American Water Heater 305 Merkblatt

Turn off all hot water taps. Press ON/OFF twice. 

03

Ensure approved venting materials are being used. 

Check that nothing is blocking the flue inlet or exhaust. 

Check all vent components for proper connections. 

Ensure vent length is within limits. 

Ensure condensation collar was installed correctly. 

Verify dip switches are set properly. 

Check fan for blockage. 

Check that the gas is turned on at the water heater and gas 
meter. Check for obstructions in the flue outlet. 

Ensure gas line, meter, and/or regulator is sized properly. 

Ensure gas type and pressure is correct. 

Bleed all air from gas lines. 

Ensure proper venting material was installed. 

Ensure condensation collar was installed properly. 

Ensure vent length is within limits. 

Verify dip switches are set properly. 

Ensure appliance is properly grounded. 

Disconnect keypad. 

Disconnect EZConnect or MSA controls to isolate the problem. 

Check power supply for loose connections. 

Check power supply for proper voltage and voltage drops. 

Ensure flame rod wire is connected. 

Check flame rod for carbon build-up. 

Disconnect and re-connect all wiring harnesses on unit and PC 
board. 

Check all components for electrical short. 

Check gas solenoid valves for open or short circuits. 

Remove burner plate and inspect burner surface for 
condensation or debris. 

Service Call 

02

10

Check that the gas is turned on at the water heater, gas meter, 
or cylinder. 

Ensure gas type and pressure is correct. 

Ensure gas line, meter, and/or regulator is sized properly. 

Bleed all air from gas lines. 

Verify dip switches are set properly. 

Ensure appliance is properly grounded. 

Disconnect EZConnect or MSA controls to isolate the problem. 

Ensure igniter is operational. 

Check igniter wiring harness for damage. 

Check gas solenoid valves for open or short circuits. 

Remove burner cover and ensure all burners are properly 
seated.

Remove burner plate and inspect burner surface for 
condensation or debris. 

11

Check gas type of unit and ensure it matches gas type being 
used.

Check for restrictions in air flow around unit and vent terminal. 

Check for low water flow in a circulating system causing short-
cycling. 

Ensure dip switches are set to the proper position. 

Check for foreign materials in combustion chamber and/or 
exhaust piping. 

Check heat exchanger for cracks and/or separations. 

Check heat exchanger surface for hot spots which indicate 
blockage due to scale build up.  Refer to instructions in manual 
for flushing heat exchanger. 

Measure resistance of safety circuit. 

Ensure high fire and low fire manifold pressure is correct. 

Check for improper conversion of product. 

14

Check for restrictions in air flow around unit and vent terminal. 

Check for low water flow in a circulating system causing short-
cycling. 

Check for foreign materials in combustion chamber and/or 
exhaust piping. 

Check for clogged heat exchanger. 

16

Check sensor wiring for damage. 

Measure resistance of sensor. 

Clean sensor of scale build up. 

Replace sensor. 

32

Check sensor wiring for damage. 

Measure resistance of sensor. 

Clean sensor of scale build up. 

Replace sensor. 

33

Check for restrictions in air flow around unit and vent terminal. 

Check sensor wiring for damage. 

Measure resistance of sensor. 

Clean sensor of scale build up. 

Ensure fan blade is tight on motor shaft and is in good 
condition.

Replace sensor. 

34

Check modulating gas solenoid valve wiring harness for loose 
or damage terminals. 

Measure resistance of valve coil. 

52

Ensure fan will turn freely. 

Check wiring harness to motor for damaged and/or loose 
connections. 

Measure resistance of motor winding. 

61

If blank screen is present on remote control then the flow control 
has shorted out.  Unplug flow control.  If remote lights up and unit 
starts operating then replace flow control assembly. 

65

Check wiring harness to all solenoids for damage and/or loose 
connections. 

Measure resistance of each solenoid valve coil. 

71

Ensure flame rod is touching flame when unit fires. 

Check all wiring to flame rod for damage. 

Remove flame rod and check for carbon build-up; clean with 
sand paper. 

Check inside burner chamber for any foreign material blocking 
flame at flame rod. 

Measure micro amp output of sensor circuit with flame present. 

Replace flame rod. 

72

Flush heat exchanger.  Refer to instructions in manual. 

Replace heat exchanger. 

Scale Build-up in Heat Exchanger   (when checking 
maintenance code history “00” is substituted for “LC”) 

LC

Clean inlet water supply filter. 

On new installations ensure hot and cold water lines are not 
reversed.

