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Troubleshooting
on the water heater and prevent an adequate flow of
water through it. To confirm there is no crossover in
the plumbing, shut off the cold water supply feed to
the water heater. Individually open each of the hot
water taps. There should be no water flowing under
a constant pressure. If there is a constant flow of
water then the plumbing crossover must be
corrected before the heater can operate properly.
WATER IS TOO HOT
• Temperature selection too high
Lower temperature adjustment on heater or wireless
remote control accessory, see chapter 3.2.
WATER IS NOT HOT ENOUGH
• Temperature selection too low
Increase temperature adjustment on heater or
wireless remote control accessory, see chapter 3.2
• Btu input is too low due to inadequate gas line
sizing
See specifications in chapter 2.10 - 2.12. The
GWH-635-ES requires adequate gas pressure to
reach desired temperatures, to compensate for
inadequate gas supply or lack of gas pressure the
GWH-635-ES will effectively reach the selected
output temperature by reducing the hot water flow
rate. Its motorized water valve makes this adjustment
• Cold water is mixing with the hot water outlet
(crossover)
Test by following 4th bullet under BURNERS DO
NOT IGNITE WHEN HOT WATER IS TURNED ON.
LOW WATER FLOW/PRESSURE
• Too many hot water applications are being
used simultaneously or too much flow is being
demanded
The GWH-635-ES will effectively support two 2.0-
2.5 gpm shower heads simultaneously or multiple
sink applications. Greater draws will result in
increased pressure drop and reduced flow at taps.
See flow/temperature chart on page 23.
• Btu input is too low due to inadequate gas line
sizing
See specifications in chapter 2.10 - 2.12. The
GWH-635-ES requires adequate gas pressure to
reach expected temperatures and flow rates, to
compensate for inadequate gas supply or lack of gas
pressure the GWH-635-ES will effectively reach the
selected output temperature, but only by reducing
the hot water flow rate. Its motorized water valve
makes this adjustment. Proper gas pressure will
need to be delivered before the motorized water
valve will allow greater flow rates through it. Lowering
the set temperature will also allow increased water
flow rate through the motorized water valve. See
flow/temperature chart on page 23.
• Cold water inlet filter screen is dirty
Remove water inlet filter screen and clean. The
26
screen is located at the inlet connection to the water
heater, disconnecting the main cold supply line at the
heater is required. Check and clean faucet aerator
screens too.
HOT WATER TEMPERATURE FLUCTUATES /
UNIT DEACTIVATED
• Unbalanced pressure in water lines
Any restriction caused by the water heater 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 (manually or
automatically through a mix-type shower valve) the
lower hot water pressure may be overpowered by the
higher cold water pressure in the building and cause
the hot water flow rate to fall below the minimum rate
required. A pressure balance valve will help to
resolve this symptom.
• Temperature balance valves
If the outlet water temperature is set too high, the
heater can produce temperatures that are too hot. A
temperature balance shower valve can automatically
mix in cold water to reduce such hot water
temperature.
In the event of any temperature
instability with the use of a temperature balance
shower valve, refer to shower valve manufacturer's
instructions
for
internal
Adjustments should be made to the hottest setting in
the shower valve. Additionally the temperature
control of the heater can be lowered to produce a
more comfortable hot water temperature.
• Inlet
water
pressure
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 30-50 psi (2.07-3.45 bar). The use
of a pressure reducing valve after the pressure tank
is also an effective way to maintain a constant water
pressure to the water heater. Watts brand 25AUB-
¾" or N35B-¾" pressure relief valves or equivalent
are suggested.
adjustment
setting.
is
erratic
due
to
6 720 607 072 (16 January)
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