Water is TOO HOT

6.Check Blower Fan. Is it operating when burner comes on?

7.Check flapper in outside vent termination for free movement.

1.Check for lime build-up. (See mineral scale p. 16)

2.Temperature Selection too high

Turn the temperature adjustment knob counter-clockwise (to the left) to lower the maximum water temperature. Note: This will increase the activation flow rate.

3.Inlet water temperature is too hot (as with preheated water.)

4.Insufficient water pressure

WATER IS NOT HOT ENOUGH

1. Temperature selection too low.

Change the setting. Turn the temperature adjustment knob clockwise (to the right).

Note: This will decrease the activation flow rate.

2.Water flow through the heater is higher than the capacity of the Bosch to heat it.

This can be due to too high water inlet pressure (60 psi max. for best results) or due to acid water erosion of venturi. Check venturi (Part #39, Fig. 19 page 20).

3.Btu input is too low due to insufficient gas pressure. It is extremely important for a tankless instantaneous water heater to have the right size gas line to obtain the correct gas pressure.

See specifications on page 15, table 1. Unlike storage tank water heaters, the burners of a tankless water heater must be very powerful to heat water instantaneously since they do this only at the time hot water is actually being used. It is therefore imperative that the gas pressure requirement be met exactly. Insufficient gas pressure will directly affect the water temperature at the time of usage. See page 15 for correct gas pressure settings and fig. 11 for locations where gas pressures are taken.

4.Btu input is too low due to insufficient gas supply. Make sure your main gas line is fully opened. If using LP gas, be sure that the size of the propane tank is adequate to supply the required gas pressure.

5.Cold water is mixing with the hot water between the Bosch and the outlet.

Compare water temperature at outlet of the Bosch (hold the Bosch’s outlet pipe with your hand) and at the tap. If these two are very different, check for mixing valve or plumbing crossover (see “NO SPARK AT THE PILOT” paragraph #4). Where automatic “anti-scald” valves are required by code, lower the temperature setting on the Bosch as much as possible and balance the pressure between cold and hot water after the Bosch.

6.Parts in water flow valve are corroded so that the gas passage is not fully opening.

Contact your service person or call:

Canada 1-800-663-8405, U.S.A. 1-800-824-7337.

HOT WATER TEMPE RATUR E

FLUCTUATES

1. Unbalanced pressure in waterlines.

The added restriction caused by the Bosch in the hot water system can result in uneven pressures between the cold and the hot. In such cases when mixing cold water at the tap, the lower hot water pressure may be overpowered by a much higher cold water pressure, which may cause the Bosch burners to shut down. Make sure faucet aerators or shower heads are free of minerals. Do not add any flow restrictor to the shower head.

2.Cold water is mixing with the hot water between the Bosch and the outlet.

See 4 under “NO SPARK AT THE PILOT”.

3.Inlet water pressure is erratic due to inadequate supply water pressure or saturated pressure tank on well system.

Check the inlet water pressure. On a private well, raise minimum pressure setting to 40 psi. Confirm that the pressure tank is not water logged.

4.Gas pressure is too low.

See page 15 for correct specifications.

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