Two simple questions with a lot controversy

OldMedUser said:

If you have a dusty environment pushing the air into the can filter will plug it up inside. I got one here a buddy gave me and that's how they ran it. I hooked it up with my 6" and couldn't keep the temps below 82 or so at full speed and I had no problem keeping it 75 with it running 1/2 speed before. When I unhooked the duct on the out side of the fan there was bugger all air flow. My cheap little 6" duct fan would push more air by itself and my inline is 400cfm at least. Has no markings on it but blows better than a $100 hooker. Going: filter -> fan -> 1ft duct -> outside. Was running a 1000W HPS with an open batwing reflector in my 7x8x6.5h underground concrete bunker for a grow room.

Got the no-name fan off my buddy too and it's sounding like it might be on it's last legs. Just a grumble sometimes and a bit of vibration when you touch the housing. I have it suspended from the ceiling on a bungee cord so any vibration doesn't transmit thru the ceiling up here into my man cave. I'm literally sitting on my grow room.

Click to expand...

It's in my kitchen, so no it's not that dusty . Even if it was dusty wouldn't clog it up any more than if it was inside the tent, you just take the pre-filter and put it inside the filter, , and it catches the dust. . Wish I had a basement for this little activity

coreywebster said:

Where was the thermometer when you took the readings? If its right under the light then your getting a false reading. It should be above the light line to measure air temps which are what you want to measure. The IR in the HPS heats up the thermometer very quickly. Plants can take a lot more radiant heat than they can high air temps.
If this is what you have done I would try another test run and would be surprised if you didn't see a drop of 5-10 degrees F

Click to expand...

I took it right under the light, as that is what i read most people talk about "temperature at the canopy", had no idea about that, that plants can take up more radiant heat, you say "a lot", so is that to mean that my temps were actually ok? Above the lamp it must have been around 75-77. Anyway now is too late, my reflector is packed, and going back tomorrow, and my Cool tube should arrive tomorrow as well. Ill have some more freedom with the cooltube then, I can lower the rpm on the fan, and even relax with my worries about too many ducting bends and loss of Cfm

Yeah you would of been fine as you were. Its a common mistake people make when trying to get temps in range.
Air temp is what we need to keep in that perfect range. Canopy temp is difficult to get a reading on without a laser thermometer. Which is why folks use the hand test, if you can put your hand at canopy without it been uncomfortable then you are all good.
You can put a thermometer under a white card at canopy level too.

The article below shows the massive difference between the plants tolerance for air temp and radiant heat.

http://cannabis.com/faqs/growing/growroom-how-do-i-measure-temperature-correctly.html

As you say, the bonus since you have the cooltube coming anyway is been able to turn down the fan, making it much quieter and you can drop down the light closer to the plants (or raise the plants to the light) as long as your still maintaining a good spread of light.

coreywebster said:

Yeah you would of been fine as you were. Its a common mistake people make when trying to get temps in range.
Air temp is what we need to keep in that perfect range. Canopy temp is difficult to get a reading on without a laser thermometer. Which is why folks use the hand test, if you can put your hand at canopy without it been uncomfortable then you are all good.
You can put a thermometer under a white card at canopy level too.

The article below shows the massive difference between the plants tolerance for air temp and radiant heat.

http://cannabis.com/faqs/growing/growroom-how-do-i-measure-temperature-correctly.html

As you say, the bonus since you have the cooltube coming anyway is been able to turn down the fan, making it much quieter and you can drop down the light closer to the plants (or raise the plants to the light) as long as your still maintaining a good spread of light.

Click to expand...

Oh wow, thanks for the link and update, learned something new and important today strange how the show where i bought the stuff for didnt ask me or told me this when i messaged them about the issue.

I just tested on my 150Watt hps now, holding the hand 3-4 inches under the bulb i could do quite comfortably, with a 72cfm 140mm PC fan blowing straight under the lamp. While I have my termometer in the pot of a seedling 12inches from the bulb and the termometer shows 86F. I alse tested the temp 4 inches over the hood, and its 82F.

I've run both ways. Sucking through the filter is more efficient. These fans are designed to be at the end of the duct run, creating a vacuum in the system and venting out freely.

My tents now are set up with a "T" between them, plumbed into 6" rigid venting through a 440cfm 6" inline fan into the carbon scrubber. I wanted the extra space in the tent, so I moved the scrubber outside. I have to run my fans at a higher speed to get the same cooling as if I was pulling through the scrubber, I think due to the resistance. My lights are on their own cooling circuit with a separate fan. I'm planning on building a sealed box in between the tent and fan to mount my filter in so it's pulling through the filter, trying to get done more cooking capacity back.

