37
IOM, XT Models
Enertech Global
Microprocessor Features and Operation
Enertech Global geothermal heat pump controls
provide a unique modular approach for controlling
heat pump operation. The control system uses one,
two, or three printed circuit boards, depending
upon the features of a particular unit. This approach
simplifies installation and troubleshooting, and
eliminates features that are not applicable for some
units.
A microprocessor-based printed circuit board
controls the inputs to the unit as well as outputs for
status mode, faults, and diagnostics. A status LED
and an LED for each fault is provided for diagnostics.
An ECM control module provides field selectable
options for airflow and dehumidification mode, plus
an LED to indicate CFM (100 CFM per flash).
Removable low voltage terminal strips provide all
necessary terminals for field connections. Not only
are the thermostat inputs included, but there are
also two additional removable terminal strips for all
of the accessory and electric heat wiring for ease of
installation and troubleshooting.
Startup/Random Start
The unit will not operate until all the inputs and
safety controls are checked for normal conditions.
At first power-up, the compressor is energized after a
five minute delay. In addition, a zero to sixty second
random start delay is added at first power-up to
avoid multiple units from being energized at the
same time.
Short Cycle Protection
A built-in five minute anti-short cycle
timer provides short cycle protection of
the compressor.
Component Sequencing Delays
Components are sequenced and delayed for
optimum space conditioning performance and to
make any startup noise less noticeable.
Test Mode
The microprocessor control allows the technician to
shorten most timing delays for faster diagnostics by
changing the position of a jumper located on the
lockout board.
Water Solenoid Valve Connections
Two accessory relay outputs at the terminal strip
provide a field connection for two types of water
solenoid valves, a standard 24VAC solenoid valve,
or a 24VAC solenoid valve with an end switch.
Additional field wiring is no longer required for
operation of the end switch.
Humidifier/Dehumidification Connections
Connections for a humidistat are provided, which
automatically engages the fan when the humidistat
contact closes. In addition, a field connection is
provided at the terminal strip for external control of
the On Demand Dehumidification (ODD) feature for
the variable speed ECM motor, which automatically
lowers the fan speed when the space humidity is
higher than set point. Either connection may be
used with a thermostat that includes humidifier/
dehumidification outputs. Not applicable for splits/
water-to-water.
Airflow Monitor
An LED on the ECM control module flashes one time
per 100 CFM when the unit’s fan is operating to
indicate airflow.
Resistance Heat Control
The electric heat control module contains the
appropriate high-voltage control relays. Low
voltage control signals from the compressor
section energize the relays in the electric heat
module to engage backup electric heat when
necessary.
Electronic Condensate Overflow Protection
The control board utilizes an impedance sensing
liquid sensor at the top of the drain pan. Since the
drain pan is grounded, when water touches the
sensor for 30 continuous seconds, the sensor sends a
ground signal to the lockout board, indicating that a
condensate overflow fault has occurred.
Loop Pump Circuit Breakers
The loop pump(s) and desuperheater pump are
protected by control box mounted circuit breakers
for easy wiring of pumps during installation. Circuit
breakers eliminate the need to replace fuses.
Section 9: Controls