temp too high?

[GREENIE_420]

My plants are 3-5 inches away from T5HO's I'm running a 6 bulb fixture with 4 bulbs on. The temp at the tops of my young plants is 91, is that too high? Ihave a good vent system but the way my fixture is designed the only way to get it cooler is to custom build an airtight hood connected to a chimney with an inline fan. Over summer, at best it will be 80 at the surface. Will the hood be worth it?

 

[The Hemp Goddess]

How far away is the light from the plants? Do you have an oscillating fan in there? How big is your space? Tell us about your ventilation--telling us you have a good vent system with no description gives us no way to try and offer suggestions.

 

[pcduck]

I would not make a a/c hood for the t-5's, to much lumens lost. I would get better ventilation, a bigger fan or more intake. But hard to really say as we have no idea what ventilation you do have.

 

[Budders Keeper]

First thing I would do if you don't have one...stick an oscillating fan blowing between plant canopy and t-5's. I have mine angled slightly upward so it is blowing on bottom of bulbs. My 2ft 8bulb doesn't even get warm.

You will definately need some kind of inline fan or atleast a booster fan exhausting from top of room/grow space. You will also need fresh air coming in preferably from bottom of space. If you have a strong exhaust fan this can be done passively through crack under door or vent hole.

 

[GREENIE_420]

I posted that plants are 3-5 inches away. Its not the exhaust either,I have excellent exhaust, inset fan in the wall, two 4"chimneys with 4" inline fans with hoods at the end for variable lights, all except for one 2'x4' I planned on using MH lights originally. The vents are cut into the floor the air underneath is or will be 80 degrees tops over summer. My grow space is 6' high, 9'wide and 3.5' deep theres is plenty of air moving through I don't need a bigger fan, Yes I do have a small fan for the 3-5" in. inbetween angle up aliitle towards the bulbs also. Another fan oscillating to move the air a round for the whole space. It is impossible to lose lumens with a hood. There is no light coming from the top. These are not average fixtures either they have german aluminum 9 symetrical sided reflectors for each of the 6 bulbs. If the light were 10' overhead it is impossible to tell how many bulbs are there it looks like fifty. These reflectors have the top closed of pretty good thats why I think it is too warm at 3-5 in. away.The plants should be closer still anyways right? about 1 in. away the lights should be moved or sooner if you expect more than an inch or so of growth before you can return from a long day. right? Don't think there is something wrong with the lights either, I tested the pins on the ballast for the correct output and there fine. A simple hood will solve the problem.So, simply.... is 90 to hot or not? and how close do you guys let them get before moving

 

[Growdude]

Unless its 91 ambient temp. outside of your grow, you dont have enough air movement.

91 is to hot without co2.

 

[The Hemp Goddess]

I doubt that the inset fan in the wall is nearly enough cfms to be doing the job you need it to do. I don't understand your exhaust system at all: "inset fan in the wall, two 4"chimneys with 4" inline fans with hoods at the end for variable lights" ????? Chimneys? inline fan with hoods? I'm confused. You need air cooler than 80 degrees if you want to cool your space.

I do not know why you believe that it is impossible to loose lumens with a hood....you do. Everytime the light is refracted you loose lumens.

However as to your question....I do not believe that temps of 90 are too warm at the canopy if you have good air movement. However I suspect that you do not have strong enough fans to be moving the air like you need to. Your plant is going to tell you if it is.

 

[pcduck]

If your intake is 80 degrees and t-5's are heating it up to 91 degrees your exhaust is not sufficient. I do not recommend a 90+ degree grow room without co2. And more lumens.

I have my t-5's set at 1 inch above canopy, sometimes if I do not raise them soon enough they even touch the t-5's without burning, as long as they are not touching for a real long time.

 

[GREENIE_420]

