How can I know if the lack of cool air coming from the register is a damper issue or something else?

Question

Zone 3 has almost no cool air coming out even though the thermostat is set to 50 and the room reads 85. How do I know if this is a damper shut? What exactly is the damper suppose to look like when it is open?

Answer 1

If little or no air (either cool or hot) is coming out of a register, the zone damper could be closed, a "balancing damper" could be closed, or the duct could be disconnected either at the register or somewhere along the way.  Are there other registers in the zone that are getting air flow?  Check all the duct connections from the air handler to the register for breaks.  (Standard "cloth" duct tape should not be used for making ducting connections.)  Duct mastic painted on the joints is the best solution, but there are better duct tapes on the market.  Check the electrical connections on the zone damper.  They are commonly "opposed blade" dampers and look like little window blinds, but you won't see them unless you can see inside the duct.  Balancing dampers have little handles on the outside of the duct.  If the handle is parallel to the duct, it will be fully open.  Also, setting the tstat at 50 won't make it cool faster.  Set it to the temperature you want it to be.  Setting it to an extreme feels better, but it won't make the system work harder.