Bosch 38B LP Installation And Operating Instructions Manual page 12

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 9 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
repair kit from CEC (part#8 703 406 204).
4. Water is too hot causing overheat sensor to shut
heater down
Reduce burners by sliding gas control to single flame
position or set control knob to a lower setting.
WATER IS TOO HOT
1. Burners are too strong
Note: If the inlet water is quite warm, slide gas valve control
to single flame symbol ( ) and the heater will function on
a minimum burner output.
2. Temperature selection is too hot
Turn the temperature adjustment knob to the left.
WATER IS NOT HOT ENOUGH
1. Temperature adjustment knob is set too low.
Change the setting. Turn the temperature adjustment knob
clockwise (to the right).
2. Water flow through the heater is higher than the
capacity of the AquaStar to heat it
Reduce the flow demand at the faucet. See flow rates at
specific temperature rises on page 2.
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 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 pages 2
and 6 respectively for correct gas pressure settings and
where gas pressures are taken.
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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 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 "BURNERS DO NOT IGNITE
WHEN HOT WATER IS TURNED ON" 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.
6. Parts in water flow valve are corroded so that the
gas passage is not fully opening.
HOT WATER TEMPERATURE FLUCTUATES
1. Unbalanced pressure in waterlines
The added restriction caused by the Aquastar 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 Aquastar 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 AquaStar and the outlet
See # 6 under "Burners do Not Ignite When Hot Water is
Turned On".
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 30 psi. Confirm that the
pressure tank is not water logged.
4. Insufficient gas pressure
Check gas pressure requirements (page 2) and consult
gas service person.