8x8 tent, humidifier, FAN exhaust and HVAC questions!?!?!?!?

[Renfro]

https://www.amazon.com/Hydrofarm-Autopilot-Desktop-Monitor-Logger/dp/B01FYWU2IS/ref=sr_1_fkmr1_1?keywords=autopilot+co2+logger&qid=1562882864&s=gateway&sr=8-1-fkmr1

That is a cheap way to monitor CO2 levels. I have Co2 controllers in my rooms but I also use some of these to check microclimates and make sure I don't have any stale spots. It can log the CO2, Temp and RH%.

 

[Renfro]

Awesome, thanks a lot!
May very well solve some potential issues

Basically it's sorta a lung room. Toss a big carbon scrubber in there is you wanna keep odors down.

 

[SatIndy]

Basically it's sorta a lung room. Toss a big carbon scrubber in there is you wanna keep odors down.

Whereabouts in the system would that go?
I have no room in my 32" x 32" tent (I really need a bigger tent & then somewhere to put it).

And, since you're kind enough to answer my questions... a 4" inline should be fine for that size, right? Not really sure what to expect from it, so hard to say if it's adequate - or should just go to a 6"?
Thanks again.

 

[Renfro]

Whereabouts in the system would that go?
I have no room in my 32" x 32" tent (I really need a bigger tent & then somewhere to put it).

And, since you're kind enough to answer my questions... a 4" inline should be fine for that size, right? Not really sure what to expect from it, so hard to say if it's adequate - or should just go to a 6"?
Thanks again.

If you are using the room the tent is in as a lung room then you put the carbon filter in there as a scrubber, just sucking air thru the filter and blowing it back into the room. The 4 inch fans are worthless IMO, go 6 inch at least. Centrifugal blowers are loud but move a lot of air. The axial and mixed flow ones don't handle static pressure loss well.

 

[JungleSlut]

Whereabouts in the system would that go?
I have no room in my 32" x 32" tent (I really need a bigger tent & then somewhere to put it).

And, since you're kind enough to answer my questions... a 4" inline should be fine for that size, right? Not really sure what to expect from it, so hard to say if it's adequate - or should just go to a 6"?
Thanks again.

To keeps temps sensible I have a 4" running non stop in my veg tent which is 3.5 by 3.5 feet. It does the trick

 

[SatIndy]

If you are using the room the tent is in as a lung room then you put the carbon filter in there as a scrubber, just sucking air thru the filter and blowing it back into the room. The 4 inch fans are worthless IMO, go 6 inch at least. Centrifugal blowers are loud but move a lot of air. The axial and mixed flow ones don't handle static pressure loss well.

Nice.
Guess the 4" is going back. Should've come here first.
Thanks

 

[JungleSlut]

Nice.
Guess the 4" is going back. Should've come here first.
Thanks

I'm saying it works. I'm not saying it's better than a 6".......a 4" obviously has to work harder than the 6" and takes longer to exhaust hot air.

 

[SatIndy]

To keeps temps sensible I have a 4" running non stop in my veg tent which is 3.5 by 3.5 feet. It does the trick

Ah, that reply was supposed to be for Renfro's input

Well, your situation sounds encouraging but I'm about to flip and it's going to get a lot hotter soon... Trying to tackle the heat & humidity before it gets out of control. So, how would your set-up do in flower? I know it's hard to say b/c environment is different everywhere though...

Would a 6" maybe help lower humidity & heat a bit better though? Without running the 4" full-on?
Thanks

 

[SatIndy]

If you are using the room the tent is in as a lung room then you put the carbon filter in there as a scrubber, just sucking air thru the filter and blowing it back into the room. The 4 inch fans are worthless IMO, go 6 inch at least. Centrifugal blowers are loud but move a lot of air. The axial and mixed flow ones don't handle static pressure loss well.

Okay, if I don't ask, I won't be able to sleep nights...
Dare I ask what 'static pressure loss' is? I could google it I suppose... but it's more fun asking you.

 

[Renfro]

Okay, if I don't ask, I won't be able to sleep nights...
Dare I ask what 'static pressure loss' is? I could google it I suppose... but it's more fun asking you.

