T5 to CMH Distance

[finku]

Hi, 

Have some littluns, seed > root riots > 1.5L pots. They always love it under the T5's but one unit broke so need swap to a single CMH 315w.

Under the T5 they are just a few inches away. What distance should the CMH be to get similar ppf?

In the past had the CMH really high but it's always been guess work.

Anyone with one of those fancy light meter gadgets know?

Cheers.

[catweazle1]

Have you got an IR thermometer? Is the lamp vertical or horizontal? I think I set mine to 16"/40cm in the vertical shade setup for plants passed sixth node. If you have a shiny metal horizontal then try 20" 50cm. They throw down more heat. With HIDs it's a case of not scorching the canopy, that''s why I mentioned IR thermometers to read leaf surface temp. That would be about the max light you could exploit with HID.

Edited January 8, 2023 by catweazle1

[finku]

10 hours ago, catweazle1 said:

Have you got an IR thermometer? Is the lamp vertical or horizontal? I think I set mine to 16"/40cm in the vertical shade setup for plants passed sixth node. If you have a shiny metal horizontal then try 20" 50cm. They throw down more heat. With HIDs it's a case of not scorching the canopy, that''s why I mentioned IR thermometers to read leaf surface temp. That would be about the max light you could exploit with HID.

 

It's a horizontal Maxibright focus reflector. The temps i'm currently getting under the T5 are: Room temp 26°C, leaf temp 24°C They look are very happy at the moment.

Is switching over to the CMH and then adjusting the height to get the same temps a reliable method?

Edited January 9, 2023 by finku

[catweazle1]

@finku I'll get my cmh out later today and meter it but I'm sure it will be ok.

[KC]

I have mine a similar height to what I used to have my 400w so about 12 inches, I wouldn't go less than that for seedlings or small rooted cuttings.

[finku]

7 hours ago, catweazle1 said:

@finku I'll get my cmh out later today and meter it but I'm sure it will be ok.

 

That would be great!

 

5 hours ago, KC said:

I have mine a similar height to what I used to have my 400w so about 12 inches, I wouldn't go less than that for seedlings or small rooted cuttings.

 

That feels ultra close to me. In the past i would most likely start at 2 to 3 feet above, then gradually bring the light down while the plant grew up towards it. They are still very small.