24
Enertech Global
HP IOM, Rev. B
Section 7: Controls
Lockout Board Jumper Selection
The lockout board includes four jumpers for field selection of
various board features.
Load/Source HX Temperature Sensing (FS)
When the FS jumper is installed (T1 and T4 monitored, FS
terminals ignored), the board operates in the load and source
heat exchanger temperature sensing mode, which is the
factory setting.
Anti-Freeze (A-FRZ)
When the jumper is installed, the board operates in open
loop mode. The setpoint for the source heat exchanger freeze
sensor is 30°F. When the A-FRZ jumper is removed, the board
operates in the closed loop mode. The setpoint for the source
heat exchanger freeze sensor is 15°F.
Test Mode (TEST)
When the TEST jumper is installed, the board operates in
the normal mode. When the jumper is removed, the board
operates in test mode, which speeds up all delays for easier
troubleshooting. While in the test mode the T1 & T4 sensors
will be checked for the proper location based on temperature.
Sensors are swapped if T1>T4 in cooling or T1<T4 in heating.
This fault will only show up in the test mode. When service is
complete, the jumper must be re-installed in order to make
sure the unit operates with normal sequencing delays. While
the test jumper is removed, the status light (bottom green) will
remain off. If the test jumper is not re-installed the control will
revert to normal mode after one (1) hour, green status light
blinking.
Over/Under Voltage Disable (O/U)
When the O/U jumper is installed, the over/under voltage
feature is active. When the jumper is removed, the over/under
voltage feature is disabled. On rare occasions, variations in
voltage will be outside the range of the over/under voltage
feature, which may require removal of the jumper. However,
removal of the jumper could cause the unit to run under
adverse conditions, and therefore should not be removed
without contacting technical services. An over/under voltage
condition could cause premature component failure or
damage to the unit controls. Any condition causing this fault
must be thoroughly investigated before taking any action
regarding the jumper removal.
Sequence of Operation
This description is based on the HP Water-to-Water Units,
Single-Stage Compressor, heating only.
Timings assume the ASC timer (8 min) is expired. If the ASC
timer is not expired the accessory, compressor, and loop pump
operation do not start until the ASC timer is expired.
The Accessory (A) terminal output is energized after the
random start timer (10s-20s) expires. After another 10 second
delay, the compressor and the loop pump(s) are energized.
This unit utilizes two contactors and a bi-metal normally
closed temperature switch located on the leaving water line to
comply with UL/CSA requirements for units providing domestic
hot water. Operation is as follows:
1� When the aqua-stat calls for heating, the Y terminal at the
lockout board is energized. If the unit is not in fault mode
and the ASC timer has expired, the lockout board will send
24 VAC to the pump contactor coil (labeled "contactor #1"
on the wiring diagram), which will energize the pumps and
provide line voltage to the compressor contactor (labeled
"contactor #2" on the wiring diagram).
2� At the same time the Y terminal is energized at the
lockout board, the compressor contactor coil is energized.
If the pump contactor is energized AND the bi-metal
switch is closed, the compressor will be energized. The
pumps and the compressor are normally energized at the
same time. Even though contactor #2 may be energized
before contactor #1, it cannot get power until contactor
#1 is energized.
3� The bi-metal switch is part of the safety circuit and opens
at 150 deg. F (normally closed -- opens on temperature
rise). Once the switch opens, it closes again when the
water line cools to 135 deg. F. The pumps will continue to
run, even if the bi-metal cut-off is open, as long as there is
still a call from the aqua-stat.
