Where to pull intake air from?

[Fraggle Rock]

Ok, let me clarify some things, just so you have them for reference. Most houses are set to around 70F year round. This means the ambient air you are drawing from the rest of the house, no matter the means, is around 70F.

That means that even if your temps are running a whopping 15 degrees above ambient, you're only at 85, which is perfectly fine for our favorite plant. With the amount of air those fans can move, you shouldn't be running anywhere near 15 degrees above ambient. As you stated, you're already running just a few degrees above ambient.

When I was running a similar setup, I used just a single 8" Vortex 747 cfm to cool 2 kw, and my only intake was the central air. Using just that, my temps were only 1-2 degrees F above ambient. By the way, a 6 inch fan for flouros, WOW

Also, as far as upsetting the balance of the system, you are severely underestimating the amount of air a central unit moves I can say, from experience, that it will not have any noticeable effect on the temperature of the rest of the house.

Hope that helps for a bit deeper understanding of what we're dealing with in temp control

Man, thanks for that...It makes sense. I will use the central AC vent and see what happens....I know my 6" is overkill, but it keeps the temps and humidity in check. I could probably use a speed controller for that one and turn it down just a bit.

 

[Danseur]

You have some good fans, nice! It is also become more clear your situation.

IMO adequate intake for those fans should be at least double to triple the duct size. Meaning at least 12" intake for the 6" fan and at least 16" intake for the 8 inch fan (unless they are run inline to each other). This is just a rough aprox. because the area of your space and other variable environmental factors should be considered. It is a starting place at the least to try and reduce your whooshing sound.

Have you thought about utilizing the a/c vent in the summer when the a/c is on, and in the winter use the outside cooler ambient air for intake? It would require a splitter or dampener (not sure i think this is the correct term) so that you could choose which intake source you would like to use. If you do not want to use a splitter and dampener you can manually change the intake source 2 times a year. Once before winter to take intake from outside cooler temps, and then again after winter as summer approaches when you start using your central a/c.

IMO one single vent (say 6" max) in the room and spaces under the door are not going to be enough intake while eliminating the whooshing sound. To eliminate that sound you need much more intake surface area. Have you thought about a control for your fans to slow them down? Or will that not work because of environmental and heat issues?

You are already grabbing air from the dwelling simply by using those fans to exhaust. It is come from under your door, and if you add intake from another source in the dwelling it will grab from that place also. You are grabbing air from your dwelling in most all of these scenarios, the only scenario I notice that does not grab air from your dwelling is if you source the intake from outside.

The difference between how much you are grabbing from the rest of the house has to do with how much is available. Right now just the gaps at the door are available, and it is not enough which gives the whooshing sound you are trying to eliminate. Giving the space more intake to eliminate this sound, in turn will grab more air from your dwelling (unless sourcing air from outside).

 

[NiteTiger]

Man, thanks for that...It makes sense. I will use the central AC vent and see what happens....I know my 6" is overkill, but it keeps the temps and humidity in check. I could probably use a speed controller for that one and turn it down just a bit.

Better to overkill than find yourself short, especially in ventilation. Plus, there's room for expansion

I use "The Speedster" fan control, only $30 at my local hydro shop.

 

[NiteTiger]

IMO adequate intake for those fans should be at least double to triple the duct size. Meaning at least 12" intake for the 6" fan and at least 16" intake for the 8 inch fan (unless they are run inline to each other). This is just a rough aprox. because the area of your space and other variable environmental factors should be considered. It is a starting place at the least to try and reduce your whooshing sound.

Posted at the same time

This would be accurate, if we were talking about a passive intake. An active intake (such as a central unit vent) does not require that kind of volume.

 

[Danseur]

lol yes I should have put "passive" you brat! lol I was still thinking OP was going with dummy vents.

So much help going on so fast I didn't get to see you and his post that he was going with the central a/c and not dummy vents. BTW

Ok, let me clarify some things, just so you have them for reference. Most houses are set to around 70F year round. This means the ambient air you are drawing from the rest of the house, no matter the means, is around 70F.

^^ that advice is solid gold brother!

p.s. to say it again in case op missed it, if using the central a/c set the fan to "always on" and not auto if there is the option.

NT do you happen to know if heat acts similar to a/c in that when a/c is run say at set point of 70 the actual air out of the vents is a few degree cooler. Does heater work the similar way? I do not think this would affect the OP but I am unsure if they work in a similar fashion. Either way with that proper exhaust you should be running near ambient like NT's example. It is a wonder what aircooled lights and proper exhaust can do for removing heat isn't it.

 

[fishheadbob]

How about one inch. Nobody should notice that litle bit, and on a 32 inch door that's an additional 32 square inches of intake, same as a 4 by 8 intake duct. That's a lot of pre-conditioned air from your AC House.

 

[NiteTiger]

lol yes I should have put "passive" you brat! lol I was still thinking OP was going with dummy vents.

I was wondering

NT do you happen to know if heat acts similar to a/c in that when a/c is run say at set point of 70 the actual air out of the vents is a few degree cooler. Does heater work the similar way?

Yes, in my experience it does work the same, with the air coming out being warm instead of cold, of course. Some people are concerned their grow will heat up because of that. That has not been my experience though. It is winter after all, you're not going to spike your ambient air temp to 80 degrees in that room

It is a wonder what aircooled lights and proper exhaust can do for removing heat isn't it.

