Midco G69B - Manual (Page 8)

gas pressure. Air shutter adjustments will effect
manifold pressure and input. Clock the meter gas
rate and (if necessary) reset the main regulator to
control gas flow at about 10% over burner rating or
over desired input with Main Manual Shut-Off Valve
wide open. Turning the adjustment screw clockwise
on main regulator
increases pressure and flow
rate, reverse decreases. Do not adjust the regulator
past the point where no further change in gas flow is
noted. ÒCloseÓ off Butterfly Valve to the desired
maximum input rate, secure gland nut, and replace
cap. Reset the blower air shutter to provide fairly long
flame, blue at the burner face, orange or red at the
tips. Flashes of yellow may be visible. Close firing
door for a few seconds; then open and quickly
observe fire. If a purple haze is noted at the rear of the
firebox, lack of air is indicated and air shutter should
be opened wider.
Refer to Table 4 pg. 9 if the manifold pressure is to
be used as a guide to gas input.
12. Check the flue gas temperature at the boiler flue
outlet. It should be above 325 o but not exceeding
550 o . Excessive flue temperatures result in low
efficiencies. Low flue gas temperatures may cause
excessive condensation. Reset input if necessary to
adjust stack temperature; or if
temperature is too
low, portions of the heat exchanger surface can be
blocked off with insulating firebrick.
13. Make the final setting of the air shutter by checking
the flue gases with an "Orsat" or similar combustion
testing
instrument. There should be no carbon
monoxide and the carbon dioxide content should be
approximately 9.5% for NATURAL and 12.1% for
PROPANE, or within the limits prescribed by the local
fuel supplier.
14. Check the draft control to make sure there is no
spillage of flue products into the boiler room. This test
should be performed under the most severe possible
ventilating conditions. For example, perform this test
with all doors and windows tightly shut and any
ventilating fans in the building operating.
15. Start and stop the burner several times with the
controller and the limit controls to check their
operation.
16. Reset controller and limits controls to their desired
settings.
*Refer to Trouble Chart
After the initial start-up procedure the following steps can
be followed for routine start-up and shut-down on a
seasonal or extended basis.
BURNER START-UP
1. Make sure line switch is off.
2. Set controller to call for heat.
3. Open firing door
4. Open Main and Pilot Manual Valves.
5. Reset flame safeguard.
6. Turn on line switch.
7. Close firing door after main flame ignites.
8. Reset controller to desired setting.
BURNER SHUT DOWN
1. Turn off main line switch.
2. Close Main Manual Valve
3. Close pilot manual Valve
-8-
6. Turn on the line switch, and allow motor to run through
the pre-purge and ignition cycle. Check the blower
wheel for proper rotation. Viewing from the motor
shaft end (Blower Inlet side), rotation should be
counter clockwise. After a short run, the flame
safeguard will lock out, stopping the motor. Wait one
minute, then reset the flame safeguard.
7. Turn on pilot manual valve. With Main Manual
Shut-Off Valve still closed, turn on main line switch.
Motor will start. When pre-purge period has elapsed,
flame safeguard will energize pilot solenoid valve and
spark generator. When flamerod senses pilot
flame, the flame safeguard will energize the main
valves. No main flame will occur due to closed Main
Manual Shut-Off Valve. Quickly observe pilot flame . If
no flame, or if weak, screw in pilot regulator
adjustment. If the flame is rich and floating from the
pilot tip, back off the pilot regulator. Set to achieve the
largest stable blue flame with a base that burns firmly
within the pilot tip. The best operating pressure is
usually 3-1/2" to 4" W.C.. Test for ignition and stability
several times, cycling the burner with both open
and closed air shutter. Ignition and
relay response
will be prompt with a good flame. Check flame signal
with a AC micrometer. Pilot should be set
to yield
the highest steady reading, at least 2 microamps AC
and as high as 5 microamps.
8. Check operation of the electronic flame detection
circuit by turning off the pilot manual valve with pilot
burning and main manual shut-off valve still closed.
The circuit to the main automatic valve should be
broken when the pilot goes out.
*9. Turn off line switch to stop the burner. Reset flame
safeguard. Set blower air shutter about 1/4 open.
Loosen gland nut on Butterfly Valve and temporarily
lock air shutter wide open (slot in shaft parallel to
flow).
10. Turn on main line switch. After the main valve is
energized, slowly open main manual shut-off valve
until the main flame ignites. Then, opening the air
shutter as required to maintain a suitable flame, slowly
open the main manual shut-off valve to the wide open
position or until, with the air shutter wide open, the
main flame becomes excessively rich.
*11. The manifold pressures shown in tables 1 and 5
may be used to determine the approximate gas input
settings. The gas input for Natural gas models can be
determined by timing the gas meter. Accurately time
test dial for the number of seconds for one revolution
and use the following formula. All other gas utilization
equipment must be off.
3600 x test dial size x BTU value
no. of seconds for one rev. test dial
Then divide by 1,000 for MBH value.
Example 3600 x 1 x 1000
5
For Propane gas, consult your supplier for method of
determining firing rate.
CAUTION: The manifold pressures shown in
tables are both the blower air pressure and the
= BTU/Hr.
= 720,000 BTU/Hr. = 720 MBH