Temperature/RH question

[Purple Goose]

Just finished installing all my ventilation and circulating fans and found the room will reach a max temp of about 80-82 degrees 55% RH lights on and drop down to about 70 degrees with the lights off. I have a 350cfm exhaust fan cooling my reflector with 1000w mh/hp and a 250cfm fan for intake should this is about the coolest I can get without adding extra air conditioning. One thing I am wondering is will I get better cooling if I run another air duct from the open end of the reflector up to ceiling to draw heat from the roof.

 

[ChicagoJoe]

that seems probably since heat rises, you would be taking the air from the top of the cab and venting it out .

 

[Hogdady]

The light is, of course, your source of heat. Better cooling of the light will lower room temps. Can you get a cooler source of air to cool the light? Any air leaks around the light housing? Do you have a reflector blanket?

 

[Purple Goose]

Nope there are no air leaks but I hadn't installed a duct to run up to the ceiling to draw off the ambient heat from the ceiling did that now the temp is down to 78-80 degrees now. also the way my intake works is I have installed a 6 inch air duct on the inside of the door with a vent on the outside the air duct has a inline 250cfm intake but I forgot that currently my carbon filter is directly over the intake vent maybe by 5' away from the intake. So if I move it 25'away that should return the temp of the air where the intake is located back to 65'degree's instead it is currently around 75 degree's think this should lower the temp some more ? And if it doesnt will 80 be okay?

Oh forgot to also mention that I dont have a reflector blanket but the glass of the reflector and the hood itself can be touched without it becoming to uncomfortable oh and I am so dumb the present 78-80 degrees is taken from about 12 inches below the reflector does this make a difference?

 

[Hogdady]

So if I move it 25'away that should return the temp of the air where the intake is located back to 65'degree's instead it is currently around 75 degree's think this should lower the temp some more ?

yes

And if it doesnt will 80 be okay?

if 80 is your max, yes

Oh forgot to also mention that I dont have a reflector blanket but the glass of the reflector and the hood itself can be touched without it becoming to uncomfortable oh and I am so dumb the present 78-80 degrees is taken from about 12 inches below the reflector does this make a difference?

I like to read the temp at plant level...

 

[Purple Goose]

Thanks much HD I will be moving the carbon filter tomorrow and place it directly beside the heater/central air circulation fan so the excess heat will be spread equally throught the house.

 

[Hogdady]

 

[Purple Goose]

Well moved the exhaust 18' away from the intake area and temps in the room are now holding around 75-77 dont have a digital thermometer just a analog that goes up in intervals of 2. So from everything I have read 75-77 and RH of 55% should be pretty damn good only thing I have noticed is that overnight when lights are out my RH climbs to around 70% is this normal for humidity to rise when temps drop?

 

[Hogdady]

Well moved the exhaust 18' away from the intake area and temps in the room are now holding around 75-77 dont have a digital thermometer just a analog that goes up in intervals of 2. So from everything I have read 75-77 and RH of 55% should be pretty damn good only thing I have noticed is that overnight when lights are out my RH climbs to around 70% is this normal for humidity to rise when temps drop?

your gonna need to keep an eye on that. 70% is kinda pushin it. just watch it for awhile. but if it doesn't change or gets worse, you are gonna have to address it.

 

[Purple Goose]

your gonna need to keep an eye on that. 70% is kinda pushin it. just watch it for awhile. but if it doesn't change or gets worse, you are gonna have to address it.

K here is the really weird thing now my temps is holding at 78 right on the nose and rh is down to 45% . As I remember relative humidity is based on the amount of moisture the air can hold before it begins to precipitate, and the warmer it is the greater the capacity it has to contain water vapor. Would it matter that my temp when the lights go out also drops down to 65 degrees which would lower the airs capacity to contain water vapor.

Do you have a hygrometer that shows you the max humidity and min humidity as well as present humidity or just one that shows the current humidity ,I only ask because it may be a common thing. But as you said I would have to deal with it I take it you mean pick up a dehumidifier and have it run at night ,this is the weirdest thing though that the humidity would be so low with the lights on and would rise so much with the light off.

 

[Purple Goose]

Okay this is going beyond bizzare now after a full 18 hour period I monitored all my conditions throughout the day and when lights came on humidity was up to 65-70% 10 minutes after lights came on it had dropped to 45% and at the end of the cycle humidity had reached 35%. But the temp change was as follows 65 degrees when lights came on 1 hour later temp was up to 78-80 degrees hard to tell as I am using one of those dial meters that graduates in points of 2 so not sure if I was closer to 78 or 80 and held that temp no problem all day . Lights have been out 2 hours and temp is down to 65 and humidity is up to 55% again and seems to be climbing. only thing I can think of is that I did do some wood working in the room and the boards got soaked in the rain before I could get them cut so it could be they are retaining water could it be coming to the surface when lights are out to cause the humidity increase ? if so would probably continue untill they fully dry .

 

[chronic213]

Cateros, it's totally normal to see RH increase with a decrease in temp. The actual volume of moisure in the air probably isn't changing, but relative to the maximum amount of moisture the air can hold, the % goes up as temp goes down. When the lights come back on and your temp creeps up, the volume of moisture the air CAN hold goes up, but the volume it IS holding doesn't change, therefore the relative humidity drops. Thats where the 'relative' part comes from.

Sounds like you have good temp max and mins. Personally i don't think you have a problem here!!

Good luck!

 

[Purple Goose]

Cateros, it's totally normal to see RH increase with a decrease in temp. The actual volume of moisure in the air probably isn't changing, but relative to the maximum amount of moisture the air can hold, the % goes up as temp goes down. When the lights come back on and your temp creeps up, the volume of moisture the air CAN hold goes up, but the volume it IS holding doesn't change, therefore the relative humidity drops. Thats where the 'relative' part comes from.

Sounds like you have good temp max and mins. Personally i don't think you have a problem here!!

Good luck!

Thanks much thats what I was hoping I woudl imagine that most growers if they use the digital hygrometer showing the max humidity and min humidity would probably show what I am seeing which is basically a 1% increase in humidity for every degree in temp as it drops. But after a few more adjustments temp is now holding steady at about 79-80 cant be sure as my thermometer only goes up by intervals of 2, and rh is 40% when it goes dark temp drops to 65 and rh is now holding at 55% for dark hours. So I guess that should prevent any bud rot due to high humidity?

I just was thinking with the fact that the humidity goes up and down with the temp when growers are stating the rh of the grow room needs to be around 40 ish is that reading being taken at low temp time of higher temp time, as far as I know it would cause heat stress if temps were kept the same at all times every book I have read recommends that there be a 10-15 degree variation in day and night temperatures, and one last thing about resin production is during the winter months I can lower my grow room temperatures to 60 at night would this help increase resin production or is that a myth? I always get caught on that one becuase I have read research on grow temperatures and how they effect potency and found that the warm schedule of 65night 80day overall produces more potent buds consistently.