
6 720 607 909
Installation instructions
25
3.8
Measuring gas pressure
Connecting manometer
B
Turn power off.
B
Shut off gas supply.
B
Remove front cover and locate the inlet gas
measuring point (see Fig. 29).
B
Loosen screw inside test point fitting (do not remove)
and connect manometer tube on test point.
Fig. 29 Gas pressure measuring (lower tapping)
Static pressure test
B
Turn gas supply on.
B
Keep unit off and record
static pressure reading
in
Table 11.
Operating pressure test
B
Place a demand for heat by turning external tank
thermostat control to maximum for unit to fire at
maximum input.
B
Press On/Off button to turn heater On.
For this test the unit has to be put in Diagnostic
Mode.
B
After 10 seconds, press and hold the reset button
.
B
Rotate the recirculating water temperature selector
(left knob) to the minimum and then to maximum.
B
Release the reset button and the display should
show * (blinking).
The unit has now entered Diagnostic Mode.
B
Operate all other gas appliances on same gas piping
system at maximum output.
B
Record operating pressure reading in Table 11.
B
Press On/Off button to turn heater Off and exit
Diagnostic Mode.
Operating gas pressures lower than 5.5" W.C. for nat-
ural gas or 11" W.C. for LP will result in improper oper-
ation and must be corrected. See Chapter 3.7 for gas
line sizing requirements.
Manifold pressure test
B
To confirm manifold pressure connect manometer to
upper tapping on gas valve. See Fig. 30.
Fig. 30
B
Follow instructions in "operating pressure test” to
place unit into Diagnostic Mode.
B
Place a demand for heat by turning external tank
thermostat control to maximum for unit to fire at
maximum input.
B
Operate all other gas appliances on same gas piping
system at maximum output.
B
Compare manometer values with those found in
Table 12 below.
B
Press On/Off button to turn heater Off and exit Diag-
nostic Mode.
i
Note: after verification tighten the screw
inside the test point.
Static
Gas Pressure Reading (see Chapter
3.8
)
enter here:
___________________
Operating
Gas Pressure Reading (see Chapter
3.8
)
enter here:
___________________
Table 11
Gas valve
pressure in W.C.
GWH345
GWH450
Min.
Max.
Min.
Max.
Natural Gas
-0.3
3.5
0.5
4.0
Liquid Gas
0.2
8.2
0.0
9.0
Table 12
6720607909-34.1JS