TemperZone UC8 User manual

Temperzone UC8 Troubleshooting Guide
Page 1 of 24
UNIT CONTROLLER 8 (UC8)
Troubleshooting guide
Date: 21 April 2017
Issue: 3

Temperzone UC8 Troubleshooting Guide
Page 2 of 24
Contents
1. Cautions........................................................................................................................................... 3
2. Recommended service tool set ........................................................................................................ 3
3. Recommended set of spare parts ..................................................................................................... 3
4. Items to check first........................................................................................................................... 3
5. Controller start-up procedure........................................................................................................... 4
6. Viewing system information ........................................................................................................... 5
7. Controller test mode ........................................................................................................................ 6
8. Commissioning mode...................................................................................................................... 7
9. Timer durations................................................................................................................................ 7
10. Troubleshooting procedure.............................................................................................................. 8
11. Fault messages............................................................................................................................... 10
12. Fault codes..................................................................................................................................... 13
13. Inverter fault codes........................................................................................................................ 16
14. Fault codes shown on a room thermostat ...................................................................................... 17
TZT-100 room thermostat fault codes ................................................................................. 17
SAT-3 room thermostat fault codes..................................................................................... 17
SAT-3 internal fault codes ................................................................................................... 17
SAT-3 + Zone controller fault codes ................................................................................... 17
SAT-3 + UC8 fault codes..................................................................................................... 18
15. Protection function details............................................................................................................. 19
High pressure protection (HP).............................................................................................. 19
Low pressure protection (LP)............................................................................................... 19
Indoor coil frost protection................................................................................................... 19
High temperature protection................................................................................................. 19
High suction line / evaporating temperature protection....................................................... 20
Low discharge side superheat protection............................................................................. 20
High discharge side superheat protection............................................................................. 20
Freeze protection.................................................................................................................. 20
Reverse cycle valve fault protection .................................................................................... 21
Overload protection.............................................................................................................. 21
High compression ratio protection....................................................................................... 21
Low compression ratio protection........................................................................................ 22
16. Lock-out......................................................................................................................................... 22
17. Unit log.......................................................................................................................................... 23

Temperzone UC8 Troubleshooting Guide
Page 3 of 24
1. Cautions
 Turn off mains power before opening the electrical panel of a unit.
 When disconnecting and connecting connectors hold them by the housing. Do not pull on the
wires.
 Use as little force as possible when replacing electronic circuit boards.
 Never pull on individual electronic components.
2. Recommended service tool set
Set of screwdrivers of various sizes: blades, pozi-drive and Phillips
Socket set (6mm to 19mm metric)
Allan keys (5mm to 10mm metric)
Small and medium size crescent
Long nose pliers
Multi-meter and probe leads of good quality
Bottle with R410a refrigerant
Refrigerant scales
Mobile telephone / Smart-phone
Additional potentially useful items:
Amp-meter clamp
Temperature probe
Length of appliance wire, mains voltage rated
Wire cutting and stripping tool
Roll of electrical insulation tape
Quick-connect (spade) terminals (6.3mm, 0.25”) (plastic or rubber insulating boots are useful too)
Quick-connect (spade) crimp tool
Pressure gauges for R410a refrigerant
Torch or other battery powered lamp (e.g. headlamp)
Temperzone wireless service tool (WSU) and a smart phone
Laptop computer with USB to RS485 converter (Hyperterm or TeraTerm program installed)
3. Recommended set of spare parts
Known good UC8 controller circuit board, programmed with software version 2.1.9 or later
Set of Temperzone standard temperature sensors (yellow, blue, red and white leads)
34.5 bar and 45 bar pressure transducers
Temperzone pressure transducer leads
4. Items to check first
What exactly is the complaint? Does the unit run at all?
Under which conditions does the problem occur?
Check mains power is properly connected and is the mains voltage correct.
Check control wires between indoor and outdoor units and to the thermostat or other controller.
Check all unit internal wiring is securely fastened and connected.
Check that DIP switch settings agree with information given in the unit documentation.
Take careful note of any information shown on the controller board display.

