32
Service Tool
A B C
NO USE
COND C W1 Y1 Y2 0
A150782
Fig. 25 -- Service Tool Connection
When working on the outdoor unit of a split system, the technician
would usually need to repeatedly walk between the indoor wall
control and the unit outside. To save time, the communicating
controls offer a service tool feature.
By wiring the service tool into the UPM board, the technician can
have a wall control capable of running the system right at the
outdoor unit.
To use a service tool, connect the A and B communication bus
wires from this second communicating control to the terminals
marked A and B on the terminal strip located in the bottom left
corner of the UPM board (see Fig. 25). But instead of connecting
the wires on the service tool to the terminals marked C and D,
connect the C and D wires from the service tool to the 24V and C
on ST1 as shown in Fig. 25.
When the service tool is connected and powered up, the
communicating controls inside the home will ”go to sleep” and let
the service tool take control of the system. In this manner, the
service technician can run the diagnostic checkouts right at the
outdoor unit using the service tool.
After the checkouts are completed and it is no longer necessary to
use the service tool, remove it from the communicating controls
and the indoor communicating controls will regain control in about
two minutes.
HRP Troubleshooting
The HR pump will be enabled when compressor d ischarge
temperature is 120_F (48.9_C) or above.
The circulating pump will be disabled if water temperature reaches
140_F(60_C) or amperage exceeds 0.4 amps.
HRP Troubleshooting
Problem Possible Cause Checks and Corrections
NO FLOW
LOW FLOW
No Power Check power supply
On/O Switch Position Set switch to “ON” position
Compressor Contactor Engage heat pump contactor
Broken or loose wires
Repair or tighten wires
Air Lock Purge air from piping system
Stuck pump shaft/impeller Remove pump cartridge and clean
Defective pump Replace pump
Kinked or under sized water piping Repair kink and check for proper line size
HIGH WATER
TEMPERATURE
Water temp limit closed
Stuck limit switch
Sensor not attached securely to line
LOW HEAT OUTPUT Clean heat exchangerScaled or fouled heat exchanger
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