Measuring Gas Pressure - Bosch C 950 Installation Manual

36 | Installation instructions
Fig. 45 Pressure drop curve
4.14

Measuring gas pressure

Confirm gas pressure upon installation.
Connecting manometer
▶ Shut off gas supply at installer supplied shutoff valve for this water
heater.
▶ Remove front cover and locate inlet gas pressure test port (see
Fig.47).
▶ Loosen screw inside left test point fitting (do not remove) and
connect manometer tube to test point (see Fig. 47).
Static Pressure Test
▶ Turn gas supply back on.
▶ Record static gas pressure reading in table 45.
Operating Pressure Test
▶ Press ON/OFF button into ON.
▶ Press and hold simultaneously buttons
seconds, until display reads P2.
Fig. 46
▶ Press to enter P2 adjustment. The current setting will appear on
P
the display (factory default).
+
▶ Press or until P1 appears.
Note: While in this mode the appliance will run constantly at maximum
power and allow maximum water flow.
For inlet gas pressure adjustment consider the following table:
6 720 805 440 (2014/11)
+
or and for 3
P
Gas type
p 3.5" WC
in
Table 44 Minimum inlet gas pressure under full operation
▶ Operate all other gas appliances (except heater) on same gas piping
system at maximum output.
▶ Turn on high volume of hot water flow (at least 6 gpm) and burner will
light. If heater display reverts to P2, open more hot water fixtures to
allow sufficient flow. Press
▶ Record lowest operating gas pressure reading in table 45.
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 4.8, page 29.
P1 fan speed:
Factory default: NG: 51, LP: 52
Lowering P1 fan speed reduces the maximum BTU input.
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 44). After upgrading gas line, reset
appliance to P1 factory default setting (NG: 51, LP: 52) or setting from
Section 4.3.8.
NG LPG
8" WC
+
until P1 reappears on the display.
Greentherm