8 6 720 606 560
Your appliance dealer and/or 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 WR400-7.K.. 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 WR400-7.K.. attempts to maintain the set temperature
rise across the heater. This temperature rise can be set in
range of 25ºC-to-50ºC (45ºF-to-90ºF), by means of the water
flow selector. See figure 11. When the water flow selector is
turned to the right hand stop the water heater is set for 50ºC
(90ºF) temperature rise; when the water flow selector is set
to the left hand stop it is set for 25ºC (45ºF) 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 show 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.
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 10) while the heater is
operating at full input.
Gas pressures read at burner test point D (see fig.7 (a)) will
usually read 1-1.5’’ W.C. less than below.
Table 1
Appliance Regulator Pressure Setting
* 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. the National Fuel Gas Code,
ANSI 1-1988, recommends for high altitude installations,
above 2000 feet that the input rate be reduced 4% for
each 1.000 feet above sea level.
MANIFOLD TEST
PRESSURE TAP
ADJUSTABLE
PRESSURE REGULATOR
T
Figure 10
G661_004
Temperature Adjustment Knob
Decrease
temperature and
increase flow
Increases
temperature and
decreases flow
Figure 11 - Principles of Operation
With the water flow selector turned to its right hand stop
position (50ºC rise setting) and with an inlet water
temperature of 10ºC (50ºF) the outlet water temperature will
be maintained at approximately 60ºC (140ºF) in the water
flow rate range of approximately 2 litres/min (0.5 U.S. gals./
min.) to 8 litres /min. (2.1 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 flow rate exceeds 8 litres/min
(2.1 U.S. gals./min.) the temperature rise across 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 90ºC (195ºF). If the water temperature at
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 corrected.
kPa Inches, W.C.
natural 1.41 5.7
standart
propane 2.61 10.5
(0.2,000 ft.)
natural 1.14 4.6
high*
propane 2.09 8.4
(2,000-4,500 ft.
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