Enertech VS Series - Section 9: Controls; Microprocessor Operation and Features; Unit Start-up and Protection; Special Connections and Features

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Enertech Global IOM, VS/VT Models, Rev A
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
simplies 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 LED(s) for each fault are provided
for diagnostics. Water-to-air models may offer an
ECM control board option providing eld selectable
airow and dehumidication mode, plus an LED to
indicate CFM (100 CFM p/ash).
A removable low voltage terminal strip provides the
necessary terminals for thermostat connections.
Some models offer an additional removable
terminal strip for accessory wiring connections.
Startup/Random Start
The unit will not operate until all the inputs and
safety controls are checked for normal conditions. A
ten to twenty second random start delay is added
at power up and whenever an Y1 call is received.
This avoids multiple units from being energized at the
same time after power loss or other situations.
Short Cycle Protection
A built-in ve 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. There is
a short delay between the blower motor and the
compressor start up.
Test Mode
The microprocessor control allows the technician
to shorten timing delays for faster diagnostics by
removing the TEST jumper located on the lockout
board. It should be reinstalled for normal operation
after testing. The status LED will not be illuminated
during the TEST mode.
Water Solenoid Valve Connections
When provided, the YT & YU on the accessory
terminal strip provides a eld connection for a valve
with an end switch, which is recommended. (The YT
terminal can be used to power the solenoid valve
and end switch. The YU terminal can be powered
through the end switch and connects to the Y1
circuit of the unit controls - see wiring diagram).
An accessory relay terminal, “A”, can be used
for solenoid valves without an end switch. This
terminal is energized 10 seconds before the
compressor contactor. A valve without an end
switch could cause a water hammer issue and is not
recommended.
In models without an accessory terminal strip
provided, connect the valve with an end switch in
between Y1 of thermostat and Y1 at the thermostat
terminal strip. Also, a valve without an end switch
can be connected via the spade terminal labeled
(A) on the lock out board.
Humidier/Dehumidication Connections
Connections for a humidistat are provided for
some models, which automatically engage
the fan when the humidistat contact closes. In
addition, a eld connection is provided at the
terminal strip for external control of the On Demand
Dehumidication (ODD) feature for the variable
speed ECM fan motor, which automatically lowers
the fan speed when the space humidity is higher
than the set point. Either connection may be
used with a thermostat that includes humidier/
dehumidication outputs.
In ECM equipped models without an accessory
terminal strip provided, connect ODD and G on
the ECM board directly (package units only). For
units equipped with PSC blower motors, connect
thermostat’s humidier terminal to G on the unit’s
thermostat terminal strip.
Airow Monitor
When provided, a LED on the ECM fan control
board ashes one time per 100 CFM when the unit’s
fan is operating to indicate airow.
Resistance Heat Control
The resistance heat control module contains the
appropriate high-voltage control relays. Low
voltage control signals from the lockout board
energize the relays in the resistance heat module to
engage backup resistance heat when necessary.
The lockout board offers a pass through W1 (1st
stage) and a relay output for W2 (2nd stage). See
staging in sequence of operation section.
Electronic Condensate Overow Protection
The control board utilizes an impedance sensing
liquid sensor at the top of the drain pan.
When water touches the sensor for 30 continuous
seconds, the sensor sends a ground signal to the
lockout board indicates a condensate overow
fault has occurred.
Section 9: Controls