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Measuring Gas Pressure - Bosch 940 ESO Instruction Manual

Suitable for heating potable water and space heating
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Measuring gas pressure

Confirm gas pressure upon installation.
Connecting manometer
B Shut off gas supply at installer supplied shutoff valve
for this water heater.
B Remove front cover and locate inlet gas pressure
measuring point (see Fig. 34).
B Loosen screw inside left test point fitting (do not
remove) and connect manometer tube to test point.
Remove screw completely if correct size tapping is
Static Pressure Test
B Turn gas supply back on.
B Record static gas pressure reading in table 4.
Operating Pressure Test
B Press ON/OFF button to turn off the appliance.
B Press and hold "Program" (P) button and press ON/
OFF button to turn appliance ON.
Fig. 33
B As soon as '188' is displayed, release "Program"
, button and the display should read P2.
B Press
until P1 appears.
Note: While in this mode the appliance will run
maximum water flow.
For inlet gas pressure adjustment consider the
following table:
Gas type
3.5" WC
Table 3
Minimum inlet gas pressure under full operation
B Turn on high volume of hot water flow (at least 6
gpm) and heater will ignite. If heater display reverts to
P2, open more hot water fixtures to allow sufficient
flow. Press
until P1 reappears on display.
B Operate all other gas appliances (except this heater)
on same gas piping system at maximum output.
6 720 644 956
8" WC
B Record lowest operating gas pressure reading in
table 4.
Gas pressures lower than 3.5" W.C. for Natural Gas or
8" W.C. for LPG will result in insufficient degree rise to
the hot water being used, reduced hot water volume,
possible error code faults and must be corrected. See
Gas Connections, chapter 7.1, page 18.
P1 fan speed:
Factory default: NG: 54, LP: 46
Lowering P1 fan speed reduces the maximum BTU
As a temporary measure if the gas pressure in P1 is
below specification, lower P1 fan speed incrementally
until minimum inlet gas pressure reaches specified
range (table 3). After upgrading gas line, reset
appliance to P1 factory default setting (NG: 54, LP: 46)
or setting from Section 9.8.1.
Fig. 34 Gas pressure test port (left tapping)
Static Gas Pressure Reading (see Chapter 7.6)
enter here: ___________________ Date: ___________
Operating Gas Pressure Reading (see Chapter 7.6)
enter here: ___________________ Date: ___________
Table 4
Installation instructions



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