DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (
-   HVAC (
-   -   Floor Register & Boot Size (

kmachn 01-16-2012 12:11 PM

Floor Register & Boot Size
I am upgrading the ductwork on my home since we hope to install a smaller unit after finishing energy efficiency upgrades. Some of the details regarding the Manual D can be found on this thread.

My question has to do with the size of the boot, and ultimately the type of register. Specifically, we are upgrading 4 current 6" ducts to 7" ducts. According to Manual D, they will deliver approximately as follows:

7" Round Sheet Metal Ducts
#1-117 CFM - Cathedral Ceiling
#2-112 CFM - Cathedral Ceiling
#3-134 CFM - 9' ceiling
#4-134 CFM - 9' ceiling

My question is, what parameters should I use to determine the boot & register size? The grill we will most likely use are the Hart & Cooley #411, so I am not sure if I should install 4"x12" boots or 6"x10" boots.

According to the engineering data for the #411..

-the 4"x12" will have a face velocity of ~550-650FPM with 9'-11' throw.
-the 6"x10" will have a face velocity of ~450-550FPM with 5'-6' throw.

Am I looking at this correctly, and would one of these sizes be preferable to another? Would it be better to use a register other than the H&C #411? We live in the midwest (St. Louis area) so our heat pump gets more of a workout than the A/C, but we also use alternative heat sources (i.e. wood) in the winter to assist in very cold weather. Not sure if that makes a difference, thanks

beenthere 01-16-2012 03:52 PM

If you also have central A/C, you want a long throw.

kmachn 01-16-2012 05:26 PM

Yes, central A/C also. So the 4"x12" is the better way to go?

beenthere 01-16-2012 06:02 PM


Originally Posted by kmachn (Post 824839)
Yes, central A/C also. So the 4"x12" is the better way to go?

Yes, it will help with your cooling. it will cause the air to mix better.

kmachn 01-16-2012 07:13 PM

Once again, thanks for the help beenthere.

All times are GMT -5. The time now is 09:34 AM.

User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.

Search Engine Friendly URLs by vBSEO 3.6.1