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This wire is included in
factory harness
Variable Frequency Drive
The unit is equipped with a Variable Frequency Drive (VFD)
to control the indoor fan in sequence with the unit's ventila-
tion, cooling, and heating operation. The VFD is controlled
through a 0-10vdc signal that is provided by the Unit Control
Board (UCB) in the control box. Per ASHRAE 90.1-2016
and IECC-2015 standards, during the first stage of cooling
operation, the VFD will adjust the fan motor to provide 66%
of the design airflow rate for the unit. When the call for the
second stage of cooling is required, the VFD will allow the
design airflow rate for the unit established (100%). During
heating mode, the VFD will allow total design airflow rate
(100%) operation. During ventilation mode, the VFD will op-
erate the fan motor at 66% of full speed.
The ABB ACS320 model (see Fig. 16) is used on 208/230v
and 460v units, while the ABB ACH550 model (see Fig. 17)
is used on 575v units.
See Fig. 18-19 for location of the VFD.
18
IDCB
BLU
Y1
Y2
BLU
ORN
X
TSTAT CB
BLU
Y1
Y2
BLU
ORN
X
Fig. 15 — 3-Stage Cooling Diagram
Specifications subject to change without notice.
UCB
DDC
TSTAT
GRA
Disconnect this wire
from TSTAT CB-X and
insulate.
Fig. 16 — ACS320 Variable Frequency Drive (VFD)
ORN
BLU
COMP
FASFHS150-180-01SI
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