St0ney

Hello all... I found this surfing the web and wanted to share it with you..

Air handling for an indoor garden can take several forms. General ventilation to provide air for plants, forced air cooling to exhaust heat from a HID light, and air conditioning such as an ozone or negative ion generator.

Caption for picture: A commercial grade blower pulls hot, moist air from the top of the space and exhausts it outside. Air enters from a large opening in the bottom of the space. Note that no air cam be exhausted from an airtight space, and too small an air inlet restricts the amount of air exhausted by the blower. Since the blower is only sized to provide fresh air for the plants, it runs continually whenever the light is on. An oscillating fan keeps the air among the plants fresh. A surge strip is plugged into the light timer, protecting the light from voltage surges and allows one timer to control the light, exhaust fan and oscillating fan. The ballast is set off the floor in case water is spilled.

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St0ney

Good ventilation accomplishes several things:
1. Provides continual CO2 (the main component of air) which plants need in abundance for good growth. In commercial greenhouses, air drawn in one end by large fans may have nearly all the CO2 exhausted by the time it exits the other end.

2. Vents out moisture transpired by the plants. This may amount to gallons of water per day.

3. Reduces heat buildup from artificial lights or sunlight. Depending on the size of the space and wattage of light(s), this may eliminate heat buildup.

A good rule of thumb is to completely exchange the air in a growing area every 5 minutes. A commercial grade blower is used. Place the blower so air is drawn from the top of the space where the air is hottest and vented out. Size it by the required CFM (see application guide below). Blowers are rated by the amount of air they move in CFM (Cubic Feet per Minute). Bear in mind that with any duct attached, a blower will only move about 1/2 the rated CFM.

(thats 160 for the 10 x 10. wouldn't let me put it there )

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St0ney

HID lights emit a good deal of heat. In confined spaces this heat can build up, resulting in unacceptable temperatures (greater than 85F). General venting alone may not provide enough air to maintain moderate temperatures.
This venting scheme is similar to general venting, but using a larger commercial grade blower. Its size is based not on the volume of the space but on the wattage of the lights.

Place the blower so air is drawn from the top of the space where the air is hottest and vented out. Size it by the required CFM (see application guide below). Blowers are rated by the amount of air they move in CFM (Cubic Feet per Minute). Bear in mind that with any duct attached, a blower will only move about 1/2 the rated CFM.

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St0ney

This scheme (above) is similar to general venting except the blower is larger, sized to vent the heat from the HID light. A commercial grade blower pulls hot, moist air from the top of the space and exhausts it outside. Air enters from a large opening in the bottom of the space. Note that no air can be exhausted from an airtight space, and too small an air inlet restricts the amount of air exhausted by the blower. Since the blower is larger than what is needed to provide fresh air for the plants, it is actuated by a controller. This controller is a combination humidistat and thermostat. If the temperature or humidity rises above set levels, the blower is activated, rapidly venting air from the space. Although the blower may operate quite often, set the temperature / humidity so the blower operates at least every 30-60 minutes. This is to provide fresh air for the plants. An oscillating fan keeps the air among the plants fresh. A surge strip is plugged into the light timer, protecting the light from voltage surges and allows one timer to control the light and oscillating fan. The ballast is set off the floor in case water is spilled.
If you find the blower does not operate often enough to provide fresh air for the plants, a better method would be to combine general venting with this blower. A small blower runs whenever the light is on, exchanging the air every five minutes. A more powerful blower sized to vent the HID heat is controlled by the thermostat / humidistat. Thus fresh air is continually provided for the plants and if the temperature or humidity rises too high, the powerful blower kicks on, rapidly venting the space.

