External light grow room

[Woz from Oz]

Hi Folks I would appreciate some comments on a grow cupboard I’m planning.

The cupboard is 80x40x100cms. I plan on using a 400W HPS. I have a Ablite air cooled reflector which I want to install externally on the top of the cupboard. The reflector comes with a glass insert which I expect would keep the temperature inside the cupboard relatively low with this set up. I had planned on having holes in the floor of the cupboard for a passive air intake. and a passive outlet in the top of the cupboard. Inside the cupboard there would be a fan to circulate the air and shake the plants.

Is a 400W lamp overkill in a cupboard this size – would a 250W be more practical and of course cheaper?

Can I get away with allowing the outside air cool the light – that is without sucking air through the reflector ( I have a 140mm inline fan I can rig up to suck the air out of the cupboard and through the reflector as an alternative)? I will probably be growing at night so the outside temperature will be lower than through the day.

[wietlover]

Yes it is over kill imo

I grow in a slightly larger space than that with a 250 watt in a cool tube( with a 125mm inlne fan) and a 125 mm centrifugal fan for the exhaust .

I think you will get alot of heat issues in a space that small.

have a look at the cannaversity section ..it has grow room calculators for light /power etc

hope it helps

wiet

[Woz from Oz]

Yes it is over kill imo

I grow in a slightly larger space than that with a 250 watt in a cool tube( with a 125mm inlne fan) and a 125 mm centrifugal fan for the exhaust .

I think you will get alot of heat issues in a space that small.

have a look at the cannaversity section ..it has grow room calculators for light /power etc

hope it helps

wiet

Thanks for your reply Wietlover. Don't forget I've got the light outside the cupboard and the downward movement of heat from the light is prevented from entering the plant area by a sheet of glass that slides into the base of the reflector. However it's a lot of light for a space that size and I don't know if it's practical to cut the flowering time too drastically - say 8 hours. The other thing to consider is the cost of electricity. 0 Man has that risen in recent times - especially when taken in with everything in a family home that uses electricity!

[Auntynorm]

G'day Woz.

 

If I understand you correctly you have cut a hole in the top of the cupboard and the light is mounted on top of the cupboard? With an air cooled lamp, use your fan to push cool air over the lamp, not draw out hot air. So if that is the case you could use the 400w. Sure it will use a bit more power/$, but hey, there's no free lunch. The 400 will supply higher luminosity, that won't hurt the plants, far from it. Heat doesn't travel downward unless it is forced, hot air rises, this is why hot air balloons fly. I have a 600w HPS in a cooltube, a similar process to yours, it's fan cooled with a $3 desk fan from Kmart, and I can leave my hand on the glass of the tube for a fair while, without it becoming uncomfortable. I cant do it with the 1000w HPS, very warm, it has a 150mm in line fan dedicated to it, forcing cold air through. If you have a look at MJfish's thread you will see how I rigged the small fan to the cooltube.

Having the cool air being drawn from down low is good, your idea for your in line fan is a good one, I'd go with that, as it's drawing fresh, cool air into the grow area, then that is fine to then cool your reflector. Using your other fan in the area to act as a mild breeze, is a necessity, otherwise the plants won't have any trunk strength to hold them upright. :guitar:

[Woz from Oz]

G'day Woz.

 

If I understand you correctly you have cut a hole in the top of the cupboard and the light is mounted on top of the cupboard? With an air cooled lamp, use your fan to push cool air over the lamp, not draw out hot air. So if that is the case you could use the 400w. Sure it will use a bit more power/$, but hey, there's no free lunch. The 400 will supply higher luminosity, that won't hurt the plants, far from it. Heat doesn't travel downward unless it is forced, hot air rises, this is why hot air balloons fly. I have a 600w HPS in a cooltube, a similar process to yours, it's fan cooled with a $3 desk fan from Kmart, and I can leave my hand on the glass of the tube for a fair while, without it becoming uncomfortable. I cant do it with the 1000w HPS, very warm, it has a 150mm in line fan dedicated to it, forcing cold air through. If you have a look at MJfish's thread you will see how I rigged the small fan to the cooltube.

Having the cool air being drawn from down low is good, your idea for your in line fan is a good one, I'd go with that, as it's drawing fresh, cool air into the grow area, then that is fine to then cool your reflector. Using your other fan in the area to act as a mild breeze, is a necessity, otherwise the plants won't have any trunk strength to hold them upright. :guitar:

Thanks for replying Auntynorm

With the sheet of glass in the bottom of the reflector the heat would be retained within the reflector. A lot of this heat would have been taken up by the metal reflector and dissipated into the surrounding air.The hood has vent holes on either side allowing for a passive air flow. Wouldn't this be sufficient to keep the temperature around the bulb low enough not to damage the bulb.

[El Gato]

you will want to raise/lower the light or the plants. Too far away and you will get stretch.

 

I may have missed something due to many pipes but u should not have heat issues.

[Auntynorm]

G'day Woz.

 

I just like to have a fan for cooling the inside of the cooltubes/reflectors, it can get very hot in there, hot enough to bugger your lamp, this gets expensive and dangerous, fire is a possibility,this is not a good outcome. This is because all that heat is contained in a small area, with only limited ways to dissipate. So a $3 fan is a very prudent investment. For my 1000w HPS I have a 150mm in line fan cooling the tube and a large desk fan cooling the ballast. For my 600w HPS, I have one of the Kmart $3 fans cooling the tube, and a box fan cooling the ballast and providing airflow for the plant. The more airflow you can get, the better for your equipment and plants. Put up a pic of the reflector to show us what you have, this will make things a lot easier. :guitar: