Bosch Appliances 125B NG, 125B LP specifications Water is TOO HOT, Water is not HOT Enough

5. Crossover in household plumbing

The AquaStar burner activates when there is sufficient water pressure drop in the AquaStar water valve assembly — i.e. when a hot water faucet is opened. If there is a crossover in the plumbing, the necessary pressure drop in the AquaStar will be insufficient, or totally eliminated. A plumbing crossover can be caused by a bad washer at a single lever faucet or incorrect plumbing or a mixing valve in the line, etc. which permits hot and cold water to mix in the plumbing. The crossover will create a back pressure in the system preventing the pressure drop in the Aquastar — i.e. cold water is entering the water heater from both sides and the burners will not come on. To confirm there is no crossover in the plumbing, shut off the cold water supply to the AquaStar. Open your hot water taps. There should not be any water flowing. If there is water flowing, there is a crossover in the plumbing. This is a plumbing problem, not an Aquastar problem. Please contact your plumber.

6.Water valve parts may be dirty or components damaged.

Water valve and component parts must be totally free of dirt. First check that the venturi is free of dirt particles. In hard water areas, mineral deposits can eventually (3 to 5 years in hard water areas) corrode the water valve parts to a point where they will need replacing. Any sign of moisture or corrosion at the joint of the water valve and the gas valve is a sign that the water valve assembly components need to be serviced immediately. Note: Water valve for model 125B is part# 8707002649 for both LP and NG models. (Contact service person to clean water valve or replace if corrosion is present).

PILOT LIGHT GOES OUT DURING OR IMMEDIATELY AFTER HOT WATER HAS BEEN USED

1. Gas pressure too low

Very low gas pressure may be caused by low delivered gas pressure, a jammed gas regulator or undersized gas lines. If the gas lines are undersized, there may still be the specified static gas line pressure. However when the water valve opens, and gas enters the burners, the pressure could drop sharply, causing the pilot flame to go out. Have a gas technician confirm the gas pressure both static and at maximum Btu output. Specifications for your heater are on page 2.

2. Pilot may be dirty or weak

See Page 14 for instructions on pilot maintenance.

3.Burners are not shutting down immediately when hot water is turned off

Note: If burners don’t shut down immediately when the hot water is turned off, the heater will overheat and the ECO will shut-off the gas. Rebuild the water valve assembly. Contact service person to clean or rebuild water valve.

4.ECO (overheat sensor) tripped due to overheating Re-ignite the appliance 10 minutes later. If it happens again, contact your service person.

5.Flue gas safety device tripped

Ventilate the room and re-ignite the appliance 10 minutes later. If it happens again, contact your service person.

setting to reduce the burner output and/or turn the temperature adjustment knob counterclockwise to lower the maximum water temperature. Note: turning the knob counterclockwise will increase the activation flow rate.

2. Inlet water temperature is very warm

Increased seasonal ground water temperatures will affect the hot water output temperature. Reduce the burner output if the inlet water is very warm (60-75F) by positioning the gas control slide to the single flame ( ) setting. The temperature adjustment knob setting may also be lowered if necessary, reference SETTING THE WATER TEMPERATURE section.

WATER IS NOT HOT ENOUGH

1. Temperature selection too low.

Change the setting. Turn the temperature adjustment knob clockwise and/or slide the gas control to the winter mode setting for increased burner output.

Note: This will decrease the activation flow rate.

2.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 2. 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 2 for correct gas pressure settings and page 10 for locations where gas pressures are taken.

3.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.

4.Cold water is mixing with the hot water between the AquaStar and the outlet

Compare water temperature at outlet of the AquaStar (hold the AquaStar’s outlet pipe with your hand) and at the tap. If these two are very different, check for mixing valve or plumbing crossover (see “MAIN BURNERS WILL NOT IGNITE...” paragraph #6). Where automatic “anti-scald” valves are required by code, lower the temperature setting on the AquaStar as much as possible and balance the pressure between cold and hot water after the AquaStar.

5. Parts in water valve are dirty or damaged, which will prevent the gas valve from being fully opened.

Water valve maintenance needs to be performed, see #7 under BURNERS DO NOT IGNITE WHEN HOT WATER IS TURNED ON.