squirrel cage fans

anyone here currently using a squirrel cage fan as a exhaust fan? yea i know a inline fan is much better, but in my case the fan is free.

i recently installed a new furnace and looking at the old unit i noted a fairly new squirrel cage fan in there so i ripped it out for use another day. not sure the cfm's but i do know it was a 125,000btu furnace, and a nice sized fan about 18in tall and atleast 12in wide. fan also has a hi/lo feature.

fired that sucker up and it does move some air. should work fine for exhausting a single room.

probably install a solid state switch to vary the speed. and install the fan inside a insulated wooden box with a 8in intake into my room. probably find its home in the attic.

just wondering if anyone has done this considering its fairly easy and cheap to acquire the fans. let me know if it worked good for your setup or maybe offer some suggestions.

thinkin this should work good because currently i have a dryer squirrel cage in place but just doesnt exhaust the smell completely some days.

any thoughts would be great.

That sounds pretty good, to work with standard round ducting you will probably want to use some sort of transition from the square/rectangle shaped outlet of the squirrel cage fan to the ducting.

Ex: fan has a 4.5" square outlet, need to fabricate joint for tight airflow.

Sounds like a nice fan, might be a loud one though could even build a baffle/muffler box for it.
:woohoo:

yea i'll probably house the squirrel cage inside a larger wooden box. this way i can run an 8" or 6" insulated ducting from my grow box into the side of the fan. not going to put in the same room as my grow box, like you said it will probably be to loud. also building the box will allow me to insulate for sound along with the insulated ducting. muffler if things are still too loud. cool thing this should work nice.

I have used many of these types of fans for both intake and out take air flow. Although it does work, its not that good at keeping the temps down. I know you dont know what the cfm is, but what about the room? How many cubic feet are you working with? You need the air to move out at about 3 times the cubic feet of the room, especially if your using a passive intake. If you notice that your having heat issues, then your prolly not running a strong enough fan. If this does happen, consider a small intake fan to assist with the intake of new, fresh air. Your idea about building the box to insulate fan noise is a good one. It will work, and makes mounting the fan easy. You just mount it inside your fan box, and put the box where ever you want! :) Good luck and be safe.

the room in which im working is 10'X12'. inside this room i opted to build a 6'X6' cab for flowering and a 4'X4' cab for veg. didnt want to deck out the whole room for other reasons so im working with these cabs and plan to run an 8" exhaust tube for the flower and either 6" or 4" exhaust for the veg.

by passive intake are you referring to no fan for the air inlet? the exhaust fan will be drawing fresh air into the cab from the intake? thats the plan at first but if temp is a prob i was thinking a ducting fan to help bring in more fresh air.

all this is in the works. i just started construction on the cabs and will be upgrading my exhaust next. then move the equipment from my closet grow. should be a nice upgrade from what im use to!.

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Originally Posted by swisha

anyone here currently using a squirrel cage fan as a exhaust fan? yea i know a inline fan is much better, but in my case the fan is free.

i recently installed a new furnace and looking at the old unit i noted a fairly new squirrel cage fan in there so i ripped it out for use another day. not sure the cfm's but i do know it was a 125,000btu furnace, and a nice sized fan about 18in tall and atleast 12in wide. fan also has a hi/lo feature.

fired that sucker up and it does move some air. should work fine for exhausting a single room.

probably install a solid state switch to vary the speed.

.

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Furnace blowers are high velocity with the associated pressure... for a 125MBTU furnace, the blower is probably rated for 1600 - 2000 CFM... thats a massive amount of air. Probably a 3/4 hp motor.

Assuming that the blower is direct drive, it should have 4 speeds. If I can get the make/model of the old furnace, I can probably get the blower curve for it.

There is a solid state device that is available to run that blower as a variable speed, but they are not cheap($300) and available only to legitmate HVAC companies.

Best bet is to build a box to put the blower in so you have something to attach the ductwork to. That particular blower will need the box to be 24 X 24 X however long you want to make it.


And, yes, I am an HVAC tech :D

its a bryant 125,000btu furance. model # 394fad036125, serial # AEA.

looks like the motor is newer than the furnace and has a hi/low setting. after cleaning the fan up it runs quite well and is pretty quite. so i might not even need the solid state switch. just have to hook it all up and add the switch if needed.

hope that info helps.

btw in the old furnace the fan box was around 24X24X36. wouldn't have a prob building a box that size.

I was actually thinking about using the blower motor from an old car. They should move air pretty good if you set up the intake and exhaust correctly and they are only 12 volts.

Just remember that if your exhausting 2,000 cubic feet of air per minute, you have to have 2,000 cubic feet per minute of air for supply air or you could theoreticaly suck that little grow room inside out.