1 HVAC SHEET METAL SHEET METAL THEORY

2 THE AIR DISTRIBUTION SYSTEM SHEET METAL IS USED FOR: – PLENUM’S (RETURN & SUPPLY) –TRUNK LINES –RETURN AIR GRILLS – SUPPLY AIR REGISTERS – AC COIL CASES. DUCT WORK DELIVERS THE CORECT QUANTITY OF CONDITIONED AIR THROUGHOUT THE STRUCTURE TO THE OCCUPIED SPACE. SHEET METAL IS USED FOR: – PLENUM’S (RETURN & SUPPLY) –TRUNK LINES –RETURN AIR GRILLS – SUPPLY AIR REGISTERS – AC COIL CASES. DUCT WORK DELIVERS THE CORECT QUANTITY OF CONDITIONED AIR THROUGHOUT THE STRUCTURE TO THE OCCUPIED SPACE.

3 TYPES OF DUCT SYSTEMS 1. PLENUM OR SPIDER SYSTEM

4 EXTENDED PLENUM

5 REDUCING EXTENDED PLENUM

6 PERIMETER LOOP SYSTEM

7 DUCT MATERIAL 1. GALVANIZED STEEL 2. GALVANIZED SPIRAL DUCT 3. ALUMINUM DUCT 4. FIBERGLASS DUCT BOARD 5. VINYL OR FOIL BACKED FLEXIBLE DUCT 1. GALVANIZED STEEL 2. GALVANIZED SPIRAL DUCT 3. ALUMINUM DUCT 4. FIBERGLASS DUCT BOARD 5. VINYL OR FOIL BACKED FLEXIBLE DUCT

8 DUCT SYSTEM FITTINGS FITTINGS ARE REQUIRED TO ALLOW THE BRANCH DUCTS TO CONNECT TO THE MAIN OR TRUNK AND SUPPLY DIFFUSERS. 1. TAKEOFFS 2. BOOT 3. ELBOWS 4. TEES 5. Y’s 6. TRANSITION FITTING 7. REDUCING DOLLARS 8. END CAPS 9. DAMPERS FITTINGS ARE REQUIRED TO ALLOW THE BRANCH DUCTS TO CONNECT TO THE MAIN OR TRUNK AND SUPPLY DIFFUSERS. 1. TAKEOFFS 2. BOOT 3. ELBOWS 4. TEES 5. Y’s 6. TRANSITION FITTING 7. REDUCING DOLLARS 8. END CAPS 9. DAMPERS

9 DIFFUSERS DIFFUSERS ARE USED TO BREAK UP THE AIR AND MIX THE AIR WITH THE ROOM AIR. DIFFUSER STYLES –CEILING MOUNT – WALL MOUNT –BASEBOARD MOUNT –FLOOR MOUNT DIFFUSERS ARE USED TO BREAK UP THE AIR AND MIX THE AIR WITH THE ROOM AIR. DIFFUSER STYLES –CEILING MOUNT – WALL MOUNT –BASEBOARD MOUNT –FLOOR MOUNT

10 RETURN AIR GRILLES THE PURPOSE OF RETURN AIR GRILLES IS TO ALLOW ROOM AIR TO BE PULLED FROM THE ROOM INTO THE RETURN AIR DUCT WHERE IT CAN BE CONDITIONED AND RECIRCULATED TO THE SPACE.

11 TYPES OF RETURN AIR GRILLES CEILING, WALL, AND FLOOR MOUNT SUSPENDED CEILING NEVER HAVE ADJUSTABLE LOUVERS MOST HAVE DAMPERS INSTALLED IN RETURN DUCT TYPES OF RETURN AIR GRILLES CEILING, WALL, AND FLOOR MOUNT SUSPENDED CEILING NEVER HAVE ADJUSTABLE LOUVERS MOST HAVE DAMPERS INSTALLED IN RETURN DUCT

12 CONNECTING METAL DUCT DRIVE CLEATS “S” LOCK METAL FINGERS DRIVE CLEATS “S” LOCK METAL FINGERS

13 SUPPORTING DUCT WORK GOOD PRACTICE IS TO SUPPORT THE DUCT EVERY 4’ FEET OF RUN WITH METAL HANGER STRAPS. SQUARE, RECTAGLE, AND ROUND DUCT SHOULD BE SUPPORTED INCLUDING ALL BRANCH LINES. GOOD PRACTICE IS TO SUPPORT THE DUCT EVERY 4’ FEET OF RUN WITH METAL HANGER STRAPS. SQUARE, RECTAGLE, AND ROUND DUCT SHOULD BE SUPPORTED INCLUDING ALL BRANCH LINES.

14 SYSTEM OPERATION DUCT PRESSURES AND VELOCITY –LOW DUCT PRESSURES –SYSTEM WILL RUN LESS EFFICIENT LONGER RUNNING TIMES –HIGH DUCT PRESSURES –SYSTEM WILL BE NOISY DUCT PRESSURES AND VELOCITY –LOW DUCT PRESSURES –SYSTEM WILL RUN LESS EFFICIENT LONGER RUNNING TIMES –HIGH DUCT PRESSURES –SYSTEM WILL BE NOISY

15 VELOCITY READ WITH A VELOMETER –MEASURED IN FEET PER MINUTE –Commonly accepted duct velocities can be found in the table below. READ WITH A VELOMETER –MEASURED IN FEET PER MINUTE –Commonly accepted duct velocities can be found in the table below. ServicePublic Areas Ft/min Industrial Areas Ft/min. Air intakes from outside ft/min ft/min Main Supply duct Branch supply duct Supply registers and grilles Low level supply registers Main extract ducts Branch extract ducts

16 AIR FLOW AND BALANCING VELOCITY IS LOST DUE TO FRICTION –FRICTION SLOWS DOWN AIR FLOW LOST THROUGH ELBOWS AND FITTINGS –USE OF TURNING VANES CAN REDUCE FRICTION VELOCITY IS LOST DUE TO FRICTION –FRICTION SLOWS DOWN AIR FLOW LOST THROUGH ELBOWS AND FITTINGS –USE OF TURNING VANES CAN REDUCE FRICTION

17 SYSTEM MUST BE BALANCED BALANCING SYSTEM INSURES PROPER AIR FLOW TO ALL ROOMS DAMPERS MUST BE INSTALLEDAT BEGINNING OF EACH BRANCH DUCT CHECK FOR BALANCED AIR FLOW ADJUST DAMPERS AS NEEDED BALANCING SYSTEM INSURES PROPER AIR FLOW TO ALL ROOMS DAMPERS MUST BE INSTALLEDAT BEGINNING OF EACH BRANCH DUCT CHECK FOR BALANCED AIR FLOW ADJUST DAMPERS AS NEEDED

18 UNDERSTANDING DUCT CLEANING DIRTY DUCTS LEAD TO: –ALLERGIES –ILLNESS –HUMIDIFICATION PROBLEMS –Eye irritation –Sinus Congestion –Headache –Scratchy Throat –Fatigue –Tightness in chest –Wheezing and hypersensitivity –Cough DIRTY DUCTS LEAD TO: –ALLERGIES –ILLNESS –HUMIDIFICATION PROBLEMS –Eye irritation –Sinus Congestion –Headache –Scratchy Throat –Fatigue –Tightness in chest –Wheezing and hypersensitivity –Cough

19 DUCT CLEANING STARTS WITH PROPER INSTALLATION PRECAUTIONS –PROPER DESIGN – PROPER ACCESS DUCT CLEANING STARTS WITH PROPER INSTALLATION PRECAUTIONS –PROPER DESIGN – PROPER ACCESS