WeedFreak78 said:

I've run both ways. Sucking through the filter is more efficient. These fans are designed to be at the end of the duct run, creating a vacuum in the system and venting out freely.

My tents now are set up with a "T" between them, plumbed into 6" rigid venting through a 440cfm 6" inline fan into the carbon scrubber. I wanted the extra space in the tent, so I moved the scrubber outside. I have to run my fans at a higher speed to get the same cooling as if I was pulling through the scrubber, I think due to the resistance. My lights are on their own cooling circuit with a separate fan. I'm planning on building a sealed box in between the tent and fan to mount my filter in so it's pulling through the filter, trying to get done more cooking capacity back.

Click to expand...

I have now become fairly certain that going with either way concerning the placement of the filter is fine, i've heard numerous growshops and even phreshfilter representative on youtube say that its fine. The only question then remains does it actually matter to the Cfm if the fan pulls or pushes. Appreciate your opinion and experience, but I still value most a real scientific test, where someone measures with instruments.

If the fan is at the start of the system or at the end, vacuum is created anyway, as long as the ducting doesnt have leaks, and there is no active intake that surpass the exhaust.

Oneirogen said:

If the fan is at the start of the system or at the end, vacuum is created anyway, as long as the ducting doesnt have leaks, and there is no active intake that surpass the exhaust.

Click to expand...

A fan at the beginning of the ducting creates positive pressure, pushing through the ducting. A fan at the end creates negative pressure. Negative pressure is better than positive on ventilation systems. It'll work both ways, just much more efficient pulling than pushing. If you want more technical info, look into HVAC publications, it's how I figured out how to set up a decent vent system. They've done all the technical testing you could want.

WeedFreak78 said:

A fan at the beginning of the ducting creates positive pressure, pushing through the ducting. A fan at the end creates negative pressure. Negative pressure is better than positive on ventilation systems. It'll work both ways, just much more efficient pulling than pushing. If you want more technical info, look into HVAC publications, it's how I figured out how to set up a decent vent system. They've done all the technical testing you could want.

Click to expand...

Maybe we are both right in different ways. What I think about when I say negative pressure, is the pressure in the tent. So for example if you have 1 inlet and 1 outlet with 1 fan in each, If the fan in the outlet is stronger it creates negative pressure in the tent, since it sucks faster than the other blows in, so some of the air will be sucked from tent leaks and other openings. Were the tent 100% sealed, then the inlet fan should speed up a bit, while the outlet fan will slow down. The other way. if the inlet fan is stronger, its positive pressure, since there is more air coming in than the outlet can blow out., and air will slip out through leaks. So in this sense placing the fan either directly before the cool tube or at the end of the ducting outside the effect would still be negative pressure in the tent as a whole.

Its the same principle they use when talking about PC case cooling. All fans equal, if you have 2 fans blowing in, 1 out, its positive pressure, which is desireable since its prevents dust coming in if it were the other way around, and dust would be sucked in through difference holes and leaks.

coreywebster said:

Where was the thermometer when you took the readings? If its right under the light then your getting a false reading. It should be above the light line to measure air temps which are what you want to measure. The IR in the HPS heats up the thermometer very quickly. Plants can take a lot more radiant heat than they can high air temps.
If this is what you have done I would try another test run and would be surprised if you didn't see a drop of 5-10 degrees F

Click to expand...

It's not my first rodeo pardner. I have 3 themometers/RH meters at various places in the room and the RH/Heat controller for my fan and the thermostat for the heater are all on a shelf away from the grow light about 2/3 of the way up an inside wall. One of the thermometers is a remote one and it's temp shows on my Atomic clock that is just above my computer monitor in the man cave here. There is a 16" fan aimed so it blows air toward the light and mixes the air really good in that space so a foot from the floor or ceiling the temp is the same anywhere in the room.

I use a laser thermometer to check the leaf temps under the light to make sure that they don't get warmer than 80 as the light passes over them or while it pauses at each end. The 1000W can be as close as 1ft without exceeding that temp.

I've been growing in that room for 14 years so I've got to know it pretty well.

Thanks for your concern but I think I've got it covered.

Oneirogen said:

ts the same principle they use when talking about PC case cooling. All fans equal, if you have 2 fans blowing in, 1 out, its positive pressure, which is desireable since its prevents dust coming in if it were the other way around, and dust would be sucked in through difference holes and leaks

Click to expand...

