Hoshizaki Steelheart Series Service Manual page 17

1b) Manual-Initiation: To initiate or terminate a manual defrost cycle: Turn the rail
control dial clockwise to put the rail control dial 9 setting in the 12 o'clock position,
pause for 3 to 5 sec., then turn the rail control dial counterclockwise to any position
below setting 7 in the 12 o'clock position. Defrost initiates or terminates within
5 sec. Note: When defrost is manually initiated it continues through the normal
defrost cycle unless manually terminated. Compressor must be on for a minimum of
2 min. to initiate defrost and off for a minimum of 2 min. to terminate defrost.
12 o'clock
Clockwise
2) Defrost-Termination:
(1) DTh warms to 41°F (5°C). DH de-energizes. 3-min. drip off time starts.
(2) 3-min. drip off time terminates. Comp and ConFM energize. If DTh is at
36°F (2.2°C) or lower, EvapFM/CabFM(s) energize. 6-hr. defrost interval timer
resets. Note: If DTh is 37°F (3°C) or higher when 3-min. drip off time terminates,
EvapFM/CabFM(s) remain off until DTh is 36°F (2.2°C) or lower.
Defrost Diagnosis:
1a) Defrost Time/Temperature Initiation Diagnosis: 6-hr. defrost timer terminates.
RCM checks DTh status. If DTh is at or below 41°F (5°C), defrost starts. Comp,
ConFM, EvapFM(s), CabFMR and CabFM(s) de-energize. If 6-hr. defrost timer
terminates and defrost does not start, check DTh. See "II.C. Thermistor Check."
Replace if needed. If DTh is at or below 41°F (5°C) and defrost does not start,
replace RCM. If DTh is at or above 42°F (5.5°C), RCM continues in cooling mode.
1b) Defrost Manual-Initiation Diagnosis: Turn the rail control dial clockwise to put the
rail control dial 9 setting in the 12 o'clock position, pause for 3 to 5 sec., then turn
the rail control dial counterclockwise to any position below rail control dial setting
7 in the 12 o'clock position. Defrost initiates or terminates within 5 sec. If not, replace
RCM and RCD.
Note: Compressor must be on for a minimum of 2 min. to initiate defrost and off for a
minimum of 2 min. to terminate defrost.
Check the following:
(1) DH Diagnosis: Confirm DH energizes. If not, check for 115VAC at RCM 4(H)
red (R) wire to neutral white (W) wire. If 115VAC is not present, replace RCM.
If 115VAC is present, check continuity of DST. If open, let cool and reset.
If DST does not close, replace DST. If DST is closed, check DH amp draw and
continuity. Replace if necessary.
(2) Comp and ConFM Diagnosis: Confirm Comp and ConFM de-energize.
If not, check for 115VAC at RCM 1(C) violet (V) wire to neutral white (W) wire.
If 115VAC is present, replace RCM.
(3) RCM and CabFMR Diagnosis: Confirm EvapFM(s), CabFMR, and CabFM(s)
de-energize. If not, check for 115VAC at RCM 5(F) dark blue (DBU) wire to
neutral white (W) wire. If 115VAC is present, replace RCM. If 115VAC is not
present and CabFM(s) continue, check for 115VAC at CabFMR white/blue
(W/DBU) wire to neutral white (W) wire. If 115VAC is present (cooling icon on),
replace CabFMR.
12 o'clock
Control Knob
Counterclockwise
Fig. 1
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