Temperzone UC8 Troubleshooting Guide
Page 4 of 24
5. Controller start-up procedure
When mains power to the UC8 controller is switched on it follows a defined start-up procedure. The
controller start-up procedure is, in this order:
1. The yellow light marked Power must illuminate.
2. The display must show the characters UC8 (one character at a time).
3. The display must show the software version as three numbers with two dots (decimal points)
in between. Example: 2.1.9
4. If the unit was locked out due to repeated trips, then it will next show the cause of the most
recent lock-out. Note this is not a fault! The message will be shown for about half a minute
after which the controller will continue the normal start-up sequence. This message will no
longer be shown after the unit has completed at least one normal cooling or heating cycle.
5. The display will show the type/model of the compressor it is configured for. Refer to the table
below for a list of available compressors.
6. A controller configured as a master (DIP switches 11 and 12 both OFF) will show the message
dELAY, for between 10 to 20 seconds.
Air-to-air units only: A controller configured as a slave (one or both DIP switches 11 and 12
ON) will show the message ctrL, until the master controller has made contact with the slave.
7. The display must show a flashing decimal point (a dot). The flashing dot indicates the unit has
commenced normal operation and no faults are reported.
List of available compressors:
Compressor
Drive
UC8 display
indication
DIP switch 2
setting
Fixed capacity
Not required
dF
Off
Digital scroll
On
Copeland ZPV038
Carel Power+ PSD1024400
038
-
Toshiba DA550
Carel Power+ PSD1018400
Or PSD1024400
550
Siam ANB66
Carel Power+ PSD1024400
66
-
Siam ANB78
Carel Power+ PSD1024400
Or PSD1035420
78
-
Siam ANB87
Carel Power+ PSD1035420
87
-
Copeland ZPV063
Emerson CSD100
063
-
Other inverter
Type with 0-10V input
010
-

Temperzone UC8 Troubleshooting Guide
Page 5 of 24
6. Viewing system information
When the controller is operating normally the display will show a flashing dot or, if operating in
commissioning mode, a flashing letter c. Under those conditions it is possible to use the display on the
UC8 controller to view information on pressures, temperatures, superheat, expansion valve opening,
capacity and the controller Modbus address. This is available regardless whether the compressor is on
or off. It is not available when the controller is reporting a fault.
To view system information:
Repeatedly press the pushbutton to cycle the display through the options (in a round robin fashion).
-Temperatures are shown in degrees Celsius (°C). If the indicated temperature is below 0°C then a
minus sign is shown before the value. If the unit has one or two pressure transducers then the
condensing and/or evaporating temperatures shown are converted from pressure readings.
-Pressures are shown in kPa. Divide by 6.895 (roughly 7) to convert to PSI.
-If a sensor reading is not available then the display shows a dash, for example: SLP –
-If the unit does not have electronic expansion valves then it shows value 0; example: EE1 0
-After 2 minutes the display automatically returns to a flashing dot (or c).
Display
Meaning
Units
● or c
Normal mode (default)
SLP
Compressor suction line pressure
kPa
Et
Evaporating temperature
°C
SLt
Compressor suction line temperature
°C
SSH
Suction side superheat
K
dLP
Compressor discharge line pressure
kPa
Ct
Condensing temperature
°C
dLt
Compressor discharge line temperature
°C
dSH
Discharge side superheat
K
ICEt
Outdoor coil de-ice sensor temperature
°C
CAP
Unit capacity (duty)
%
EE1
Expansion valve 1 opening
%
EE2
Expansion valve 2 opening
%
Add
Controller Modbus address
-

Temperzone UC8 Troubleshooting Guide
Page 6 of 24
7. Controller test mode
A controller test mode is available that can provide a quick check of the operation of relays, contactors
and fans. Test mode can only be activated when the unit is not already in commissioning mode, the
compressor must be off and the thermostat or BMS must not request to start.
To activate test mode hold down pushbutton SW3 until the display shows the letter ‘t’, then release the
button.
During test mode following outputs are activated one by one, in the order indicated in the table below,
with a brief pause between each step. When the test sequence is complete the UC8 returns to normal
mode and the display will show the suction line pressure (letters SLP followed by the pressure in kPa)
or it may return to show a flashing decimal point.
Step
Test
Duration (seconds)
Notes
1
Output R/V (reverse-cycle valve)
2
2
Outdoor fan low speed
7
1, 3, 4, 5
3
Outdoor fan medium speed
7
4
Outdoor fan high speed
15
5
Indoor fan low speed
7
2, 3, 6, 7, 8
6
Indoor fan medium speed
7
7
Indoor fan high speed
15
8
Output SSR1
2
9
Output SSR2
2
10
Output AUX
2
11
Pressure transducer test
1
9
12
Output CMC (compressor contactor)
2
Notes:
1Steps 2, 3 and 4 are skipped on hydronic units (no outdoor fan).
2Steps 5, 6 and 7 are skipped on chillers and water-heating units (no indoor fan).
3If the fan is a three speed type then relays Low, Medium and High activate in turn.
4If the outdoor fan is a variable speed type (0-10V control) then relay Medium will activate, but
only if this relay is not required for a three-speed indoor fan.
5If the outdoor fan is a single-speed type then relay Medium activates for 29 seconds in total.
6If the indoor fan is a variable speed type (0-10V control) then relay High will activate, but only
if this relay is not required for a three-speed outdoor fan.
7If the indoor fan is a single-speed type then relay High activates for 29 seconds in total.
8If the unit is a split type and the indoor unit has an indoor unit controller (IUC) then the indoor
fan is tested via the IUC and steps 5, 6 and 7 will not activate any output on the UC8 controller.
9Step 11 is skipped if the unit does not have both the low- and the high-pressure transducers. If
the test is performed then pressure readings are expected to be approximately equal. If they are
found to be very different then fault F34 is reported. The fault is cleared automatically when
pressures are sufficiently equalised.

