Dimmable ballast, which lights to turn down to 400?

Hi guys,

I have 4x 600w dimmable ballasts running my four 600w bulbs in a 2x2x2m tent

Every fortnight I put 5 plants under a light, therefore harvesting every fortnight

It's sitting at 30 degrees now, but I expect the weather to pick up and it get a lot hotter

I've got some serious extraction and air cooled hoods etc

My question is, if I was to turn down a couple of the lights to 400w, hopefully it wouldn't be as hot

Would it be more beneficial to turn down the light where the plants are in their 0-2 week and 2-4 week or should I turn them down in 4-6 and 6-8 weeks?

Hope I've explained myself correctly!!

Thanks guys

I assumed the same thing with my 600w dimmable ballast, it did lower the temp a few degrees but not as much as i'd like... It gets to be over 100 degrees F most days of the summer where I live, so I usually stop growing in June and don't begin again until October. I believe it would make more sense to turn the lights down earlier in veg

Where is your exhaust air going to when it leaves the tent?

What temperature is the intake air?

If you dim a 600w bulb it changes its spectral output.

If you have a 400w setting run a 400w lamp.

Depending upon the footprint occupied by the plants you could use a 400w lamp over any area that doesn't exceed 1mX1m.

Probably your first 2 stages.



J

Do you grow these 5 plants you put under your 600's in another area?

8 weeks total flower time? Including the stretch period???

Or do you allow them to stretch elsewhere giving them their full flowering time within the 2x2x2?



J

Thanks for the replies guys

I bring air in from a window on one side of house, and exhaust out the other window on other side

I veg in a 1.2 tent which sits at a nice 26-27 Celsius

Every fortnight I move 4-5-6 to the 4 light system, so I need to use an 8 week flower strain

So from flip to harvest is 8 weeks

They are positioned under stationary lights and are propped up accordingly to be 16-18" from the light

Every 2 weeks I move them around until the ones I put in 8 weeks ago are taken out and harvested, same day 4 or 5 more go in

Temps are going to be crazy in the sun

What are those blue ac fans that I've seen online?

jondamon said:

Where is your exhaust air going to when it leaves the tent?

What temperature is the intake air?

If you dim a 600w bulb it changes its spectral output.

If you have a 400w setting run a 400w lamp.

Depending upon the footprint occupied by the plants you could use a 400w lamp over any area that doesn't exceed 1mX1m.

Probably your first 2 stages.



J

Click to expand...

Do you know the exact effect of spectrum change when you dim a bulb? I run a 600w dimmed to 450w to control heat issues as well

Budbrother69 said:

Do you know the exact effect of spectrum change when you dim a bulb? I run a 600w dimmed to 450w to control heat issues as well

Click to expand...

There are spectral change charts out there.

Not sure where though.

Its something I read a while back

With a 600 dimmed to 450 its not really possible to get a 450 bulb and I wouldn't recommend blasting a 400 @ 450w as this will shorten the bulbs life.



J

JMC what rating is your exhaust fan?

With 4 600's I would expect at least 500CFM or around 750m3/h of exhaust fan in order to adequately remove enough heat created by the lights.



J

It's an 8" ISO max can fan

Will have to check cfm

900m3/h

I was always under the impression that if one has a dimmable ballast, you should use a properly matched bulb for the watt setting. A larger rated bulb burning at a lower watt may not fire when cycled and if it does, the life expediency of the bulb could be reduced along with the light not being right. I may be wrong, but with the high costs of special grow bulbs, I would tend to be on the safe side.

Jmcsupplies said:

900m3/h

Click to expand...

Are you air cooling the lights or are they in open reflectors?


J

I've just done the workings out for your tent.

My calculations for one air exchange per minute with 4 open 600's with carbon filter attached is a fan rated at 1110m3/h.


J

all four lights are air cooled mate. all insulated ducting. a pair of lights have a 6" rvk running through them. the intake is also a 6" rvk

Only thing I can think of, is I have 5m of ducting then fan, then another 5m of ducting, so quite a lot of ducting on the extraction

maybe that's not shifting enough heat..... the hood extraction is boiling hot!

Yes that's a lot of ducting.

For every 10ft it reduces something like 20% of your fan efficiency.

You could try mounting the fans closer to the tent.



J

Dirty Harry said:

I was always under the impression that if one has a dimmable ballast, you should use a properly matched bulb for the watt setting. A larger rated bulb burning at a lower watt may not fire when cycled and if it does, the life expediency of the bulb could be reduced along with the light not being right. I may be wrong, but with the high costs of special grow bulbs, I would tend to be on the safe side.

Click to expand...

I can't say this as a fact but the guy that owns my local hydro shop said you can run them that way and it won't hurt anything but as far as the light spectrum I never thought to ask him that???