Tapping sound in attic associated with AC

Hello, I was hoping someone could help me. I bought a new house (new build) and moved in 3 weeks ago. Since day one, there has been this rhythmic tapping sound coming from the attic. I hear it through the exhaust vent in the master bedroom and only happens when the AC is on. The HVAC company that installed the system was unable to identify it, although it is definitively associated with the AC, I can't tell if it caused by any parts of the HVAC system but it only happens when the AC is on. Day and night during the summer. Any ideas would be greatly appreciated. Here is the link to the sound. https://drive.google.com/file/d/1LbI...ew?usp=sharing

 

Welcome to the forums.

Ok.... problem. Your video says dripping sound.
That is not a dripping sound unless you have the camera sitting in the drain pan.

Is the sound actually that loud ?
If it was..... your neighbors should be able to hear it.

 

Correct, it's not dripping. I had named the file "dripping" because that is what I thought it was the very first time I heard it and didn't change the file name. That recording was made with my cell phone placed against the exhaust fan vent in the ceiling. So, no, it's not that loud at floor level but at 3 am, it can wake you up. Any idea of what it could be? Thank you!

 

It's a rhythmic and evenly repeated sound. It sounds identical to a belt driven blower with a belt going bad. That thump would be the sound of a belt bad spot hitting the pulley. Most newer systems are direct drive so that may be an older air handler.

There should be an access cover over the blower area for inspection.
You could post the model number off the air handler.

 

We found the culprit. The construction manager for the new community came and heard the sound and immediately said it was the backdraft damper in the exhaust fan for the master bathroom. Apparently, it is happening in many other houses in this new community. He suggested to remove the flap for the backdraft damper and the sound will disappear. Well, I did that and effectively the sound stopped. Now I wonder, what would be the side effect of removing the flap for the backdraft damper, but that will be a matter for a different forum at another time. Thank you all for your ideas.

 

That does not make sense. The HVAC system is not connected to that duct. If the blower running causes that damper to open and close...... there is a positive or negative air pressure problem within the house.

With some systems..... the installer connects a fresh air duct from outside into the A/C return duct. This will cause positive pressure in the house. That could make that damper move.

That damper is there for a reason. It keeps the cold air out in the winter.

 

Hi, do you have the capability of just running the AC fan by switching the Stat to Fan/On, as Pete said sure sounds like a belt, but I doubt it’s belt driven.

Geo🇺🇸