Heat Problems with 600w in 1x1 Tent

[Devilman]

Hey all, hoping I can get some help / advice. Im currently having big problems getting temps low enough in a 1x1m tent I have.

Its setup in a pretty small space (it used to be a bathroom, but still has the shower in) but I never thought it would be this much of an issue.

The layout is as such that there is an open top-window just behind the tent, with a fan drawing air in and down to the bottom of the vent via ducting. scrubber / fan hangs internally with pipework as such.. Scrubber -> cooltube -> fan -> out the top.

Im worried that some of the problem may be the length (and number) of 90degree bends in the extraction pipework, It turns 90 from fan through top of the tent, then 90 across the top, 90 down the side to ground level, 90 again away from the tent, then 90 through a wall.

Even though the fan running the show is an SD 250, working from the temperature / CFM chart in the Ventilation 101 thread, It seems as If I am really struggling for airflow.

For reference, at the time of testing, outside air temp was approx 20c / 68f, Ambient room temp was approx 24c / 75f. The problem is, the temp inside the tent even with lights off is always around 24c to start with due to room temp (lets face it, tents arent exactly insulted lol). Lights-on temps seem to stabilise in the 30-31c range (86-88f) and exhaust temps from the cooltube / scrubber end up leveling-out at around 43-45c (109-113f)

Looking at the chart in the Vent 101, that would seem to suggest Im only achieving maybe 55-60CFM? I tried removing the scrubber and that did indeed lower exhaust temps a little (to be expected, since they reduce airflow) but did almost nothing to the tent itself. I also tried unzipping the bottom of the tent, to see if the inlet was undersized and reducing the output of the exhaust fan, but likewise, very little change.

I can try to get some pictures tonight hopefully, but I honestly never thought it would be so hard to keep a 600w HPS in a 1x1 tent cool in good old England.

1 Last thing I wanted to ask also... might sound strange but, obviously the tent is currently empty while things are being setup etc.. what can I expect once the plants are in, do temps typically rise a bit or fall? Im hoping at least someone out there may have noticed if their temps changed a bit once some of the airspace was taken up by plants / pots etc ?


Thanks all.

 

[Hydro-Soil]

With that many 90's you're going to need a MUCH bigger fan.

Unless you can straighten out the bends, that's your only option.

Stay Safe!

 

[Devilman]

I could possibly vent directly out of the window behind the tent, but then I would have to resort to using room-air for the intake, which is less then ideal, although it may significantly increase the efficiency of the cooltube setup.

As it stands at the moment, TD-250 is barely making 50CFM from the temperature figures, which is no doubt what is causing chamber(tent) temps to be more than just a couple degrees above ambient, which seems to be the "butter zone".

I Also have a 400w HPS which I could possibly run until things cool down a bit outside (maybe switch to 600w around 4 weeks into flower, so in theory in 1 months time airtemps should be lower)

Any thoughts / suggestions? (Also, sorry to ask again, but anyone know whether to expect a temp rise or fall once plants are in?)

 

[resinryder]

Don't quote me on it but believe I was told years ago that every 90 degree turn drops the efficiency of the fan by a 1/4th. May have been more than that but I can't remember. at the moment.

 

[rives]

I take it that you are using both an inlet and an exhaust fan, and the exhaust fan is 250cfm. How big is the inlet fan? What size ducts are you using? In dealing with line restrictions, you need a fan that can handle higher static pressure rather than a fan with higher volume - sometimes one comes with the other, sometimes not. Over-sizing the duct diameter can help mitigate the losses from the 90's.

 

[medmaker420]

I would just run dryer flexible ducting and remove the intake fan and use a larger exhaust fan set on a speed regulator switch so you can speed up or slow down to where you need it and have the inline fan right before the scrubber.

For example my scrubber is a 5 gallon bucket with holes drilled all around that I have filled with activated carbon that my inline fan blows into. Having a larger diameter scrubber compared to the ducting will help with allowing better airflow as well.

Tents are never air or light tight so having that intake fan isn't really stopping the air movement from getting into the tent BUT with just one GOOD exhaust fan and then have that intake fan IN the tent blowing that hot air up and out towards the exhaust ducting would be better and more efficient.

 

[rives]

I would just run dryer flexible ducting and remove the intake fan and use a larger exhaust fan set on a speed regulator switch so you can speed up or slow down to where you need it and have the inline fan right before the scrubber.

I don't think that a passive single dryer flex duct would keep up with his existing fan..... maybe if he brought several in to different points, it would help distribute the air better and get an adequate air supply. Rule of thumb on a passive inlet is double the area of the exhaust, and Mountain Air filters recommends having 6x the inlet area.

 

[Devilman]

I take it that you are using both an inlet and an exhaust fan, and the exhaust fan is 250cfm. How big is the inlet fan? What size ducts are you using? In dealing with line restrictions, you need a fan that can handle higher static pressure rather than a fan with higher volume - sometimes one comes with the other, sometimes not. Over-sizing the duct diameter can help mitigate the losses from the 90's.

