andrews R18 Series, Technical Documentation Manual

Page: 48 / 71

18IP22B
40
b. Carry out step a) above and close the pilot manual cock
once the pilot burner has ignited. Check that the water
heater proceeds to lock-out.
c. Connect a pressure gauge to pressure test point 10/3 (see
gas train fig. 34) and carry out step a) above. Check that
pilot burner pressure is as indicated in table 9, with the
pilot burner on test the pilot pipe and connections from the
pilot manual cock to the burner connection or gas sound.
d. Connect a pressure gauge to the main burner manifold,
test point 10/4 and re-connect the electrical connections
from the main safety shut off valves into the front electrical
tray.
Switch the on/off switch to on and the water heater will
ignite in the sequence described in a) above with the main
burners igniting from the pilot burner at minimum rate.
Check ignition of the main burners is smooth. Observe
that the modulating air damper opens and the gas rate
increases to maximum. Check the main burner pressure
on maximum is as indicated in table 15 and adjust if
necessary.
Check all pipework and connections downstream of the
safety shut off valves for gas leaks with a suitable leak
detection fluid.
Switch off the water heater, remove pressure gauge and
reseal test point.
e. Connect a µA-meter (0 - 50 µA) in series with the flame
detection circuit. While measuring ionisation the main
burner should stay switched off. To do this, disconnect the
main gas valve by breaking the electrical connection by
removing the plug. Connect the black wire (-) (1) of the
µA-meter with the ionisation connector electrode (2) on
the water heater (fig. 27). Connect the red wire (+) (3) of
the µA-meter with the ionisation cap (4). The ionisation of
the pilot burner must show a minimum of 5 µA during 10
seconds after which the burner falls into flame detection
lockout. Wire the main gas valve back to its originally
conditions.
Repeat the test by starting the water heater to maximum
operation. Check that the µA-meter reads at least 5 µA
after 10 seconds.
f. Switch on the water heater. Check for spillage of products
of combustion from the draught diverter opening with a
smoke detector or other suitable apparatus, ensuring that
any openable windows, doors etc., fitted in the water
heater space are shut and any extraction fans are operat-
ing. Spillage checks should be done with the water
heater cold and when the system has heated up, both on
maximum and minimum rates.