Excessive whistling Noise

[markb]

I have a 3 zone system (powered by a HEIL propane furnace). When the heating is on in 1/3 of the zones, I get a loud whistling noise from one of the other zones that is closed. I can tell it's coming from around the "dampner vanes" just by putting by ear next to it.

when I open the "noisy" vanes the whistling disappears.

What are the options to try to reduce/eliminate the noise?

Thanks in advance for your help!

Best Regards,

Mark

[Eric K.]

Mark,

Is there a by-pass installed in this system? A by-pass is used to relieve the pressure that builds up when 1 or more zones are closed.

Another option is to allow some air to bleed past the zones that are closed. The motor actuators have an adjustment to allow the damper to be set to 10-20% open (when powered to close), allowing for relief of the excess air.

Eric

[markb]

Thanks for the reply Erik.

do you mean the mechanical stop "points" on the motors. I'll try adjusting the damper.

There is currently no by-pass on the system. Would this require an additional damper on the by-pass pipe?

Thanks again for your help.

Mark

[Eric K.]

I am referring to the stop points on the motors.

The by-pass is a separate duct that is connected between the Supply and Return ducts. There must be a damper installed on the by-pass duct in order to regulate the amount of air being bypassed.

Eric