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

2. Section 2.1 Duct System Repair and Installation: Planning Repairs

3. 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;

4. 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.

5. Safety

6. Repairing Faulty Duct Systems

7. 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.

8. Repairing Faulty Duct Systems

9. 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.

10. 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.

11. 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.

12. 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.

13. Plan the Repair Job

14. Duct System Sketch

15. 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 .

16. Evaluate Structural Integrity and Fitness for Repair

17. 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

18. 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.