Temperzone UC8 Troubleshooting Guide
Page 7 of 24
8. Commissioning mode
A controller commissioning mode is available that allows doing a quick check of the operation of the
entire unit. Commissioning mode can only be activated when the compressor is off and the thermostat
or BMS must not request to start.
To activate commissioning mode hold down pushbutton SW3 until the display shows the letter ‘c’, then
release the button.
Commissioning mode starts immediately and ends automatically after 30 minutes. It is also possible to
manually end commissioning mode either by cycling mains power off and on again, or by pressing the
pushbutton again until the display again shows the letter ‘c’ and then release. When commissioning
mode ends the controller returns to normal operating mode.
During commissioning mode some delay times are reduced:
Minimum On-Off time (‘Run’-time) 20 seconds (note)
Minimum Off-On time (‘Off’-time) 20 seconds
Minimum On-On time (‘Cycle’-time) 1 minute
Cool to heat change-over time 1 minute
Heat to cool change-over time 1 minute
De-ice mode hold-off time 3 minutes
Note:
If the unit has a variable speed compressor then the Minimum On-Off time (‘Run’-time) remains set to
90 seconds regardless whether the controller is placed in commissioning mode or not.
9. Timer durations
Safety timer
Duration
Unit start-up delay (after mains power-on)
2 minutes
Minimum compressor run-time
(On-to-Off duration)
90 seconds
Minimum compressor off-time
(Off-to-On duration)
3 minutes
Minimum compressor cycle-time
(On-to-On duration)
6 minutes
(a maximum of ten compressor starts per hour)
Hydronic unit compressor start delay
(allows time for a water valve to open)
45 seconds
HP protection
3 minutes
LP protection
3 minutes
Compressor high discharge pipe temperature
protection
3 minutes
Indoor coil frost protection
6 minutes
Hydronic unit water freeze protection
3 minutes
High suction line temperature/pressure
protection
3 minutes
Low / high discharge superheat protection
3 minutes
Overload protection
3 minutes
High / low compression ratio protection
3 minutes

Temperzone UC8 Troubleshooting Guide
Page 8 of 24
10. Troubleshooting procedure
Check:
1. Mains power is supplied to the unit.
2. The main isolating switch and the control circuit
breaker are on.
3. All mains wiring and connectors are OK.
4. Mains phases connect in the right sequence.
5. 230V AC voltage is present across the UC8 L and N
terminals.
6. No short circuit exists between UC8 terminals 12 and
0V.
No
Yes
No
Yes
The UC8 and/or IUC remote On/Off input is/are open
circuit.
No
Yes
A compressor safety timer is active.
Wait until the timer expires.
Power light is
on?
Display shows
flashing dash
▬?
Display shows
HOLd and a
number?
Check:
1. Check power is switched on to the compressor driver
(inverter).
2. Check the connections between the UC8 and the
compressor driver.
3. Check the DIP switches inside the compressor driver
agree with the instructions on the wiring diagram.
Display shows
code F100?
No
Yes
Display shows
code ctrL?
No
Yes
Is this a slave
unit?
No
Yes
Check:
1. Mains power to this slave-
controller was applied at the
same time (or before) as to the
master-controller.
2. Connections between the
master and the controllers.
3. No short circuit exists between
terminals A1 and B1 (slave-
controller) or between A2 and
B2 (master unit).
Check:
DIP switches 11 and 12 are
both set to OFF. Correct if
necessary, then cycle mains
power off and on again.
Continued next page.
Unit does not run

