I am getting my HPS light tomorrow. How far from plants? (pics)

Right now I have 4 plants under a single 3,900 lumen CFL and they have been doing good for the past 3 weeks and tomorrow I am upgrading to a 400w cool sun HPS light.

Well right now my CFL is about 10 inches from the plants, how far do I put the HPS so as not to melt the lil girls?

Also my plants are all in a mixture of pearlite and vermiculite since I was just letting them grow into seedlings. When should I move them into bigger pots with soil?

I would say anywhere from 18-24inches. I assume you have will proper airflow right? When you start upgrading to 400 wattl ight systems temp is crucial as well.

Keep these things in mind.

Hank.

its an air cooled unit but I do not have the fan or tubing yet and plan to install that when I move it from my closet (temporary grow room) into my official room out in the shed.

How much heat does a 400w put out? Will a room fan circulate enough air inside a closet to keep it cool until I move the op into the main room?

https://www.rollitup.org/newbie-central/88372-light-distance.html
that will answer ur light distance questions.
for cooling i reccomend a 260 cfm like this one 265 CFM Active Air Shaded Pole Blower#
ha ha im buying my hps system tomorrow as well lol