passive cooling fan questions

[sir-tokes-alot]

on a 400wt MH/HPS light with an 1800 cfm squirrel cage cooling fan, should the fan run continuously with the light or should it be on separate timer cycling on and off ?? fan is mounted to roof blowing out a roof vent, drawing air through a large sun systems reflector hood. 2x5x7 closet... just ask if if left out any pertinent info...

 

[thegloman]

MH/HPS give off a Lot of heat.
If it were me, I'd run the fan when the light is on for sure.
Heat build up will not only hurt your plants but excess heat can damage your equipment too.
Good idea venting out the roof.
I wish I had access to a vent.

 

[oldfogey8]

if that is ventilating your grow area, it should run all the time. plants need fresh air.

 

[The Hemp Goddess]

Fans are for more than cooling your space. Plants need a continual supply of fresh air (actually CO2) all the time the lights are on for proper photosynthesis. Are you pulling fresh air into the tent with the fan or is it set up as a closed system, cooling only the light?

 

[umbra]

I use 2 separate timers so I can start the blower before the lights come on and let it run after the lights are off to cool down the room some.

 

[sir-tokes-alot]

pulling air outta closet threw hood and then out roof vent, should draw fresh air in the vent in wall that's open to craw space that's got vented eves, fan sposed to change out the air every 2 minutes.