Temperzone UC8 Troubleshooting Guide
Page 9 of 24
No
Yes
No
Yes
DRED energy restriction is active:
Wait until DRED energy restriction condition ends.
If DRED function is not required:
Air-to-air units: Inputs D1, D2, D3 should be open
circuit (Note: Inputs D1 and D2 may be used to
control Quiet and Dry modes.)
Hydronic units: Input D3 should be open circuit.
Chillers: Inputs D1, D2, D3 should be open circuit
Display shows a
flashing dot ●?
Display shows dr?
Display shows a
code listed in
chapters 11, 12
or 13?
The controller has detected a fault.
Refer to chapters 11, 12 and 13.
Yes
es
No
Contact Temperzone customer service.
Check wiring between UC8 and
the thermostat.
Continued from previous page.
Satellite dish shown
on t-stat display?
Yes
No
TZT-100 or SAT-3
wall thermostat?
No
Yes
Display shows
diFF-P?
Pressure differential is too high to allow the inverter
compressor to start:
Wait until the pressures have equalised.
Ensure valves are open.
Ensure the EEV operates correctly.
Yes
es
No
Correct
compressor
model selected?
Change the compressor model selection.
Yes
es
No

Temperzone UC8 Troubleshooting Guide
Page 10 of 24
11. Fault messages
Display
Meaning
Possible causes
Possible remedy
LP
Low pressure
protection
Check for refrigerant leaks.
Fix leak, evacuate unit, then recharge.
Expansion valve (EEV) is
closed.
Check valve coil is properly fitted onto the valve
body.
Check UC8 DIP switch settings.
Repair wiring to the valve.
Replace expansion valve.
Faulty transducer cable.
Faulty transducer.
Faulty LP switch.
Repair transducer cable.
Replace transducer.
Replace LP switch.
Service valve is closed.
Open service valves.
Indoor fan does not start
(cooling mode) or
outdoor fan does not start
(heating mode).
Repair fan wiring.
Replace fan.
Incorrect DIP switch settings.
Change DIP switch settings then restart the
controller.
HP
High pressure
protection
Outdoor fan does not start
(cooling mode) or
indoor fan does not start
(heating mode).
Repair fan wiring.
Replace fan.
Unit is overcharged.
Remove excess refrigerant charge.
EEV is closed.
Check UC8 DIP switch settings.
Repair wiring to the expansion valve.
Replace expansion valve.
Faulty transducer cable.
Faulty transducer.
Faulty HP switch.
Repair cable to the transducer.
Replace transducer.
Replace HP switch.
Service valve is closed.
Open service valves.
Incorrect DIP switch settings.
Change DIP switch settings then restart the
controller.
HI-t
High
temperature
protection
Insufficient refrigerant.
Add refrigerant.
Faulty discharge line
temperature sensor.
Replace sensor.
Incorrect DIP switch settings.
Change DIP switch settings then restart the
controller.
FROSt
Indoor coil
frost
protection
Air filter blocked.
Clean or replace air filter.
Dampers closed.
Check dampers and damper controls.
Excess amount of cold fresh
air introduced.
Check fresh air damper and damper controls.
Indoor fan speed too low.
Increase indoor fan speed.
Faulty indoor fan motor.
Faulty indoor fan speed
controller.
Replace indoor fan motor.
Replace indoor fan speed controller.
Return air temperature too
low.
Ensure unit is not operated in cooling mode
with very low return air temperature.
Insufficient refrigerant.
Add refrigerant.

Temperzone UC8 Troubleshooting Guide
Page 11 of 24
Display
Meaning
Possible causes
Possible remedy
HI-SL
High suction
line
temperature
protection
Insufficient refrigerant.
Add refrigerant.
Very high room temperature
(cooling mode).
Reduce indoor fan speed (temporarily).
Very high outdoor ambient
temperature (heating mode).
Do not operate the unit in heating mode with
very high outdoor ambient temperature.
Faulty suction line
temperature sensor.
Replace sensor.
Lo-dSH
Low discharge
superheat
protection
Unit is overcharged.
Remove excess refrigerant charge.
Discharge line temperature
sensor not properly fitted.
Securely fit the temperature sensor on the
compressor discharge pipe and insulate.
Suction line temperature
sensor not properly fitted.
Securely fit the temperature sensor on the
compressor suction pipe and insulate.
Faulty discharge line
temperature sensor.
Replace sensor.
Incorrect expansion valve
selection
Correct the DIP switch settings for switches 7, 8,
9 and 10
HI-dSH
High discharge
superheat
protection
Loss of refrigerant.
Find refrigerant leak and repair. Replace
refrigerant with correct charge.
Faulty discharge line high
pressure transducer.
Replace transducer.
Suction line temperature
sensor not properly fitted.
Securely fit the temperature sensor on the
compressor suction pipe and insulate.
Incorrect expansion valve
selection
Correct the DIP switch settings for switches 7, 8,
9 and 10
LO-t
Water freeze
protection
Insufficient flow of water
Ensure water circulating pump operates.
Ensure water valves are open.
Bleed air out of the water circuit to prevent air-
locks.
Supply water temperature too
low.
Ensure supply water temperature is above
+10°C.
Lack of refrigerant charge.
Add refrigerant.
FLOOd
Sump
condensate
flooding
protection
Condensate drain pipe is
blocked
Unblock condensate drain pipe.
Condensate drain pipe slope is
insufficient
Increase pipe slope or install sump condensate
pump and float switch.
No U-trap installed
Install U-trap
Faulty sump condensate float
switch.
Replace float switch.
Faulty sump condensate
pump.
Replace pump.
OL
Overload
protection
Indoor fan is overloaded.
Check indoor fan.
Check airflow is not obstructed.
Outdoor fan is overloaded.
Check outdoor fan.
Check airflow is not obstructed.
Compressor overheated.
Wait until compressor has cooled down
sufficiently. Check system has adequate
refrigerant charge. System design must ensure
adequate return of compressor lubricating oil.
Faulty wiring / connection to
input IN#2.
Repair wiring.

