I had my package AC system replaced a couple weeks ago with a York box. The
unit works great but when it shuts off I can hear a moderately loud thump
coming from the ducting after the blower spins down. Is this something I
should call the contractor back to check out or is it nothing to worry
It is not hurting anything other than your ears. It is some duct
somewhere that is flexing due to the difference in pressure with the fan on
vs. the fan off. It is likely close to or part of the new work, but it
could be almost anywhere. If you can locate it by following the noise, you
may be able to fix it by adding a brace with a few screws. You may want to
contact the contractor if you find it is part of the new work and he will
likely fix it for you free. If it is part of your existing ductwork I would
not expect him to fix it free, but for the good will he might.
Note, the new system may be using a little more pressure and that could
cause the problem in an old duct that did not have a problem with the older
lower pressure unit.
Call the contractor back, and have him find the section of duct that is
flexing on start..what you are hearing is the duct popping back down when
the pressure is off it..
While you are at it..you COULD pull the right hand cover off, and see what
the fan motor is set at...its possible hes got it on the high setting, and
all you would need is med, or low...very simple changeover..
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