Bosch GWH 2700 ES LP - Manual (Page 44)

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44
Problem solving
No flame ionization detected with
water flow. 1. Verify that all manual gas shut off valves are open.
2. Check gas type, see
Fig. 2 , page 6 .
3. Reset error code and open a water tap to cycle the heater in an
effort to purge air on new installations. Cycling hot water tap on
and off multiple times may be necessary. If heater still faults with
EA error code, have a licensed gas technician properly purge air
out of the gas line leading to the water heater.
4. Check three wire connections to ignition group on the lower
front of the heat exchanger are secure.
5. Check gas pressure, see
chapter 3.12 , page 27 .
6. Check venting specifications are met. Improper venting may
cause premature failure of the flame sensor rod.
7. Check that the minimum power fan speed has been adjusted to
the proper value. See page 18.
8. Observe inside the viewing window of the heat exchanger when
a hot water tap is opened. Sparking should be followed by a
steady blue flame. If flame is unstable or yellow with proper gas
pressure, confirm CO
2
readings per section 6.4 .
Ionization failure during operation. 1. Check gas type, see Fig. 2 , page 6 .
2. Check three wire connections to ignition group on the lower
front of the heat exchanger are secure.
3. Check venting specifications are met. Improper venting may
cause unstable burner flames and loss of flame ionization.
4. Check that the minimum power fan speed has been adjusted to
the proper value. See page 18.
5. Check gas pressure, see section 3.12 , page 27 .
6. Check and adjust CO
2
readings, see section 6.4, page 33.
Ionization error at standby. 1. Loose connection to the flame ionization rod. Verify that the
thinner wire leading from the control unit is securely connected to
the flame sensor located on the lower front of the heat exchanger.
See Fig.
64 , page 49.
2. Flame ionization rod or control unit may be damaged. Contact
Bosch Water Heating for further instruction.
Gas leakage error, gas valve circuit
not closing properly. 1. Disconnect power supply cord and check wire connections on
gas valve and the two connectors on the control board.
2. Flow water out of a hot water tap above the minimum activation
point of 0.65 GPM. Measure voltage at the gas valve wire plug
connection. The voltage should measure 24VDC between the left
pair of wires and 24VDC between the right pair of wires when the
unit is operating. If voltage is not proper, contact Bosch Water
Heating for further instruction.
3. Gas valve may be defective, contact Bosch Water Heating for
further instruction.
Display Cause Solution
Table 20
* By installer or service technician only.