HPS Light Question

Lestat2888

Lestat2888

Active Member
I have a 400 watt hps light that i am using for a grow. I need to know the distance the light should be from the plants in the first couple of weeks, the rest of the vegatative state, and then the flowering. My only option is the hps by the way, for some reason my ballast, or socket, wont power the mh light. Also how many lumens is ideal to be hitting the plant? Also, how much should i water during the first couple weeks, veg state, and flowering. Any help would be great, thank you all for reading. By the way this is my first post, so congratulations to myself and nice to meet you all.
 
C

C_Pac

Well-Known Member
I keep my seedlings under fluorescents until they are a few inches tall. When I move them to the 400w I put the light about 4 feet away at first and slowly move it closer about 6 inches per day. After they adjust to the intensity, it's just a matter of heat. I've had a 400 watter 5-6 inches away from the tops of the tallest plants with a fan blowing right on the light to keep it cool. No probs. Light intensity decreases drastically with distance, so that 3-4 feet away you have lost about 80-90% of your lumens.

For watering, it's the same throughout the whole grow. I drench thoroughly every time, and don't water again until the soil near the bottom is dry. As the plant grows, assuming the same pot size, you will water more frequently.

Be sure you are trying a "MH conversion" bulb. Normal metal halides do not work with hps ballasts. Your socket isn't relevant. All it does is hold the bulb and conduct electricity.

I shouldn't be the welcome wagon since my first post was a couple weeks ago and I don't post often. But Welcome anyway!
 
J

jphamac

Active Member
C_Pac said:
I keep my seedlings under fluorescents until they are a few inches tall. When I move them to the 400w I put the light about 4 feet away at first and slowly move it closer about 6 inches per day. After they adjust to the intensity, it's just a matter of heat. I've had a 400 watter 5-6 inches away from the tops of the tallest plants with a fan blowing right on the light to keep it cool. No probs. Light intensity decreases drastically with distance, so that 3-4 feet away you have lost about 80-90% of your lumens.

For watering, it's the same throughout the whole grow. I drench thoroughly every time, and don't water again until the soil near the bottom is dry. As the plant grows, assuming the same pot size, you will water more frequently.

Be sure you are trying a "MH conversion" bulb. Normal metal halides do not work with hps ballasts. Your socket isn't relevant. All it does is hold the bulb and conduct electricity.

I shouldn't be the welcome wagon since my first post was a couple weeks ago and I don't post often. But Welcome anyway!
Click to expand...

C_Pac , you said "5-6 inches away from the tops of the tallest plants with a fan blowing right on the light to keep it cool"...

I'm curious if you have a cool tube? I have a 400 watt and i want to put it closer to my girls but am afraid to burn them. Never thought about pointing the fan right at the bulb. thanks for the idea!
 
Jetson

Jetson

Active Member
cpac summed it up but if you want to find how close you can put it, lower it to where you think its right (as long as its not like 1 or 2 inches away) then watch for the first signs of a burn and then raise it up as need be.
 
TheGardenMan

TheGardenMan

Dea, FBI, ATF MuthaFucker
Lestat2888 said:
I have a 400 watt hps light that i am using for a grow. I need to know the distance the light should be from the plants in the first couple of weeks, the rest of the vegatative state, and then the flowering. My only option is the hps by the way, for some reason my ballast, or socket, wont power the mh light. Also how many lumens is ideal to be hitting the plant? Also, how much should i water during the first couple weeks, veg state, and flowering. Any help would be great, thank you all for reading. By the way this is my first post, so congratulations to myself and nice to meet you all.
Click to expand...
as long as you have good ventilation and a fan blowing on the plants you should be able to keep the light about 10 inches away from the plants, i usually keep my 400w about 6'' away only because i know i can keep the plants cool with fans.
 
J

jphamac

Active Member
TheGardenMan said:
as long as you have good ventilation and a fan blowing on the plants you should be able to keep the light about 10 inches away from the plants, i usually keep my 400w about 6'' away only because i know i can keep the plants cool with fans.
Click to expand...
Do you have a cool tube or do you just have a bunch of fans on the light? What is your ventilation setup? thanks
 
TheGardenMan

TheGardenMan

Dea, FBI, ATF MuthaFucker
jphamac said:
Do you have a cool tube or do you just have a bunch of fans on the light? What is your ventilation setup? thanks
Click to expand...
got a 500cfm fan blowing cool air in, and a 500cfm blowing the hot air out, than i have a 16'' fan mounted on the wall blowing directly on the light keeping it cool, than i have a 10'' fan ciculating :mrgreen:

grow ehm big :blsmoke:
 
J

jphamac

Active Member
TheGardenMan said:
got a 500cfm fan blowing cool air in, and a 500cfm blowing the hot air out, than i have a 16'' fan mounted on the wall blowing directly on the light keeping it cool, than i have a 10'' fan ciculating :mrgreen:

grow ehm big :blsmoke:
Click to expand...
Thats insane! do you have the 500cfm connected to your light reflector? sorry for the many questions. I need to upgrade my ventilation and this info is a big help. Thank you.
 
C

C_Pac

Well-Known Member
jphamac said:
C_Pac , you said "5-6 inches away from the tops of the tallest plants with a fan blowing right on the light to keep it cool"...

I'm curious if you have a cool tube? I have a 400 watt and i want to put it closer to my girls but am afraid to burn them. Never thought about pointing the fan right at the bulb. thanks for the idea!
Click to expand...
No cool tube, just a desk fan pointed right at the light bulb from about 2-3 feet away. I had buds growing right up into the hood area. Room temp was 70-75 f. I use the hand test. I put my hand next to the bud for about 30 secs. If it feels uncomfortable at all, it's too hot. I guess it's risky too, since if the fan motor died during the day my best plant would've smoked itself.

I'm using bigger lights now so they're farther away.
 
CALIGROWN

CALIGROWN

Well-Known Member
use the hand test...put your hand over the top of the plants ..if its not comfortable for your hand then its not comfortable for the plant, and the light will need to be raised...
 
Lestat2888

Lestat2888

Active Member
thanks for all your help, unfortunately another two plants on the side of my setup receiving about 500 lumens peeled over during their six hours last night.
 
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