Hot Water Temperature Fluctuates At Tap - Bosch C 950 Installation Manual

48 | Troubleshooting
8.6

Hot water temperature fluctuates at tap

1. Hot water is very hot out of the water heater, requiring mixing in cold
water in order to attain a usable hot water temperature. The addition
of too much cold will overpower hot water flow from the tankless
water heater.
If this slows the flow through the tankless water heater below its
activation point, it will shut off the burners. The end result is nothing
but cold water coming out of the outlet. Consult www.bosch-
climate.us for a detailed service bulletin on overcoming temperature
fluctuations.
2. Unbalanced pressure in water lines. Any restriction in the water
heater, such as a clogged inlet 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 fell below the minimum flow
rate required for activation. Verify inlet filter screen is clean and clear
of debris. See chapter7.1, page 41 for inlet filter cleaning
instructions.
3. 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 the hot water
temperature. In the event of any temperature instability at a fixture
using a temperature balancing valve, refer to the valve manufacturer
for instructions on internal adjustment setting. An adjustment should
be made to minimize 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.
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 40
- 60 psi (2.75 - 4.15 bar). Consult your installer or local plumber for
effective ways to maintain constant water pressure to the appliance
when on a well system.
6 720 805 440 (2014/11) Greentherm