Parts Guide

BK:BLACK
P:PURPLE
LB:LIGHT BLUE
B
L
:
B
L
U
E
G;GREEN
Y:YELLOW
O:ORANGE
BR:BROWN
If the error code is indicated on the 7-Seg-LED on the PCB (Part #702) of the water heater (and/or
the remote controller), refer to Section B.
<< It takes long time to get hot water at the fixtures >>
・ The time it takes to deliver hot water from the water heater to your fixtures depends on
the length of piping between the two. The longer the distance or the bigger the pipes,
the longer it will take to get hot water.
・ If you would like to receive hot water to your fixtures quicker, you may want to consider a
hot water recirculation system.
<< The water is not hot enough or turns cold and stays cold >>
・ Compare the flow and temperature. Refer to the “Output temperature chart” of the
installation manual.
・ Check cross plumbing between cold water lines and hot water lines.
・ Check if the gas supply valve fully open, the gas line sized properly and the gas supplies
pressure enough. Refer to the “Gas supply and gas pipe sizing” of the installation manual.
・ Check the set temperature, and change the dipswitch setting. Refer to Section D.
・ Refer to “Water circuit” in this section.
<<The water is too hot>>
・ Check the set temperature, lower setting temperature.
<<The hot water is not available when a fixture is opened>>
・ Refer to the “Power supply circuit” and “Water circuit” in this section.
<<Fluctuation in hot water temperature>>
・ Check if the filter on the cold water inlet cleaned. (Part #437)
・ Check if the gas line sized properly and the supply gas pressure sufficient.
・ Check for cross connection between cold water lines and hot water lines.
・ Refer to “Water circuit” in this section.
<<Unit does not ignite when water goes through the water heater>>
・ Refer to the “Power supply circuit” and “Water circuit” in this section.
・ If you use the remote controller, turn the power button on and then the green LED will
light up.
・ Check if the filter on the cold water inlet cleaned. (Part #437)
・ Refer to “Water circuit” in this section.
B. Error codes
031:
Incorrect d
ipswitch setting
・ Check the dipswitch settings on the PCB. Refer to Section D.
101: Warning for the “991” error code
・ Check the gas type of the water heater. If it’s wrong gas type model, replace the water
heater to correct one.
・ Check if there is any blockage (For example, Damper sticking, Vent Flaps installed on the
terminator, Snow build up around terminator, Installed in a closet (No ventilation or lack
of combustion air)) in the intake air and/or exhaust. Refer to the “Vent termination
clearances” of the installation manual.
・ If the water heater is installed as a direct-vent system, check whether there is enough
distance between the intake air terminal and the exhaust terminal. Refer to the “Vent
termination clearances” of the installation manual.
・ Check if the total vent length doesn’t exceed 50 ft and the # of elbows is less than 5Ea.
・ Check the altitude/elevation of area of where the water heater installed.
・ Check if there is grease and/or dirt in the burner (Part #101) and the fan motor (Part
#416), especially if the water heater has been installed in a contaminated area.
・ Check if there is dust and lint in heat exchanger.
・ Check the manifold pressure of the water heater. Refer to installation manual.
111: Ignition failure
1. Check gas supply and inlet gas pressure.
2. Check if the Hi-limit switch (Part #403) is properly functioning.
3. Check for connection/breakage of wires (Part #111, 402, 705, 707), burn marks on the
computer board (Part #701), and/or soot on the flame rod (Part #103). And then if
O.H.C.F (Part #402) is breakage, Consult the manufacturer.
4. Check if there is a buzzing spark ignition sound coming from the burner (Part #101) when
water heater prepares for combustion.
5. Listen for the double “clunk” sound coming from the gas valve assembly (Part #114)
when water heater goes into combustion.
6. (Only no sparking and/or kick sound) Check voltage on each wire to gas valves assembly
(Part #114) and/or the igniter (Part #102). Refer to the “Appendix A” in Section C.
*No sparking sound >>>>> Refer to the #1 at “Appendix A” in Section C.
*No kick sound >>>>> Refer to the #2 at “Appendix A” in Section C.
7. Check if there is leaking from heat exchanger (Part #401 or 444).
8. Check if there is dust and lint in nozzles of the manifold (Part #114).
9. Check current on the flame rod (Part #103). Refer to the #3 at “Appendix A” in Section C.
121: Loss of flame
1. Check gas supply and inlet gas pressure.
2. Check if the Hi-limit switch (Part #403) is properly functioning.
3. Check for connection/breakage of wires (Part #111, 402, 705, 707), burn marks on the
computer board (Part #701), and/or soot on the flame rod (Part #103). And then if
O.H.C.F (Part #402) is breakage, Consult the manufacturer.
