Bosch Appliances 2400E NG manual Low water flow/pressure, Hot water temperature fluctuates at tap

7.Cold water is mixing into the hot water lines (plumbing crossover). A plumbing crossover can unintentionally mix cold water with the hot water leaving the heater. The end result is a cooler water temperature than desired. To check for a plumbing crossover, shut off the cold water supply feed to the water heater. Then open all of the hot water taps served by the heater. Wait 10 minutes and check all taps for water flow. There should be no water flowing. Any continuous flow of water, small or large, indicates a crossover and must be corrected. Failing single lever faucets and mixing valves are common causes of plumbing crossovers.

8.Ensure that both temperature sensors are making contact and firmly mounted on their respective cold and hot water pipes. The hot water sensor should be located on the horizontal section of the hot water pipe before it exits the heater. The cold water sensor is located on the first horizontal section of pipe as the water comes into the heater.

6.5Low water flow/pressure

1.Too many hot water applications are being used simultaneously or too much flow is demanded. The water heater will effectively support two 2.0-2.5 GPM shower heads simultaneously or multiple sink applications. Greater draws will result in a water pressure drop and reduced flow at taps.

2.Ensure that gas pressure is in accordance with specifications in chapter 3.8. A gas pressure reading is needed to proceed further. Contact your original installer or a local certified gas technician to obtain this reading. If gas pressure is inadequate, the water heater will close its motorized water valve, reducing the hot water flow rate in an attempt to reach the selected output temperature.

3.If selected temperature on the unit is set too high for the demanded flow rate, the water heater will close its motorized water valve, reducing the hot water flow rate in an attempt to reach the selected output temperature. Lowering the selected temperature will allow the motorized water valve to open up for increased water flow rate.

4.Clean inlet filter screen per chapter 5.1.

5.Inspect the water path for obstructions. Make sure all showerheads, faucet aerators and whole house filters are clear of debris.

6.6Hot water temperature fluctuates at tap

Note: Temperature fluctuations from hot to cold during use are typically caused by a restriction in the hot water flow from the tankless heater. This slows the flow within the tankless heater, decreasing it below the activation flow rate, which shuts off the burners. The end result is nothing but cold water coming out of the outlet. Follow

each step below before proceeding to the next. After each step, test the hot water flow to see if it remains constant without turning cold.

1.Check for restrictions in plumbing outlets, which could limit hot water flow and may contribute to heater deactivation. For sinks, remove faucet aerator. Flush and clean screen and reinstall. For showers, remove showerhead and flush. If plugged with min- eral deposits, clean according to manufacturer’s sug- gestions or replace shower head. (If showerhead is wand style/hand held, corrugated tube connecting to head may be too restrictive. Use a larger tube or replace with a normal showerhead.)

2.Clean inlet filter screen per chapter 5.2.

3.Check for a plumbing crossover by closing the installer supplied cold water shut off valve (if none installed, install before proceeding) and opening all hot water taps supplied by the heater. Wait 5 minutes and check all taps. The water flow should come to a complete stop at every tap. Any water running, even a trickle, is a sign of a plumbing crossover. Consult a local plumber or service person for help. This condition must be corrected before the heater can operate properly.

4.Confirm water pressure is adequate and constant.. Water pressure must stay above 30psi during heater operation. For installation on a private well system with the use of a pressure tank, the lowest pressure range setting recommended is 30-50 psi (2.07-3.45 bar). The use of a pressure reducing/regulating valve directly after the pressure tank is an effective way to maintain constant water pressure to the water heater. Watts brand 25AUB-¾” or N35B-¾” pressure reducing/regulating valves or equivalent is suggested.

5.Heater deactivated by temperature balancing valves. If the outlet water temperature is set too high, the heater can produce temperatures that are too hot. A temperature balance shower valve will automatically mix in cold water to reduce such hot water tempera- ture. In the event of any temperature instability at a fix- ture using a temperature balancing valve, refer to the valve manufacturer for instructions on internal adjust- ment setting. An adjustment should be made to min- imize the amount of cold water the valve is adding. Additionally, the temperature setting on the heater can be lowered to prevent the temperature balance valve from mixing in too much cold.

6.7Noisy burner/heater during operation

1.Sealed combustion leak. Make sure cover is securely fastened. Ensure the exhaust vent adaptor is properly sealed with supplied gasket. Leaky seals create improper combustion resulting in noise.