4 foot would be a safe distance, but could stretch the seedlings making them weak-legged...

like stated in other replies...get light as close as possible to canopy with a constant fan blowing between the light and the canopy, without melting them...a good test. After you set your light, let's say, 18" above the canopy...place your hand right at the top of your canopy, and if your hand does not start to burn after a minute; You are OK. check often, or even back your lamp off a 2-4" if you "feel" that your lamp is too close. hope this helps. lw

Make sure you have a nice little fan that blows cool air between the lamp and the plants.
latewood Reviewed by latewood on . Recommend height for MH lighting i have some seedlings starting i was reading that having ur mh light to low will fry ur seedlings and then having it to high causes it to stretch , from what ive read 5 feet is the norm, but i was wondering what u guys thought about 4 feet high for the seedlings and im not to sure after they start growing like during veg and bloom how high i should keep it. thx guys, my average temp is between 72-78 night and day so any help or suggestions would be nice, i know i gotta test it for my self as Rating: 5