4. Check if there is leakage from heat exchanger (Part #401 or 444).
5. Check if there is dust and lint in nozzles of the manifold (Part #114).
6. Check current on the flame rod (Part #103). Refer to the #3 at “Appendix A” in Section C.
311,321,331: Disconnected/short-circuited thermistor
・ Check for connection/breakage of wires and/or debris on thermistor (Part #405, 424, 430, 704).
・ Check thermistor resistance. Refer to the “Appendix D” in Section C.
M
M
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6
6
3
3
V
V
1
1
5
5
1
1
A. Troubleshooting
C
.
Wiring Diag
ram and check point of th
e
Water heater
The
lower
bank
has settings for
three functions, shown below.
<Lower bank of dipswitches>
391: Air
-
fuel Ratio Rod failure
・ Check for connection/breakage of wires (Part #705) and/or soot on the AFR rod. (Part #103) .
441: Flow Sensor failure (Only Easy-Link system)
・ Check for connection/breakage of wires and/or debris on the flow sensor impeller (Part
#421).
510,551: Abnormal Main and Gas Solenoid Valve
・ Check for connection/breakage of wires (Part #707) and/or burn marks on the computer
board (Part #701).
・ Reset power supply of the water heater.
・ Check voltage on the each valve on the gas valves assembly (Part #114). Refer to the
“Appendix C” in Section C.
611: Fan motor fault
・ Check for connection/breakage of wires, dust buildup in the fan motor (Part #416) and/or
burn marks on the computer board (Part #701).
・ Check for frozen/corrosion of connectors of the fan motor (Part #416).
・ Check voltage between blue wire and each wire of the fan motor (Part #416), and check
resistance between white wire and red wire. Refer to the “Appendix B” in Section C.
631: External pump failure
・ Check whether the pump connected to MC50 PCB works properly.
651,661: Water control valve fault (Only Easy-Link system)
・ Check the water control valve (Part #418), connection/breakage of wires (Part #418),
motor drive locked due to scale buildup, and/or water leakage.
・ Check voltage between black wire and red wire. Refer to the “Appendix F” in Section C.
681: External fan motor failure
・ Check whether the external fan motor connected to MC50 PCB works properly.
701: Computer board fault
・ Check for connection/breakage of wires (Part #707) and/or burn marks on the computer
board (Part #701).
721: False flame detection
1. Clean the flame rod (Part #103).
2. For indoor models, check if condensate drain is installed on the vent collar of the water heater.
3. Check if there is leaking from heat exchanger (Part #401 or 444).
741: Miscommunication between water heater and remote controller
1. Check the model type of the remote controller. Model No. 9007603005 is the correct one.
2. Inspect the connections between the water heater and remote controller. Refer to the
“Remote controller connections” of the Installation manual.
3. Check the power supply of the water heater.
4. If this error code appears only the 7-Seg LED on the PCB (Part #702), check the voltage on
the remote controller terminal on the PCB. Refer to the “Appendix E” in Section C.
5. If this error code appears only remote controller, replace the PCB (Part #702).
6. If this error code appears both the PCB (Part #702) and the remote controller, replace the
remote controller.
761: Miscommunication between Parent unit and Child units for Easy-link system
・ Check if the connections between the parent unit and the child units are correct. Refer to
“Easy-Link system” section in the Installation manual.
991: Imperfect combustion
・ Refer to the “101” error code in this section.
<<The fan motor still spinning after operation has stopped>>
・ This is normal. After operation has stopped, the fan motor keeps running from 35
seconds in order to re-ignite quickly, as well as purge all the exhaust gas out of the flue.
<<Abnormal sound from water heater>>
・ An abnormal sound from the water heaters is caused by not enough air supply or wrong
installations. The water heater needs more combustion air. Refer to the “101” error code
in the section B.
<<Power supply circuit>>
1. If the remote controller installed, press the “ON/OFF” button of the remote controller,
and make sure that the green LED on the “ON/OFF” button of the remote controller is lit.
Restart the water heater.
2. Check if that the 7-Seg LED on the PCB (Part #702) of the water heater is lit. If so, the
power supply circuit of the water heater is under normal condition. Next, refer to the
“Water circuit” in this section.
