Hoshizaki RTC-A series User manual

NO. T012-784
ISSUED: JUN. 26, 2009
REVISED:
HOSHIZAKI
UNDERCOUNTER
REFRIGERATOR/FREEZER
MODEL RTC-A series
FTC-A series
SERVICE MANUAL

i
CONTENTS PAGE
I. GENERAL INFORMATION --------------------------------------------------------------------------1
1. SAFETY INSTRUCTIONS-------------------------------------------------------------------------1
2. DIMENSIONS/SPECIFICATIONS ---------------------------------------------------------------3
[a] RTC-120SNA -------------------------------------------------------------------------------------3
[b] RTC-120SDA -------------------------------------------------------------------------------------4
[c] RTC-150SNA -------------------------------------------------------------------------------------5
[d] RTC-150SDA -------------------------------------------------------------------------------------6
[e] RTC-180SNA -------------------------------------------------------------------------------------7
[f] RTC-180SDA -------------------------------------------------------------------------------------8
II. TECHNICAL INFORMATION-----------------------------------------------------------------------9
1. WIRING DIAGRAM----------------------------------------------------------------------------------9
2. REFRIGERATION CIRCUIT -------------------------------------------------------------------- 10
3. ELECTRONIC CONTROLS --------------------------------------------------------------------- 11
[a] SET POINT TEMPERATURE -------------------------------------------------------------- 11
[b] CABINET TEMPERATURE DIFFERENTIAL ------------------------------------------- 11
[c] DEFROST CYCLE ---------------------------------------------------------------------------- 11
[d] DEFROST COMPLETION TEMPERATURE ------------------------------------------- 11
[e] CLOGGED CONDENSER DETECTION TEMPERATURE------------------------- 11
[f] TEMPERATURE DISPLAY CYCLE ------------------------------------------------------- 11
[g] COMPRESSOR SOFT START------------------------------------------------------------- 12
[h] CABINET TEMPERATURE AND TEMPERATURE DISPLAY---------------------- 12
[i] RESOLUTION ---------------------------------------------------------------------------------- 13
[j] SET POINT TEMPERATURE AND CABINET TEMPERATURE------------------- 13
[k] CHECKING AND ADJUSTING SET POINT TEMPERATURE --------------------- 13
[l] MANUAL DEFROST -------------------------------------------------------------------------- 14
[m] CANCELLING SOFT START -------------------------------------------------------------- 14
4. ERROR CODES ----------------------------------------------------------------------------------- 14
[a] EEPROM WRITE ERROR (EA) ----------------------------------------------------------- 14
[b] EEPROM VERIFY ERROR (ED) ---------------------------------------------------------- 15
[c] CABINET TEMPERATURE TOO HIGH (E1) ------------------------------------------- 15
[d] CABINET TEMPERATURE TOO LOW (E2)-------------------------------------------- 16
[e] DEFROST CYCLE TOO LONG (E3) ----------------------------------------------------- 16
[f] ABNORMAL PRESSURE (E4) ------------------------------------------------------------- 17
[g] CONDENSER CLOGGED (E7)------------------------------------------------------------ 18
[h] DEFROST THERMISTOR DEFECTIVE (E8) ------------------------------------------ 18
[i] CLOG THERMISTOR DEFECTIVE (E9) ------------------------------------------------ 19
5. ENERGY SAVING CONTROL------------------------------------------------------------------ 19
[a] STANDARD MODE --------------------------------------------------------------------------- 19
[b] ENERGY SAVING MODE ------------------------------------------------------------------- 20
[c] CABINET TEMPERATURE CORRECTION -------------------------------------------- 20
6. TIMING CHART ------------------------------------------------------------------------------------ 21
[a] STANDARD MODE (RTC series) --------------------------------------------------------- 21
[b] ENERGY SAVING MODE (RTC series) ------------------------------------------------- 22
[c] STANDARD MODE (FTC series) ---------------------------------------------------------- 23
[d] ENERGY SAVING MODE (FTC series) ------------------------------------------------- 24
[e] FORCED STARTUP (CANCELING SOFT START)----------------------------------- 24

