Bathroom vent fan in living room wall??

[Derrick0580]

I’m considering installing a bathroom vent exhaust toward the peak of my vaulted ceiling to help remove CO2 from the room where my display tank is. The fan I’m looking at is 434 cfm rated for 285 sq ft which is exactly the area of my living room 15x19. This option is substantially cheaper than an erv. The area it would go is just next to the master bath fan in the attic. Would I be able to tap into that fan’s duct line so I wouldn’t have to run new duct work and splice into the electrical wiring so to control it I would just turn the bathroom fan on to turn the living room fan on. Someone said it’s possible if one turns on before the other it could cause the other to spin backward which doesn’t make any sense. Is this feasible or am I going to need to shell out a couple grand for an erv?

 

[KrisReef]

I don’t know if this set up will lower your inside CO2 enough to even notice improvements in your tank, especially if you don’t cut an extra vent in your roof (I am not suggesting that you should add a hole) but hvac is not my specialty, just to be clear.

I would suggest you run your existing bathroom fan for 24 hours and see if you notice an improvement in your tank pH (I presume this is the motivation for the project?)

In theory you can do what you suggested. I don’t think you will achieve your goal with your method and fear that you will have a noisy living room for no benefit to the tank.
The airflow info the home may improve slightly but your source of CO2 (occupants) will still be present breathing.
the reason people plumb an outside air source to their skimmer is to have low CO2 air pushing the CO2 out of the water at the skimmer. The high CO2 air in the building is always pushing CO2 into the tank at all the water surfaces. The latter force is difficult to overcome with only minor room CO2 reductions. A bathroom fan never really clears the air very efficiently. I believe that they make them noisy to signal to other folks who might enter the bathroom that the air might not be suitable for breathing?
Hth.

 

[Dan_P]

I’m considering installing a bathroom vent exhaust toward the peak of my vaulted ceiling to help remove CO2 from the room where my display tank is. The fan I’m looking at is 434 cfm rated for 285 sq ft which is exactly the area of my living room 15x19. This option is substantially cheaper than an erv. The area it would go is just next to the master bath fan in the attic. Would I be able to tap into that fan’s duct line so I wouldn’t have to run new duct work and splice into the electrical wiring so to control it I would just turn the bathroom fan on to turn the living room fan on. Someone said it’s possible if one turns on before the other it could cause the other to spin backward which doesn’t make any sense. Is this feasible or am I going to need to shell out a couple grand for an erv?

I would be concerned about two fans pumping air into the same duct.

If both fans weren’t on, the air from the fan that is on would pump air back through the fan that is not running. Possibly a one way flapper valve on each fan would prevent the back draft. Maybe these are on the fans already. Make sure the duct can handle the two fan exhaust or the flow could be choked when both fans are on, lowering the exhaust rate.

 

[homegrowncichlid]

Using my high school engineering... yes, you can place the fan into the existing duct, however I'm not sure of the air path, ie upside down Y or T duct work, or perhaps a side ways T.

Let me picture this in my mind, so if you flip one switch and both fans turn on, the air will blow upwards, if one fan is stronger than the other, it will dampen the flow from the weaker fan and possibly blow against the fan, as air pressure builds inside the duct. also I'm assuming one fan is located on a different floor, so the distance between the fans to the attic are different, which would also affect air flow.

This can be resolved by either placing a single larger exhaust fan at the attic, instead of 2 smaller individual intake fans. When you turn on the fan, it will suck air equally from each vent, depending not on distance, but the size of the vent. if one was 100 square inches and the other 50, then twice as much air will move though the 100.

I think the easiest thing for you to do, for just a few bucks, is to install a one way damper behind each fan, these dampers are used for laundry dryer vent to outside wall, are only $10 from home depot and made of plastic. the damper may not fit perfectly into your duct, but use your knife to trim it, then MacGuyver it into the duct with duct tape. Next, you'll have to use 2 independent switches, so when one fan is on, the other fan should be switched off. Only the moving fan will have an open damper, the off fan's damper would be closed. You alternate the air flows, I assume the aquarium fan will be on always, but if you do use the bathroom, the aquarium fan will turn off, thus closing it's damper.
I'm uncertain how you want to do it, but I hope I have given you some ideas.