seems high to me. I have no data to back this. I guess those ballasts do get pretty warm though. Anyway, if I had 3 of these lights (and forget the ballast for the moment) with no exhaust, would I just need an A/C unit capable of 3*3600 BTUs/h to handle this heat? Thanks.

 

[MadMike1337]

MadMike, I'm curious about something. Well, a couple of things actually. I'm not familiar with BTUs being equivalent to or related to tons. I'm also used to seeing AC units rated in just BTUs. I've never seen them rated in tons, ever. I don't think that it's correct that energy is equivalent to weight. I mean, yes, you can convert mass to energy (E=mc^2, thank you Dr. Einstein), but you need the c^2 units (m^2/s^2) to make the units work out right, so even that isn't a straight conversion. Mass isn't the same as Weight, which a ton is measurement of. But I digress... So when you say ton, are you talking about 2000 pounds or something else? It must be another kind of ton that I'm not familiar with. Anyway, what I wonder is, if a 1000 W HPS light puts off 3600 BTU/h, what percent of that is heat and what percent is light, would you guess? I also have to question the ratio of heat given off by a digital ballast compared to a 1000 W HPS bulb. That much heat from the ballast relative to the bulb just seems too high to me, intuitively. I mean, it just seems high to me. I have no data to back this. I guess those ballasts do get pretty warm though. Anyway, if I had 3 of these lights (and forget the ballast for the moment) with no exhaust, would I just need an A/C unit capable of 3*3600 BTUs/h to handle this heat? Thanks.

A "Ton" in AC terminology is a unit equivalent to approximately 12,000 BTU/h. It is roughly equivalent to 1 Horsepower, or 746 Watts.
The 3600 BTU I referred to is ONLY the waste heat produced by the bulbs thermal radiation and by heat produced by the light's interaction with surfaces in the room.
There is some truth to your statements regarding digital ballasts compered to traditional cap and coil ballasts with respect to efficiency. BUT, there is still a set of coils inside the ballast that are still carrying 1000 watts of power. The feet of conductors in the transformers still experience what are known as "Current Loss" or I2R loss. The digital ballast simply has a percentage less 'extra' heat due to inefficiencies.

The "anyway" question at the end has 'no' as the short answer; there are more factors to consider than just the bulbs. I would pad by 10% at a minimum per light due to basic fluctuations and unforeseen factors. If you want to remove the heat from JUST the 1000 watt lamps x 3 I would suggest 4000 BTU/Hr per bulb so 12,000 BTU Minimum.
That doesn't account for the room, nor for the moisture of the grow room, nor heat from a dehumidifier. Lot's of other heat sources start to become a factor when the room is sealed.

I think I got all your questions, let me know if I missed something.

MM