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St0ney

This method is required with CO2 enrichment. Air from outside the growing space is passed through the reflector and back outside. This removes heat directly from the light without pulling the atmosphere from the room. A second blower is required for periodic general venting to prevent excessive moisture buildup in the air (excessively high humidity).
Place the HID blower so it pulls air from the light, and size it from the above application guide for Venting of Heat from HID Light. Place the general venting blower so air is drawn from the top of the space where the air is hottest and vented out. Size it by the above application guide for General Venting. Blowers are rated by the amount of air they move in CFM (Cubic Feet per Minute). Bear in mind that with any duct attached, a blower will only move about 1/2 the rated CFM.

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St0ney

This scheme (above) is used to cool a HID light when the space is CO2 enriched. Outside air is ducted into the HID reflector (with a lens) and pumped out with a commercial grade blower (blower #1 above). This blower is controlled by a thermostat (controller #1 above) set at 85 F, which is an excellent temperature for CO2 enrichment. If the space temp. drops below 85 F the blower is shut off and the light heats the room. When the temp. rises above 85 F the blower turns on and the HID heat is vented.
A second blower is used to vent the air from the space itself. This blower (blower #2 above) is controlled by a combination humidistat and thermostat (controller #2 above). The humidistat is set at a reasonable level like 50 % to 75 % and the thermostat at 95 F. If the humidity rises above the setpoint the room's moist air is vented. This controller's thermostat is used as a safety in case blower #1 or controller #1 fail for some reason. If the room temp. rises above 95 F the room itself is vented. This defeats the CO2 enrichment but will save the plants until the problem is fixed.

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St0ney

Fans and blowers are rated by CFM delivered with NO BACK-PRESSURE. Back-pressure is the force required to push air down a duct or through any other constriction. Louvers on light reflectors, air filters, anything that hinders the free flow of air caused back-pressure. It is not unusual that a typical blower connected to a simple flex duct pumps only 1/2 to 1/3 the air that it is rated for. Fans connected to ducting are even worse.

Always remember that to pull air out of a space with a fan or blower, you must provide a way for air to enter the space as well. Try this: open and close the door to a vented space and see if you hear the fan or blower change pitch. If so, you may not be providing enough inlet air. Air inlets are usually large and have filters over them to prevent bugs and dust from entering.

Seem like a lot of numbers? Remember: numbers are good. Numbers are natural. The world is full of numbers! Just remember this, numbers are like dogs: just don't show fear and you'll be OK! Here are a few application tips for now. More detailed information will require some quality time with my calculator and the stereo volume either way up or way down.

Fans
Use fans to freely move air only. Example: a fan mounted in a hole cut into a door or wall with large spaces on each side.
Do not use a fan to force air down a duct, they are poor at providing pressure.

If a filter is required, cut down a furnace filter. They are designed to minimize back-pressure.

With no filter or other hindrance to air flow, select a fan that is rated for the CFM needed.

Provide an air inlet into the space that is at least three times the size of the fan.

When using a filter, grill or other hindrance to air flow with a fan, select a fan with a CFM rating 50% to 100% higher. This is to account for back-pressure losses.

Blowers
Use the minimum of flex ducting. Use rigid aluminum ducting for straight runs and 90 degree turns wherever possible.
Remove any louvers that may exist on the HID reflector for maximum blower efficiency.

Provide an air inlet into the space that is at least eight times the area of the blower exit.

With any ducting attached, select a blower that is at least double the needed CFM to account for back-pressure losses.


St0ney
Hope this helps someone

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St0ney

Go check out this other thread I created:

Lighting Wavelength Diagrams Lots of information about HID lights.

And Vote!! Nobody here votes on threads.. Look right there at the bottom of the page.. see it in the right hand corner..? Where it says 'Rate This Thread'....

St0ney
Surfin the WeB

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TonDerudesKa

Outstanding thread StOney!!!!


To all members:
Let this be an example.....don't just sit there and let us tell you what to do and how to do it. Get up and learn. Read. Research. Knowledge is Power. Growing very good pot is not that hard. It is also not that easy. UNLESS...you know what you are doing.

Cy

brianithicus

I agree. Excellent thread. Keep up the good work St0ney.

Later