20 ton package unit rattels ceiling during start up

[stever2006]

my unit comes and makes a loud bank it sounds like air is bursting the building

[xersw]

alot of things to take into cosideration. the duct size supply and return ,more fosus on return.gauge metal. is the duct lined i hope so.how thick is the lining.if this isnt an open style plenum for your return.your only focus should be supply duct. tell me more about this installation.lining ,gauge metal,return style.

[roc service]

The sound you're hearing is probably the fan filling the duct with air on start up. To prevent this the sheetmetal fabricators should have cross breaked the first few sections of duct comming off of the unit. They actually fold an X design across the top and bottom of the supply duct. If it's not constant and only at start up then you might have to live with the sound or brace it with some sort of angle material.

[master mechanic]

Set your controls to operate the blower during occupied times and cycle blower during unnocupied. Running blower continous will allow for better ventilation and temperature control as well as positive preasure on building. I also suspect poor duct design ,possibly no canvas connections on supply and return, or no cross breaking on sheetmetal as mentioned earlier. Traverse supply inorder to confirm required air volume.

[Diceman]

I think they about covered it all for ya.

[crooned]

Well you could sell him a VFD and that would start the fan slower