13
NOVA PLUS Installation & Operation Manual -
POWER FLAME INCORPORATED
DC4 DRAFT CONTROL
ENTER
ESC
®
21. Increase the rate to high fire position and repeat the test done for the mid point
adjustment. Results should range in the area of 6% to 9% O
2
with little or no CO. The
metering device setting and air damper openings should be marked and noted to obtain
high fire reference points. Note that an additional point of fire adjustment may be obtained
by modifying the regulated gas pressure delivered to the burner metering device. The
burner pressure regulator is used to obtain this adjustment and can be used within
available pressure limits to obtain optimum firing conditions.
22. On linkage systems, operate the modulating lever arm on the modulating motor through
the three previously referenced points. Minor setting modifications may be required to
ensure that the reference points are acquired.
23. Determine that the required gas input rate is being achieved by clocking the gas flow at
the gas meter. The gas utility should be consulted to determine if any correction factors
have to be applied to the indicated meter flow rates.
24. Intermittently operate the burner until the water is warm in the boiler, or follow specific
initial firing recommendations provided by the heat exchanger manufacturer.
25. Tighten all linkages and permanently mark settings.
26. Limit control check should be made as follows:
A)
Permit the burner to run until the limit control settings have been reached.
B)
The burner should turn off when the set temperature or pressure has been
reached. Set the controls so that the burner will go to the low fire position before
the operating limit control turns the burner off.
C)
After a differential pressure or temperature drop, the burner should re-start
automatically.
D)
With the unit running normally, open the blow down valve and remove water to the
point below the Low Water Cut Off setting. The burner should turn off and re-start
automatically when the proper water level is re-established. (If a manual reset type
Low Water Cut Off is used, it will have to be reset.)
27. Set and check operation of:
A)
Low and high gas pressure switches. See gas pressure switch manufacturer’s
instructions for detailed procedures.
1)
For initial start up:
Once the burner’s normal operational gas pressure has been set, adjust
the low and high gas pressure switches as follows:
(a)
Low gas pressure switch. With the burner running, slowly close
the main gas train manual shutoff cock and adjust the switch to
open its circuit when the pressure falls to a maximum of 50%
below its normal value. The burner will shut down. Open the
14
NOVA PLUS Installation & Operation Manual -
POWER FLAME INCORPORATED
DC4 DRAFT CONTROL
ENTER
ESC
®
manual gas shutoff cock to the full open position and manually
reset the Low Gas Pressure Switch. The burner will re-start.
(b)
High gas pressure switch. With the burner running, adjust the
switch to a point where the switch opens its circuit. The burner
will shut down. Manually reset the switch and re-adjust the cutout
point to be made at the normal operating pressure, but to open as
the pressure goes slightly above normal or to a maximum of 50%
above.
B)
All burner and heat exchanger controls and operating devices.
C)
Blower Combustion Air Flow Switch.
1)
Shut burner power off.
2)
Disconnect both wires at the air flow switch and temporarily clip them
together. Make sure that they cannot ground against anything, since they
will be powered with 110 volts during the test.
3)
Put a continuity meter across the common and normally open terminals
on the air switch.
4)
Close the gas train checking cock.
5)
Start the blower motor. The meter should read electrical continuity as
soon as the blower starts.
6)
Disconnect the wire which energizes coil of blower motor relay (starter),
or open the main power disconnect switch to the burner. Within 3 to 4
seconds after the blower motor is de-energized, the meter should indicate
an open air flow switch circuit (no continuity).
7)
If the switch does not open in 3 to 4 seconds, re-adjust accordingly. Turn
the air flow switch adjustment screw clockwise to shorten cut-off response
time and counter-clock-wise to lengthen cut-off response time.
8)
Turn the burner power off. Remove the shorting clip from the two
disconnected wires, cover them with electrical tape and let them hang loose
(they will be powered with 110 volts, so don’t let them ground out).
9)
Open the gas train checking cock. Turn the burner on. With the wires
disconnected, the burner should go into a purge cycle, although neither
the ignition nor the main fuel valve circuits will be energized. If they do
energize, there is a wiring problem. Correct as required.
10)
Turn power off. Reconnect the air flow switch wires to the air flow switch
terminals. Place burner back into normal operation.
28.
The Owner’s Operating Instructions,
page 23
of this manual, should be posted in a
clearly visible location close to the burner.
