Height Above Seeds For Metal Halide Light

[Decado]

I'm using a 400 watt metal halide light to start my seeds, how far above the seeds should I have the light?

[serial_killer]

Ateast 4-5 feet till they're established plants, I am a huge fan of HID lighting but you don't need it and are wasting power for starting seeds, it will kill them.

Once they are established you can use your hand as a guide, put the back of your hand at plant height and leave it there for a minute, if the light is hot for you it'll be hot for the plants.

What kind of hood are you running? Cooled or non? Does it have a glass cover at least if its non cooled?

[Decado]

Ateast 4-5 feet till they're established plants, I am a huge fan of HID lighting but you don't need it and are wasting power for starting seeds, it will kill them.

Once they are established you can use your hand as a guide, put the back of your hand at plant height and leave it there for a minute, if the light is hot for you it'll be hot for the plants.

What kind of hood are you running? Cooled or non? Does it have a glass cover at least if its non cooled?

I'm not sure if it's cooled or not, here's a link to it https://www.amazon.com/Watt-Electronic-Ballast-Hydroponic-Light/dp/B002J7PYSU/ref=cm_cr_pr_product_top the reason I got this one is because I wanted to grow veggies in the winter. I'll be using a fan, will that help? Will it kill the seedlings if I keep it at 4-5 feet?

[serial_killer]

No, what will kill them is the heat, so at a good distance you will be fine. Cooled means there is a fan moving air over the light bulb and exhausting it away to keep the heat down, so that is non cooled.

A fan will help, it will serve more purpose helping to strengthen the plants, not at cooling the light.

You could pick up a cheap fluorescent shop light to start seeds under, that way you can hold off on having to run the MH for a little longer.

[Decado]

No, what will kill them is the heat, so at a good distance you will be fine. Cooled means there is a fan moving air over the light bulb and exhausting it away to keep the heat down, so that is non cooled.

A fan will help, it will serve more purpose helping to strengthen the plants, not at cooling the light.

You could pick up a cheap fluorescent shop light to start seeds under, that way you can hold off on having to run the MH for a little longer.

The problem is that I can't really afford another light after spending the money on this one. Not to mention 1 shop light probably wouldn't cover enough area for all the seeds I want to start.

[serial_killer]

Ok well just keep it high, that will also create a bigger "footprint" so you can fit more seeds under it.

[applestar]

FWIW -- I use an old bedside lamp with a harp lampshade brace, rigged with an aluminum pie-tin as a reflector to cast a SIDE-WAYS supplemental light using a 100W CFL bulb in one of my windowsill gardens. Supplemental light doesn't have to be expensive.

Surrounding the grow area with reflective surface -- and it sounds like "white flat painted" is the winner for overall, even exposure, especially with your high-hung lamp -- will keep the available light within the intended area.

For example: I rushed into my garage this morning thinking that the Fluorescent lights for my seedlings had failed to turn on -- it turned out that I did such a good job that there was hardly any light escaping the Grow Light Area.

Make sure to have a fan within the area (or at least design a passive thermal airflow) for good air circulation. Stronger powered airflow would assure sturdy growth though.

[Decado]

FWIW -- I use an old bedside lamp with a harp lampshade brace, rigged with an aluminum pie-tin as a reflector to cast a SIDE-WAYS supplemental light using a 100W CFL bulb in one of my windowsill gardens. Supplemental light doesn't have to be expensive.

Surrounding the grow area with reflective surface -- and it sounds like "white flat painted" is the winner for overall, even exposure, especially with your high-hung lamp -- will keep the available light within the intended area.

For example: I rushed into my garage this morning thinking that the Fluorescent lights for my seedlings had failed to turn on -- it turned out that I did such a good job that there was hardly any light escaping the Grow Light Area.

Make sure to have a fan within the area (or at least design a passive thermal airflow) for good air circulation. Stronger powered airflow would assure sturdy growth though.

I do plan on using a box fan, what speed should I use? Low, medium, or high?

[applestar]

I'm not using a fan right now -- passive thermal -- while the seedlings are just starting to peek out, but I'll be using an oscillating fan set on low. Medium tended to blow away stuff.

As I recall, this is how it went -- CLICK -- hmm that looks pretty good, ... let's try ... CLICK,CLICK -- OOOHHH KAAAYY!!!! that's a little too strong!

[Decado]

So would you recommend I not use the fan for a while as they're seedlings? Or since I have no other way of heat dissipation I should use a fan?

[serial_killer]

Since its a box fan your best bet is to set it near the little seedlings pointed away, best is a oscillating fan so its not blowing on them constantly.

[Decado]

So the light is about 3 feet from the seeds, and the temperature at the top of the seed flats without the fan is 75, I'm guessing that's alright?