Rinnai E50CRN User's Information Manual page 12

Replenishing the central heating system
The central heating installation needs to be filled with potable (drinking)
water. For topping up the installation you use the filling loop according to the
following procedure:
i
NOTICE
1 Switch all functions off (heating, DHW and pump);
2 Briefly push the 'STEP'-button: P x.x = water pressure in PSI;
3 Slowly open the filling loop (Indication on display increases);
4 Fill up slowly to between 16 and 18 PSI (1.1 and 1.3 bar);
5 STOP appears on the display;
6 Close the filling loop;
7 De-aerate the complete installation, start at the lowest point;
8 Check the water pressure and if necessary top it up;
9 Close the filling loop;
10 Activate functions required (heating
11 If A xx appears on the display, wait for 17 minutes;
12 Check the waterpressure
13 Close the filling loop;
14 Press the 'STEP'-button;
15 Be sure that the filling loop is closed.
After the automatic de-aeration programm (A xx) is finished the boiler will
return to the Good reading or Technical reading.
12
Contact your licensed professional installer if
your installation is not provided with a filling
loop.
, DHW
and if necessary top it up to 16 to 18 PSI (1.1 and 1.3 bar)
and/or pump );