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NORA Oilheat Technicians Manual

the opening on the furnace and be at least 14" long or high. Trunks: These are usually rectangular ducts that connect to the plenums and are run out through central areas of the house. Branches: These are smaller ducts, either round or rectangular, which connect the trunk lines to the individual registers. It is a good idea to install locking dampers on each branch to allow for system balancing. Troubleshooting warm air systems Not enough heat When responding to a service call for “not enough heat” or certain rooms in the house “not heating,” first see if the burner, controls and blower are operating properly, then look to the distribution system. Some common problems to check are: Chapter 13 Heating Systems 13-6 Heating Systems 1. Is there adequate return air? As a general rule of thumb, there should be an equal amount of return coming back to the furnace as there is going out on the supply side. As a minimum, the return should never be less than 80% of the supply. (100% is better and with air conditioning 120%.) If the ducts appear to be adequate then check to see if any return grills are blocked by furniture or rugs. 2. Is the system balanced? Turn the system on and open any dampers. Check each register to see that the same amount of air comes out of each. If an imbalance is found, then the register should be checked to be sure it is open. The individual branches should then be checked to be sure that dampers are properly adjusted. Figure 13-6: Warm air distribution system


NORA Oilheat Technicians Manual
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