Help me Plz !ventilation issues!

Hi Guys n Gals I’m in need of abit of advice.Ok I have a 740 cfm 8 inch Centrifugal with 8 inch insulated ducting the fan is pulling air through a xxl air cooled hood 1000watt hps.So my problem is I only have 2 holes to vent outside one is 4inch the other is 5 inch I cannot make these larger So my question is can i make up some type of a Y one into two so from the end of the 8inch duct I’ll have a Y connector with one venting to the 4 Inch exhaust outlet and the other going to the 5inch so all up I’m venting through 9 inches will this work if not any tips on what to do would be greatly appreciated thanks I’ll put some pictures hopefully that will help you understand what I mean Thanks again WANTED

i mean.... yes and no

you can do that but youd have to add some ducting to join the 8inch to the 2 smaller holes and this will give you a reduction in CFM because its no longer a straight shot to the vent. also if you dont seal it properly thatll contribute to even more loss of CFMs from your fan

Id just hook the 8inch ducting to the 5 inch vent, seal the 4 inch and badda bing! call it a day lol hope that helps

bf80255 said:

i mean.... yes and no

you can do that but youd have to add some ducting to join the 8inch to the 2 smaller holes and this will give you a reduction in CFM because its no longer a straight shot to the vent. also if you dont seal it properly thatll contribute to even more loss of CFMs from your fan

Id just hook the 8inch ducting to the 5 inch vent, seal the 4 inch and badda bing! call it a day lol hope that helps

Click to expand...

bf80255 said:

i mean.... yes and no

you can do that but youd have to add some ducting to join the 8inch to the 2 smaller holes and this will give you a reduction in CFM because its no longer a straight shot to the vent. also if you dont seal it properly thatll contribute to even more loss of CFMs from your fan

Id just hook the 8inch ducting to the 5 inch vent, seal the 4 inch and badda bing! call it a day lol hope that helps

Click to expand...

Thanks I’m definitely joining and sealing all the ducting the photos are for example. with joining the 8 inch to 5 everything I’ve read suggests that air flows like water so 8 into 5 is going to restrict it and put unnecessary pressure on the fan my theory is even tho it’s spread between two outlets I understand ill lose some cfm due to the split but the fan is to big for its job so I can afford to lose some cfm I’m thinking that 5inch + the 4inch vent has to better then just the five inch? I don’t know for sure hence the Post Cheers

wanted1180 said:

Thanks I’m definitely joining and sealing all the ducting the photos are for example. with joining the 8 inch to 5 everything I’ve read suggests that air flows like water so 8 into 5 is going to restrict it and put unnecessary pressure on the fan my theory is even tho it’s spread between two outlets I understand ill lose some cfm due to the split but the fan is to big for its job so I can afford to lose some cfm I’m thinking that 5inch + the 4inch vent has to better then just the five inch? I don’t know for sure hence the Post Cheers

Click to expand...

do you have a controller for your fan?

Like you said... visualize the airflow like you would water, does water flow better from a pipe or from a pipe with a fork in the end? where arre the vent holes in relation to the light? it would help if you had a picture or drawing of the whole setup

A 5" plus a 4" is nowhere equal to 9" or even 8"

The area of a 9" hole is 63.62"
The combined area of 5" and 4" is only 32.2"

All that said though a good inline fan will handle the pressure needed to push through the Y splitter and make use of both outlets together. The cfm reduction will be minimal especially when compared to the loss of just using the 5" on its own.

The lengths after the Y must be equal in length and/or resistance or the air will simply flow through the path of least resistance with only the air that can't pass going through the restrictive side.