Comfort-Aire HMB**V*1E SERIES - Manual (Page 10)

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a conduit connector for connecting the supply wires to
the unit. Aluminum supply wire may be used if a heater
kit is installed.
• If replacing any of the original wires supplied with the
unit, the replacement wire must be copper wire consisting
of the same gauge and temperature rating.
• Provide power supply for the unit in accordance with the
unit wiring diagram, and the unit rating plate. Use UL
listed conduit and conduit connectors for connecting the
supply wires to the unit and for proper grounding. Field
supplied bushings for the power supply cables must be
added to support and protect the power supply cables.
• All 208/230 Volt units are shipped from the factory wired
for 240 volt operation. For 208V operation, remove the
lead from the transformer terminal marked 240V and
connect it to the terminal marked 208V.
Thermostat Connections
• Thermostat connections shall be in accordance with the
instructions supplied with the thermostat. The thermostat
used with this equipment must operate in conjunction
with any installed accessories. Typical AC and air handler
hookups are shown in Figure 10 (page 22).
CAUTION:
Isolation must be maintained from the external
Class 2 output of any transformer in a cooling
circuit. Use a thermostat with isolating contacts
to prevent inter-connection of Class 2 outputs.
• Where local codes require that the thermostat wiring
must be routed through a conduit or raceway, splices
can be made inside the unit; however, all wiring must
be NEC Class 1 and must be separated from incoming
power leads.
• The thermostat should be mounted about 5 feet above the
floor on an inside wall. DO NOT install the thermostat on
an outside wall or any other location where its operation
may be adversely affected by radiant heat from fireplaces,
sunlight, or lighting fixtures, and convective heat from
warm air registers or electrical appliances. Refer to the
thermostat manufacturer’s instruction sheet for detailed
mounting and installation information.
• Install the grommet, which is packed with the unit, in
the hole for low-voltage wires. Properly connect the
low-voltage wiring between the thermostat, outdoor
unit, and control board. NOTE: When the low voltage
wires are positioned in this grommet, the grommet will
prevent chafing and/or shorting of the low voltage leads
Important! On variable speed models when the unit is
used in an air conditioning system, connect the O terminal
to the Y terminal. See Figure 10 (page 22).
Control Board
The control board in the air handler controls the timing
sequence of the elements. Depending on the thermostat
connection, there are multiple timing sequence variations
that can be chosen. The board also is equipped with a 3
second blower on delay and a 15 second blower off delay.
See Figures 11 - 14 (pages 23 & 24) for control board
layout and Tables 10 & 11 (pages 28-30) for element
sequences.
Twinning
HMB series air handlers are not supplied with a built
in twinning capability. To connect two air handlers to a
common single stage AC condensing unit or heat pump,
a twinning kit is available for field installation.
IMPORTANT: Variable speed air handlers cannot be
twinned. Please follow the instructions supplied with
the kit.
Heater Kits
Field-installed electric heater kits are available. Instructions
for installing the electric heaters are included with the
heaters. Additional heater kit information can be found
in the units Technical Specifications.
Air handlers set up with 15 kw or more of electric heat will
normally be configured for multiple-circuit power supply.
They may, however, be connected to a single-circuit power
supply with the addition of a single circuit accessory
kit. Select the wire size and over-current protection
in accordance with the minimum circuit ampacity and
maximum over-current protection shown in Table 9 (page
21). See also the units Technical Specifications.
When electric heat packages with circuit breakers are
field-installed, the circuit breaker may be used as a
disconnecting means in most applications. Reference
the NEC and local codes for disconnect requirements.
If a heater kit is installed:
The HMB series air handler is shipped from the factory
without an electric heater kit installed. If Electric heat is
desired, the H6HK heater kit may be purchased separately
and field installed. Determine the correct size heater kit
for your unit by referring to the list below or the units
rating label.
24K & 30K BTUH ........................................... 15Kw max
36K & 42K BTUH ........................................... 20Kw max
48K & 60K BTUH ........................................... 20Kw max
1. Connect the 2 wire plug of the air handler to the mating
2 wire plug of the heater kit.
2. Connect the line voltage leads to the circuit breaker or
terminal block provided.
3. Connect the heater kit plug with the mating receptacle
on the air handler control board.