Temperzone UC8 Troubleshooting Guide
Page 12 of 24
Display
Meaning
Possible causes
Possible remedy
CRL
Low
compression
ratio
Incorrect compressor model
selected.
Select the correct compressor model.
Compressor does not start.
Check compressor contactor.
Check compressor and contactor wiring.
CRH
High
compression
ratio
Unit is overcharged.
Remove excess refrigerant charge.
EEV does not operate
correctly.
Check settings of DIP switches 7, 8, 9, 10.
Check wiring to the EEV.
Check EEV coil is fitted properly.
Indoor fan speed too low.
Increase indoor fan speed.
Air filter is blocked.
Clean or replace air filter.
Lockout
Unit is locked
out
Unit has locked out three
times in a row without making
any successful (complete)
cooling or heating cycle.
To unlock the following steps MUST be followed
in order:
1. Press the UC8 pushbutton to unlock.
2. Fix the cause of the repeating problem.
3. Allow the unit to make at least one
successful (complete) cooling or heating
cycle.

Temperzone UC8 Troubleshooting Guide
Page 13 of 24
12. Fault codes.
Display
Fault
Possible causes
Possible remedy
F10
Outdoor fan
Incorrect DIP switch settings.
Change DIP switch settings.
Loose wiring between UC8 board and
outdoor fan speed controller board.
Repair wiring.
No power to outdoor fan speed
controller.
Ensure power is present.
Faulty outdoor fan speed controller
board.
Replace outdoor fan speed
controller.
F11
Indoor fan
Incorrect DIP switch settings.
Change DIP switch settings.
Loose wiring between UC8 board and
indoor fan speed controller board.
Repair wiring.
No power to indoor fan speed
controller.
Ensure power is present.
Faulty indoor fan speed controller
board.
Replace indoor fan speed
controller.
F12
No low pressure
transducer.
Cable has disconnected.
Reconnect cable.
Incorrect DIP switch settings.
Change DIP switch settings.
Faulty transducer.
Replace transducer.
F13
No high pressure
transducer.
Cable has disconnected.
Reconnect cable.
Incorrect DIP switch settings.
Change DIP switch settings.
Faulty transducer.
Replace transducer.
F14
Suction line
temperature
sensor
Loose connection.
Repair connections.
Faulty temperature sensor.
Replace sensor.
F15
Discharge line
temperature
sensor
Loose connection.
Repair connections.
Faulty temperature sensor.
Replace sensor.
F16
De-Ice temperature
sensor
Loose connection.
Repair connections.
Faulty temperature sensor.
Replace sensor.
F17
Outdoor coil
temperature
sensor
Loose connection.
Repair connections.
Faulty temperature sensor.
Replace sensor.
F18
Indoor coil
temperature
sensor
Loose connection.
Repair connections.
Faulty temperature sensor.
Replace sensor.
F19
Outdoor ambient
temperature
sensor
Loose connection.
Repair connections.
Faulty temperature sensor.
Replace sensor.
F20
Superheat
unknown
Check: low pressure transducer, suction line temperature sensor, high
pressure transducer, discharge line temperature sensor, outdoor coil
temperature sensor, indoor coil temperature sensor, DIP switch settings.
F21
Thermostat serial
comms lost
Loose wiring.
Repair connections.
Electrical interference.
Use twisted pair screened cable.
Signals A and B must form a pair.
Connect screen to 0V at the UC8.
Re-route cable away from other
cables.

