A FAN

[FANMON]

I HAVE AN AIRHANDLER FAN MOTOR THAT SEEMS TO SPEEDUP AND THEN SLOWDOWN DURING OPERATION. IT ALMOST SOUNDS LIKE THE STATIC
PRESSURE IS CONSTANTLY CHANGING CAUSING , SO TO SPEAK, CAVITATION.
I RECALL READING ARTICLE AWHILE BACK REGARDING THIS, BUT I HAVE COMPLETELY FORGOTTEN....THKS FANMON

 

[Islander]

is the ahu controlled by a variable frequency drive?
have vav boxes on the supply duct?
belts tight?

..most commonly i see this problem on vfd driven ahu's..i usually get the control people to program the vfd so that it does not let the ahu respond so quickly to what ever static pressure reading it senses..seems to steady them out usually.