3. Check the fuse on the surge box (Part #722), and if it has a brown spot, need to replace it.
4. Check the power supply, and make sure that the water heater has 120 VAC.
5. If the 7-Seg LED on the PCB (Part #702) isn’t lit, some electrical parts can be broken.
Consult the manufacturer.
<<Water circuit>>
1. If you set the remote controller, turn the power button on and then the green LED will
light up.
2. Open all hot water faucets, and make sure that there is enough water flow. This water
heater needs at least 0.5 GPM water flow to operate.
3. Check for reverse connection and cross connection.
4. Check if the filter on the cold water inlet cleaned. (Part #437)
5. Check if there is no debris or obstruction on the fixtures.
6. Check if water ways in the water heater are frozen. If so, unfreeze them. And refer to
installation manual to protect your water heater from freeze.
7. Check if the inlet water pressure is higher than 40 psi. And if it’s lower than 40 psi, need
to increase the pressure.
8. Check for connections and breakage of wires (Part #418, 421).
9. Check if the motor drive of the water control valve (Part #418) is locked due to scale
buildup, and/or water leakage. Consult the manufacturer.
<Upper bank of dipswitches>
The
upper
bank
has certain
special functions and generally
should not need adjustment.
Appendix D (For error code 311, 321 and 331)
・ Mixing thermistor (Find the marking of No.113 on the connector)
Check point “E1”
・ Output thermistor (Find the marking of No.12 on the connector)
Check point “E2”
・ Inlet thermistor (Find the marking of No.42 on the connector)
Check point “E3”
Check resistance between black wire and black wire.
°F 50 59 68 77 86 95
Temperature
°C 10 15 20 25 30 35
Resistance kΩ 15.4 12.6 10.3 8.5 7.0 5.9
All check points are normal?
Yes >> Replace the PCB. (Part #701)
No >> Replace the wrong thermistor. (Part #405, 424, 430)
Appendix E (For error code 741)
Refer to check point “F” on the wiring diagram above.
Check voltage on the remote controller terminal on the PCB.
(Normal: DC 11 to 15 V)
This check point is normal?
Yes >> Replace the remote controller.
No >> Replace the PCB. (Part #702)
Appendix C (For error code 510 and 551)
Refer to check point “C” in the diagram to the left and followings.
Check voltage on the each valve on the gas valves assembly.
・ Between blue wire and light blue wire (#3). (Normal: DC 78 to 100 V)
・ Between blue wire and green wire. (#9). (Normal: DC 78 to 100 V)
・ Between blue wire and orange wire (#53). (Normal: DC 78 to 100 V)
・ Between blue wire and red wire (#73). (Normal: DC 78 to 100 V)
All check points are normal?
Yes >> Replace the gas valves assembly. (Part #114)
No >> Replace the PCB. (Part #701)
Appendix B (For error code 611)
Refer to check point “G” in the diagram to the left and followings.
・ Check voltage between red wire and blue wire.
(Normal: DC 110 to 160 V)
・ Check voltage between yellow wire and blue wire.
(Normal: DC 13 to 17 V)
・ Check voltage between orange wire and blue wire
(Normal: DC 2.0 to 6.5 V)
All check points are normal?
Yes >> Replace the fan motor. (Part #416)
No >> Replace the PCB. (Part #701)
Appendix F (For error code 651 and 661)
Refer to check point “J” on the wiring diagram above.
Check voltage between black wire and red wire. (Normal: DC 13 to 16 V)
This check point is normal?
Yes >> Replace the Water control valve. (Part #418)
No >> Replace the PCB. (Part #701)
D. Dipswitch Settings on the computer board of the water heater
Change the
dipswitch
settings when the power supply is turning off.
The dark square is the direction the dipswitch should be set to.
DEFAULT is the factory setting.
Appendix A (For error code 111)
Check these points during ignition stage.
# 1. Refer to check point “B” on the wiring diagram above.
Check voltage between purple wires.
(Normal: AC 90 to 110 V)
This Check point is normal?
Yes >> Replace the igniter (Part #102)
No >> Go to Next
# 2. Refer to check point “C” and “H1” on the wiring diagram above.
Check the voltage bellows.
C: Between blue wire and light blue wire (#3).
(Normal: DC78 to 100 V)
C: Between blue wire and orange wire (#53).
(Normal: DC78 to 100 V)
H1: Check the voltage between white wire and red wire.
(Normal: DC 1 to 15 V)
These check points are normal?