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III. SERVICE DIAGNOSIS---------------------------------------------------------------------------- 25
1. FLOWCHART--------------------------------------------------------------------------------------- 25
2. SERVICE DIAGNOSIS --------------------------------------------------------------------------- 26
3. CONTROLLER BOARD-------------------------------------------------------------------------- 28
[a] SERVICING CONTROLLER BOARD ---------------------------------------------------- 28
[b] CHECKING THERMISTOR ----------------------------------------------------------------- 29
IV. REMOVAL AND REPLACEMENT OF COMPONENTS ---------------------------------- 31
1. REFRIGERATION UNIT-------------------------------------------------------------------------- 31
2. REFRIGERATION CIRCUIT -------------------------------------------------------------------- 31
[a] REFRIGERANT-------------------------------------------------------------------------------- 31
[b] COMPRESSOR-------------------------------------------------------------------------------- 32
[c] EVAPORATOR AND DEFROST HEATER ---------------------------------------------- 32
[d] CONDENSER ---------------------------------------------------------------------------------- 33
3. CONTROL BOX ------------------------------------------------------------------------------------ 34
4. FAN MOTORS -------------------------------------------------------------------------------------- 34
[a] CONDENSER FAN MOTOR---------------------------------------------------------------- 34
[b] INTERIOR FAN MOTOR -------------------------------------------------------------------- 35
5. THERMISTORS ------------------------------------------------------------------------------------ 35
[a] INTERIOR THERMISTOR ------------------------------------------------------------------ 35
[b] DEFROST THERMISTOR------------------------------------------------------------------- 35
[c] CLOG THERMISTOR ------------------------------------------------------------------------ 35
6. DOOR GASKET------------------------------------------------------------------------------------ 36
[a] REMOVAL --------------------------------------------------------------------------------------- 36
[b] REPLACEMENT------------------------------------------------------------------------------- 36
Symbol Meaning
Keep Dry
Cabinet Temperature
Increasing Temperature
Decreasing Temperature

1
I. GENERAL INFORMATION
1. SAFETY INSTRUCTIONS
The following instructions contain important safety precautions and should be strictly
observed. The terms used here are dened as follows:
WARNING: There is a possibility of death or serious injury to the service person and
a third party or the user due to improper service operations or defects in
serviced products.
CAUTION: There is a possibility of injury to the service person and a third party or the
user or damage to their property* due to improper service operations or
defects in serviced products.
* The term “damage to their property” here refers to extensive damage to household
effects, houses and pets.
WARNING
1. Always ask the user to keep children away from the work area. They may be injured by
tools or disassembled products.
2. When there is no need to energize the unit during disassembly or cleaning, be sure to
unplug the unit or disconnect the main power supply before servicing the unit to prevent
electric shocks.
3. If the unit must be energized for inspection of the electric circuit, use rubber gloves to
avoid contact with any live parts resulting in electric shocks.
4. Keep the following in mind when servicing the refrigeration circuit:
(1) Be sure to recover the refrigerant. Do not discharge it into the atmosphere. It will
affect the environment.
(2) Check for any ames in the vicinity, and ensure good ventilation.
(3) If the refrigerant should leak in servicing, immediately put out any re used in the
vicinity.
(4) When unbrazing the refrigeration circuit connections, check that the circuit is
completely evacuated. The refrigerant may produce a poisonous gas when coming
in contact with an open ame.
(5) Do not braze in an enclosed room to prevent carbon monoxide poisoning.
(6) In case of a refrigerant leak, locate and repair the leaking part completely before
recharging the refrigerant and checking for further leaks. If the leaking part cannot