Check for bleed over. Isolate unit from building by turning off 
hot water line to building.  Isolate the circulating system if 
present.  Open your pressure relief valve; if unit fires, there is 
bleed over in your plumbing. 

Ensure you have at least the minimum flow rate required to fire 
unit.

Ensure turbine spins freely. 

Measure the resistance of the water flow control sensor. 

Remote control does not light up but you have 12 VDC at the 
terminals for controls. 

No Code (Nothing happens when water flow is activated.) 

12

Water

Inlet Max.

Gas Inlet
Min./Max

Forced Low

Table 1

Forced High

NAT.G

5"W.C.

/10.5"W.C.

8"W.C.

/13.5"W.C.

LPG

NAT.G

LPG

NAT.G

LPG

.

C

.

W

"

8

8

.

0

.

C

.

W

"

6

5

.

0

I

S

P

 

0

5

1

505

305

COLOR CODING

W :White
BK:Black
BR:Brown
R :Red
BL:Blue
Y :Yellow
P :Pink
O :Orange
G :Green
GY:Gray

1

3

BR

3

1

B

1
2

O
F
F

Dip SW1

3

8

7

6

5

4

F

5

W
W

B

1

BK
BK

MIN

MAX

MODULATING VALVE 
CURRENT ADJUSTING

Gas pressure

F

4

W
W

W
P

W

W

OUTGOING WATER
THERMISTOR

HEAT EXCHANGER
THERMISTOR

Y

BR

O

R

W

BR

R

O

Y

W

BK

R

W

for 2-Unit Connection
(Optional)

1

13

WATER FLOW
SENSOR

BK

F

2

Y

R

R

Y

BK

QS

BY-PASS FLOW
CONTROL DEVICE

Y

BK

R

FREEZE PROTECTION
           OPTION

G

W

W

W
O

F

3

W

W

O

P

BL

R

BR

Y

GY

WATER FLOW
CONTROL DEVICE

R

BL

BR

Y

GY

G
R

AIR TEMPERATURE
THERMISTOR

R

BL BR

Y

INDOOR MODEL ONLY

COMBUSTION FAN

FM

R

BK

Y

W

E

1

W

4

1

Y

BK

R

BY-PASS SERVO MODEL ONLY

1

1

THERMAL FUSES

R

R

OVERHEAT
SWITCH

H

2

H

1

MODULATING
SOLENOID VALVE

POV

H

3

P

P

H

4

Y

FLAME ROD

H

5

SV1

H

7

H

6

SV0

BL
BK

SV2

BK

P

Y

BK

MAIN SOLENOID VALVE

SOLENOID VALVE 1

SOLENOID VALVE 2

F

6

Y

BR

BL

BK

P

P

(CN2)

Y

P

R

12

1

SOLENOID VALVE 3

H

8

BR
BK

SV3

GY

C

1

IG

GY
GY

IGNITER

GND

GY

SURGE
PROTECTOR

3

1

BR

BL

G/Y

D

2

W

BK

1

3

GND

FUSE
(3A)

BK

W

W

BL

BL

D

4

ANTI-FROST HEATER

AC120V

AC120V

HOT

NEUTRAL

HOT

NEUTRAL
GROUND

G/Y

D

1

GND

D

5

ANTI-FROST HEATER

BL

BL

D

3

FROST SENSING
SWITCH

W

BL

REMOTE CONTROLLER

SPARK
ELECTRODE

5

4

Spare Parts Only

Gas type

1
2
3

O
F
F

Dip SW2

6

A

C

D

E

F

G

H

F

1

G

1

(CN3)

(CN4)

(CN1)

(CN12)

(CN5)

(CN7)

(CN9)

 5

 3

R
R

F

7

(W) (W)

505

305

505
305

3.3"W.C. 5.1"W.C.

2.9"W.C. 4.2"W.C.

Models 305 and 505 have a default maximum temperature 
of 120

°F (49°C) and an option to increase the maximum 

temperature to 140

°F (60°C).   Temperature settings from 

125-140

°F (52-60°C) are available by setting dip switch 6 to 

ON in the SW1 bank of 8 dip switches.   

Outdoor

DO NOT adjust the other dip switches unless specifically instructed 
to do so.  Incorrect Dip Switch Settings can cause the water heater
to operate in an unsafe condition and may damage the water heater
and void the warranty.

