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Multi-zone Heat Pump Condensing Units
MultI-zonE condEnSEr SEquEncE of oPErAtIon
EMI America Series multi-zone heat
pump condensers are designed to operate
with EMI America Series indoor air han-
dlers. Both the condenser (outdoor unit)
and evaporator (indoor unit) have a high
Volt service connection. Each is to be inde-
pendently connected to the electrical ser-
vice panel. (See the unit name plate for the
correct breaker type and size). The outdoor
and indoor units are also connected to each
other through a low Volt interconnect wiring.
A 24V transformer located in the indoor unit
provides the low Volt power source.
The S & T series (S2HB, T2HB, T3HB &
T4HB) heat pumps will provide comfort
cooling or heat pump operation operate
at an outdoor temperature range between
35°F and 115°F for cooling, 0°F and 75°F
for (heat pump) heating.
The S & T series (S2HB, T2HB, T3HB
& T4HB) heat pump condensers are de-
signed to operate as a single stage cool-
ing, two stage heating unit. For full opera-
tion the unit should be matched with an
appropriate EMI indoor unit with electric
heat and unit mounted controls or a wall
mounted thermostat.
For two stage heating operation the indoor
unit must be equipped with an electric strip
heater.
See the instruction manual for the indoor
unit on the selection of the proper thermo-
stat for the system.
Condenser Operation:
The transformer located in the indoor unit
provides 24V, low-Volt control power to the
condenser (outdoor unit). This can be mea-
sured across low-Volt terminals “R” and “C”.
Heat pump condensers utilize a reversing
valve to provide reverse cycle operation.
Therefore the outdoor unit will act as ei-
ther a condenser or an evaporator there-
by providing comfort cooling or heating to
the indoor space. The reversing valve is
energized in cooling. Should the valve fail
to actuate, the system will default to the
heating mode of operation.
Cooling operation, Multi-zone Heat
Pump:
Cooling mode operation requires that the
control (either unit mount or remote wall
mount thermostat) make a connection be-
tween low-Volt terminals “R” and “Y” along
with “R” and “O”. When the indoor control
is placed in cooling mode, with the set point
temperature below the room temperature,
the reversing valve will energize (R & O)
along with the compressor and outdoor fan
(R & Y). When the indoor control is satis-
ed and the room temperature falls below
the set temperature, the compressor and
fan will de-energize. The EMI indoor unit
is equipped with an anti-short cycle timer
(ASCT) will prevent the compressor from
re-starting for three minutes.
Heating operation, Multi-zone Heat
Pump:
Heating mode operation requires that the
control (either unit mount or remote wall
mount thermostat) make a connection
between low-Volt terminals “R” and “Y”
only. When the indoor control is placed
in heating mode, with the set point tem-
perature above room temperature, the
compressor and outdoor fan (R & Y) will
energize. When the indoor control is satis-
ed and the room temperature rises above
the set temperature, the compressor and
fan will de-energize. The EMI indoor unit
is equipped with an anti-short cycle timer
(ASCT) will prevent the compressor from
re-starting for three minutes.
Note: For full operation the indoor unit
must have an electric heater.