2
be located, be sure to check again for further leaks after recharging the refrigerant.
Leaked refrigerant may produce a poisonous gas when coming in contact with an
open ame of a gas cooking stove or a fan heater.
(7) Before servicing, check the surface temperature of the refrigeration circuit to
prevent a burn.
5. Keep the following in mind when making electrical connections:
(1) Check for proper earth connections, and repair if necessary to prevent electric
shocks.
(2) Always use service parts intended for the applicable model for replacement of
defective parts. Use proper tools to secure the wiring. Otherwise abnormal
operation or trouble may occur and cause electric leaks or re.
(3) Check for proper part installations, wiring conditions and soldered or solderless
terminal connections to avoid re, heat or electric shocks.
(4) Be sure to replace damaged or deteriorated power cords and lead wires to prevent
re, heat or electric shocks.
(5) Cut-off lead wires must be bound using closed end connectors or the like, with their
closed ends up to avoid entrance of moisture that could lead to electric leaks or
re.
(6) After servicing, always use a megohmmeter (500V DC) to check for the insulation
resistance of at least 1 megohm between the live part (attachment plug) and the
dead metal part (earth terminal).
(7) Do not service the electrical parts with wet hands to prevent electric shocks.
(8) The capacitors used for the compressor and other components may be under high
voltage and should be discharged properly before servicing.
CAUTION
1. After servicing, follow the instructions below:
(1) Always check the unit for proper operation before nishing services.
(2) Be sure to reassemble the parts completely. Loose assembly of such parts
as control box cover may cause entrance of vermins resulting in a short circuit
between terminals and possible ignition.

3
2. DIMENSIONS/SPECIFICATIONS
[a] RTC-120SNA

4
[b] RTC-120SDA

5
[c] RTC-150SNA

6
[d] RTC-150SDA

7
[e] RTC-180SNA

8
[f] RTC-180SDA

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II. TECHNICAL INFORMATION
1. WIRING DIAGRAM

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2. REFRIGERATION CIRCUIT
Refrigerant: HFC-134a (RTC series)
HFC-404A (FTC series)
Interior Fan Motor
Evaporator
Heat Exchange 500mm long
Compressor
Drier
Capillary Tube
Condenser
Condenser Fan Motor

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3. ELECTRONIC CONTROLS
[a] SET POINT TEMPERATURE (mean temperature
between compressor ON and OFF temperatures)
RTC series: -6 to +12°C
FTC series: -25 to -7°C
[b] CABINET TEMPERATURE DIFFERENTIAL
3.5 K OFF temperature = Set point temp - 2.0 K
ON temperature = Set point temp + 1.5 K
Note: On the Controller Board only. Actual differential may be larger.
[c] DEFROST CYCLE
Every 6 hours
Note: During a defrost cycle, the Temperature Display Window indicates “dF”. See “6.
TIMING CHART” for further details.
[d] DEFROST COMPLETION TEMPERATURE
RTC series: 15°C
FTC series: 5°C
[e] CLOGGED CONDENSER DETECTION TEMPERATURE
RTC series: 58°C for 2 minutes
FTC series: 55°C for 2 minutes
[f] TEMPERATURE DISPLAY CYCLE
The Temperature Display Window renews its cabinet temperature display every 30
seconds. The display remains the same for 30 seconds even if the actual temperature
changes in the meantime. During a defrost cycle, the Temperature Display Window
indicates “dF”.
Set Point Temperature
Interior Thermistor Temperature
3.5 K
Compressor
ON
OFF
Time

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[g] COMPRESSOR SOFT START
1) Startup
When the power supply is turned on, the Interior Fan Motor starts up and the Temperature
Display Window shows the cabinet temperature, but the Compressor and Condenser Fan
Motor start up with a 3.5 minute delay.
This delay is intended to minimize the difference between the high-side and low-side
pressures and to reduce the load on the Compressor so that it can start easily in case of a
short (especially instantaneous) power failure.
2) Normal Control
When the Compressor turns off during normal control, it has a mandatory 3.5 minute delay
before startup. For example, if the Compressor turns off by its Thermistor and the Door
is opened immediately after (causing the cabinet temperature to immediately exceed the
restart temperature), the Compressor will still not start until 3.5 minutes have passed since
its shutdown.
[h] CABINET TEMPERATURE AND TEMPERATURE DISPLAY
Power ON
3.5 min
Compressor
Condenser Fan Motor
Interior Fan Motor
Cabinet Temp Display
ON
OFF
ON
OFF
ON
OFF
Cabinet
Temp
Temp
Display Included
Not included
Compressor
Condenser Fan Motor
Interior Thermistor
ON
OFF
ON
OFF Min
3.5 min
Min
3.5 min

