Mechanical Installation
www.DaikinApplied.com
9
IM 971-3 • MAVERICK I
Variable Frequency Drive (VFD)
No adjustments of the VFD are required for installation or
operation of this unit.
Location: Control Section (front left) of the unit.
VFD Model:
Schneider Altivar 212 (factory programmed).
Replacement
The VFD is horsepower and voltage specific therefore;
replacement must be the same model as the existing. A
preprogrammed VFD is recommended and available from
ProStock. A nonprogrammed Schneider Altivar 212 may be
used but must be programmed exactly per the included VFD
programming guide for safe and proper function.
Operation
The purpose of the VFD is to allow airflow in Fan Only (G),
Low Reheat and First Stage Cooling (y1) operation of a two
stage unit. Unit air balancing should be performed at High
Airflow (100% at RTUC, 60Hz at VFD) by adjusting the blower
motor sheave. High Airflow always occurs during a W1, W2,
or y2 call. For air balancing, without heating or cooling, the
fan only speed can be temporarily increased to 100% by
adjustment through the RTU-C keypad. To meet ASHRAE
90.1-2010 and for best performance, First Stage Cool and
Fan Only speeds are factory set at 50% airflow (30 Hz at
VFD). Both of these speeds are independently adjustable at
the RTU-C. The VFD display will indicate an equivalent value
in Hz (i.e. Low Cool adjusted to 60% at RTU-C will display
as 36 Hz at the VFD). A 20 second (adjustable at the VFD)
ramp-up or rampdown is used whenever the blower speed
is increased or decreased. Low speed blower operation first
ramps to 75%, to close fan proving switch, before ramping to
the desired speed. Since the VFD operates on 24VDC control
voltage, a blower relay (with 24VAC across the coil) is used
to turn the VFD on. Blower speeds are changed via Modbus
communication from the RTU-C.
Outdoor Fan Motor Controller
(OFMC)
Location: Control Section (front left) of the unit.
During Low Reheat Mode the OFMC slows the outdoor fans
to increase the discharge pressure/temperature to maintain an
optimized amount of reheat required to provide neutral air to
the occupied space. The OFMC is located in the control box
section. The factory setting for the outdoor fan motor controller
is unit specific (
). The setpoint temperature will provide
neutral air +1 to -5ºF from entering air temperature (example
if the entering or return air temperature is 75ºF the leaving or
supply air temperature will be 76º to 70ºF during the reheat
mode). If field adjustment is required to raise or lower the
leaving air temperature, this may be accomplished by turning
the temperature control dial on the OFMC (
). Turning
the dial to a higher temperature setting will increase the leaving
or supply air temperature and turning the dial to a lower setting
will reduce the leaving or supply temperature. During cooling
modes the OFMC will operate at full speed (green light –
). During reheat modes the OFMC will typically operate
at variable speed (amber light –
full speed or off (no lights) depending on the reheat capacity
required. During high reheat, the 71/2 and 10 ton models must
operate the OFMC at full speed to prevent excessive head
pressure on system 2.
Table 4: OFMC Factory Settings
Unit
Setpoint
090
90ºF
102
90ºF
120
94ºF
150
87ºF
Figure 8: OFMC Unit
Summary of Contents for Maverick I MPSA07D
Page 93: ......