Bosch WR400 K T2 Series Installation Operation & Maintenance page 8

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 pressure 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 of the unit, or 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 value shown on the rating plate, or
Table 1, below, for standard altitude.
The gas pressure specified below refer to flow pressuretaken
at the pressure tap in the gas inlet pipe (just above pressure
regulator), figure 9, while the heater is operating at full input.
PRESSURE TAP
PRESSURE REGULATOR
MANUAL GAS VALVE IN OFF
POSITION
Figure 9
Appliance Regulator Pressure Setting
Model Type of Gas
kPa
natural 1.36
WR325
propane 2.61
natural 1.09
WR325
propane 2.11
natural 1.41
WR400
propane 2.61
natural 1.14
WR400
propane 2.09
* Note: The high altitude ratings listed are Canadien 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 Z223. 1 /NFPA 54,
recommends for high altitude installations, above
2,000 feet, that the input rate be reduced 4% for
each 1,000 feet above sea level.
Your appliance dealer and/or your local gas supplier should
be consulted in regard to any high altitude installation. If
filed adjustment is required it should be performed by a
qualified serviceman experienced in such work.
8
Pressure tap
Altitude
Inches, W.C.
5.5 standard
10.5 (0-2,000 ft.)
4.4 high *
8.5 (2,000 - 4,500 ft.)
5.7 standard
10.5 (0-2,000 ft.)
4.6 high *
8.4 (2,000 - 4,500 ft.)
TEMPERATURE REGULATION
The BOSCH WR325 K and WR400 K are wall mounted,
high efficiency, thermostatically controlled instantaneous gas
water heaters designed to provide approximately 60º C (140
º F) water temperature at flow rates from as low as 2 litres/
min. (0.5 U.S. gals./min.) to 8 litres/min. (2. 1 U.S. gals./min.)
for the WR400 K model or 6.5 litres/min. (1.7 U.S. gals./
min.) for the WR325 K model.
If flow rate through the heater is lower than 2 litres/min.
(0.5 U.S. gal./min.) the main burner will not fire. The minimum
flow rate for main burner operation is the "THRESHOLD
FLOW RATE" referred to in the lighting instructions.
If flow rate through the heaters exceeds 8 litres/min. on
WR400, or 6.5 litres/min. for WR325, the temperature
exiting the heater will be flow rate dependent, decreasing
with increasing flow.
To assure that full gas input is obtained open faucet fully to
a min. flow of 10 litres/min. (2.6 U.S. gals./min.).
Should overheating occur or the gas supply fail to shut off,
turn off the manual gas control valve to the appliance and
have the heater checked by a qualified serviceman to
determine the reason for the malfunction.
WATER FLOW ADJUSTMENT
Maximum flow rate through the heater can be adjustment
by turning the water throttle screw (see figure 8).
HIGH TEMPERATURE LIMIT SWITCH
The BOSCH WR series instantaneous gas water heaters
are equipped with a high temperature limit switch with a set
point of approximately 90ºC (194ºF). 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. To relight the pilot, follow
instructions provided on the unit.