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Troubleshooting
• 3. Inlet water is preheated. This model does not have
a thermostat and will not modulate flame height in
order to prevent overheating. It is designed for a cold
water feed only. Replumb the heater with cold water
to the inlet.
• 4. Increase flow rate. Restrictions in the water path
can slow the flow of water through the heater,
resulting in very hot outlet temperatures. Restrictive
showerheads and faucet aerators should be cleaned
out or upgraded with less restrictive ones. In
addition, the inlet filter on the water heater should be
cleaned and inspected. See chapter 5.2.
• 5. If water is still too hot, consult service bulletins on
www.boschhotwater.com
to
lower
outlet
temperatures further.
• 6. If the water has a high mineral content, the heat
exchanger may be scaled internally. This restricts the
water path, causing the water to boil and produce
extremely hot temperatures. To descale the heat
exchanger,
consult
service
bulletins
on
www.boschhotwater.com.
6.8
Water is not hot enough
• 1. Verify gas type indicated in the rating sticker
located on the cover's right hand side, coincides with
the gas type you are using. NG is a natural gas unit
and LP is for liquid propane (see chapter 2.2).
• 2. Flow at one particular tap is too great or too many
fixtures are running at one time. Lower flow to stay
within heater's specifications.
• 3. Ensure the power adjustment knob is all the way
clockwise for highest temperatures. In addition, the
temperature adjustment knob maybe set too low.
Raise the setting and test the water temperature.
This dial turns counterclockwise for lower
temperatures and clockwise for higher temperatures.
• 4. Close installer supplied cold water shut off valve (if
none installed, install before proceeding). Open all
hot water taps supplied by the heater. Wait 5
minutes and check all taps. Any water running is a
sign of a plumbing crossover. Consult local plumber
or service person for help correcting a plumbing
crossover.
• 5. Inspect the water path outside the heater for
obstructions. Make sure all outlets (i.e. showerheads,
faucet aerators and whole house filters) are clear of
debris. Also, the water heater's inlet filter should be
inspected and cleaned. See chapter 5.2.
• 6. The water valve assembly, which allows gas flow
to the burners, requires periodic maintenance (every
2-5 years depending on water quality and use). Visit
www.boschhotwater.com to purchase water valve
rebuild kit to service the water valve.
• 7. Gas pressure is too low. Ensure gas pressure is in
accordance with specifications in the installation
manual. See chapter 3.9. A gas pressure reading is
needed to proceed further. Contact your original
installer or a local certified gas technician to obtain
this reading.
6.9
Burners ignite without water flow
• 1. The water valve may be dirty and sticking,
prohibiting it from fully closing the gas valve. This part
requires periodic maintenance (every 2-5 years
depending on water quality and use). Visit
www.boschhotwater.com to purchase water valve
rebuild kit to service the water valve.
6.10 Low hot water pressure
• 1. Confirm adequate flow rate through the unit. With
cold supply shut off to the unit, disconnect hot outlet
side to the unit. Place a gallon jug under hot water
outlet to catch water. Open cold water supply and
measure flow rate out of the unit. With temperature
adjustment knob set all the way clockwise, the flow
rate should be close to 2GPM (filling the jug in 30
seconds or less). If the flow rate is not adequate,
inspect and clean inlet filter screen. See chapter 5.2.
• 2. Confirm the incoming water pressure to the unit is
above the required 30psi.
• 3. Inspect the water path outside the heater for
obstructions. Make sure all outlets (i.e. showerheads,
faucet aerators and whole house filters) are clear of
debris.
• 4. Be sure to run only one major fixture at a time with
this water heater. Opening too many taps at one time
can disperse water flow resulting in diminished flow/
pressure at all outlets.
• 5. If the water has a high mineral content, the heat
exchanger may be scaled internally. This restricts the
water path, causing diminished water flow. To
descale the heat exchanger, consult service bulletins
at www.boschhotwater.com.
6.11 Noise when heater is running
• 1. Confirm adequate flow rate through the unit. With
cold supply shut off to the unit, disconnect hot outlet
side to the unit. Place a gallon jug under hot water
outlet to catch water. Open cold water supply and
measure flow rate out of the unit. With temperature
adjustment knob set all the way clockwise, the flow
rate should be close to 2GPM (filling the jug in 30
seconds or less). If the flow rate is not adequate,
inspect and clean inlet filter screen. See chapter 5.2.
• 2. Inspect the water path for obstructions. Make sure
all outlets (i.e. showerheads, faucet aerators and
whole house filters) are clear of debris. Restrictions
