Part 4 Technician’s Guide & Workbook for Duct Diagnostics and Repair

Section 2.1 Duct System Repair and Installation: Planning Repairs

Safety Before any inspection is attempted, it is assumed that technicians are familiar with basic safety rules that need to be followed when working on heating systems. The following is a useful checklist: Guard against falls, cuts, and other personal injuries; Recognized the electrical hazard posed by knob and tube wiring Unless you are a trained electrical controls technician, do not open up or probe into any electrical devices, wires, or connections;

Safety Wear an approved mask if you go into an area with fiberglass or loose fill insulation; and Before you touch any un-insulated duct, hold your hand about an inch from the duct to check if it is hot. This is especially important in furnaces fueled with gas or oil, because what looks like a small duct might actually be the vent pipe, and it might actually be hot enough to burn your hand.

Safety

Repairing Faulty Duct Systems

Repairing Faulty Duct Systems Duct should be repaired using the same material types that are used to install new duct that is equivalent to the existing duct type.

Repairing Faulty Duct Systems

General Considerations Health and safety issues: These include introduction of unwanted gases, vapors, and particulates, into the duct system; interference with the operation of combustion appliances; and biological growth caused by poor humidity control.

General Considerations Thermal comfort problems: These include inadequate cooling capacity, poor control of humidity, air delivered at temperatures that are considered too-low (generally a concern with heat pumps), and individual rooms that are inadequately conditioned.

General Considerations Low distribution efficiency: Often duct systems are undersized and the HVAC equipment is oversized in older buildings. Thus, in some cases, the whole system may need to be replaced as sealing may actually harm the HVAC system’s operation where the duct is already undersized. When replacement is recommended, for most customers, comfort is the main consideration and a good payback is icing on the cake.

General Considerations “Double-dip” benefits of duct repair: In some cases, repairing the duct system may provide a double benefit. Fixing duct leakage can improve efficiency and eliminate health risks at the same time. In heat-pump systems, fixing the ducts may improve the heat pump’s efficiency as well as that of the duct system itself. If equipment needs replacing, fixing the ducts may enable the contractor to specify a smaller unit, saving the customer money that way in addition to the savings on energy.

Plan the Repair Job

Duct System Sketch

Plan the Repair Job 1. Sketch the duct work. 2. Evaluate the system’s condition. 3. Ducts sealing. 4. Duct insulation. 5. Room by room CFM calculations. 6. Combustion safety check .

Evaluate Structural Integrity and Fitness for Repair

Plan the Repair Job Evaluate Structural Integrity and Fitness For Repair Replacement of a section may be required when: Structural integrity is damaged. Building cavities used instead of sealed ducting. Replacement less costly than repair

Lessons Learned You should now be able to explain what types of tape and mastic is required. You should now be able to develop a repair plan based on a visual inspection and sketch. You should be able to explain why replacing duct may be the best solution. You should be able to list numerous things to look for during a duct inspection.