MH distance with cooled hood?

Hey everyone I am new and its my first time finally all hooked up.

I have a 400w MH with a cooled hood pulling heat away and a glass piece.

I just really need to know how far I can keep the MH light with my cooled hood, the glass is cool to the touch and at around 22 inches I still only read around 74 degrees. And I have searched its just I can find anything specific on a cooled hood.

thanks in advance.

make sure the light has been on for a good 45 minutes and stick your hand right under the glass. move it down until your hand no longer feels like it is burning. this is where your plants will be comfortable. seedlings should be a little further but this is the general rule of thumb.

I have a non air cooled 400w and I can keep it 9 inches from the top.

I have mine about 18" but my babies are only 1 1/2 months old and I'm new..