McQuay AGS 225D, Operating Manual

Page: 46 / 82

46 OM AGSD-1
•
Fantrol fans on = 0 AND Fan speed output = min speed setpoint AND Condenser
Saturated Temp < 70
o
F
•
Compressor State = Off
Stage Up Compensation
In order to create a smoother transition when another fan is staged on, the VFD compensates
by slowing down initially. This is accomplished by adding the new fan stage up deadband
to the VFD target. The higher target causes the VFD logic to decrease fan speed. Then,
every 5 seconds, 0.5 degrees F is subtracted from the VFD target until it is equal to the
saturated condenser temperature target setpoint. This will allow the VFD to slowly bring
the saturated condenser temperature back down.
Fan Stages With or Without VFD Option
There are up to 8 stages of Fantrol available. When the VFD option is selected, the fan
stage 1 is VFD enable.
Fan Staging For a 6 or 9 Fan Circuit:
Fantrol Stage Fans On
1 1
2 1,2
3 1,3,4
4 1,2,3,4
5 1,3,4,5,6
6 1,2,3,4,5,6
7 1,2,5,6,7,8,9
8 1,2,3,4,5,6,7,8,9
Fan Staging For a 7 Fan Circuit:
Fantrol Stage Fans On
1 1
2 1,2
3 1,3,4
4 1,2,3,4
5 1,3,4,5,6
6 1,2,3,4,5,6
7 1,2,3,4,5,6,7
Fan Staging For a 8 Fan Circuit:
Fantrol Stage Fans On
1 1
2 1,2
3 1,3,4
4 1,2,3,4
5 1,3,4,5,6
6 1,2,3,4,5,6
7 1,3,4,5,6,7,8
8 1,2,3,4,5,6,7,8
Staging Up
There are six Stage-Up dead bands that apply to the Fantrol stages. Stages one through five
use their respective dead bands. Stage six to eight share the sixth Stage-Up dead band.
When the saturated condenser temperature is above the the active deadband, a
Stage-Up error is accumulated.