Temperzone UC8 Troubleshooting Guide
Page 14 of 24
Display
Fault
Possible causes
Possible remedy
F22
F23
F24
F25
System 1 or BMS
serial comms lost
System 2 serial
comms lost
System 3 serial
comms lost
System 4 serial
comms lost
Loose wiring.
Repair connections.
Slave system or BMS controller off.
Turn master system or BMS on.
Slave system or BMS communications
intermittent.
Ensure BMS communicates at least
once every 5 minutes.
Electrical interference.
Use twisted pair screened cables.
Signals A and B must form a pair.
Connect screen to 0V at the UC8.
Re-route cables away from other
cabling where possible.
Incorrect DIP switch settings.
Check DIP switch settings.
F26
Cannot read DIP
switches
Moisture on controller circuit board.
Allow controller to dry.
Faulty controller.
Replace controller circuit board.
F27
Invalid fan
selection
Incorrect DIP switch settings.
Correct DIP switch settings.
Indoor unit not detected.
Ensure indoor unit powers up at
the same time, or before, the
outdoor unit.
Check connections with the indoor
unit.
F28
Missing outdoor
coil de-ice
temperature
sensor
Control signals request heating mode
on a cooling-only unit.
Remove heating mode request
signal.
Loose wiring.
Repair connections.
Faulty outdoor coil de-ice sensor.
Replace sensor.
F29
Microcontroller
temperature too
high
Wait until the unit has cooled down.
Find the cause of extremely high temperature in the electrical compartment.
F30
Supply voltage out
of bounds
Check that 230V AC mains power supply voltage is stable.
F31
A slave system
reports a fault
Check slave systems.
F32
Internal comms
problem
Moisture on controller circuit board.
Allow controller to dry.
Faulty controller.
Replace controller circuit board.
F33
Refer to “high discharge superheat” (HI-dSH)
F34
Problem with
readings from the
pressure
transducers
Transducer wires swapped.
Correct transducer wiring.
Transducers fitted to wrong pipe.
Swap transducers.
Incorrect transducer type.
Fit correct transducer.
Expansion valve closed.
Repair EEV wires.
Faulty transducer.
Replace transducer.
F35
Reverse cycle valve
Loose wiring.
Repair wiring.
Faulty reverse cycle valve.
Replace reverse cycle valve.
F36
Invalid DIP switch
setting on TZT-100
thermostat
Check TZT-100 thermostat DIP switch 4 is ON: The reverse cycle valve is ON
when the unit operates in heating mode.

Temperzone UC8 Troubleshooting Guide
Page 15 of 24
Display
Fault
Possible causes
Possible remedy
F37
Indoor unit serial
comms lost
Loose wiring.
Repair connections.
Indoor unit has no power.
Restore power to the indoor unit.
Electrical interference.
Use a twisted pair screened cable.
Signals A and B must form a pair.
Connect screen to 0V at the UC8.
Re-route cables away from other
cabling where possible.
The indoor unit should use the
same earth point as the outdoor
unit.
Faulty indoor unit controller.
Replace indoor unit controller.
F38
Indoor unit
controller reports a
fault
Loose temperature sensor wiring in
indoor unit.
Repair temperature sensor wiring
in the indoor unit.
F39
Problem with
variable speed
compressor
inverter
Loose wiring.
Repair connections.
Inverter has no power.
Restore power to the inverter.
Faulty inverter.
Replace inverter.
F40
Refer to high compression ratio protection (CRH).
F41
Refer to low compression ratio protection (CRL).
F42
High evaporating
temperature
Very high room temperature
combined with high indoor fan speed
(cooling mode).
Temporarily reduce indoor fan
speed.
Excess introduction of fresh (hot
outdoor) air.
Reduce amount of fresh air.
F43
Low condensing
temperature
Very low room temperature combined
with high indoor fan speed (heating
mode).
Temporarily reduce indoor fan
speed.
Excess introduction of fresh (cold
outdoor) air.
Reduce amount of fresh air.
Outdoor coil exposed to strong cold
wind (cooling mode).
Shelter outdoor unit from strong
winds.
F44
Invalid EEV mode
selection
Indoor unit not detected.
Ensure indoor unit powers up at
the same time, or before, the
outdoor unit.
Check wiring between outdoor and
indoor units.
Incorrect DIP switch settings.
Change DIP switch settings, then
reset the controller.

