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*Note: The high altitude ratings listed are Canadian Gas Association
high altitude ratings for the appliances and are only valid in
Canada. In the U.S.A. the National Fuel Gas Code, ANSI 1-
1988, recommends for high altitude installations, above 2,000
feet, that the input rate be reduced 4% for each 1,000 feet
above sea level.
Figure 11
The gas pressures specified below refer to flow pressure
taken at the pressure tap in the gas inlet pipe just above the
pressure regulator, (see figure 11) while the heater is
operating at full input.
Gas pressures read at burner test point D (see fig. 7(a)
page 12.
Table 1.
Appliance Regulator Pressure Setting
Your appliance dealer and/or your local gas supplier should
be consulted in regard to any high altitude installation. If
field adjustment is required it should be performed by a
qualified serviceman experienced in such work.
TEMPERATURE REGULATION
The BOSCH WR430-3K is equipped with a modulating
gas valve which adjusts the flow of gas to the main burner
in proportion to the water flow rate. Within its heating
capacity the WR430-3K attempts to maintain the set
temperature rise across the heater. This temperature rise
can be set in range of 25C° - to - 50C° (45F° - to - 90F°),
by means of the water flow selector. See Figure 12. When
the water flow selector is turned to the right hand stop the
water heater is set for 50C° (90F°) temperature rise; when
the water flow seletor is set to the left hand stop it is set for
25C° (45F°) temperature rise.
PRESSURE REGULATION
The pressure regulator supplied with the water heater is
adjusted to operate on the gas specified on the rating plate
and:
• in Canada, is factory preset to deliver gas at the high
altitude setting listed on the rating plate and as shown
below.
• in the U.S.A., is factory preset to deliver gas at the
standard altitude setting listed on the rating plate and as
shown below.
The pressure setting of the gas pressure regulator should
be checked at installation to assure that the setting is correct
for the gas being used and the altitude at which the
appliance is installed. See rating plate on the unit, Table 1,
below, for proper setting.
In Canada, for a heater being installed at standard altitude
(0-2,000 ft above sea level) the manifold pressure should
be reset at installation to the value shown on the rating
plate, or Table 1, below, for standard altitude.
Increases temperature
and decreases flow
Temperature Adjustment Knob
Decreases temperature
and increases flow
Figure 12 - Principles of Operation
Figure 12
With the water flow selector turned to its right hand stop
position (50C° rise setting) and with an inlet water
temperature of 10°C (50F°) the outlet water temperature
will be maintained at approximately 60C° (140F°) in the
water flow rate range of approximately 2 litres/min. (0.5 U.S.
gals./min.) to 9.5 litres/min. (2.5 U.S. gals./min.).
The minimum flow rate for operation, the “Threshold Flow
Rate” referred to in the lighting instructions is 2 litres/min
(0.5 U.S. gals./min.). If the water flow rate is below this level
the main burner will not fire. If the flow rate exceeds 9.5
litres/min (2.5 U.S. gals./min.) the temperature rise aross
the heater will decrease in proportion to the rate above this
temperature.
HIGH TEMPERATURE LIMIT SWITCH
The BOSCH series instantaneous gas water heaters are
equipped with a high temperature limit switch with a set
point of approximately 90°C (195°F). If the water temperature
at the sensing points exceeds the set point the switch will
open, interrupting the safety circuit and stopping gas flow
to the pilot and main burner.
Outage as the result of high limit operation indicates that
the heater is not functioning properly. The heater should be
checked by a qualified serviceman and the reason for the
malfunction is corrected.
REGULATOR
SUPPLY TEST
PRESSURE TAP T
ADJUSTABLE
PRESSURE REGULATOR
kPa Inches, W.C.
natural 1.41 5.38 standard
propane 2.61 9.9 (0-2,000 ft.)
natural 1.14 4.4 high*
propane 2.09 7.9 (2,000-4,500 ft.)
Altitude
WR430-3K
Model Type of Gas
Regulator Pressure Supply