So the two fans blowing in have filters so they don't blow in the dust? I tried that but it restricted air flow too much and my hardware monitor showed my CPU and video card temps went up almost 10C. So once a month or when the temps are a few degrees above normal I just get the shop vac and my can of air duster and blast the heat sinks clean.

OldMedUser said:

I've been growing in that room for 14 years so I've got to know it pretty well.

Thanks for your concern but I think I've got it covered.

Click to expand...

Not sure why you thought my comment was aimed at you OMU, it was for the OP .
I know you don't need any advice from me dude.

coreywebster said:

Not sure why you thought my comment was aimed at you OMU, it was for the OP .
I know you don't need any advice from me dude.

Click to expand...

My bad. Was just starting my first cup of coffee and know better than to start posting until the 3rd cup.

Ah well. Maybe somebody will learn something from my babblings so not all is lost.

OldMedUser said:

So the two fans blowing in have filters so they don't blow in the dust? I tried that but it restricted air flow too much and my hardware monitor showed my CPU and video card temps went up almost 10C. So once a month or when the temps are a few degrees above normal I just get the shop vac and my can of air duster and blast the heat sinks clean.

Click to expand...

Well of course some dust come in that way also, but best remedy for that besides having a dust free room, is raising your PC case at least 1 feet off the ground, second best option is of course having dust filter för the intake, third best option is to have Positive pressure so that the intake fans actually push out air through any springs . Raising the Pc a feet of the ground renders the positive negative pressure aspect almost useless, since there is not too much dust at that height and higher. But if you had a dusty room, and had your PC case on the ground with negative pressure inside the case, it would suck in dust from the floor and every time you walk passe it and stirr the dust around


Regarding your issue with dust filter, depends on the quality of the filter of course and also on the Case if it allows enough access to air, and also on the static pressure of the fans. I have 2 fans with filter in my front without any issues, once every 2 months i take them (filter) out and brush them off, I have to really hold them in an certain angle against the light to even see the little dust on them . I have a Fractal design R5 case , highly recommended

My mid-tower case is sitting on my desk so it's almost 3 feet off the floor. Not my first rodeo with computers either. Been building them for fun and profit for almost 30 years. This case has had at least 5 rebuilds and overdue for another. Couple of leaking capacitors on the motherboard so it's only a matter of time.

I smoke cigs so all that crap my lungs don't get the computer catches it so I don't suffer from second hand smoke.

It's got a fan in the middle of the side that blows right on to the motherboard and the 650W PS has a huge fan in it that is quiet as a mouse. I can tell when the heat sinks need cleaning as the CPU fan runs at high speed more often than usual.

As soon as I can afford a new MB and likely new ram and CPU I'll retire XP Pro and go with some flavour of Linux.

30 years, you clearly have some experience and knowledge then .

Cigarette smoke though should at worst cause some yellowing, but i doubt it creates any particles that would have any effect on your cooling. Dont know your components, case and cooling configuration so I cant give any comments to the what seems to frequent need to clean the heatsink. You can see my rig below, Ive had it for 1½ year, and looks clean as a whistle without me having to do anything internally, only cleaning the fan filter every couple of months or so.

Wow, still on XP pro! haha, I'm hanging on to windows 7 though as long as I can, Microsoft has become a total A-hole with Win 10 and the telemetry and spying and forced updates crap.

I grabbed a pic of mine and it looks like it's almost time for a cleaning.



The wife has a laptop with Win8.1 on it and they tried to push Win10 but I found something online to prevent them uploading it in the background and stop the nag screen popups.

We live in the middle of farmland so there's a lot of dust in the air anytime snow isn't covering the ground. The only place dust doesn't build up on everything is the grow room because all the air going in there is filtered.

OldMedUser said:

I grabbed a pic of mine and it looks like it's almost time for a cleaning.

View attachment 3959301

The wife has a laptop with Win8.1 on it and they tried to push Win10 but I found something online to prevent them uploading it in the background and stop the nag screen popups.

We live in the middle of farmland so there's a lot of dust in the air anytime snow isn't covering the ground. The only place dust doesn't build up on everything is the grow room because all the air going in there is filtered.

Click to expand...

Oh shit, I never seen anything like this, its a wonder that Pc still runs, haha.
Obviously we live in 2 very different enviroments

Anyone got any comments on this type of setup? I started a thread on it, but nobody replied...

The air from the small grow cab comes through the pipe on the right... the fan is pulling at the end of the ducting on the left.

Would this work?