All installations and services must be performed by qualified service personnel.
Figure 10: Typical Observation of Main Burner Flames
If long, rather poorly defined, mostly yellow in color, and nearly opaque burner flames are observed, this is an indication the quality of combustion is poor. (Under adverse conditions, black smoke and some sooting may be noticeable as well.) Some of the causes of poor combustion are, too high an input rate (“over- firing”), too little or a contaminated supply of combustion air, or a partially blocked heat exchanger or vent terminal. Should any of these conditions occur, they must be corrected immediately. Call your qualified heating contractor for assistance.
D. Setting Supply Air Temperature Rise
All MHA1/MDA1models are designed and wired at the factory for a blower speed during heating that should result in an approximate temperature rise of 70°F. The temperature rise through the heating section, for any given blower speed may vary depending on a number of factors. A few of these factors are, changes in the actual resistance of the duct system to airflow at any time,
Temperature rise = supply air temperature - return air temperature.
After 15 to 20 minutes of continuous operation, the temperature rise through the furnace must fall within a range of 55° to 85° F. If the outlet or supply duct temperature is too high, check to make sure the return air filter is clean, the return air registers are free from obstruction, the outlet registers are properly adjusted and clear, and the supply and return air ducts are open.
The circulating air blower is not moving enough air if the supply air temperature is still too high. Before proceeding further, turn off the power supply to the appliance and remove the blower access door. The speed of the blower must be increased by changing the speed tap from the motor to the next higher tap, refer to Figure 8.
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