43
IOM, ZS/ZT Models
Enertech Global
SECTION 6: CONTROLS
Sequence of Operation
The description below is based on Water-to-Air
Units, Two-Stage Compressor, with ECM Fan.
Timings assume the ASC timer is expired. If the
ASC timer is not expired the ECM fan will start
immediately but the accessory, compressor,
and loop pump operation do not start until the
ASC timer is expired.
Heating 1st Stage, (Y1, G) ZS and ZT models
The ECM fan immediately ramps up to 75% of
1st stage airflow (CFM) level (based on DIP
switch settings), the Accessory (A) terminal
output is energized after the random start timer
(10s-20s) expires. Next, after another 10s delay,
the compressor first stage and the loop pump(s)
are energized. Then the ECM fan adjusts to
100% (of 1st stage operation) CFM level 90
seconds after the “Y1” input.
Heating 2nd Stage, (Y1, Y2, G) ZT models
The ECM fan adjusts to 2nd stage airflow (CFM)
level (based on DIP switch settings), and the
compressors second stage (full load) solenoid is
energized.
Heating 3rd Stage, (Y1, Y2, W1, G) ZT models
Heating 2nd Stage, (Y1, W1, G) ZS models
ECM fan remains at 100% of 2nd stage airflow
(CFM) level (based on DIP switch settings), and
the first stage of electric heat is energized.
Second stage of electric heat (W2) is energized
ten minutes after first stage electric heat (W1) is
energized. (W2 is only available with 10kW, 15kW
and 20kW electric heaters)
Emergency Heat (W1, G) ZS and ZT models
The fan is started immediately at 2nd stage
airflow (CFM) level (based on DIP switch
settings), and the electric heat is energized.
Second stage of electric heat (W2) is energized
two minutes after first stage electric heat (W1) is
energized. (W2 is only available with 10kW, 15kW
and 20kW electric heaters)
Cooling Operation
The reversing valve is energized for cooling
operation. Terminal “O” from the thermostat is
connected to the reversing valve solenoid.
Cooling 1st stage (Y1, 0, G) ZS and ZT models
ECM fan immediately ramps up to 75% of 1st
stage airflow (CFM) level (based on DIP switch
settings), the Accessory (A) terminal output is
energized after the random start timer (10s-20s)
expires then first stage compressor and the
loop pump(s) are energized 10 seconds after
A. The ECM fan adjusts to 100% (of 1st stage
operation) CFM level 90 seconds after the “Y1”
input.
Cooling 2nd Stage (Y1, Y2, O, G) ZT models
The ECM fan adjusts to 2nd stage airflow (CFM)
level (based on DIP switch settings), and the
compressors second stage (full load) solenoid is
energized.
Cooling, Dehumidification Mode
The ECM fan control board includes two
types of dehumidification modes, Constant
Dehumidification mode, and On Demand
Dehumidification (ODD). If the ECM control
board is set to Constant Dehumidification
mode, the ECM fan runs at normal airflow
(CFM) in all heating stages, but all cooling
operation will be 85% of the current stage
airflow (CFM) level (based on DIP switch
settings). The dehumidification mode lowers
the airflow (CFM) through the evaporator coil,
to improve latent (dehumidification) capacity.
In ODD mode, a humidistat or a thermostat
with a dehumidification output (output must
be reverse logic -- i.e. it must operate like a
humidistat) is connected to the ODD terminal.
When the module receives a call for
dehumidification, the fan runs at 85% of the
current stage airflow (CFM) in the cooling
mode. Otherwise, the airflow is at the normal
airflow (CFM) level. The signal is ignored in the
heating mode.
Fan Only
When the ECM control module receives a “G”
call without a call for heating or cooling, the
fan operates at 50% of the full load airflow
(CFM) level (based on DIP switch settings shown
in following table).