Troubleshooting; Introduction; Burner Does Not Ignite When Hot Water Is Turned On - Bosch 520PN Applications Manual

40 | Troubleshooting

Diagnostic menu
9F 9th most recent error
10F 10th most recent error
1P* Appliance type - Cd (Condensing)
Appliance type - nC (Non condensing)
2P* Appliance power - 210/ 225 (kBTU)
3P* Temperature range - H (100-140°F)
Temperature range - C (100-180°F)
H0 Numbers of hours - mode 0
H1 Numbers of hours - mode 1
H2 Numbers of hours - mode 2
C0 Number of cycles - mode 0
C1 Number of cycles - mode 1
C2 Number of cycles - mode 2
Table 35 * Settings define from factory
7.7.1 Working hours
To see how many hours the appliance has worked, please enter the
"Diagnostic menu" (chapter 7.7);
▶ Select the sub-mode "H0".
Write the number that shows in the display.
▶ Select the sub-mode "H1".
Write the number that shows in the display.
▶ Select the sub-mode "H2".
Write the number that shows in the display.
After checking the sub-modes H0, H1 and H2, introduce the values in
the table below;
Working hours
Number in H0 ______
Number in H1 ______ (X 100) =
Number in H2 ______ (X 10 000) =
(H0 + H1 + H2) = Total of hours
Table 36
8 Troubleshooting
WARNING:
▶ If you are unable to perform the tasks listed below, or
need additional assistance please contact your
original installer or a licensed gas technician.
8.1

Introduction

Many of the questions customers ask regarding operation of this unit can
be answered by following the troubleshooting steps as outlined below.
Visit our web site at www.boschpro.com for more detailed
troubleshooting. For best results, perform each step before proceeding
to the next. The suggested solutions may require that the cover be taken
off. (See fig. 3, page 8).
8.2

Burner does not ignite when hot water is turned ON

It is recommended to use "Control board diagnostics" page 39, chapter
7.7 as a tool for problem solving. If the display is showing a blinking two
digit code, refer to this section.
6 720 644 887 (2013/02)
Example:
Calculation of number of working hours,
Working hours
Number in H0
Number in H1
Number in H2
(H0 + H1 + H2) = Total of hours
Table 37
7.7.2 Number of cycles
To see how many cycles the appliance has done, please enter the
"Diagnostic menu" (chapter 7.7);
▶ Select the sub-mode "C0".
Write the number that shows in the display.
▶ Select the sub-mode "C1".
Write the number that shows in the display.
▶ Select the sub-mode "C2".
Write the number that shows in the display.
After checking the sub-modes C0, C1 and C2, introduce the values in a
table as the example;
Example:
Calculation of number of cycles (1 cycle = 1 ignition),
Number of cycles
Number in C0
Number in C1
Number in C2
(C0 + C1 + C2) = Total of cycles
Table 38
_______ +
_______ +
_______
__________
1. If the display is blank, verify power to outlet. (120VAC/60Hz properly
grounded circuit required). Verify that the heater power button is
pressed ON.
2. Verify the fuses in the control board are good. To access fuses, the
control board must be removed. See chapter 5.2, page 32.
3. Make sure cold water inlet connection is plumbed to the right side of
heater when facing unit. See Fig.31, page 27.
4. A minimum of 0.5 gallons per minute (1.9 l/m) of hot water demand is
required to activate the heater. Confirm at least 0.5 gpm flow by
timing how long it takes to fill a container. A quart container should fill
in 23 seconds or less, from hot water tap only, to activate heater. In
unusual circumstances with high inlet water temperatures and low set
temperatures, the heater may increase the activation rate above 0.5
gpm to avoid overheating at low flows. Gradually increase water flow
(hot water demand) through the heater to determine if the heater
activates with higher flow.
5. Clean inlet filter screen per chapter 4.9, page 27.
60 60 +
5 (X 100) = 500 +
0 (X 10 000) =
560
40 40 +
6 (X 100) = 600 +
1 (X 10 000) = 10 000
10 640
0
C 1210 ES/ESC