Temperzone UC8 Troubleshooting Guide
Page 16 of 24
13. Inverter fault codes
The following fault codes apply only to units with a variable speed compressor and Carel power+
compressor driver (inverter).
Notes:
The fault code shown on the UC8 display is F100 + the error code reported by the Power+
driver.
For detailed information about the Power+ fault codes refer to the Carel Power+ speed drive
user manual, chapter 8.3: Alarms table.
A brief summary follows here:
Display
Meaning
F100
No communications between Power+ drive and UC8
F101
Motor over-current
F102
Motor overload
F103
Over-voltage
F104
Under-voltage
F105
Drive too hot
F106
Drive too cold
F107
Drive over-current
F108
Motor too hot
F109
Reserved
F110
Drive internal error
F111
Incorrect parameter
F112
Excessive drive DC bus ripple (unbalanced mains phase voltages)
F113
Communication fault
F114
Internal fault
F115
Auto-tuning fault
F116
Drive disabled (input STO open circuit)
F117
Motor phase fault (possibly a motor wire has become loose)
F118
Drive internal fan fault
F119
Speed fault
F120
Power factor correction circuit overload
F121
Mains input voltage too high
F122
Mains input voltage too low
F123
Drive internal fault
F124
Reserved
F125
High earth current fault
F126
Drive processor overload
F127
Drive memory loss
F128
Drive overload protection
F197
Drive reports incorrect compressor speed
F198
Drive and compressor mismatch
F199
Drive configuration fault

Temperzone UC8 Troubleshooting Guide
Page 17 of 24
14. Fault codes shown on a room thermostat
TZT-100 room thermostat fault codes
When the UC8 is connected to a TZT-100 room thermostat and a fault is detected then the thermostat
will show the word FAULT on the display (flashing slowly). The TZT-100 room thermostat cannot
show individual fault codes.
SAT-3 room thermostat fault codes
The SAT-3 room thermostat is able to show fault codes on the thermostat display (bottom right corner
of the display). The tables provide details for the codes.
Notes:
(1) The SAT-3 display shows each fault code number twice and repeats. For example fault code
“A1 A2” is shown on the SAT-3 display as “A1 A1 A2 A2 ……” repeating continuously.
(2) Codes must be read in sequence from lowest to highest. Thus, for example, codes “A1 A2” and
“A2 A1” are the same code.
SAT-3 internal fault codes
SAT-3
display code
Fault description
Possible remedy
t1
Internal temperature sensor error
Replace thermostat
t2
External temperature sensor error
Repair external sensor connections
t3
No communications between SAT-3 and zone
controller or UC8
Repair connections between SAT-3
and zone controller or UC8
SAT-3 + Zone controller fault codes
SAT-3
display code
Fault description
Possible remedy
A1
Damper calibration not completed
Wait until dampers are calibrated
A2
Damper calibration failed
Make sure dampers operate freely
Repair damper connections
A3
No communications between zone controller
and UC8
Repair connections between zone
controller and UC8
A1 A2
Combinations of above three faults.
A1 A3
A2 A3
A1 A2 A3

Temperzone UC8 Troubleshooting Guide
Page 18 of 24
SAT-3 + UC8 fault codes
SAT-3
display code
UC8 display
code
Fault
Notes
Blank
●
No faults
A4
Lock out
UC8 display shows the cause.
A1 A4
HP
HP trip
A1 A5
LP
LP trip
A3 A6
OL
Overload
A1 A6
Frost
Indoor coil frost protection
A5 A6
Lo-t
Water freeze protection
HWP and chillers only.
A1 A7
Hi-t
Discharge line high temperature
A1 A8
Hi-SL
Suction line high temperature
A5 A7
Flood
Flooded condensate sump
HWP only.
A5 A8
No-Flo
No circulating water flow
HWP and chillers only.
A3 A4
Lo-DSH
Low discharge superheat
A3 A7
F10
Outdoor fan fault
F11
Indoor fan fault
A3 A8
F12
Low pressure transducer
F13
High pressure transducer
F14
Suction line temp sensor
F15
Discharge line temp sensor
F16
De-ice ambient sensor
F17
Outdoor temp sensor
F18
Indoor coil temp sensor
F19
Outdoor ambient sensor
A1 A2 A8
F20
Superheat unknown
A1 A2 A4
F21
No communications, thermostat
Code cannot be shown.
A2 A4
F22
No communications, BMS
A2 A5
F23
No communications, system 2
A2 A6
F24
No communications, system 3
A2 A7
F25
No communications, system 4
A1 A2 A6
F26
Cannot read DIP switches
F27
Illegal fan selection
F28
Illegal mode
F29
High board temperature
F30
Supply voltage brown-out
A2 A3 A4
F31
Slave reports a fault
A1 A2 A6
F32
UC8 internal problem
Same code as F26…F30.
A3 A5
Hi-DSH
High discharge superheat
A4 A8
F34
Pressures not equalising
A2 A3
F35
Reverse cycle valve fault
A1 A2
F36
TZT-100 DIP switch setting
Code cannot be shown.
A2 A8
F37
No communications, IUC
A7 A8
F38
IUC reports a fault
A6 A7
F39
Inverter reports a fault
A4 A5
F40
Compression ratio too high
A4 A6
F41
Compression ratio too low
A4 A7
F42
Evaporating temp too high
A4 A8
F43
Condensing temp too low
A1 A2 A5
All other UC8 faults