Yeah, I always get a little tickled when I realize I've completely nullified a space heater with nothing more than good airflow

 

[Squire5683]

Hey guys... not trying to hijack thread, but I intake all my air from under my house. Ever notice how its always cool under a house even during hot summer months! Its a natural A/C and its nice and dry. Ive got a dumb question that I havent seen anyone cover.... BUGS... How do you filter your incoming air for pollen, bugs, etc? I have just started my 25 plant grow, and im petrified to look in there some day and see a lot of gnats, flies, etc. Any ideas. Im currently running a typical A/C filter at my intake, but I think little bastards might crawl through. Thanks for the read!

 

[NiteTiger]

Hey guys... not trying to hijack thread, but I intake all my air from under my house. Ever notice how its always cool under a house even during hot summer months! Its a natural A/C and its nice and dry. Ive got a dumb question that I havent seen anyone cover.... BUGS... How do you filter your incoming air for pollen, bugs, etc? I have just started my 25 plant grow, and im petrified to look in there some day and see a lot of gnats, flies, etc. Any ideas. Im currently running a typical A/C filter at my intake, but I think little bastards might crawl through. Thanks for the read!

Like you said, I just use a typical a/c type filter. Nothing to restrictive though. In many cases I've used simple window screening. Never had an issue

 

[puff adder]

I do exactly the same thing!

2 screws undid the central air duct (which I plugged up), leaving the rectangle hole for the grate open-you can look down through to the ground from above.

I have an 8" Vortek fan in the attic, air is pulled from the scrubber, across 4 lights, and out into the attic.

The negative pressure is great, and the air being sucked in from under the house is freezing cold even on really hot days. I stretched some panty hose over a flange as a filter and velocity indicator/wind sock.

My temps are 75 degrees lights-on with 4 1000 watt lights in a 11x13 room with no AC. In winter I actually need to turn the fan down or it gets too cold.

This is 100% stealth, and 0% damage to the house (other than the hole in the ceiling for the fan, which you already have). The central AC ducting can just be unplugged and reinstalled in 5 minutes.

 

[Kalicokitty]

You say there's a closet in the bedroom? where do the walls of the closet back up to?
I ask because I added a vent to the back wall of the closet in the room once, the wall on the other side was the wall of another bedrooms closet, plenty of airflow and unnoticeble(just lean something over the vent in the closet so even if someone looks in it they won't see it)

 

[Fraggle Rock]

SO I opened the central AC vent....that will not work right now. Maybe during the summer when the actual AC is running. Currently my house is set to 70 and maintains that temperature during the hours I am home....as soon as the heater kicked on, my bedroom temps jumped up about 10+ degrees from mid 70's to high 80's - Now I know everyone's environment is different, I am just posting my results from this thread so far...

I think that taking ambient air from another room in the house is the best bet....the air that comes directly out of the vents is a little hotter or cooler depending on the climate setting....

This thread is great! Thanks to everyone for the replies!! I hope to help other people with the same issues!!

 

[puff adder]

I was suggesting to unhook the duct from the central AC/heat vent and plug it up, (so in the room=no heat or AC) and if you remove the vent grate you can look directly down to the ground.

The heat and AC settings from the house then will have no effect on your room temps.

The negative pressure from your fans will draw cold air up from under the house.

 

[Fraggle Rock]

I was suggesting to unhook the duct from the central AC/heat vent and plug it up, (so in the room=no heat or AC) and if you remove the vent grate you can look directly down to the ground.

The heat and AC settings from the house then will have no effect on your room temps.

The negative pressure from your fans will draw cold air up from under the house.

My bad, I didn't address this earlier. I have a single story home that is on a concrete slab foundation. So no crawl space under the house.

That's why I was thinking I could use the vent on the ceiling and use ducting in the attic to bring air from another part of the house...

Some people were suggesting that I can just use that HVAC vent and when I finally opened it yesterday, my room temps spiked 10+ degrees. My house is set at 70, but I think the air is much warmer as it leaves the vent.

 

[Fraggle Rock]

You say there's a closet in the bedroom? where do the walls of the closet back up to?
I ask because I added a vent to the back wall of the closet in the room once, the wall on the other side was the wall of another bedrooms closet, plenty of airflow and unnoticeble(just lean something over the vent in the closet so even if someone looks in it they won't see it)

The closet backs up to the master bedroom closet. Probably not a good idea in my situation to vent from there.

 

[Fraggle Rock]

I do exactly the same thing!

2 screws undid the central air duct (which I plugged up), leaving the rectangle hole for the grate open-you can look down through to the ground from above.

I have an 8" Vortek fan in the attic, air is pulled from the scrubber, across 4 lights, and out into the attic.

The negative pressure is great, and the air being sucked in from under the house is freezing cold even on really hot days. I stretched some panty hose over a flange as a filter and velocity indicator/wind sock.

My temps are 75 degrees lights-on with 4 1000 watt lights in a 11x13 room with no AC. In winter I actually need to turn the fan down or it gets too cold.

This is 100% stealth, and 0% damage to the house (other than the hole in the ceiling for the fan, which you already have). The central AC ducting can just be unplugged and reinstalled in 5 minutes.

I really like this idea!! I wish I had a crawl space below my house!!

 

[InducedSerenity]

This thread is great! Thanks to everyone for the replies!! I hope to help other people with the same issues!!

You and the others in the thread indeed have. I'll also be plugging a heat return vent and pulling intake from inside the ducting and vents in my house... good to know that it indeed works. Have you hooked this up, fraggle, and if so how much ducting are you pulling through and at what fan speeds/cfm?

I was considering putting vents in the back of my room facing into another closet but that's only if i have to.

 

[Fraggle Rock]

I still haven't officially made my intake. I have not decided 100% what I am going to do in my specific situation. All of the recommendations made in this thread are solid and would work!!