O.k. to all those confused and trying to help I realized now that the picture I'm painting is blury, I'm being to general. The end result is time wasted for all. Inset fan in the wall- If you have a small fan sitting on a table beside a large window blowing the air out of the room. yes it moves the air outside but the path of least resistance to replace the air is most likely right back in the same window just higher up or to the side. If you had a large fan, the same size as the window (sqaure fan, square window) and you place that fan on the windowsill or in the window the air in the room moves out at a much faster rate. The "power vent" roof vents that I install are the same, the hole in the roof is 16" in diameter. The blades of the fan are about 15" and it sits in the hole. Half the width of the fan is out of the hole the other half is in the attic so it is centered. when installed properly one 16' fan can pull the hot air out of an attic space thats the size of, so it's easy to relate I'll say the size of a 2 car garage x 3. In short-1vent is sufficient for an average 3bdr/2bth house. Of course it's high powered, don't think its like a reg fan! This is the same system in my g-space, it's in the wall with a round hole cut out to the outside, it's not a reg fan either it's high powered or high rpm. This one fan alone moves the air plenty which is coming from underneath the shed by vents in the floor. Underneath the shed it will always be 10- 15 degrees cooler than the outside air. This fan would still be enough if I doulbed my g-space. I may not know how to grow yet but I knew I could hit the mark with venting my space! No, the temp in my space is not 90 its around 75-80 It was reaching 90 directly underneath the lights which I see now is called the canopy. The 4" chimneys- O.k. this is simple, in your hands you have a large 6"wide funnel, take the cardboard tube of a roll of papper towels and put it on the funnel to "extend" it. Now imagine a light bulb facing upright close to your face, blinding you and you can feel the heat. Take the funnel with the tube, turn it upside down and put the funnel over the bulb. You now have a 2"chimney with a 6" hood, Please, no one reply and tell me the cardboard tube is not 2" because I'm guessing! I'm sure you know what the inline fan is right? If not, whatever size your tube or pipe the fan ever so slighty smaller fitting inside for maximum pull of air. I called mine chimneys because they are going through the roof and venting outside. I called them adjustable because the pipe will slide up and down. There are two peices-The peice through the ceiling is fixed, it does not move at all, it comes through about 1' and the moveable peice is slightly smaller and slides up and down through the one in the ceiling with enough overlap so it does not effect the suction, they are still airtight. Even have lil chimney caps for the rain. The hoods I made will fit over many different lights and styles. I was undecided on the lights at the time. It gets HOT,HOT where I live so I started with vent system because I cannot use A.C. Safe to say, I nailed it and I'm proud of it! If that explanantion doesn't help just think of the anteater cartoon with pink panther. The ant being the unwanted heat, the anteater being the chimney with one hell of an inline fan!
Last but not least, the hood for my light I was talking about, first off are you guys thinking that I meant underneath the lights? A hooded sweatshirt covers the top of your head. Your car hood covers your engine! That's the only thing I can think of. I'm talking about on the top, if it were airtight with a"hood" narrowing down, actually up, to a round pipe like a funnel with a inline fan it would pull the air from directly above and around the lights. Henceforth, cooling the canopy. I'm not moving the light away from the plants. The light's not moving at all. Keep in mind this fixture is quite different than the normal ones because of the reflectors, probably why it's hotter than norm. Only a hood on top will change this because the fan blowing at the space between changes the temp a few degrees.

 

[pcduck]

I use a Vortex 6 inch 449 CFM High Power Inline Fan(see pic below) in my grow room with two 600 watt hps lamps both in a enclosed air cooled reflectors that exhaust to the outside with duct work. And my room temperature only rises a few degrees above ambient temperature.

While using this same fan and set-up except without the a/c reflectors, with my t-5's there is no difference in temps in the room. There may be a slight increase in temps if touching my bulbs but not enough to harm the plants.

If what you are calling hoods are really a reflector cover. These will not work unless you have a enclosed air cooled reflector. (see pic below)

In my room I make use of the fan mentioned above and a 16" oscillating fan with no worries about temps.

Also the use of paragraphs would help with understanding and reading your posts.

 

[Hushpuppy]

I know what he is saying here. If you have ever worked in a restaurant kitchen or a pizza kitchen, there are giant open hoods over the stoves that have piping going to the roof of the building. These have giant versions of the vortex fans that we use. They are open hoods that hang down over the ovens or grills to suck the heat and smoke away from the area so the heat doesn't build up in the kitchen and suffocate everyone working at those stoves. This is what Greenie is describing accept on a smaller scale. At the bottom end it forms a open funnel to grab the rising heat from whatever is below it. However I think the difference here is that his fan is a large standard type of fan rather than the centrifugal type that is in the vortex fans. And it sounds like the pipe necks down from the 15" fan housing to a 4" pipe going to the hood at the bottom.

 

[pcduck]

Oh, ok I understand now,Thanks Hushpuppy.

 

[Growdude]

The blades of the fan are about 15" and it sits in the hole.
This one fan alone moves the air plenty which is coming from underneath the shed by vents in the floor.

I believe this is where you went wrong, try to improve your passive intake.
Either its restricting air flow or the fan is not moving as much air as you believe.

If you are measuring the temperature right under the T5 bulb it might be 90+ but you should have no problem with heat from T5's with hardly any ventalation.

 

[Hushpuppy]

The problem with measuring temperature right under any light is that you will measure radiant heat as well as ambient heat. The plants can take more radiant heat(to a degree) if the ambient heat is not so high. For example; if you have a fairly dense canopy 6" below a light source and the measured temperature(with a standard thermometer) within the shade of the canopy is 80*f then move the thermometer above the canopy into the direct light, the temperature will soar rapidly to above 90*. This doesn't occur so rapidly because the air temp(ambient) is above 90, but because the radiant energy coming off the light source heats the thermometer.

This same example can be done in a room where the temperature is a constant 80*f anywhere in the room because fans are keeping the air stirred. If the thermometer is held 2' away from the light source then the temp reading may not change much from the ambient reading, but if the thermometer is moved to within 1' of the light source then you will see the temp start to rise.

The only way that this could be related to the ambient temperature being higher is if there is no air movement within the room and a pocket or bubble of hotter air has formed directly below the light source(which would be unlikely to occur beyond 1-2", and there woud have to be some kind of barrier to prevent the hotter air mass from moving out around the ends of the light source to rise above the cooler air mass).

This is the reason we use fans within the grow area, so that pockets of hotter/co2 depleted air don't form around or above the plants.