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4. Switch on the appliance power switch located on
the right side of the unit.
5. The appliance will enter the start sequence, as long
as the unit is being called for heat. The blower and
pump come on for pre-purge, then the ignitor warm-
up sequence starts and after the ignitor warm-up is
complete and all safety devices are verified, the gas
valves open. If ignition doesn’t occur, check that
there is proper gas supply. Wait 5 minutes and start
the unit again. During initial start up, air in the gas
line may cause the appliance to "lock out" during
the first few trials for ignition. If the ignition control
locks out, reset by cycling the power off and on
using the main power switch on the right side of the
cabinet.
6. When the unit is running, the supply gas pressure
must be checked. Inlet gas pressure must not exceed
10.5 in. w.c. (2.5 kPa) for Natural Gas and 13 in.
w.c. (3.2 kPa) for LP. The minimum inlet gas
pressure is 4 in. w.c. (1.2 kPa) for Natural Gas and
8 in. w.c. (2 kPa) for LP. See Table 12
7. Once the inlet gas pressure is verified, the outlet gas
pressure from each valve (manifold gas pressure)
must be checked, and adjusted, if necessary. The
manifold gas pressure must be 3.0 in. w.c. (0.62
kPa) for natural gas and 9.0 in. w.c. (2.2 kPa) for
LP. Also See Table 12
8. Set the air box pressure to 1" w.c. adjusting air
shutter on the blower as a starting point. Then adjust
the shutter to get the required CO
2
%. Closing the
shutter will increase CO
2
%.
Opening the shutter will lower the CO
2
%
9. Complete the setup by checking the CO
2
at the
outlet of the unit. The CO
2
should be 8% for natural
gas, or 9.2% for LP.
10. After placing the appliance in operation, the
Burner Safety Shutoff Device must be tested
. To
test:
(a) Close gas shutoff valve with burner operating.
(b) The flame will go out and blower will continue
to run for the post purge cycle. Three attempts to
light will follow. Ignition will not occur as the gas is
off. The ignition control will lockout, and will have
to be reset by cycling the power before the unit will
operate.
(c) Open gas shutoff valve. Restart the appliance.
The ignition sequence will start again and the
burner will start. The appliance will return to its
previous mode of operation.
11. Check all heat exchanger water connections, flange
and header gaskets for watertight integrity 24
hours after commissioning. If there are any signs
of water leakage, re-torque fasteners or re-seat
threaded connections as necessary to eliminate
leakage.
6.F.2 High Altitude Adjustment and Set-Up
High altitude adjustment must not be made on
appliances operating at elevations below 2500 ft. (762 m).
No orifice changes are required to adjust this
appliance for high altitude. High altitude adjustment is
accomplished by adjustment of the air shutter. A CO
2
or O
2
analyzer is required to make these adjustments.
Start the adjustment process by checking the CO
2
in the “as installed” condition. Adjust the air shutter(s)
so that the CO
2
is about 8% or the O
2
is about 6.8%
for appliances operating on natural gas. For appliances
operating on LP Gas adjust the air shutter(s) so that the
CO
2
is about 9.2% or the O
2
is about 6.8%.
If the appropriate CO
2
/ O
2
levels cannot be
achieved by adjusting the air shutter. Contact the
phone number shown on the back page.
The amount of derate will vary depending on
heating value of the fuel and the elevation at the
installation site.
Supply
MIN MAX
w.c.
kPa
w.c.
kPa
Manifold
w.c. kPa
Nat
4
1.0
10.5
2.5
3 0.
7
LP
8
2.0
13
3.2
9
2.2
Table 12. Gas Pressure in inches (w.c.)
LAARS Heating Systems