13
[i] RESOLUTION
0.5 K (1 K for temperature setting and display)
[j] SET POINT TEMPERATURE AND CABINET TEMPERATURE
(Compressor OFF temperature / Compressor ON temperature)
Refrigerator
(RTC series)
Set Point Temp (°C) 12 11 10 9 8 7
Cabinet Temp (°C) 10/13 9/12 8/11 7/10 6/9 5/8
Set Point Temp (°C) 6 5 4 3 2 1
Cabinet Temp (°C) 4/7 3/6 2/5 1/4 0/3 -1/2
Set Point Temp (°C) 0 -1 -2 -3 -4 -5
Cabinet Temp (°C) -2/1 -3/0 -4/-1 -5/-2 -6/-3 -7/-4
Set Point Temp (°C) -6
Cabinet Temp (°C) -8/-5
Freezer
(FTC series)
Set Point Temp (°C) -7 -8 -9 -10 -11 -12
Cabinet Temp (°C) -9/-6 -10/-7 -11/-8 -12/-9 -13/-10 -14/-11
Set Point Temp (°C) -13 -14 -15 -16 -17 -18
Cabinet Temp (°C) -15/-12 -16/-13 -17/-14 -18/-15 -19/-16 -20/-17
Set Point Temp (°C) -19 -20 -21 -22 -23 -24
Cabinet Temp (°C) -21/-18 -22/-19 -23/-20 -24/-21 -25/-22 -26/-23
Set Point Temp (°C) -25
Cabinet Temp (°C) -27/-24
[k] CHECKING AND ADJUSTING SET POINT TEMPERATURE
Set Point Button
Temperature
Display Window
Temperature
Control Button
250V-10A
Press the Set Point Button to display the
set point temperature on the Temperature
Display Window. To change the set point
temperature, hold down the Set Point
Button and press the Temperature Control
Button.
The set point temperature cannot be
memorized until 10 seconds have passed
since its adjustment. That is, if the power
supply is turned off within 10 seconds after
adjustment, the set point temperature will
remain the same as before when the power
supply is turned back on.

14
[l] MANUAL DEFROST
When the two Temperature Control Buttons are pressed at the same time for 3 seconds,
the refrigerator/freezer will start a manual defrost cycle. The refrigerator/freezer will start
repeating automatic defrost cycles 6 hours after the Temperature Control Buttons are
pressed.
Note: The refrigerator/freezer will not start a manual defrost cycle if the Defrost Thermistor
senses a temperature of 15°C or more (RTC series) or 5°C or more (FTC series).
[m] CANCELING SOFT START
To cancel the “Soft Start” (3.5 minute delay), turn on the power supply while pressing the
Set Point Button. The Compressor and Condenser Fan Motor will start at the same time
after the Temperature Display Window shows the data code for 0.5 second.
Data code: RTC series A5
FTC series B5
4. ERROR CODES
In case of trouble, the Temperature Display Window will alternately flash every second
between one of the following error codes and the cabinet temperature or “dF” during a
defrost cycle. The error codes are displayed in the following order of priority:
Priority Code Error
1 ED EEPROM Verify Error
2 EA EEPROM Write Error
3 E8 Defrost Thermistor Defective
4 E9 Clog Thermistor Defective
5 E4 Abnormal Pressure
6 E7 Condenser Clogged
7 E3 Defrost Cycle Too Long
8 E1 Cabinet Temperature Too High
9 E2 Cabinet Temperature Too Low
[a] EEPROM WRITE ERROR (EA)
When the values written on EEPROM (IC3) differ from those retrieved for verication, “EA”
will be displayed.
The “EA” display will not reset until the power supply is turned off.
The EEPROM (IC3) may be defective. Replace the Controller Board.