Yeh have just a kinda crappy extractor type fan hooked on for the inlet, maybe 1foot of ductig to the window, and another 4 feet inside the tent. The fan Im running is an S&P TD-Silent 250, which as I found out when checking earlier, is rated at 250m3/hr (about 150cfm).

The Ductwork between the scrubber, cooltube and fan is (I think) 4" flexi ducting. After the fan is a short (2-3feet) section of the same 4" ducting going up out the top of the tent, then joining to 5" ducting the rest of the run.

The biggest thing that surprised me tbh was seeing most people quoting figures of chamber / tent temps only 2f-5f over ambient, while I'm unfortunatly seeing closer to 12f-15f over ambient.

should I perhaps change the fan location so that its pushing more of the time instead of pulling? currently airflow goes ... Scrubber -> CoolTube -> Fan -> Exhaust Ducting.

Would it be better to have the fan right after the scrubber and before the cooltube? Might help the fan a bit not having to "eat" hot air from the cooltube I guess? (not sure what safe temps these are rated up to, but having 45c / 113f air going through it maybe shortens its lifespan or affects the fans ability to generate as much static pressure, im thinking hot air is less dense, but how much it would make a difference, I dont know)

 

[astartes]

Try extracting the air rather than pushing it out. This orientation will drop your temps, but also mean that your fan and filter are outside the tent. Go Hood>>>duct>>>fan>>>filter.

a.

 

[Devilman]

Unfortunatly that configuration is not really possible with my scrubber setup etc.. without it just dumping exhausted heat into the room, which kinda defeats the purpose of the cooltube etc.. =/

What If I re-located the fan much closer to the end of the exhaust ducting? So it was more like... Scrubber -> Cooltube -> Exhaust Ducting -> Fan. Reason for asking is my exhaust run is probably about 20-25ft and has about 6 bends in it (mostly 90degree ones) and I dont know if it would be better to try and suck the air through the bends, or push it through (as it is now).

 

[unclefishstick]

i am running a 4 foot x 4 foot tent with a 1000w lamp and not having any troubles keeping my tent cool.the first pic shows the exhaust set up, a 6x20 inch phat filter,then a 6 inch vortex fan,then a u-bend of flex duct,then out through the reflector and out the tent.
the second pic shows the intake side,im hooked up to the duct for the house cooling system,then to a 6 inch inline booster fan (185 cfm) then to a 6x6x6 "Y" ,then through 2 6 inch flex ducts into the tent.the other two open duct spots in the tent have 6 inch flex duct in them so 4 of the tents 5 duct ports are intake,only one exhaust..
im able to get a well balanced amount of negative pressure without sucking the tent walls in,and it only runs a couple degrees above ambient.

 

[sso]

its gonna get alot cooler in that tent, once you have some plants of some size in there.


and ive found that in vegstate, 30c heat does not matter so much (its plants from places like frigging afghanistan and india for christs sake. )

and the denser canopy in flowering will bring the temps down at least 5c (if full canopy.)

and what matters the most, is keeping the roots cool.

that being said, if you could get rid of some bends in your ductwork, that would be cool.

 

[joe guy]

Try moving the fan that may work and its free... my idea would be get one or two of those lil in line booster fans I belive they are only 30 or 40 bucks.. they are rated for 90 to 200 cfm so I'm sure u would see a diffrence then.. my set up goes scrubber, fan, light , exahust.. no intake just a fan speed controller that dimms a 345 cfm down a tad so the neighbors don't hear it.. and only 1 or two degrees warmer than ambient

 

[Devilman]

Well, the tent is being setup for them to go into flower, hence the concern about temps being in the 30-31c range, but its good to know that temps should drop a few degrees just from having it full of plants. That plus the cooler weather which is on the way should hopefully keep things about right.

1 More thing... after looking at the pdf's for the S&P TD-Silent 250 fan, it seems as though having it after the cooltube may not be adviseable, as its listed temp range is -10 - +40 and my exhaust temps are in the 40-45c range. I dont want to damage the fan from having it sucking air thats too hot for it.

 

[rives]

There seems to be a difference between fans by that model name on each side of the pond - the US version is a big damn fan (10", 550/750 cfm). The fan that looks equivalent to yours here (4" inlet/outlet, 135 cfm) is not going to be able to handle your application. Even a vastly oversized carbon filter (a Mountain Air 8'" x 20") it is going to have enough restriction to drop your air flow by over 30% without considering the ducting. Those mixed vent fans are nice and quiet, but don't deal with back pressure well.

You need to find a table that lists cfm vs static pressure for your fan, and get the pressure drop curve for your carbon filter. That will at least tell you what you are starting with before all of the other choke points are factored in.

