Download  Print this page

Troubleshooting; Introduction; Burner Does Not Ignite When Hot Water Is Turned On; Water Is Too Hot - Bosch 940 ES Installation And Operating Instructions Manual

Indoor model natural gas/ liquefied petroleum (lp) gas
Hide thumbs

Advertisement

8

Troubleshooting

CAUTION:
▶ If you are unable to perform the tasks listed below, or need
additional assistance please contact a qualified 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.bosch-
climate.us 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 12).
8.2
Burner does not ignite when hot water is
turned ON
It is recommended to use "Control board diagnostics" page 56,
chapter 7.6 as a tool for problem solving. If the display is
showing a blinking two digit code, refer to this section.
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 46.
3. Make sure cold water inlet connection is plumbed to the
right side of heater when facing unit. See fig. 32, page 40.
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 4.10, page 40.
6. Inspect the water path for obstructions. Make sure all
shower heads, faucet aerators and whole house filters are
clear of debris.
7. Check for plumbing crossover. A crossover in the hot and
cold plumbing pipes creates back pressure on the water
flowing through the heater. Therefore, a higher flow rate
than normal is needed to force the heater to activate. To
check for a plumbing crossover, shut off the cold water
940 ES – 6 720 644 930 (2019/09)
supply to the water heater. Then open all of the hot water
taps served by the heater. Wait 10 minutes and check for
water flow at each tap. There should be no water flowing.
Any continuous flow of water, small or large, indicates a
crossover is present and must be corrected. Consult a
professional plumber for help in correcting a crossover.
Failing single lever faucet mixing valves are common causes
of plumbing crossovers.
8. With the power button pressed switch turned to OFF and
the power supply cord unplugged, remove the unit's front
cover (See fig. 3, page 12). Check wire connections
between the water valve, control unit and electrode set.
See chapter 13.2, page 69 for location of these parts.
9. Water heater in solar mode. If inlet water temperatures
exceed the water heater's set temperature, the burners will
not ignite and the solar mode indicator will show on the
display. See fig. 48, page 47.
8.3

Water is too hot

1. Selected temperature on the unit is too high. To lower
output temperature, see chapter 6.4, page 48.
2. Clean inlet filter screen per chapter 7.1, page 51 to
increase flow through the heater.
3. Inspect the water path for obstructions. Make sure all
shower heads, faucet aerators and whole house filters are
clear of debris.
4. Confirm the heater's gas type coincides with the type of gas
being supplied. See fig. 2, page 12 for location of rating
plate.
5. Avoid restrictive outlets. Clean all shower heads and faucet
aerators. It may be necessary to upgrade to higher flow rate
shower heads if allowable by local code.
6. In areas where the water has a high mineral content,
periodic descaling may necessary. See chapter 7.3,
page 52 for directions.
8.4

Water is not hot enough

1. Selected temperature on the unit is too low. To raise output
temperature, see chapter 6.4, page 48.
2. Clean inlet filter screen. See chapter 7.1, page 51 to
increase flow through the heater.
3. Inspect the water path for obstructions. Make sure all
showerheads, faucet aerators and whole house filters are
clear of debris.
4. Confirm the heater's gas type coincides with the type of gas
being supplied. See fig. 2, page 12 for location of rating
plate.
5. Check inlet gas particle screen for blockage at gas inlet
connection on bottom of unit.
Troubleshooting
57

Advertisement

loading

  Also See for Bosch 940 ES

  Related Manuals for Bosch 940 ES