Temperzone UC8 Troubleshooting Guide
Page 19 of 24
15. Protection function details
High pressure protection (HP)
Protects a unit from excessively high refrigerant pressure.
Conditions: Unit with HP switch: When the switch activates (open circuit).
Unit with high pressure transducer: When compressor discharge pressure exceeds 4151
kPa (602 PSI, equivalent to +65°C condensing temperature).
Hydronic reverse cycle units where the high pressure transducer is switched to the
suction line when heating: When the indoor coil temperature exceeds 56°C.
Low pressure protection (LP)
Protects a unit from excessively low refrigerant pressure.
Conditions: Unit with LP switch: As soon as the switch activates (open circuit).
If a low pressure transducer is connected there are two levels:
Transient level: When pressure is below 114 kPa (16.5 PSI, equivalent to -35°C).
Normal level: When pressure is below 228 kPa (33.0 PSI, equivalent to -25°C).
Notes: The transient level is always applied.
The normal level is applied when more than 90 seconds have expired since the compressor
started and also when more than 90 seconds have expired since the end of a de-ice cycle.
Indoor coil frost protection
Protects a unit from forming too much ice on the indoor coil. Applied only when a unit is cooling in
normal mode, not applied when a unit is de-icing the outdoor coil.
The frost protection function activates when the indoor coil condition remains very cold for longer
than the frost-protect delay time of 6 minutes.
Conditions: When the evaporating temperature remains below -8°C for longer than 6 minutes
or when the compressor suction pipe temperature remains below -4°C for longer than
6 minutes.
High temperature protection
Protects the compressor from overheating which could otherwise cause damage to the compressor
motor, to the compression scroll or rotary compression stage, or cause deterioration of the
compressor lubricating oil.
On a unit with electric heating protects the unit from becoming extremely hot and burn-out of the
electric heating element.
Conditions: When the compressor discharge pipe temperature remains above
+120°C for longer than 2 seconds or
+110°C for longer than 30 minutes.
Hydronic units with electric heating only:
When the fast-acting heating safety temperature sensor (connected to input AMB)
remains above +75°C for longer than 2 seconds.

Temperzone UC8 Troubleshooting Guide
Page 20 of 24
High suction line / evaporating temperature protection
Protects the compressor motor from overheating.
If the unit has a variable duty compressor (digital scroll or variable speed) then high suction pipe /
evaporating temperature protection is applied only when capacity is at 50% of nominal duty or higher.
If the unit has a fixed duty compressor this protection is always applied.
Conditions: When the evaporating temperature remains above +27.5°C (1665 kPa, 241.5 PSI)
and/or the compressor suction pipe temperature remains above +30°C for longer than
15 minutes.
Low discharge side superheat protection
Protects a unit with an electronic expansion valve (EEV) from prolonged flooding of the compressor
which otherwise might cause damage to the motor bearings or to the compression stage.
This protection does not apply to units that use accurators.
Discharge side superheat is defined as the difference between the compressor discharge pipe
temperature and the condensing temperature.
Conditions for units with fixed duty compressor:
When discharge side superheat remains below 10K for longer than 15 minutes.
Conditions for units with variable duty compressor (digital scroll and variable speed types):
At nominal duty and higher: When discharge side superheat remains below 10K for longer
than 15 minutes.
Between standard minimum and nominal duty: Minimum discharge side superheat varies
linearly with capacity from 0K at standard minimum duty to 10K at nominal duty.
At standard minimum duty and below: Protection not applied.
Standard minimum duty: 40%
Nominal duty: 100%
High discharge side superheat protection
Protects a unit from prolonged running with a lack of refrigerant or where the compressor remains
otherwise starved of refrigerant. Applied only when the unit operates in normal mode, not applied
when a unit is de-icing the outdoor coil.
Discharge side superheat is defined as the difference between the compressor discharge pipe
temperature and the condensing temperature.
Conditions: When discharge side superheat remains above 45K for longer than 30 minutes.
Freeze protection
Protects against freezing of the circulating water.
Applies to hydronic reverse cycle units when the unit is heating the room and thus cooling the water.
Also applies to chillers when the unit is cooling the water.
Conditions: When the compressor suction pipe temperature remains below 0°C for longer than 1
minute or when the evaporating temperature remains below -4°C for longer than 1
minute.