Yes >> Replace the gas valves assembly. (Part #114)
No >> Replace the PCB. (Part #701)
# 3. Check current thought the orange flame rod wire (Part #705).
(Normal: more than 1μA)
This check point is normal during operation?
Yes >> Replace the PCB. (Part #701)
No >> Replace the flame rod. (Part #103)
A
A
T
T
M
M
5
5
0
0
Single unit is the same as the child unit.
(40 C)
104 F
(74 C)
165 F
(63 C)
145 F
(49 C)
120 F
DEFAULT
1 2 3 4 5 6 7 8
O F F
O N
1 2 3 4 5 6 7 8
O F F
O N
1 2 3 4 5 6 7 8
O F F
O N
1 2 3 4 5 6 7 8
O F F
O N
(46 C)
115 F
(85 C)
185 F
(68 C)
155 F
1 2 3 4 5 6 7 8
O F F
O N
1 2 3 4 5 6 7 8
O F F
O N
1 2 3 4 5 6 7 8
O F F
O N
1 2 3 4 5 6 7 8
O F F
O N
(57 C)
135 F
Temperature set
Upper
bank
Lower
bank
The Gas Type dipswitch
should already be
properly preset from
the factory.
Propane
1 2 3 4 5 6 7 8
O F F
O N
Natural
Gas
1 2 3 4 5 6 7 8
O F F
O N
Gas type
Ch il d
U ni t
DEFA ULT
Pa re nt
U ni t
1 2 3 4 5 6 7 8
O F F
O N
1 2 3 4 5 6 7 8
O F F
O N
Easy
-
Link system
H
e
a
t
e
r
Thermostat
Inlet
thermistor
Output
thermistor
Mixing
thermistor
BK
B K
B K
GF I
T ra ns-
f or mer
123 45 6
OFF
BR
BR
AC120V
10A
G
Ground
W
BK
BR
Ground
Air-fuel
ratio rod
Ground
Flame
rod
1
2 34 5 6
O FF
1
2 34 5 6
O FF
MV
SV1
SV2
SV3
Re m ote
co n tro lle r
Parent
W
W
Elect
rod
IG
Ground
Ground
Inlet
thermistor
Output
thermistor
Mixing
thermistor
BK
BK
BK
123 45 6
OFF
Air-fuel
ratio rod
Ground
Flame
rod
MV
SV1
SV2
SV3
FM
Elect
rod
IG
Heater
Heater
Heater
Heater
Heater
7
7
8
8
R
Y
G
W
B K
BL
R
O
Y
G
W
BK
BL
R
Y
G
W
BK
BL
R
O
Y
G
W
BK
BL
Water
Control
valve
Water
Control
valve
BK
BK
BK
BK
B K
B K
B K
B K
Y
G
O
O
G
Y
B K BK
W
W
BL
BK
BK
R
R
BL
BL
GG
R
B L
Y
O
W
P
PP
PP
PP
P
Porpor-
tional
Valve
G
WR
B K
W
R
WR
B K R
W
B L
LB
G
O
R
W
B K
Y
W
B K
W
BK
B L
L B
G
O
R
BK
W
BK
W
W
BK
B K
W
W
W
W
W
W
W
Porpor-
tional
Valve
Flow
Sensor
WR
BK
W
R
WR
BK R
W
Hi-
limit
BL
O.H.C.F
BL
BL BL
BL
FM
R
B L
Y
O
W
BL
Hi-
lim it
BL
O.H.C.F
BL
BL BL
BL
BL
Flow
Sensor
Left side unit
Right side unit
Surge
box
BK
W
MAX button
MIN button
Increase button
Decrease button
Burning lamp
Communication
lamp (right)
Communication
lamp (left)
Multi-system
on line lamp
Dipswitches
Dipswitches
7 Seg LED
Pump test run
Error call
button
Burning lamp
FM
port
Pump
port
Button to check
unit number
Priority SW
Alarm
contact
Draft switch
Dipswitc hes
MAX button
MIN button
Increase button
Decrease button
2
1
Dipsw itches
L
H2
A3
I
A
B
H
1
C
A1
J
K
F
D1
D2
E1
E2
E3
L
G
M
N
A
A
A2
L
L
L
L
L
I
A
B
H
1
H2
C
J
E1
E2
E3
C1
C
2
G
C1
C2
O F F
O N
1 2 3 4 5 6 7 8
Direct
vent
O F F
O N
1 2 3 4 5 6 7 8
Outdoor
O F F
O N
1 2 3 4 5 6 7 8
Indoor
DEF AU LT
Installation
type
MC50 Computer board