Dip Switch Setting; Automatic Switch To Backup Heat Source Operation - Mitsubishi Electric EHST20C-VM6HB Service Manual

6-13. Dip switch setting

Located on the FTC4 printed circuit board are 4 sets of small white switches
known as Dip switches. The Dip switch number is printed on the circuit board
next to the relevant switches. The word ON is printed on the circuit board and on
the Dip switch block itself. To move the switch you will need to use a pin or the
corner of a thin metal ruler or similar.
Dip switch settings are listed below in the table below.
Before changing any switch settings, ensure power supplies to indoor and out-
door units are isolated/powered off.
Dip switch Function
SW1 SW1-1 Boiler
SW1- Heat pump maximum outlet water temperature 55ºC
SW1- DHW tank
SW1-4 Immersion heater
SW1-5 Booster heater
SW1-6 Booster heater function
SW1-7 Outdoor unit type
SW1-8 Wireless remote controller
SW SW-1 Room thermostat1 input (IN1) logic change Zone1 operation stop at thermostat short Zone1 operation stop at thermostat open
SW- Flow switch1 input (IN2) logic change
SW- Booster heater capacity restriction
SW-4
Automatic switch to backup heat source
SW-5
operation (When outdoor unit stops by error)
SW-6 Mixing tank
SW-7 2-zone temperature control
SW-8
SW SW-1 Room thermostat 2 input (IN6) logic change
SW- Flow switch 2 input (IN3) logic change
SW- Flow switch 3 input (IN7) logic change
SW-4
SW-5 Heating mode function *3
SW-6
SW-7
SW-8
SW4 SW4-1
SW4-
SW4-
SW4-4
SW4-5 Emergency mode (Heater only operation) Normal
SW4-6 Emergency mode (Boiler operation)
Note: 1. When the cylinder unit is connected with a PUHZ-RP outdoor unit of which maximum outlet water temperature is 55ºC, Dip SW1-2 must be
changed to OFF.
2. External output (OUT11) will be available. For safety reasons, this function is not available for certain errors. (In that case, system opera-
tion must be stopped and only the water circulation pump keeps running.)
3 This switch functions only when the cylinder unit is connected with a PUHZ-FRP outdoor unit. When another type of outdoor unit is con-
nected, the heating mode function is active regardless of the fact that this switch is ON or OFF.
4. If emergency mode is no longer required, return the switch to OFF position.

Automatic switch to backup heat source operation

Back-up heat source operation (*1) will automatically run when the outdoor unit stops abnormally.
To enable the function, switch Dip SW 2-5 to ON.
During the back-up operation, an error code(s) and the contact number will be displayed alternately.
External output (OUT11) will be available.
To clear the fault(s), reset the power breakers on the indoor and outdoor units.
<Applicable error codes (*)>
E6 to E9, ED, P6, P8, U1 to U8, UD, UE, UF, UL, UP
(*1) Prolonged running of the back-up operation may affect the life of the heat source.
(*2) For safety reasons, this function is not available for certain faults. (System operation must be stopped and only pump keeps running.)
OCH531
WITHOUT Boiler
WITHOUT DHW tank
WITHOUT Immersion heater
WITHOUT Booster heater
For heating only
Split type
WITHOUT Wireless remote controller WITH Wireless remote controller
Failure detection at short
Inactive
—
Inactive
WITHOUT Mixing tank
Inactive
—
Zone operation stop at thermostat short Zone operation stop at thermostat open
Failure detection at short
Failure detection at short
—
Inactive
—
—
—
—
—
—
—
Normal
OFF
WITH Boiler
60ºC
WITH DHW tank
WITH Immersion heater
WITH Booster heater
For heating and DHW
Packaged type
Failure detection at open
Active
—
Active *
WITH Mixing tank
Active
—
Failure detection at open
Failure detection at open
—
Active
—
—
—
—
—
—
—
Emergency mode (Heater only operation)
(To be activated only when powered ON)
Emergency mode (Boiler operation)
(To be activated only when powered ON)

SW4
SW
SW
Default settings:
ON
Indoor unit model
OFF
ON *1
ON
OFF: Except
EHST0C-*M*HB
EHPT0-*M*HB
ON : EHST0C-*M*HB
EHPT0X-*M*HB
ON
ON
OFF: EHST20C-*M**B
ON : EHPT0X-*M**B
OFF
OFF
ON
OFF: Except
EHPT0X-VMHB
ON : EHPT0X-VMHB
OFF
—
OFF
OFF
OFF
OFF
—
OFF
OFF
OFF
OFF
—
OFF
OFF
—
OFF
—
OFF
—
OFF
—
OFF
—
OFF
—
OFF
—
OFF *4
OFF *4
SW1