White - White

N / A

See example above F5

3 - 4

Pink - White

N / A

See example above F4

3 - 11

Orange - White

N / A

See example above F3

3 - 12

Black - White

108 ~ 132 VAC

N / A

D2

1 - 3

Blue - Brown

108 ~ 132 VAC

N / A

D1

1 - 3

Terminals B1

10 ~ 13 VDC

1.5 ~ 3.0 K ohms

B

1 - 3

(Main) Pink - Black

Wire color

Voltage

Resistance

Connector #

Pin #'s

11 ~ 13 VDC

36.8 ~ 44.8 ohms

H5

6 - 7

(SV1) Black - Yellow

11 ~ 13 VDC

36.8 ~ 44.8 ohms

H6

5 - 6

(SV2) Black - Blue

11 ~ 13 VDC

36.8 ~ 44.8 ohms

H7

4 - 6

Grey - Brown

4 ~ 6 VDC

N / A

F7

5 - 7

Red - Blue

11 ~ 13 VDC

22 ~ 28 ohms

F7

9 - 10

Black - Red

11 ~ 13 VDC

5.5 ~ 6.2 K ohms

F2

1 - 3

Grey - Grey

90 ~ 110 VAC

N / A

C1

1 - 2

Yellow - Black

4 ~ 7 VDC

1 ~ 1.4 Mega ohms F2

2 - 3

Red - Red

11 ~ 13 VDC

Below 1 ohms

F6

F6 - H12

H1

Grey - Yellow

N / A

N / A

F7

5 - 8

White - Black

5 ~ 10 VDC

9.2 ~ 9.4 K ohms

E1

2 - 4

Red - Black

6 ~ 45 VDC

N / A

E1

1 - 2

Yellow - Black

11 ~ 13 VDC

3.5 ~ 3.9 K ohms

E1

2 - 3

Orange - White

2 ~ 6 VDC

15 ~ 35 ohms

G1

2 - 5

Yellow - White

(Unit in operating mode)

G1

3 - 5

5

 

-

 

1

1

G

e

ti

h

W

 

-

 

n

w

o

r

B

5

 

-

 

4

1

G

d

n

u

o

r

G

 

-

 

e

ti

h

W

-

d

e

R

(SV3) Black - Brown

11 ~ 13 VDC

36.8 ~ 44.8 ohms

H8

3 - 6

(POV) Pink - Pink

2 ~ 15 VDC

67 ~ 81 ohms

H3

9 - 10

There are a number of (live) tests that are required when fault 
finding this product.  Extreme care should be used at all times to 
avoid contact with energized components inside the water heater.  
Only trained and qualified service technicians should attempt to 
repair this product.  Before checking for resistance readings, 
disconnect the power source to the unit and isolate the item from 
the circuit (unplug it).

Check all thermistors by inserting meter leads into each end of the 
thermistor plug.  Set your meter to the 20 K scale and read 
resistance.  Applying heat to the thermistor bulb should decrease 
the resistance.  Applying ice to the thermistor bulb should increase 
the resistance.  See below for examples of typical temperatures and 
resistance readings.

140

°F = 2.2 ~ 2.7K

221

°F = 0.6 ~ 0.8K

  59

°F = 11.4 ~ 14K

  86

°F = 6.4 ~ 7.8K

113

°F = 3.6 ~ 4.5K

Example:

With the power off you can check the continuity through the surge 
protector.  Place a meter lead on the top pin #1 of the surge 
protector and pin #3 on the bottom of the surge protector.  Check 
across the top pin #3 and bottom pin #1.  If you read continuity 
across these two points then the surge protector is good.  If you do 
not get continuity then replace the surge protector.

This unit has frost protection heaters mounted at different points to 
protect the water heater from freezing.  The heaters located on the 
hot water outlet line should have a resistance reading of 180-207 
ohms through each of these heaters.  The heater located on the 
heat exchanger piping should have a resistance reading of 156-180 
ohms and the one located in the water flow sensor valve should 
have a resistance reading 24-28 ohms.

This unit has one inline (3) amp glass fuses.  Remove the fuse and 
check continuity through it.  If you have continuity through the fuse 
then it is good.  Otherwise the fuse is blown and must be replaced.

Place one lead of your meter to the flame rod and the other to ground.
With the unit running you should read between 5-150 VAC.  Set your 
meter to the 

µ amp scale and series your meter in line with the flame 

rod.  You should read 1 

µ amp or greater for proper flame circuit.  In 

the event of low flame circuit remove the flame rod and check for 
carbon or damage.

The original PC boards on the water heaters do not have the 
bank of 6 dip switches.  Only spare PC boards have this bank.

