Installation manual

45
RCT Models, 16 Feb 2012D Roth
MICROPROCESSOR FEATURES AND OPERATION
Roth 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 simplifi 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 an LED for each fault is provided
for diagnostics. An ECM control module
provides fi eld selectable options for airfl ow and
dehumidifi cation mode, plus an LED to indicate
CFM (100 CFM per fl ash). If the combination
unit is desired (combination water-to-air and
water-to-water heat pump), a third board
controls the hydronic portion of the unit,
allowing fi eld selectable hot water/forced air
priority and other options.
Removable low voltage terminal strips provide all
necessary terminals for fi eld 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 fi rst power-up, the compressor is
energized after a fi ve minute delay. In addition,
a zero to sixty second random start delay is
added at fi rst power-up to avoid multiple units
from being energized at the same time.
Short Cycle Protection
A built-in fi 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.
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 fi eld connection for two types
of water solenoid valves, a standard 24VAC
solenoid valve, or a 24VAC solenoid valve
with an end switch. Additional fi eld wiring is no
longer required for operation of the end switch.
Humidifi er/Dehumidifi cation Connections
Connections for a humidistat are provided,
which automatically engages the fan when
the humidistat contact closes. In addition, a
fi eld connection is provided at the terminal
strip for external control of the On Demand
Dehumidifi cation (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 humidifi er/
dehumidifi cation outputs. Not applicable for
splits/water-to-water.
Airfl ow Monitor
An LED on the ECM control module fl ashes
one time per 100 CFM when the unit’s fan is
operating to indicate airfl ow.
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 Overfl ow 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 overfl ow
fault has occurred.
Section 14a: Controls