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Manual 2100-563C
Page 13 of 40
5. 2-Stage Compressor Units with Newer
ECONWMT Economizers (See Note A)
1
st
stage cooling set point is the setting (SP) input into
the controller. Factory default is 77F (25C). On a call for
cooling the blower of the
lead unit will come on
immediately (if not already on – See Blower Operation),
and the Stage 1 LED will blink for 10-seconds before
going solid, at which time the lead unit Y1 cooling
output turns on. If the outdoor temperature and humidity
conditions are below the set point of the economizer
control the lead unit economizer will operate instead of
the compressor. If outdoor conditions are not acceptable
for free cooling the compressor will automatically
operate on compressor Stage 1 partial capacity instead of
the economizer.
2
nd
cooling set point is 4F (default setting, user
selectable 2-6F) warmer than Stage 1. On a call for 2
nd
stage cooling the lead unit Y2 cooling output turns on. If
the outdoor temperature and humidity conditions are
below the set point of the economizer control the lead
unit economizer will continue to operate, and the
compressor will operate on compressor Stage 1 partial
capacity. If the compressor is already operating on
Stage 1 partial capacity because outside free cooling
range the compressor will switch to compressor Stage 2
full capacity.
3
rd
cooling set point is 2F (default setting, user selectable
2-3F) warmer than Stage 2. On a call for 3
rd
Stage
cooling the blower of the lag unit will come on
immediately (if not already on – See Blower Operation),
and the Stage 3 LED will blink for 10-seconds before
going solid, at which time the lag unit Y1 cooling output
turns on. The lag unit economizer will operate if the
outdoor temperature and humidity conditions are below
the set point of the economizer control. If outdoor
conditions are not acceptable for free cooling the
compressor will automatically operate on compressor
Stage 1 partial capacity instead of the economizer.
4
th
cooling set point is 2F (default setting, user selectable
2-3F) warmer than Stage 3. On a call for 4
th
Stage
cooling the lag unit Y2 cooling output turns on
activating the compressor. If the outdoor temperature
and humidity conditions are below the set point of the
economizer control the lag unit economizer will
continue to operate, and the compressor will operate on
compressor Stage 2 full capacity. If the compressor is
already operating on Stage 1 partial capacity because
outside free cooling range the compressor will switch to
compressor Stage 2 full capacity.
Note A: Economizers in ECONWMT-Series are available
with either “T” temperature only outdoor sensor or “E”
enthalpy (temperature and humidity) outdoor sensor. The
“T” versions will have a fixed (but selectable) outdoor
temperature decision whereas on the “E” versions the
outdoor temperature decision will float based on outdoor
humidity and the selected Enthalpy curve in the
economizer control module.
HEATING SEQUENCE OF OPERATION
Note: All heating sequences for air conditioners with
electric heat or heat pumps will automatically operate in
Alternating Lead/Lag/Lead/Lag sequence even if
controller is set to Non-Alternating for cooling with or
without economizers.
1. Air Conditioners with Electric Heat
1
st
stage heating set point is the dead-band (db) below
the 1
st
stage cooling set point (the SP entered into the
program). The dead-band is adjustable from 2-40F, and
factory default is 17F.
2
nd
stage heating set point will operate at same inter-
stage differential as set for cooling mode.
2. Heat Pumps with Electric Heat
When the MC4000 controller is configured for heat
pump installations the 2
nd
-stage (Y2) outputs for both
units 1 and 2 are redefined and used to control the
reversing valves, and which are energized in heating
mode.
1
st
stage heating set point is the dead-band (db) below
the 1
st
stage cooling set point (the SP entered into the
program). The dead-band is adjustable from 2-40F, and
factory default is 17F.
1
st
-stage heating consists of lead unit blower coming on
(if not already on – See Blower Operation), and
reversing valve being energized. The Stage 1 heating
LED will blink for 10-seconds, at which time the
compressor turns on.
2
nd
heating set point is 4F (default setting, user selectable
2-6F) cooler than Stage 1. On a call for 2
nd
Stage heating
the blower of the lag unit is turned on (if not already on
– See Blower Operation), the reversing valve is
energized, and the Stage 2 LED will blink for 10-
seconds before going solid, at which time the
compressor will start.
3
rd
-stage heating will be the electric heater, if so
equipped, in the lead unit. Stage 3 heating LED comes
on solid with no blinking.
4
th
-stage heating will be the electric heater, if so
equipped, in the lag unit. Stage 4 heating LED comes on
solid with no blinking.