Closing several registers

[jeepgrady]

I've got a two zone Carrier system. The ducting is in the attic and there are only two motorized dampers that feed each zone. There are several rooms that could use a bit more air. I have a walk-in closet, a utility room and a laundry room which since they are small get a lot more airflow than is needed. I want to close those registers to redistribute air.
My question is more of a theoretical one. The main trunks run through the attic with the octopus arms branching out to the individual registers. If I close a register, the air will still travel out the octopus arm where it will stop at the closed register. How will that air benefit the remaining registers that are open?

[toocoolforschool]

You probably have dampers which could be located by a hvac guy.

[jeepgrady]

Already checked. There aren't any.

[toocoolforschool]

Yea closing dampers will redirect some air but not a good practice overall, temporary fix.

[George2]

It depend on the size of the A/C cfm requirements and the size of the ductwork to each zone. Also, is there a by-pass damper in the system? Closing some of the registers shouldn't be a problem if you don't go to extremes. This is called balancing the airflow. If you still need more airflow to a particular room, then another supply should be installed.

[martyinlincoln]

Think of air in the ducts as water in your pipes. When you open the kitchen faucet the water doesn't flow to the toilet first then back to the faucet. It flows from the source out to an opening. Air in the duct is the same. It flows from the positive pressure of a blower to opening.

[energy_rater_La]

if you put dampers at the plenum it will allow you to stop the
air flow down the duct, keeping the air in the plenum to be
distributed. closing the registers keeps air from exiting the
supply box & duct, but air still flows from plenum into the duct.

before adding dampers at the duct take offs, discuss with installer
of zoned system. you don't want to mess up air flow to zoned ducts.
keeping in mind the whole of the duct system determines where &
how to control air flow.

best of luck.

[jeepgrady]

There is no bypass damper. One zone covers the main floor and the second zone is for the 15X32 ft. room above the garage. The registers I want to close are all on the main floor. None of them are in rooms that have a return.

[George2]

There is no bypass damper. One zone covers the main floor and the second zone is for the 15X32 ft. room above the garage. The registers I want to close are all on the main floor. None of them are in rooms that have a return.

Without knowing the duct size or the amount of registers to each zone, it is hard to give advice from here without harming the equipment. If you had a by-pass damper, there would be some flexibility to reducing airflow to some of the supplies.

[jeepgrady]

There are 15 registers in the main zone. I want to close four. The second zone upstairs has two registers that will remain open.

[George2]

There are 15 registers in the main zone. I want to close four. The second zone upstairs has two registers that will remain open.

The 2 supplies to the 2nd zone must be huge. Theoretically the 2 registers should supply nearly as much air as the 15 registers in order for the equipment to work. I've heard where installers will install smaller dampers to allow for blow by. This technique can eliminate the by-pass damper.

Again, without a by-pass and not knowing the cfm requirements or duct size, I don't feel comfortable saying okay to closing 4 registers. Sounds like you need to have someone take a look see.

[energy_rater_La]

zone 2 is a frog.
high heating/cooling load unless walls are insulated & air sealed.

talk to hvac co about adding dampers so as not to mess
with zoning.

best of luck