Fresh temperate air that is well circulated forms the next most important element. James maintains that 50 percent of the evacuated air should be replenished immediately. This will create a constant vacuum in the grow room. With the proper air pressure in the room, the door should have a tiny bit of negative pressure when opened. The next trick is to replenish the air so that it is evenly dispersed in the garden. Extracting air also creates a vacuum in the room that can be used to draw air in from a passive source. Direct the air the length of the growing bed with flexible ducting. Cut one-inch holes every four inches along the length of the duct. Cover some holes with duct tape and experiment with airflow volume. Use the tape to partially cover holes to balance incoming airflow along the length of the duct. Even airflow allows a consistent air supply.

Air temperature should stay at or close to 75-80 degrees F when the lights are on. Add a fan to bring more fresh air into the room if natural flow is inadequate. The intake fan can also be attached to a thermostat to further help regulate flow.

A rule of thumb is for every 1000w of light there should be 400 m3 of suction (do you mean extractor fan?????). For example in a room with 12, 1000w lamps would have a 5000 m3 ventilation fan. (12 x 1000 = 12000/400 = 30 m3)

During the hottest 90-degree day in the Netherlands, the temperature of the 12-m2 room was 4.5 degrees C warmer (?????) than the hottest outdoor temperature.

The averages are between 0,65 and 0,8 grams per watt (or actual 1,35 to 1,6 grams per actual watt used).

The smallest area in which this system works well would be with a total of four lamps. This is so light will be overlapping enough to illuminate plants during the entire time.

The double switch boxes are also quite economical. A double-switch box for 10 lamps costs less than $500 (€400). A smaller version for 6 lamps costs $250 (€195). No matter how you cost the investment out, it is less expensive to buy a double switch box than the extra ballasts to run the lamps. The actual net decrease in electrical consumption works out to be 35 percent because the crop takes from 10-14 days longer to mature properly before harvest.

A cable is hooked up directly from the transformer to the hood. The switch boxes are placed between the ballast and the hood. Inside the switch box are switching relays that have normally open and normally closed contacts. By turning the relay on and off you can then switch the outgoing power from the ballasts between 2 different outputs (lamp hookup points). One pre for this type of system is that all of the connections have to be perfect. If one connection is faulty it can burn out the relays within 24 hours (I use flame retardant parts).

A group of growers in Poland are using the double switch box with 120, 600w lamps growing 2,500 plants with outstanding results.

Temperature control

One of the other problems James has seen is new system. It's a switch box with a thermal control. As long as the temperature in the room stays below what you adjusted the thermostat to all the lamps will be on, when the ventilation system can't cope with the temperatures and the temp. exceeds the values of the thermostat, the switch box goes over to the double switch system until the temperature in the room goes below the values you've set. Once the rooms cooled down the lights go back to full lighting until the values are once again exceeded. It should save between 25 an 35 % on power usage. It does it all automatically, so it automatically adjusts itself to the actual temperature and seasonal changes. Imagine you've got your system set up for in the winter, and you get a couple of days the are unusually warm, this new system automatically compensates that. I'm going to call the product line the Infinity Switch boxes. If possible try to mention this new system, along with the fact that I produce more than 30 standard products (speed regulators for the ventilation control, normal switch boxes, true switch boxes, double switch system, grow boxes for pre growing plants, and of course the infinity systems).

The Double Switch Box is very well accepted across Europe and is considering the move to North America. For more complete information about the Double Switch Box contact, j.d.knake@home.nl, Telephone: 011-31-630-568-767.

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