Mitsubishi Electric EHPT20Q-VM2EA Service Manual page 37

10-4. Self diagnosis and action
Check if DIP SW is set correctly. (Refer to Section 6-2.)
Error code Title and display conditions
L3 Circulation water temperature overheat
protection
<DHW/Heating/FS/OS>
Error code displayed when THW1 detects a
seconds or
seconds.
DHW : Domestic hot water mode
Heating : Heating mode
FS : Freeze stat
OS : Operation stop
TH1A/B : Room temp. thermistor
THW1 : Flow water temp. thermistor
THW3 : Flow water temp. thermistor 2 (to tank)
THW5B : Stored water temp. thermistor (lower)
L4 Tank water temperature overheat protection
<DHW/Heating/FS/OS>
Error code display when THW5A detects a
GCH15010
Possible Cause
1.
2. V
3.
4.
5. Booster heater relay (CNBH) operating
6.
7. THW1 or THW2 has become de-
tached from its holder.
THW1 or THW2 or THW3
1.
2.
3.
37
Diagnosis and action
1. Check (See
to check).
Open
Check the strainer for blockages.
Check that the flow t is within the
recommended range
operation.
Refer to P e 5 in "11. DISASSEMBLY
PROCEDURE."
2. Check al es on primary water circ t are
3.
4.
2) Operate 3-way al e
the main remote controller. (Refer to
4) Replace 3-wa al e. (Refer to P
6 in "11. DISASSEMBLY PROCEDURE."
5. Electrically test the relays (CNBH) to
6.
7. Vis y inspect location and reattach as
necessary.
Check resistance of thermistor against ta-
Compare FTC detected temperat
hand held detector.
Replace board.
1.
2) Operate 3-way al e
the main remote controller. (Refer to
4) Replace 3-way . (Refer to P
6 in "11. DISASSEMBLY PROCEDURE."
2. Check resistance of thermistor against ta-
Compare FTC detected temperat
hand held detector.
3. Replace board.
for how
r.
y sing
e
to
y sing
e
to