Adjust switches 2 and 3 in the bank of 8 depending on 
your altitude according to the table below.

SW

NOTES

No.

2

3

Level 0

0-2000ft

(0-610m)

High Altitude

Level 1

2001-5200ft

(610-1585m)

Level 2

5201-7700ft

(1585-2347m)

Level 3

7701-10200ft

(2347-3109m)

Off

On

On

Off

On

On

Off

Off

     

In Use Indicator
Indicates that hot water 
is being supplied.

Temperature Display 
Indicates temperature 
setting or flashes error 
code.

Priority Indicator 
Indicates that this 
controller is setting the 
water temperature.

Priority Button
When no water is 
being supplied, 
pressing this button 
allows this controller to 
set the water 
temperature.

1.  To display error codes, press the ON/OFF button followed by 

the 

 thermostat button to cycle through the error codes.

2.  To display the water flow through the water heater, press the 

 

thermostat button (hold for 2 seconds) and then press the 
ON/OFF button while continuing to hold the 

 thermostat 

button.

3.  To display the outlet water temperature, press the 

 thermostat 

button (hold for 2 seconds) and then press the ON/OFF button 
while continuing to hold the 

 thermostat button.

With the water heater turned off, press and hold the ON/OFF 
button until the display changes to the other temperature scale 
(about 5 seconds).

To turn the sound off (mute), press and hold both the 

 and 

 

thermostat buttons until a “beep” is heard (about 5 seconds).

NOTE:  For additional installation and commissioning information refer 
to the Operation and Installation Manual.

This appliance must be installed, serviced and removed by a trained 
and qualified person.  During pressure testing of the consumer piping, 
ensure gas valve is turned off before unit is shut off.  Failure to do so 
may result in serious injury to yourself or damage to the unit.

With all gas appliances in operation at maximum gas rate, the 
flowing inlet pressure at the incoming test point on the water 
heater should read 5” W.C. - 10.5” W.C. on natural gas and 
8” W.C. - 13.5 W.C. on propane gas.  If the pressure is lower, 
the gas supply is inadequate and the unit will not operate to 
specification.  Check the gas meter regulator and pipework for 
correct operation/sizing and correct as required.

Ensure gas pressure check under Commissioning has been 
completed first!  The regulator is electronically controlled and 
factory pre-set.  Under normal circumstances it does not require 
adjustment during installation.  Make adjustments only if the unit is 
not operating correctly and all other possible causes for incorrect 
operation have been eliminated.

1.  Turn OFF the gas supply.
2.  Turn OFF the 120 V power supply.
3.  Remove the front panel from the appliance.
4.  Check the gas type using the data plate on the side of the unit.  

If using a spare PC board, check that the gas type switches are 
in the correct position (dip switch 1 of SW2: ON for natural gas, 
NG, and OFF for propane, LPG).  See dip switch settings 
section below.  (ON is towards the right and OFF is towards the 
left.)

5.  Attach the pressure gauge to the burner test point, located on 

the gas control (Fig. 2).

6.  Turn ON the gas supply.
7.  Turn ON the 120 V power supply. 
8.  If a controller is installed, turn the unit ON with the controller.  

Select the maximum delivery temperature and open all 
available hot water taps at full.

9.  Set the unit to “Forced Low” combustion by setting No. 7 dip 

switch of the SW1 set to ON (Fig. 3).

10. Check the burner test point pressure.
11. Remove the rubber access plug and adjust the regulator screw 

on the modulating valve (Fig. 4) as required in Table 1.  
Replace the rubber access plug.

12. Set the unit to “Forced High” combustion by setting both No. 7 

and No. 8 dip switches of the SW1 set to ON (Fig. 5).  Ensure 
maximum water flow.

13. Check the burner test point pressure.
14. Adjust the high pressure potentiometer (POT) on the PC board 

as required to the pressure shown in Table 1.

15. Return the unit to normal operation by setting dip switches 7 

and 8 of the SW1 set back to OFF (Fig. 6).   Close all water 
taps.

16. Turn OFF the gas supply and 120 V power supply.
17. Remove the pressure gauge and install sealing screw.
18. Turn ON the gas supply and 120 V power supply.
19. Operate the unit and check for gas leaks at the test point.
20. Install the front panel.

SW1

SW2

High Pressure 
Potentiometer

Spare Parts
Only

1

BURNER TEST POINT

Regulator adjustment
screw access plug

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

070 00012 39526 5