# Manual D with slim ducted minisplit indoor unit?

Posted Jan 28, 2018 12:43 PM ET
Edited Jan 29, 2018 5:50 AM ET

Tags:

1.

To the best of my knowledge:

Q. "What is the effective length where the air handler's output goes straight into the main trunk duct?"

A. If the register is at the end of the straight run, and there are no takeoffs or elbows, the effective length is the length of the duct.

If there is a takeoff or an elbow between the appliance and the register, the effective length is the length of the duct(s) plus the effective length of each takeoff and the effective length of each elbow.

Q. "If the branches all occur in pairs on opposite sides of the trunk, is it fair, proper and correct to mentally divide the system into two parallel systems where each has branches from one side only?"

A. No.

Posted Jan 29, 2018 5:54 AM ET
Edited Jan 29, 2018 5:55 AM ET.

2.

Martin,
I'm confused a bit by your statement. It is my reading that each register has an effective length that is the sum of trunk length, branch length and fittings from groups 1-- 12 and the longest of these is used as the system effective length. With no change of direction from the blower to the "trunk duct" the group 1 fitting has zero length.. I'm using a very simple branch take off, a readily available rectangular duct start collar so my group 2 fitting is type 2d and by using a trunk duct size reduction it 'll either be 50'EL or 40' EL. My register " boot May be either 4n or 4A0 with EL of 45' or 40' So my longest supply "run" is 30' trunk + 20' branch + 40 group 2 + 45 group 4 =135'. With 0.1" available static blower the friction rate is0.074 and I could use 3 1/2"x10" run outs but the cost saving is tiny so I'll use 3 1/2"x12". I can use the low static fan coil units!
Edit: Here is my "jump duct" return path. https://www.bakerdist.com/search/result/?q=thru-wall
Plus I'll have a duct ed ERV with inlets from 3 bathroom areas, the laundry room and kitchen. I'm thinking that I shouldn't have jump ducts for the rooms served by the ERV so if all the bathroom and laundry doors are closed it's input will almost all come from the kitchen.

Posted Jan 29, 2018 11:07 PM ET
Edited Jan 29, 2018 11:46 PM ET.

## Other Questions in Plans Review

### Raised Floor Insulation and Foam Sheathed Walls

In Green building techniques | Asked by user-7124491 | Jul 22, 18

### Insulation Retrofit

In General questions | Asked by user-7117614 | Jul 22, 18

### Thoughts on negative pressure after balancing an Venmar X24ERV?

In Mechanicals | Asked by David Goodyear | Jul 20, 18

### How long for interior to dry out?

In General questions | Asked by Peter L | Jul 22, 18

### Looking for options: concrete pad detail

In General questions | Asked by tech1234 | Jul 22, 18