Heat in my tent, you think these temps are ok?

Testing my new winter hps setup and wondered if people think my tempurature numbers are ok.
As is, I might see if I'm able to run this through the summer (to stress test it). I think my temps are 'ok' ..all things considered (just a tad high for summer). I'm running through the night (9pm - 9am).

Temps gathered using a handheld temp. reader (double checked with standard temp. gauges) -
Outside tent, room is 26 / 27 degrees C. Outside house temps are 23 to 25 degrees C.

Inside of tent, 29.5 / 31.5 degrees higher above the canopy (towards the light fitting).

The plant top buds, when measured have a temp of between 27.5 / 29 degrees.

bottom of tent is 27 / 28 degrees C.


Set up/info -
600 watt duel spec sun master bulb (placed in a 6" cooltube) on a Digital ballast (LUMii BLACK Electronic Ballast - ballast grabbed, 2nd hand, for 25 pounds).

6" Cooltube - is 20 inches from plant tops.

A 4" axial fan (Black Orchid Axial-flo) is hanging from tent roof and blowing on the cooltube at all times - https://blackorchid.co.uk/products/extractor-fans/axial-flo
Keeps outside of cooltube (measured top of cooltube) at 33 degrees C. With a small central hot spot where the temp. is 36.1 degrees C.

Black orchid 'inline' 4" fan (on low). Sucking through C-Filter then blowing through cooltube (heated hps bulb air then vented outside) *this fan is not true inline, more of a duct booster imo* http://blackorchid.co.uk/products/ventilation/hybrid-flo

Ducting is 4" leading to the Cooltube (from the inline fan). And is 6" diameter leaving Cooltube (and leading to 'out' vent).

2 (15 watt) clip fans blowing over plant tops at all times.



does this sound 'acceptable' to you?

pics added - I need to clean up the top of the tent. ..as well as work the 'kinks' out of the cooltube ducting

fyi - the tent is 1m2 (and 2 meters high) *I meter = 3.3 feet*
tent looks smaller then it is ..as I'm using a fisheye 'style' lens in the pics

Too hot inside the tent. Increasing the exhaust duct size has robbed you of any real velocity. If anything try reversing if possible.

hotrodharley said:

Too hot inside the tent. Increasing the exhaust duct size has robbed you of any real velocity. If anything try reversing if possible.

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Just getting a bigger fan imo. Realistically a 6 inch fan is pretty small but works an hes using a 4 inch "duct booster" he knows what he needs to do, not sure why his asking tbh..

It's more efficient to push air through the filter than to try to pull it. Personally air movement and cooling a grow are more important to me than lights going in. So many issues you see here are directly related to either or both.

I've flowered kickass bud using used high bay shop lights. Fixture has this huge heavy hot ballast attached. Off with it, connect it to 10' of 10/3 copper and put it outside the flower room totally. Actually 3 of them. Got them for $100 total. Had multiple fans so no dead spaces for air movement .

hotrodharley said:

It's more efficient to push air through the filter than to try to pull it. .

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I agree with most of your post but I think you may want to double check this. I'm pretty sure you want to pull air through the carbon filter whenever possible, and have your fan on the exhaust side of your light. Compression heating an other factors.

thanks for the replies. I did think it was a little hot (for running in summer) but was hoping it might 'just' work with all the Sativa's I'm flowering at the moment (Imo - they seem to handle higher temps then indica, generally). Without stunting etc ..really was working the methodology 'on a wing and a prayer'.

Yeah the ducting sucks I know and I did figure 6" inline fan was the way to go ..I just wanted to see what I got with what I had. Basically I grabbed what I had (fan and duct wise, some of it already connected before updating to hps). And so I really just threw it together slapdash (with the idea of improving before winter kicks in and finances allow). Really, just to see the temps I got (while maintaining a specific noise level -which is why I set the fan, on the cooltube, to the low setting-'high' drops temps by 3 degrees more but is too noisy ..unless I jerry rig some sound proofing perhaps).

@hotrod, I figured the 4" to 6" ducting was retarded and robbing me of pressure. I've just happen to have found a length of 4" ducting. So I'll remove the 6" and put 4" from the cooltube to the outside vent. And see what temperature change I get. Failing that I'll connect 6" to fan>cooltube and the 4" from cooltube>outlet vent. Thxs

I could also unzip the top of the tent door (that will get me 1 degree back
I could also drawn air 'in' from outside the house (as opposed to from inside the grow tent itself via the CF). However, I'd need to reverse the whole tent setup in order to do that properly (sorry for being so lazy at the mo).
Switching the location of the fan to the 'outlet vent side sounds sensible too. I'll have to do that when I can.

