Fig. 30 Space heating diagram
Hot water outlet
Cold water inlet
Pressure relief valve
Shut off gas valve
Thermal expansion tank (as required)
Atmospheric vacuum breaker
 Thermostatic mixing valve
 Thermometer (optional)
 DHW outlet
 Water to water heat exchanger
 Space heating zone
 Zone controller
 Space heating pump
 Expansion tank
 Pressure relief valve
Measuring gas pressure
Confirm gas pressure upon installation.
▶ Shut off gas supply at installer supplied shutoff valve for this water
▶ Remove front cover and locate inlet gas pressure test port (see
▶ Loosen screw inside left test point fitting (do not remove) and
connect manometer tube to test point.
Static Pressure Test
▶ Turn gas supply back on.
▶ Record static gas pressure reading in table 13.
Operating Pressure Test
▶ Press ON/OFF button
▶ Press and hold simultaneously buttons
seconds, until display reads P2.
to enter P2 adjustment. The current setting will appear on
the display (factory default).
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:
Table 12 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 13.
Installation instructions | 23
until P1 reappears on the display.
6 720 644 956 (2016/05)