[00420]

OK guys so this come's up as or in a thread just about every other day....
with this formula a room would be able to get in the 70-72 deg range even when it's 100+ but yet still maintain humidity at night time with proper air movement

Calculating Heat Load
Heat is measured in either BTU or Kilowatts. 1KW is equivalent to 3500BTUs.
The heat load depends on a number of factor's

1.The floor area of the room
2.The heat generated by equipment
3 the heat from lighting
4.The number of room occupants
5.The ambient temp ( your room's starting temp ) this will be added asap im still playing with the #'s

1.Floor Area of Room

Room Area BTU = L x W x 40 ( H = 8foot + 5btu per foot after that)

If you have a wall that is facing the sun add in for the extra heat

Sun facing wall BTU = L x H x 40

2.Equipment
This is trickier to calculate than you might think. The wattage on equipment is the maximum power consumption rating, the actual power consumed may be less. However it is safer to overestimate the wattage than underestimate it.

Equipment BTU = Total wattage for equipment x 3.5

Ballast in room BTU = ballast wattage/2 x 3.5

3.Lighting

Lighting BTU = Total wattage for all lighting x 4

Air cooled hood BTU = wattage x 4 / 2
@
400= 200-250 cfm
600= 250-300 cfm
1k = 300-350 cfm
^ is just a guide cfm per hood will be on your ducting/SP....

4.Occupants
even being that im only there for 2 or so of the 12 hrs i like it to be able to handle the extra sweat when i smoke one.

Total Occupant BTU = Number of occupants x 400

Total Cooling Required

Add all the BTUs together.

Total Heat Load = Room Area BTU + Total Occupant BTU + Equipment BTU + Lighting BTU

If your using a portable a/c

Total Heat Load BTU x 2

^this has been from threads on this site i dont have any real experince with portable a/c's other then one and it was not in a growroom but if you plan on getting one id think about one thats bigger then you thought about


sample

so if we have a 3 x 3 room with 1k and 200 watt's in fan's/pump's

for room we need 360 btu
for fan we need 700 btu
1k = 4000btu
ballast in the room = 1500 btu

we would need a/c that is 6560 btu i would round up to the next size 7kbtu


air exchange
aka intake/exhaust
complete air exchange every 4-5 minutes is average for a grow room/greenhouse (co2 control)....
for heat control (no a/c) i like to use 2.5 minutes {1M is best imo}
m=air exchange in min's

l x w x h = cf / m = cfm

lets use are room from above as a sample
3 x 3 x 8 = 72 /2.5 = 28.8 (30)
highend turn over = 72cfm
lowend turn over = 30cfm
now for the light 1k = 300-350cfm

exhaust system and air-cooled hood should be separated but most ppl cant/dont ( it's spendy) so add them together if your using 1 fan for both

the fan size we need is 330-422 remember you have duct loss (SP) in the sample room i would use a 440 cfm fan

SEER & EER ratings NO they are not the same.....

EER, or the Energy Efficient Ratio, is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level - usually 95°F. EER is calculated as a simple ratio of BTU's to the amount of power a unit consumes in watts. Here is an example using an air conditioner with 12,000 BTU's and consuming 1500 watts of power:

EER = BTU's / Watts

12,000 / 1500 = 8

EER = 8


While it is true that the higher the EER and BTU's, the more efficient the cooling system, many make the mistake of purchasing oversized air conditioners and ignoring EER ratings. The following is an example of an air conditioner with 12,000 BTU's and 1200 watts:

12,000 / 1200 = 10

EER =10

This would mean that this second unit can produce the same amount of cooling but more energy efficiently. Therefore, to save money on your monthly electric bill, choose a cooling system by getting an appropriately sized unit with a high EER.


SEER(seasonal energy efficiency ratio) measures how efficiently a residential central cooling system (air conditioner or heat pump) will operate over an entire cooling season, as opposed to a single outdoor temperature. As with EER, a higher SEER reflects a more efficient cooling system. SEER is calculated based on the total amount of cooling (in Btu) the system will provide over the entire season divided by the total number of watt-hours it will consume:

SEER = seasonal Btu of cooling / seasonal watt-hours used

[clowntown]

Nice thread!

Originally Posted by 00420

If your using a portable a/c

Total Heat Load BTU x 2

Are you saying that portable units are roughly only half as efficient as others? A few others on another A/C-related thread seem to be saying this as well.

[FirstTracks]

another vote for stickyifiying this

thanks 00420!

Just curious, where'd you get the numbers from?

[G33k Speak]

I go with 5000 BTU's per 1W of light.

[Murphy]

Thank for the info!

[00420]

Originally Posted by clowntown

Nice thread!
Are you saying that portable units are roughly only half as efficient as others? A few others on another A/C-related thread seem to be saying this as well.

not really half as efficient but they take twice as much as a window unit atlest with the one i seen used, in a 12 x 20 no light 10,000 btu portable the lowest we could get the room was 75 max but after shorting the duct to less then a foot we where able to get 70 it took 3 hrs and never shut off the rest of the day, the next day we got a 10,000 window unit we reached the lowest setting 60 with in a hr this was not a growroom just a open room


being that you brought up efficiency im going to add how EER ratings are calculated

Originally Posted by Guest

Just curious, where'd you get the numbers from?

10 yr's experience with indoor growing
10 yr's researching indoor growing on google


potparty,FirstTracks glad you like it

Thats what i like to hear, "experience".
Somebody sticky this already!!

[clowntown]

Originally Posted by G33k Speak

I go with 5000 BTU's per 1W of light.

I've heard similar (actually 4k BTU), but for non-air-cooled lights.

I realize the BTU's put out by air-cooled lights can vary widely depending on how it's ducted, how fast the air is flowing, whether the ducting is insulated, how well the reflector is designed, and so on... but anyone have a ballpark figure / rough guesstimate on how it compares to non-air-cooled? Or perhaps a "BTU rule of thumb" for air-cooled lights?

[00420]

Originally Posted by G33k Speak

I go with 5000 BTU's per 1W of light.

i used to do the same.... but it is simply wrong

and all show you why twice

i run 3 flowering rooms....... 2 are 8 k each

8 x 5000btu = 40,000 btu

in my 2 growroom i use 1 25,000 btu a/c eachroom witch is 50,000 btu for 16,000k

40k btu is no where near what i need, 25kbtu is plenty they run 24/7 when lights are on, then about 6hrs at night ( it keeps hum down ) and on hot days ( 110+) i have to shut a lamp or 2 off. but its better the running a dehu


now in my 2 k flowering room
2 x 5kbtu =10,000btu

i run aircooled hood but the size of the room is 7.5x8x9 & one wall is in the sun 2/3rds of the day and i need 12,000 btu i had a 10,000 in there at first and it did not keep it under 80 if i was not running aircooled hoods i would need a 15/18kbtu unit

so as you can see my bigger rooms need less then 5000 btu per light but my 2k room needs more...