Krueger | 1401 N Plano Rd | Richardson, TX 75081 | 972.680.9136 | [email protected] | www.krueger-hvac.com
KAH Operation & Maintenance Guide
Page: 16 of 88
SECTION 2 - START-UP & OPERATION (CONTINUED)
Variable Frequency Drive (VFD)
The VFD controlling the speed of the AHU fan(s) needs
to be set up properly so the fan does not run at resonant
frequencies. This is true whether the VFD is field or factory
mounted. An option is available when ordering the AHU to
select Inverter Drive Balance (Sweep Balance). When the
option is selected the factory provides a document or label
attached to the fan assembly that lists any values that
exceed the peak to peak tolerance. See Figure 13 (right).
These values are referred to as Skip Frequencies (Jump or
Lockout Frequencies). The technician performing start up
of the VFD is to enter the values in the VFD programming
according to the manufacturer’s instructions. This step will
prevent continuous operation at the resonant frequencies
listed on the label. If the option was not selected on the
AHU order, it is the customer’s responsibility to have the
Inverter Drive Balance (Sweep Balance) performed and
enter any detected Skip Frequencies (Jump or Lockout
Frequencies) in the VFD program. This should be done
during start up.
Check Doors and Latches
Refer to the Service Manual for adjusting and replacing
the doors.
Doors are shipped with metal shipping spacers glued onto
the edges of each door. They are located on three edges
of each door (top, latch side & bottom). Figure 19 on page
28. The spacers should be left in place until the AHU is
placed in its final location and multiple skid AHUs are fully
assembled. After AHU installation use a channel lock pliers
or a screwdriver to remove the spacers. Do not damage
the metal door panel. Slight impressions left on the door
gasket by the spacers will rebound in approximately a
week.
Energy Recovery Wheel
Configuring the AHU
All indoor AHUs will accommodate vertical energy recovery
wheel segments in a tiered configuration as shown in
Figure 20 on page 28.
NOTE -
Krueger air modulators are, unless
otherwise selected, provided with start-up
service. See VFD.
NOTE -
Failure to properly set up the VFD before
applying power to the motor will void the fan and
motor warranty.
FIGURE 13 - EXAMPLE
OF SWEEP BALANCE
RESULTS LABEL ON
FAN HOUSING
FIGURE 15 - VERTICAL WHEEL FOR AHU
Filter
Return Air
Supply
Fan
Mixing
Box
Cooling
Coil
Energy
Wheel
Heating
Coil
Exhaust
Fan
Filter/
Mixing
Box
Outside
Air
CAUTION -
Keep hands away from rotating
wheel! Contact with the rotating wheel can cause
physical injury.
CAUTION -
When the AHU is operating normally
or temporarily, the energy recovery wheel must
rotate to prevent clogging.
CAUTION -
Many energy recovery wheels are
susceptible to damage if the AHU reaches a
maximum temperature, which can occur if the
heating valve remains open when the AHU is
off. The maximum temperatures across energy
recovery wheels:
1. Thermotech - 140°F
2. Innergy Tech - 122°F
3. NovelAire® Technologies - 200°F
4. Airxchange® - 170°F
FIGURE 14 - METAL
SPACERS ON DOORS
