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Single-zone and Dual-zone Condenser Sequence of Operation
EMI AmericaSeries condensers are designed
to operate with EMI AmericaSeries evapora-
tors. Both the condenser (outdoor unit) and
evaporator (indoor unit) have a high volt ser-
vice connection. Each is to be independently
connected to the electrical service 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.
Straight cool condensers are designed to oper-
ate as a single stage cooling unit. Heat pump
condensers are designed to operate as a single
stage cooling two stage heating unit. For proper
operation the unit must be matched with an ap-
propriate EMI indoor unit with unit mounted
controls and/or wall mounted thermostat. For
two-stage heating operation the indoor unit
must be equipped with an electric strip heater.
NOTICE
For remote wall mounted thermostat
operation be sure to select EMI p/n
240004180 or a suitable 24v, two stage
heating, heat pump thermostat.
Condenser operation
The transformer located in the indoor unit
provides 24v, low-volt control power to the
condenser (outdoor unit). This can be measured
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 either 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, single- and dual-zone
Cooling operation requires that the control
(either unit mount or remote wall mount ther-
mostat) make a connection between low-volt
terminals "R" and "Y" along with "R" and "O"
(heat pumps only). When the indoor control
is placed in cooling mode, with the set point
P/N 240007754, Rev. A [051509]
S1CG/S1HG
Single-Zone,
• Installation, Operation and Maintenance Manual •
temperature below the room temperature, the
reversing valve will energize (R & O heat pumps
only) along with the compressor and outdoor
fan (R & Y). When the indoor control is satis-
fied and the room temperature falls below the
set temperature, the compressor and fan will
de-energize. The anti-short cycle timer (ASCT)
will prevent the compressor from re-starting for
three minutes.
Heating operation
Heating operation requires that the control
(either unit mount or remote wall mount, heat
pump 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 temperature above room tem-
perature, the compressor and outdoor fan (R
& Y) will energize. When the indoor control is
satisfied and the room temperature rises above
the set temperature, the compressor and fan will
de-energize. The anti-short cycle timer (ASCT)
will prevent the compressor from re-starting for
three minutes.
Defrost controls with short cycle
protection (heat pumps only)
The unit is equipped with a logic control circuit
designed to keep system operating at peek ef-
ficiency. The 24v circuit provides control to
the indoor and outdoor systems including a
three minute, anti-short cycle timer (ASCT)
compressor protection.
The defrost control circuit is designed to keep
the condenser coil free from frost and ice during
heating mode. This is accomplished through the
precise switching sequence of the outdoor fan,
reversing valve and indoor auxiliary heater.
Defrost initiation
The defrost-sensor is located on either the end
plate or the return bend of the condenser coil.
A defrost cycle will initiate after the sensor
closes (approx. 30° F) and remains closed for
the length of time selected on the control board
(either 30, 60 or 90 minutes)*.
At the start of the defrost cycle, the revers-
ing valve will change from heating to cooling
mode. The condenser fan will also switch off
there-by allowing pressure and temperature
29
S2CG/S2HG
Dual-Zone
Made in the USA
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