45
IOM, BS/BT Models
Enertech Global
Section 9: Controls
Sequence of Operation
The description below is based on Split Units,
Single-Stage Compressor (BS Series) as well as
Two-Stage Compressor operation (BT Series).
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) – BS and BT
models
The ECM fan immediately ramps up to 1st stage
airflow (CFM) level (based on jumper 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.
Heating 2nd Stage, (Y1, Y2, G) BT models
The ECM fan adjusts to 2nd stage airflow
(CFM) level (based on jumper settings), and the
compressors second stage (full load) solenoid is
energized.
Heating 3rd Stage, (Y1, Y2, W1, G) BT
models
Heating 2nd Stage, (Y1, W1, G) BS models
ECM fan remains at 100% of 2nd stage airflow
(CFM) level (based on jumper 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.
Emergency Heat (W1, G) BS and BT models
The fan is started immediately at 2nd stage airflow
(CFM) level (based on jumper 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 some 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) BS and BT
models
ECM fan immediately ramps up to 1st
stage airflow (CFM) level (based on jumper
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.
Cooling 2nd Stage (Y1, Y2, O, G) BT models
The ECM fan adjusts to 2nd stage airflow
(CFM) level (based on jumper settings), and
the compressors second stage (full load)
solenoid is energized.
Cooling, Dehumidification Mode
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.