Exhaust Fan question for engineer guys.

[AJT]

I have installed one & am ordering a second one of these Fantech FR150.

My question is: I have 4" holes in my canopy with 4" ducting going thru a window. I ordered the 6" fan & put a reducer from 4" to 6" coming into the fan.

Is there any problem with doing this?

 

[Brian Peterson]

Personally I would contact a HVAC tech. with that question.
If you have any contacts in the heating and cooling world it should be a pretty
easy question for them to answer with experience. IPO it would increase suction
obviously. But don't know if it would increase wear in the motor?!?!
good luck. I'll be in your boat soon with issues like these.

 

[Brian Peterson]

sorry meant "IMO" :/

 

[AJT]

I do not care too much about wear on the motor. It has a 5 yr warranty & was only 124.00. I kind of thought it would still pull more air than a 4" model even with the reduction.

 

[AJT]

Unit installed

 

[dahenley]

i dont think it would hurt the fan (those fans can be controlled and ramped up and or down)
it will on the other hand, effect the CFM that the fan can suck/push

 

[mcarroll]

I have 4" holes in my canopy with 4" ducting going thru a window. I ordered the 6" fan & put a reducer from 4" to 6" coming into the fan.

Is there any problem with doing this?

I don't think with a fan in this situation you're going to have wear issues as you would if this were a water pump with a restricted intake. Instead it's all performance issues. Less area (^2 in.) in the intake opening will restrict the volume of air input....can't say by how much this may matter though.

Worse than that might be the restricted outlet though.

Did you have this 263cfm, 6" radon fan lying around or why not (if still possible) get one that's made for 4" ducts? They have the FR100 in the same series of fan you have, as well as others like this one rated for 160cfm. 60cfm more than the FR-series. You aren't likely to get close to the rated flow with the I/O restrictions on yours anyway (but I wouldn't hesitate to call FanTech though and get their take since it's already in place) and the 4" fans appear to be a bit cheaper. If needed, you can add some additional CFM with one or more 80cfm boosters like this ($14 online, $25 locally for me), which are way cheaper and add none of the bulk of a second main fan.

Anywho, if you can plumb the bottom and top cabinets into the 6" fan with something like this, then you will maximize what you spent on that first duct fan by opening up the intake almost to +200% instead of -33%! And if there's any way you can upgrade the window side to 6" - even if all else remained 4" - that would have to make a big improvement at least to get what you bargained for (cfm-wise) with the existing fan. I'm not finding the horizontally oriented part I'm looking for, but if you can catch my drift something like this combined with something like this, depending on the orientation of your window might do the trick? (I guess I don't know why the window side is restricted to 4" pipe, so maybe not. ;-) )

If you don't already have them, installing at least one vent opening in both cabinets for cold air return might not be a bad idea either. (If you find it necessary, small PC fans could be added to the cold air returns as well.) This would assure there's a good way for fresh, cool air to replace the hot air you are evacuating out via the duct fan, making sure the fan doesn't have to spend it's limited power on suction - just flow. You can see on the FanTech link how much your cfm's will drop due to restrictive pressure. (This is typical...any brand.)

Good luck!

-Matt

P.S. Another thought: Being less dense, the hot air will tend to "pool" at the top of your enclosure, so you might do some additional maximizing by tipping your ductwork elbow so it's "sucking" hot air off the "ceilings" of your canopy and cabinet. Kinda the upside down version of how Reef Dynamics sucks the more-dense bubble-free water from the bottom of their skimmer body for the outlet.

P.P.S. Overkill, but interestingâ„¢.

 

[dahenley]

P.S. Another thought: Being less dense, the hot air will tend to "pool" at the top of your enclosure, so you might do some additional maximizing by tipping your ductwork elbow so it's "sucking" hot air off the "ceilings" of your canopy and cabinet. Kinda the upside down version of how Reef Dynamics sucks the more-dense bubble-free water from the bottom of their skimmer body for the outlet.

in his canopy, he did this.
in his videos on his large tank thread, he mentions this and shows it.

 

[Reefers4Life]

I also run a fantech pb190 to remove the humidity and the only thing I have to do every three months is take it apart and clean it out with compressed air, you'll notice all the dust and salt residue that will build up over time. Everything is sealed except a couple holes in the motor housing to probly vent heat.

 

[mcarroll]

in his canopy, he did this.
in his videos on his large tank thread, he mentions this and shows it.

Thanks, I actually did see it...was even the reason I mentioned "his ductwork elbow". :beer:

I think if you look at the example I gave you'll see the difference I was suggesting. Let me know if you have questions.

-Matt

 

[AJT]

Thanks everyone for your input. I am definately no expert on this. I ordered one more fr150. I think it will pull more air even with the restriction of 6" to 4" than the FR100.

I tried the booster fans, I had 4 running & they didn't do much for sucking out th hot air. I think I will try them on the 2 other holes as input of fresh air & see how they do.

The FR150 is really pulling alot of air out & maybe with 2 it will be sufficient. I am going to "T" this one & run a 4" line down to the cabinet to see if I can get some heat out of the cabinet.

 

[jgsalwater]

Restricting flow on centrifugal fans or pumps normally always reduces loading on the fan or pump. The least amount of load would be with a discharge or intake valve nearly fully closed. So reducing a 6" fan to 4" discharge will reduce flow but will also reduce loads. The load on a centrifugal impeller is more highly effected my the flow mass than it is my the back pressure. This can be easily verified by simply taking an amperage reading on the electric motor on a centrifugal fan or pump while you open and close a valve on the suction or discharge. This is always a surprise to non-technical people.

 

[maroun.c]

got 4,5 & 6 inches turbines running on 4 inch tubing as well since months now and y observation are the following:
4 inch is the most quiet pump but the air turnover is only enough for my stand and canopy air turnover to outside (got a rather large canopy as it's a whole cabinets surrounding the tank will the ceiling
5 inch is a bit loud for my tase and I just have it venting the fishroom to outside airdraw is way more than the 4 inch even if you try the fans without connecting them to the tube the 4 inch one is much less flow.
6 inch one running on 4 inch tubing in the basement where I have a frag setup and some coral and fish Q tanks Very loud and much more flow than the 5 inch fan so eventhough its restricted its still doing a better job still the sound of the fan (even alone wihout the tubing) is annoying
now soudn might be different with different brands but with my fans running since months now I don' think it's that bad for the pump. My preferred one efficiency/Sound is the 5 inch one.

 

[AJT]

Thanks. I will install the second fan this weekend then take temp readings inside the canopy & see where I am.