5
Single-Duct and Retrofit Terminal Units IOM
NOTE:
Refer to wiring diagram attached to each unit for
specific information on that particular unit.
Single duct terminal units with electric heat are supplied
with a single point wiring connection in the heater control
box. All unit power is supplied through this connection.
Models with electric heat are factory equipped with a control
transformer. Figure 5 illustrates an example high voltage
wiring diagram that includes a unit with electric heat.
NOTE:
Refer to wiring diagram attached to each unit for
specific information on that particular unit. Units with 480-
3-60 electric heater REQUIRE 4-wire, wye connected power.
Units with 208/230v, 3-phase heater can be connected with
3-wire power. Unit airflow should not be set outside of
the range noted in Figure 6. The minimum recommended
airflow for units with electric heat must be at least 75 cfm
per kW and not drop below the minimum values listed in
Table 6.A. The maximum unit discharge temperature should
not exceed 120°F. To prevent air stratification, the ASHREA
Handbook of Fundamentals recommends a discharge
temperature not to exceed 90°F.
STEP 1 - INSTALL UNIT
A. Move unit to installation area. Remove unit from shipping
package. Do not handle by controls, flow sensors or
damper extension rod.
B. Optionally, the unit may have factory-installed hanger
brackets.
C. Suspend units from building structure with field supplied
straps, rods, or hanger wires. Secure the unit and level
it in each direction. Krueger LMHS units with electric
heat must be mounted in the horizontal position, where
airflow runs parallel to the ground.
D. Figure 3 illustrates the use of optional factory installed
hanger brackets for suspending units.
STEP 2 – MAKE DUCT CONNECTIONS
A. Install supply ductwork on each of the unit inlet collars.
It is recommended that a length of straight duct equal
to 3 times the diameter of the duct is supplied to the
inlet of the unit. An elbow put at the inlet of the unit will
create turbulence at the inlet making it difficult for the
flow sensor to accurately measure the airflow. Check that
air-supply duct connections are airtight and follow all
accepted medium-pressure duct installation procedures.
Refer to Table 6.A – LMHS, 6.B – LMHS-LC, 6.C – RVE, and
6.D - SVE for pressure and flow data.
B. Install the discharge ducts. Fully open all balancing
dampers.
STEP 3 - INSTALL SENSORS AND MAKE FIELD WIRING
CONNECTIONS
A. Refer to specific unit dimensional submittals and control
application diagrams for control specifications. All field
wiring must comply with National Electrical Code (NEC)
and local requirements. Refer to the wiring diagram on
the unit for specific wiring connections. A field-supplied
transformer is required if the unit was not equipped
with a factory installed transformer. See Figure 4 for
illustration.
INSTALLATION
Figure 3: Factory Installed Hanger Brackets (field supplied rod and nuts).
Figure 4: Wiring of Optional Factory Mounted Transformer
120VAC
208VAC
240VAC
277VAC
L1
CLASS II
TRANSFORMER
GROUND
24VAC
LEGEND
Factory Wiring
Field Wiring
ANALOG OR DDC
CONTROLLER
YELLOW
BLUE
Brown#12
Step 1
Heat Contactor
Step 2
Heat Contactor
Step 3
Heat Contactor
Brown#12
Brown#12
Brown#18
Black#18
Brown#12
Red#12
Red#12
Red#18
Red#18
Red#12
Red#12
Yellow#12
Yellow#18
Yellow#18
Yellow#12
Yellow#12
Blue#18
Blue#18
Black#18
Black#18
Black#18
Black#18
Black#18
N.O.
Yellow#12
White#12
White#12
White#12
White#18
White#18
480V
Power
Suply
Transformer
24VAC
To
Controller
AFS
Line Fuse
(Optional)
Manual
Reset
Thermal Hi-Limit
Auto-Reset(Typ)
COM
Terminal Block or
Optional Disconnect Switch
L1
L2
L3
N
G
Figure 5: Typical Power Connections for LMHS units with 3-Stage Electric Heat.
Wiring and unit ampacities are referenced in Table 7.
LEGEND
AFS: Airflow Switch
DDC: Direct Digital
Controls
Note: Drawing is
typical of 480V
3-Phase, 4 wire heater
and controller. Refer
to actual unit wiring
diagram located on
inside cover of control
enclosure.