I will do my best to explain it really simple. Static pressure is created by your fan. The loss is basically friction, resistance to the air flow. Larger duct sizes for example reduce the friction by reducing velocity. Bends will reduce flow and duct that isn't smooth like the accordion/slinky duct will reduce flow. Longer duct runs obviously increase friction. So a fan is rated at a CFM that it provides but those ratings are usually without any static pressure loss. If you wanna dive deeper than that explanation there is a ton of info on google. If you have access to a air speed meter (cheap on amazon) then you can measure the speed of the air, using that with the duct cross sectional area you can math out the flow with simple multiplication.

 

[JungleSlut]

Okay, if I don't ask, I won't be able to sleep nights...
Dare I ask what 'static pressure loss' is? I could google it I suppose... but it's more fun asking you.

If you wanna know how big of fan you need.
Find out how many cfm you need for your tent
Add 20% cfm for humid environments
Add 20% cfm for a carbon filter.
Add 5-10% cfm for each bend
Add 5-10% cfm for length of duct
And 5-10% cfm for each light

Things of that nature will dictate what size fan and ducting you need

Theres cfm recipes all over google.

 

[SatIndy]

I will do my best to explain it really simple. Static pressure is created by your fan. The loss is basically friction, resistance to the air flow. Larger duct sizes for example reduce the friction by reducing velocity. Bends will reduce flow and duct that isn't smooth like the accordion/slinky duct will reduce flow. Longer duct runs obviously increase friction. So a fan is rated at a CFM that it provides but those ratings are usually without any static pressure loss. If you wanna dive deeper than that explanation there is a ton of info on google. If you have access to a air speed meter (cheap on amazon) then you can measure the speed of the air, using that with the duct cross sectional area you can math out the flow with simple multiplication.

Got it. Awesome explanation...

 

[SatIndy]

If you wanna know how big of fan you need.
Find out how many cfm you need for your tent
Add 20% cfm for humid environments
Add 20% cfm for a carbon filter.
Add 5-10% cfm for each bend
Add 5-10% cfm for length of duct
And 5-10% cfm for each light

Things of that nature will dictate what size fan and ducting you need

Theres cfm recipes all over google.

Okay. Will be sure to find out why light affects the CFM - is it to do with heat? Makes more sense than anything else I've seen on google, lol. Duly noted.... many thanks

 

[Renfro]

Will be sure to find out why light affects the CFM - is it to do with heat?

Yes, more lighting wattage = more heat. But also the hoods restrict flow by adding friction.

 

[Dabs4babs]

Really you can play around with different setups and perhaps find something that will work but the simple clean solution if you have a dual hose portable AC and dehumidifier and run the room sealed with no venting, just vent the tents right back into the room and not outside then you can really control humidity at the expense of having to cool the entire heat load with AC and having to supplement CO2 or just run vent cycles to bring the CO2 levels up to ambient.

Can you describe a little more what you mean by running vent cycles? Are you talking about having vents open periodically, as opposed to constantly?
Also, how would you design the vents inside the room?

Thanks!

 

[Renfro]

Can you describe a little more what you mean by running vent cycles? Are you talking about having vents open periodically, as opposed to constantly?
Also, how would you design the vents inside the room?

Thanks!

A vent cycle means you aren't ventilating the room constantly. So a controller has a deadband setting. You set it to say 80 degrees and a deadband of 5 degrees. The controller will let the temp rise to 80 and kick on the exhaust and/or intake fans to cool the room. Once the room drops to 75 (deadband setting of 5 degrees) the controller turns off the fans. That is a ventilation cycle. This works when the temps rise slowly and you only have to ventilate a few times a day, maybe a couple extra on a really hot day.

A vent cycle could be done for humidity also, if the ambient humidity is lower than your target RH%.

During a vent cycle the controller disables any CO2 enrichment, no reason to blow it all out. Good systems can also be setup to disable a humidification/dehumidification device or heating/cooling device when venting for the other. So say you are venting for high temperature, there is no reason for the dehumidifier to run during the vent cycle.

As to the vents themselves, thats just a blower moving air. It could be a filtered fresh cold air intake. It could be a hot air exhaust. It could be both together. If you want to have no airflow when the blowers are off you can install dampers on the ductwork that will close and open automatically. That prevents high wind from blowing thru your intake. A dust shroom is a good filter for an intake if you can conceal it and protect it from the weather and UV light, I use them in basement window wells and they last a long time, can be washed and reused.

I hope all that helps.