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Heat Pump Controller
TROUBLESHOOTING
Invalid Thermostat Demands
The controller validates the thermostat demands
to prevent field miswiring.
THERMOSTAT
SENSOR INPUTS
OUTPUTS
TEST MODE
REAL-TIME
CLOCK
Table 6 Troubleshooting IO
Replacement Parts
Fuses
Provides protection for the Class II field
thermostat wiring.
•
Fuse 3: Fuse Auto 3A 32 VDC Blade for F4
•
Fuse 5–6: Fuse glass 5A 250 VAC 5x20 mm for
F5
•
Fuse 7: Fuse glass 1A 250 VAC 5x20mm for F7
Heat Pump Controller
IO Information
All inputs are 24 VAC from the wall thermostat and can be verified using a voltmeter
between (C) and (G), (O), (Y1), (Y2), (W1), (W2), (H).
Thermostat inputs are fused via F4 on PCB.
All sensor inputs are fused via F4 on PCB.
All switches are 24 VAC inputs.
All sensors are 3.3 VDC powered.
The thermistor resistance should be measured with the connector removed so that only
the impedance of the thermistor is measured. (See the table on page #23 for values.)
The Reversing Valve, Compressor Stage 1, Compressor Stage 2, Auxiliary Relay 1 and
Auxiliary Relay 2 are 24 VAC and can be verified using a voltmeter.
The Loop Pump and HRP Pump are 208 or 230 VAC, depending on the line voltage
connected to the unit. These can be verified using a voltmeter and their value must be
equal to the line feed on the compressor connector.
Loop Pump outputs are fused with 5 Amp rated fuses and the HRP pump output with a 1
Amp rated fuse. Fuses can be tested for continuity with a multimeter.
The Blower Motor is a PWM signal that varies from 0 to 24 VDC. The voltmeter will show
values from 0 through 24 VDC.
Test Mode will be available for 20 minutes. The HPC will enter test mode when
commanded via the Bosch EasyStart app.
The controller will require a Wi-Fi network connection from the Wireless Interface Module
(WIM) to enable communication with the Bosch EasyStart app.
The controller will require a CR2032 Battery in order to keep its Real-Time Clock (RTC) in
case of a power outage or a power loss.
It is a best practice to check that the Battery Voltage is 3 VDC as checked with a voltmeter
while on site.
Subject to change without prior notice
When an invalid call is sensed, the unit will
shutdown and the status LED will be lit for the
duration of the invalid call.
Board Battery
Battery type used is CR2032 Lithium 3V coin
20mm.
Troubleshooting | 19
8733819577 (2019/02)
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