There's lots of easy ways to dampen the sound of your fan. A 8 inch fan on a speed reducer on the lowest setting is going to still move a lot of air, and quietly. Then wrap it in a moving blanket. Cut a cardboard box and slide it over the fan, and stuff moving blankets around it. You may not even hear it standing next to it if you do it right. For real.

growingforfun said:

There's lots of easy ways to dampen the sound of your fan. A 8 inch fan on a speed reducer on the lowest setting is going to still move a lot of air, and quietly. Then wrap it in a moving blanket. Cut a cardboard box and slide it over the fan, and stuff moving blankets around it. You may not even hear it standing next to it if you do it right. For real.

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I'll look into that, it makes good sense. Thanks

growingforfun said:

I agree with most of your post but I think you may want to double check this. I'm pretty sure you want to pull air through the carbon filter whenever possible, and have your fan on the exhaust side of your light. Compression heating an other factors.

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More efficient filtration perhaps but not air flow. You can have both but not with little fans and ducting.

growingforfun said:

I agree with most of your post but I think you may want to double check this. I'm pretty sure you want to pull air through the carbon filter whenever possible, and have your fan on the exhaust side of your light. Compression heating an other factors.

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"Speculation: Does turbulent air flow explain why “filter first” is worst?

Now we’re not 100% sure on this, but based on research on guide vanes, putting a filter before the fan will make the air going into the fan turbulent. Making the fan operate in turbulent air flow (as opposed to laminar flow) has two consequences:

A. One is that the efficiency of the fan is reduced.

B. The other is that the fan will be noisier.

However, we don’t know whether this effect would be large enough to be meaningful.

Putting the filter after the fan means turbulent air (from the fan) is going into the filter. We’re unsure what effect that has on the efficiency of the filter."


https://www.quora.com/Where-should-an-air-filter-be-placed-relative-to-the-fan-for-best-efficiency

There's an engineer's response in the link but basically push or pull is relevant to design.

In other words it's duct distance that dictates fan efficiency. But go big on air and lights always. If 6" will work then go with 8".

Not trying to argue but to help.

I had a similar setup and temps. Not ideal but it worked. I eventually upgraded? to cobs and now I run at 22-24C no matter lights on or off.
You also might consider moving the filter outside of the tent to give yourself more headroom after the stretch. I’d recommend that for any tent 3x3 and under.

Chef420 said:

I had a similar setup and temps. Not ideal but it worked. I eventually upgraded? to cobs and now I run at 22-24C no matter lights on or off.
You also might consider moving the filter outside of the tent to give yourself more headroom after the stretch. I’d recommend that for any tent 3x3 and under.

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thanks for the tip

well today I fitted (with duct tape) 4" ducting to a 6" cooltube (leading to cooltube exhaust) ..it kind of looks like 'The Mummy' and I never want to do it again. Serious waste of metal duct tape but I feel no leaks so far.
The vent end doesn't 'feel' like it has a stronger flow with the 4" ducting, but I'll leave it tonight and see.

As is, we're in a muggy heat wave in the uk. It's even bloody hotter today then yesterday (29.1 degrees in the room where the tent is in ..and the window is fully open!). So I resigned myself to dimming the ballast from 600watts to 400watts (I basically view that as 50% bulb efficiency drop And I can hardly see much temperature drop either.

The temperature inside the tent now is 30.8 degrees (bottom of tent) and 31.8 above the top of the canopy. The top buds are 29.5 to 30.8 (directly below light). The outside room/corridor/floor is a natural 29 F-ing degrees!! ..maybe in someway thats 'good' tent heat management I consider the use of Air Con as a 'losing' choice I do have more fans I could hang in the tent though ..but it could get very silly

My cheap/ slightly broken 2014 500watt (true watt) Chinese cob light is calling me, saying:
"HPS heat sucks in hot summers doesn't it, all that ducting and extra fans pointing in all directions. Come, come back to the old blurple cob side! You know you don't mind lower yields when cobs give faster harvests, good product and easier (plus cheaper) climate control etc.".

When it comes to growing inside ..I HATE hot summers.

1:30 hrs into 12/12 cycle (and after cracking top of tent door - the top bud temps are now 29 to 29.9 degrees.
Bottom of tent is 30 and above the canopy it's 30.4. I guess the temps. will now gradually drop as the night goes on (I hope).

Confucius say: He who moves air glimpses enlightenment

Heat wave continues, with only one air-con unit (reserved for humans and not the grow), the room the tent is in is 83-85F at night. So I decided to drop three extra extractor fans into the tent. One 6" axial flow fan sucking air into the tent (aimed towards centre of tent - between light and plant tops), ducted to the outside of the house for cooler air. Then two 4" axial flow fans (one facing the light fitting and one at the base of the plants), these are simply using the air in the tent.
Not the best use of wattage but it's got the temps. down 'just' enough imo (not perfect but workable). Moving air really is the way
With ballast set to 600 watt (fyi - setting it to 400watts was only a couple of degrees cooler anyway). Tent is 25/28C, Cooltube itself is now 32 degrees and the plant top buds are between 78 - 85.4 F (the highest temps. being in the first and last hours of the 9pm - 9am light cycle).