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Hot Water Temperature Fluctuates At Tap; Noisy Burner/Heater During Operation; Error Codes C1, C2, Cf And/Or Ce; Error Codes Ea And/Or Ec - Bosch Greentherm T9900 SE 160 Installation And Operating Instructions Manual

Indoor residential tankless water heaters, 160 000/199 000 btu- natural gas 160 000/199 000 btu - liquefied petroleum lp gas
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Troubleshooting
8.6

Hot water temperature fluctuates at tap

1. If the water heater set point temperature is high, mixing at
the faucet could deactivate the water heater. The addition
of too much cold will overpower hot water flow from the
tankless water heater reducing its flow below the activation
point.
If this slows the flow through the tankless water heater
below its activation point, it will shut off the burner.
2. Unbalanced pressure in water lines. Any restriction in the
water heater, such as a clogged inlet water filter screen, can
result in unequal pressures between the cold and hot water
lines. In such cases, when mixing in the higher pressure
cold water at the tap, the lower pressure hot water can be
overpowered. This will shut down the burners because the
hot water flow rate falls below the minimum flow rate
required for activation. Verify that the inlet water filter
screen is clean and clear of debris. See chapter 7.1,
page 57 for inlet water filter cleaning instructions.
3. The water heater may be deactivated by temperature
balancing shower valves. If the water heater's set point
temperature is set too high, the temperature balance
shower valve will automatically mix in cold water to reduce
the hot water temperature. An adjustment should be made
to minimize the amount of cold water the valve is adding.
Additionally, the temperature setting on the water heater
can be lowered to reduce the amount of cold water that the
temperature balance valve mixes in.
4. Inlet water pressure is erratic due to fluctuating supply
water pressure. For installation on a private well system
with the use of a pressure tank, the lowest pressure range
setting recommended is 30 - 45 psi (2.06 - 3.1 bar).
Consult your installer or local plumber for effective ways to
maintain constant water pressure to the appliance when on
a well system.
8.7

Noisy burner/heater during operation

Burner noises can be heard if combustion is not properly set.
This could be caused by improper gas supply conditions (gas
pressure and/or gas composition).
Two types of noise can be heard: low pitch noise/vibration
(rumbling) and high pitch noise/vibration (whistling).
8.7.1 High pitch noise
1. Verify if correct gas type is selected (see section 6.8).
2. Verify is gas pressure is within specified range (see
section 3.2).
60
3. Ensure that the venting used is according to specifications
(see section 4.6) and cross contamination does not exist.
Ensure that intake and exhaust terminations maintain
required clearances.
If gas type is properly selected, gas pressure is within
range, the venting is according to specifications, and the
problem persists:
4. Perform the gas and air adjustment as described in
section 8.12.
8.7.2 Low pitch noise
1. Verify if correct gas type is selected (see section 6.8).
2. Verify if gas pressure is within specified range (see
section 3.2).
If gas type is properly selected, gas pressure is within
range, the venting is according to specifications, and the
problem persists:
3. Perform the gas and air adjustment as described in
section 8.12.
8.8

Error codes C1, C2, CF and/or CE

C1, C2, CF and CE errors could be caused by a too long flue
and/or an obstruction in the venting.
1. Verify if there are any venting obstructions and remove
them if that is the case.
2. Ensure that the venting used is according to specifications
(see section 4.6).
3. Reset the error by holding the On/Off button for 3s.
If there are no obstructions and venting is according to
specifications, and the problem persists:
4. Perform the gas and air adjustment as described in
section 8.12.
8.9

Error codes EA and/or EC

EA and EC errors can appear if combustion is not properly set.
This could be caused by improper gas supply conditions (gas
pressure and/or gas composition).
1. Verify if correct gas type is selected (see section 6.8).
2. Verify is gas pressure is within specified range (see
section 3.2).
If gas type is properly selected, gas pressure is within
range, the venting is according to specifications, and the
problem persists:
3. Perform the gas and air adjustment as described in
section 8.12.

8.10 Internal recirculation pump

1. Pump makes noise. Purge the recirculation water circuit.
Greentherm T9900 SE/i – 6 720 813 635 (2019/03)

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