Manual
8
Midco International Inc.
8471 38
IX - Determining the
Firing Rate
10. Turn the combination valve knob on. Turn the burner power on. Turn operating control to ON
or set thermostat above room temperature. After four seconds the blower motor will be start
to purge the combustion chamber. Main fl ame should come on after a 30 second pre-purge.
Whenever the burner fails to light during the 7-second ignition trial period, or if the fl ame
is lost during the burner run cycle and not re-established within 37 seconds, the Electronic
Burner Control will shut off the Combination Gas Valve and LOCK OUT. To RE-SET see
step 8 for restart. At the end of the purge cycle, typically 30 seconds, the combination valve
will be energized and a spark will be initiated at the same time. The trial for ignition will be
approximately seven seconds.
11. To make a preliminary setting of the burner input, determine the manifold gas pressure required
from Table 3 and adjust the Combination Valve Pressure Regulator accordingly, see Section
XIII, Combination Gas Valve.
WARNING: Repeated unsuccessful attempts to light will result in accumulated gases
in gas utilization equipment and chimney. To prevent these gases from reaching an
explosive level, periodically purge the gas and chimney.
12. If ignition failure occurs, the main power must be turned off to reset. If the burner fails again
refer to the trouble chart.
13. Readjust the combustion air shutter to provide a quiet, soft blue fl ame with well defi ned orange
and yellow tips for NATURAL gas or with well defi ned yellow tips for PROPANE.
14. Check the operation of the burner; start and stop it several times with the thermostat or
operating control.
15. With the burner running, check the operation of all limit and associated safety controls.
16. PERFORM THE FOLLOWING FINAL ADJUSTMENTS for combustion and fl ue gas
temperature. Take the fl ue gas samples and temperature immediately ahead of the draft control.
A. The fl ue gas temperature should be above 325°F but not exceeding 550°F. Excessive fl ue
gas temperatures will result in low effi ciencies. Low fl ue gas temperature may cause excessive
condensation. Reset gas input if necessary to adjust stack temperature.
B. Make the fi nal setting of the combustion air shutter by checking the fl ue gases with an
ORSAT or similar combustion testing instrument. The carbon monoxide content should conform
to local codes, or in their absence to the level specifi ed in the United States or Canadian
Standard referenced on the front cover of this manual; and the carbon dioxide content should
be approximately 9.5% for NATURAL and 12.1% for PROPANE, or within the limits prescribed
by local codes.
17. Check the draft control to make sure there is no spillage of fl ue products into the room.
Note: For subsequent normal starting and shut-off procedure, refer to CONSUMER
INSTRUCTIONS or to the lighting instruction plate mounted on the burner.
___________________________
To determine the fi ring rate for NATURAL gas accurately, use time test dial to determine the number
of seconds for one revolution and use the following formula.
3600 x test dial size x BTU value
No. of seconds for one rev. test dial.
= BTU/Hr
Then divide by 1,000 for MBH value:
Example:
3600 x 1 x 1000
20
= 180,000 BTU/Hr = 180 MBH
For PROPANE gas, consult your supplier for method of determining fi ring rate.
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VIII - Burner Set-Up/
Adjustment
Continued
Part 1 Installation