Manual D Friction Rate Issues

[Jeremyt]

Hello all. Its been a while.. I have finally decided to just tackle the HVAC design, fabrication and install on my own. Once I get past the design stage, I feel confident in making up all the ductwork, as well as getting the equipment installed and running. Currently I am designing a duct system for the second floor, which is two bedrooms, a bath and a hallway along with the stairs back down. I am planning on running a Mitsubishi SEZ-KD12NA4R1 for this area. It will be in the attic, along with associated ductwork coming down through the ceiling. This is one of three air handlers that will be installed. I started playing with the ACCA Manual D speed sheets last night and my Total Effective Length is an absurd amount. I was close to 400 feet I think? Obviously I am doing something wrong here. I have attached a screenshot, with blue being supply, and red being return air. Any advice and wisdom to share. Im sure I am just being dumb. Thank you all in advance..

 

[Fitter30]

Think your air changes aren't enough, 10 cfm for a hallway can' t hardly feel it. A builders grade bathroom exhaust fan is 50 cfm. That air handler min air flow 247 @ 4k btu 388@ 12 k have u looked at heating btu and outdoor temps where the spec was written ductulator.com for duct sizing. Scroll down for air changes

What is Air Change & How to Calculate Air Changes Per Hour

Understanding air change & how to calculate air changes per hour can help you improve comfort & indoor air quality for your customers.

hvacrcareerconnectny.com

 

[Sponsor]

 

[Jeremyt]

Think your air changes aren't enough, 10 cfm for a hallway can' t hardly feel it. A builders grade bathroom exhaust fan is 50 cfm. That air handler min air flow 247 @ 4k btu 388@ 12 k have u looked at heating btu and outdoor temps where the spec was written ductulator.com for duct sizing. Scroll down for air changes

What is Air Change & How to Calculate Air Changes Per Hour

Understanding air change & how to calculate air changes per hour can help you improve comfort & indoor air quality for your customers.

hvacrcareerconnectny.com

Thank you for your reply. The CFM listed was what I calculated. I should have specified. That unit pushes 383 CFM, so I was going to put 80 CFM through the 4 bedroom registers, and 60 CFM through the combined bath and hall register… When I was doing the speed sheet yesterday, the results said that my blower isn’t big enough, but if I put more air changes in that would exacerbate the issue I’m having now, correct? I have more images I can upload to paint a clearer picture.

 

[Jeremyt]

I have attached the Manual J calculations, room by room as well as the block load numbers. I hope this helps clear up any questions. Thanks again for the help.