 

[vukman]

I think the idea that medmaker420 said about the flexible tubing is a start. I thought that the ratio was every 90 drops air speed by 50% but there are other sites for those calculations. No matter how you slice it..way too many bends going on and not enough power.
Also, sucking the air out is the way to go instead of pushing. I mean each to their own, right.. Gonna put a pic in here again to show a point

Mind you, that isn't a cool tube but if it were, the hook-up would go through the hood instead of behind it in that manner. and the tent is shaped differently.. You've got a square where I have a rectangle which does make venting easier albeit the flex tubing does make the bend angles smoother.....

Filter/scrubber->fan->hood->out

Also, in this manner, you're saving the fan from being exposed to the high exhaust temps so less wear on the bearings due to heat.

Just a thought..as it says in my sig....my opinion only....

Good Luck

 

[Devilman]

There seems to be a difference between fans by that model name on each side of the pond - the US version is a big damn fan (10", 550/750 cfm). The fan that looks equivalent to yours here (4" inlet/outlet, 135 cfm) is not going to be able to handle your application. Even a vastly oversized carbon filter (a Mountain Air 8'" x 20") it is going to have enough restriction to drop your air flow by over 30% without considering the ducting. Those mixed vent fans are nice and quiet, but don't deal with back pressure well.

You need to find a table that lists cfm vs static pressure for your fan, and get the pressure drop curve for your carbon filter. That will at least tell you what you are starting with before all of the other choke points are factored in.

I think the main reason for the difference is that in the US they only sell the "TD-250" model, which is an entirely different fan to the "TD-Silent 250".

I have found the datasheet for it however (see below).

Unfortunatly I have yet to be able to find the resistance curve for the scrubber... is it possible to get a rough idea of its resistance curve with some "DIY Testing" or does it specifically require an airflow meter to measure CFMs, SP and so on?

View Image
I think the idea that medmaker420 said about the flexible tubing is a start. I thought that the ratio was every 90 drops air speed by 50% but there are other sites for those calculations. No matter how you slice it..way too many bends going on and not enough power.
Also, sucking the air out is the way to go instead of pushing. I mean each to their own, right.. Gonna put a pic in here again to show a point

Mind you, that isn't a cool tube but if it were, the hook-up would go through the hood instead of behind it in that manner. and the tent is shaped differently.. You've got a square where I have a rectangle which does make venting easier albeit the flex tubing does make the bend angles smoother.....

Filter/scrubber->fan->hood->out

Also, in this manner, you're saving the fan from being exposed to the high exhaust temps so less wear on the bearings due to heat.

Just a thought..as it says in my sig....my opinion only....

Good Luck

Yeh main reason I was thinking about putting the before the cooltube was to stop it chugging on 40c+ air that will no doubt reduce its bearing life etc.. but I do tend to agree with you that generally, air being pulled through a pipe is probably better than being pushed..

 

[Bush Dr]

The fan is too small ..... every 90 degree bend puts the efficiency down to 60% .. .. you need 300m3/hr of actual air movement, if the tent sides don't move inwards when the fan is switched on, the plants will never get to their full potential

Also the fans should be at the end ..... lamp>filter>fan

I assume this is vertical .... if not you're fighting an uphill battle

 

[abirdintheair]

I run the exact same thing as you, similar setup minus the duct work. does your tent have passive intakes at the bottom? with 2 passives open, a single 250cfm fan with matched filter kept lights on temps to barely 70, lower during lights off. only duct work I used was the exhaust fan straight up and out. bush dr nailed it, the tent sizes should suck in a bit during fan on.

 

[Devilman]

The fan is too small ..... every 90 degree bend puts the efficiency down to 60% .. .. you need 300m3/hr of actual air movement, if the tent sides don't move inwards when the fan is switched on, the plants will never get to their full potential

Also the fans should be at the end ..... lamp>filter>fan

I assume this is vertical .... if not you're fighting an uphill battle

Figures seem to vary on exactly how much 90degree bends cut down flow, but using the Exhaust temp charts in the Vent 101 thread, it would seem I am down to around 50-60CFM (about 85-95M3/hr).

Also, its a horizontal setup in a 1m x1m Tent, and the scrubber is not a home-made one, so I cannot easily install it after the lamp but before the fan.

I run the exact same thing as you, similar setup minus the duct work. does your tent have passive intakes at the bottom? with 2 passives open, a single 250cfm fan with matched filter kept lights on temps to barely 70, lower during lights off. only duct work I used was the exhaust fan straight up and out. bush dr nailed it, the tent sizes should suck in a bit during fan on.

It does indeed have passive intakes at the bottom, but for 2 reasons I was not opening them. One is that they are very poorly light-trapped and would need to be closed / re-opened every day, Secondly, because I tried running the tent with the bottom of the doors unzipped etc.. and it made very little difference.

Also its worth noting.. the S&P TD-Silent 250 is a 250M3/hr fan, not 250CFM (for reference, 250M3/hr is roughly 145CFM).