Potterton PRIMA 30C User Manual page 20

COMMISSIONING - Page 20
FINAL ADJUSTMENT
A. Remove the screw from the burner pressure test nipple
on the gas control valve and fit a pressure gauge to the
test nipple. See Fig 19.
B. Turn on the boiler thermostat, then check that the
pressure is in accordance with the values stated under
TECHNICAL DATA. The burner pressure is factory set
to the maximum stated.
C. If burner pressure adjustment is necessary, remove the
screwed cap from the gas control valve, see Fig 19, and
turn the screw beneath clockwise to increase pressure
and anti-clockwise to reduce pressure.
D. With the burner set to its correct pressure, the firing rate
given in TECHNICAL DATA should also be obtained
and this should be checked by meter reading 10 minutes
after the main burner has been lit.
E. Shut down the boiler, remove the pressure gauge.
Replace the screwed cap and refit the screw in the test
nipple. Re-light and test for gas soundness at the test
nipple screw.
Figure 19 GAS CONTROL VALVE
Pilot Burner
The pilot burner pressure is non-adjustable. The pilot flame
should heat the thermocouple so that the pilot safety device
is "held in" but must not cause the thermocouple to glow
bright red. Fig 20 illustrates the approximate size of a correct
flame. The E.M.F. generated by the thermocouple should be
of the order of 20-30 mV open circuit, 10-14 mV closed
circuit. Due to the voltage drop in the overheat thermostat
circuit there should be 6.5-8.5 mV closed circuit at the
connection to the gas control valve. Drop out should occur
between 1-3 mV closed circuit. If these conditions cannot be
achieved check that the inlet pressure is 20 mbar See Fig 19
for inlet pressure nipple. If this is correct contact Potterton
Myson.
F. Remove the self-adhesive arrow from the inspection
ticket tied to the burner supply pipe and stick it to the
Data Plate inside the controls cover to indicate the
appropriate burner setting pressure. Refit the controls
cover.
G. Heat the system to maximum. Check for water leaks,
turn the boiler off, drain the system whilst hot.
H. Refill the system and on sealed systems adjust to the
correct cold fill pressure. Set the pressure gauge pointer
to the system design pressure.
I. If a by-pass circuit is fitted, the by-pass valve should be
adjusted with the boiler operating under minimum load
conditions to maintain sufficient water flow through the
boiler to ensure that the overheat thermostat does not
operate under normal operating conditions.
J. Remove the temporary label from the front of the casing,
having checked compliance with the information it
contains
Figure 20 PILOT BURNER
Boiler Thermostat
At its minimum and maximum settings, the thermostat
should control the water flow temperature at approximately
55ºC-82ºC (130ºF -180ºF). The thermostat has been
calibrated by the makers and no attempt should be made to
re-calibrate it on site. Turn the thermostat to the 'O' position
and check that the main burner shuts down.
Pump Over-run Thermostat (Applicable on fully pumped
systems only)
The over-run thermostat will keep the pump running when
the boiler has shut down, as long as the combustion
chamber is hot.
20