15
[b] EEPROM VERIFY ERROR (ED)
When every value retrieved from EEPROM (IC3) for verication differs from the memory
setting of the Controller Board, “ED” will be displayed.
The “ED” display will automatically reset when retrieved values have been veried.
The EEPROM (IC3) may be defective. Replace the Controller Board.
[c] CABINET TEMPERATURE TOO HIGH (E1)
When the cabinet temperature rises to the alert temperature (10 K above the set point), the
High Temperature Alert Timer will start counting down from 120 minutes. When the Timer
counts down to zero, “E1” will be displayed. If the cabinet temperature drops below the
alert temperature before the Timer counts down to zero, the Timer will reset and “E1” will
not be displayed.
When the power supply is turned on, this function will not work until the cabinet
temperature drops below the Compressor OFF temperature. This function is available
even during a defrost cycle.
The “E1” display will automatically reset when the cabinet temperature drops below the
Compressor OFF temperature.
The cause may be:
1) The Doors are opened too frequently or left open.
2) The Interior Thermistor (black) is defective.
3) The Compressor is defective or gas is leaking.
Alert Timer
120 min
Alert Timer
less than 120 min
Alert Temp
(Set Point + 10 K)
Set Point + 1.5 K
Set Point Temp
Set Point - 2.0 K
Temp Display
Window
Differential
(3.5 K)
Cabinet Temp
Flashing “E1”
“E1” error
resets
Power ON Alert Timer resets
Cabinet temp

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Differential
(3.5 K)
Alert Timer
60 min
Alert Timer
less than 60 min
Alert Temp
(Set Point - 5 K)
Set Point + 1.5 K
Set Point Temp
Set Point - 2.0 K
Temp Display
Window
Cabinet temp Flashing “E2”
Alert Timer resets
“E2” error
resets
[d] CABINET TEMPERATURE TOO LOW (E2)
When the cabinet temperature drops to the alert temperature (5 K below the set point), the
Low Temperature Alert Timer will start counting down from 60 minutes. When the Timer
counts down to zero, “E2” will be displayed. If the cabinet temperature rises above the
alert temperature before the Timer counts down to zero, the Timer will reset and “E2” will
not be displayed.
When the power supply is turned on, the Timer will start counting if the cabinet temperature
is below the alert temperature (5 K below the set point). This function is available even
during a defrost cycle.
The “E2” display will automatically reset when the cabinet temperature rises above the
Compressor ON temperature.
The cause may be:
1) The ambient temperature is too low, or a large amount of frozen food is stored inside.
2) The Interior Thermistor (black) is defective.
[e] DEFROST CYCLE TOO LONG (E3)
When the Defrost Thermistor does not turn off after 60 minutes have passed since the
defrost cycle starts, “E3” will be displayed. In this case, the refrigerator/freezer will proceed
to the next process: (1) Defrost cycle terminated, (2) Drain, (3) Fan Motor delay, (4) “dF”
display delay, (5) Cooling cycle.
The “E3” display will not reset until the power supply is turned off.
The cause may be:
1) The Defrost Heater is defective.
2) The Thermal Fuse is brown.
3) The Defrost Thermistor (orange) is defective.
4) A large amount of moist food is stored inside.

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[f] ABNORMAL PRESSURE (E4)
When the Clog Thermistor senses a temperature above 70°C (RTC series) or 60°C (FTC
series), the refrigerator/freezer will detect an abnormal pressure to stop the Compressor
for 5 minutes. At the rst detection, the Pressure Alert Timer will start counting down from
60 minutes.
The Compressor will restart after the 5 minute interruption, if the Clog Thermistor senses
a temperature below 60°C (RTC series) or 50°C (FTC series). The Compressor will not
restart until the above conditions are satised. If an abnormal pressure is still detected,
the Compressor will stop again.
If an abnormal pressure is detected five times before the Timer counts down to zero,
“E4” will be displayed. If the Timer has already counted down by then, “E4” will not be
displayed. This function is available even during a defrost cycle.
The “E4” display will not reset until the power supply is turned off.
The cause may be:
1) The Condenser Fan Motor is locked or defective.
2) The Condenser Filter is clogged with dirt or dust.
Temp Display
Window
Defrost Heater
Compressor
ON
OFF
ON
OFF
Defrost starts
Defrost Thermistor
senses
Drain
“dF” display
delay ends
60 min
Cabinet temp “dF” “E3” / ”dF” “E3” / cabinet temp
Flashing “E3”
*70°C
(60°C)
*60°C
(50°C)
Clog Thermistor
*RTC(FTC)
ON
OFF
Compressor
Temp Display
Window
60 min 60 min
Cabinet temp Flashing “E4”
5
min
5
min
5
min 5 min 5 min 5 min 5
min
5
min 5 min