Error Piping Freeze Prevention Control - Toshiba HWS-802XWHM3-E Service Manual

[A05] Error Piping freeze prevention control
Restart
TWI 4, TWO
THO 4 is detected
Circulation pump keeps
being energized or 3 minutes
passed after the start
Water heat
exchange control board
DPSW11-1 is ON
Backup heater terminal
has 230ACV ( ± 23V)
Backup heater element
is conductive
Yes
TWI, TWO, THO
sensor characteristics
are correct
Yes
Replace water heat
exchange control board
4, or
No
Yes
No
Yes
Power is connect to
built-in heater terminal
No
(Backup heater NG)
No
(See characteristic table in page 101)
No
Yes
78
Set water heat board
DPSW11-1 to ON
Place power cable for
backup heater
Set breaker for backup heater
to ON, or Check indoor
electronic wiring
Replace backup heater
and safety valve
Replace TWI, TWO,
and THO sensors