30
6.4 Sequence
of Operation for
Conventional 24VAC
Thermostat Controls
When the (-)A20 air-conditioning system is controlled
by a conventional 24VAC 2-stage thermostat rather
than the EcoNet
TM
Control Center, the system will oper
-
ate as follows:
•
The system will operate as a 3-stage system
instead of a variable speed system.
•
When a call for 1
st
stage cooling is received from
the 2-stage thermostat, the compressor will start
and operate at the minimum capacity level and
the RHMV air-handler will deliver the minimum
air-flow level. For gas furnace applications, an
(-)802V, (-)96V, (-)97V, or (-)98V variable speed
gas furnace will operate at either 50% or 75% of
the cooling air-flow level selected by dip switches
on the furnace control board. 75% is the factory
setting.
6.0 NORMAL SEQUENCE OF OPERATION
•
After 15 minutes of operation with a continuous
1
st
stage call for operation, the compressor will
automatically ramp to a pre-determined intermedi
-
ate speed and the RHMV air-handler air-flow will
automatically increase to a pre-determined inter
-
mediate level. For gas furnace applications, the
variable speed gas furnace will remain at 50% or
75% of the selected cooling air-flow level depend
-
ing on the furnace DIP switch setting.
•
If the thermostat calls for 2
nd
stage operation, the
compressor will ramp to its full capacity speed and
the RHMV air-handler will deliver the maximum
air-flow level. For gas furnace applications, the
variable speed gas furnace will deliver 100% of the
selected cooling air-flow level.
•
If the system then cycles between 1
st
and 2
nd
stage, the compressor will cycle between the
maximum and intermediate speeds and the RHMV
air-handler will cycle between the maximum and
intermediate air-flow levels as directed by the
2-stage thermostat.
•
When the call for operation ends, the system will
shut down and remain in stand-by mode until an
-
other call for operation occurs.
•
Low-ambient cooling functions normally.
7.0 COMPONENTS & CONTROLS
7.1 Accumulator
All (-)A20 condensing units are equipped with an
accumulator for the purpose of managing possible
refrigerant flood back issues that may occur at
abnormal environmental conditions.
7.2 Choke/Inductor
The power inverter used in each (-)A20 system has a
paired choke/inductor. The choke is designed as a low
pass filter and increase inductance. By doing this the
input power can be more efficiently used by the invert
-
er and compressor.
7.3 Coil Temperature
Thermistor
(-)A20 condensing units are equipped with a coil sen
-
sor that is used for the purposes of identifying defrost
parameters and low ambient cooling operational con
-
ditions. This thermistor is provided with the suction line
thermistor as a single harness
Operation
Components
