17
3.7 Final Checks and Adjustments
With the gas input pressure established, the flue
gas analysis can now be preformed. This is done
at the stack.
The following readings should be taken but not
limited to:
CO
2
% Net Stack Temperature
O
2
% Combustion
Efficiency
CO
%
If necessary, make adjustments on burner air
shutter.
DO NOT
change the fuel input rate.
The following list covers general combustion problems
and some of the possible cures. Conditions may vary
in the field. Refer to combustion chart for efficiency.
CAUTION: Check local codes for maximum
allowable percentages and amounts of emissions.
Low Carbon Dioxide (CO
2
)
•
Fuel input too low
•
Excess burner air
•
Wrong draft setting
Detectable Carbon Monoxide (CO)
•
Fuel input too high
•
Not enough burner air
•
Restricted
draft
•
Flame
impingement
Excessive Stack Temperature
•
Draft setting too high
•
Excess burner air
•
Fuel input too high
Low Oxygen (O
2
)
•
Oxygen reading must always be a
positive percentage
Cycle burner several times to ensure smooth light off
and proper operation. Visually observe the flame
pattern. There must be no flame impingement or hot
spots on the combustion chamber that could cause
scaling.
Check voltage and amperage on all motors.
Check all dampers, linkages, and locking quadrants
to make sure they are secure and operating
correctly.
Safety and Controls Checkout
Flame Safeguard –
Close the last manual gas
valve before burner. Operate unit in heat mode.
After pilot flame has been established, close
manual pilot gas valve (if applicable). The flame
safeguard must trip out within 15 seconds.
Gas Pressure Switches –
The low gas pressure
switch will trip out and must be reset before
resuming operation when the inlet gas shut off
valve is turned off, or inlet gas pressure is lower
than the trip point. The high gas pressure switch
can be checked by reducing the setting of its trip
point lower than the burner operating pressure.
The switch should trip out and shut off the burner.
Return the adjustment to its original setting and
reset to resume operation.
Temperature Controls -
The temperature
controls are checked by adjusting control to a
higher temperature to allow burner to cycle on.
Adjust control to a lower temperature to allow
burner to cycle off. Return the adjustment to its
original setting.
Air Pressure Switches –
The air pressure
switches can be checked by turning the adjusting
screw to call for a higher pressure than is normally
used on the system. Recycle is automatic when
the switch returned to its original setting. If the
burner or draft proving switches open, this could
cause the flame safeguard to go into lockout
mode.
Limit Controls -
The limit controls are checked
by adjusting control to a lower temperature setting
while the unit is operating on high fire and observe
cut-off. Return the adjustment to its original
setting. Manual reset may be required on some
controls.
Make sure all the safety and controls are
working properly.