Two Fans Into One Duct

This lead to fan malfunctioning as i think it overheated.

Two fans into one duct.

The run is only perhaps 6ft total and i ran two 4 into a 6. Same as above only with two 800 cfm fans. The 2 fans have their own ducts but just before they vent out the roof their duct pipes are attached to a common duct upside down y which means they vent out the same hole in. It would then clear both.

Plus each fan has its own damper built into the housing. So i have an input and an output duct. I felt air coming from bathroom 2 s fan down through the metal duct pipe for venting bathroom 1. Because the 800 cfm fan won t fit in the duct i would have to build a larger frame for it then connect it with some sort of funnel to the duct.

I used the same dampers shown above the cloth ones. If you try to combine them into a common duct it will bring with it a number of problems including an unbalanced system with positive negative air pressures which play havoc with the fan motors and could cause motor failure. One of the things i did notice is that having the fan pulling air through the ducts means that the hot air is flowing directly over the fan. You should not put more than one fan into a common duct each fan should have its own duct run to atmosphere.

Was replacing bathroom fan 1 and while it was disconnected from its duct pipe the fan in the bathroom 2 was on and. The fan is to take air from in the house run it thru the heater then back into the house. Rather than two cheap axial fans into one duct outlet how about two ducts into a more powerful centrifugal fan which is a bit more expensive but has a lot more oomph. You d often blow air from one bathroom into the other and local building inspectors wouldn t approve it.