26Q3B - Sheetmetal, Installation, Codes and EPA - D1 - EMM
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98 Terms
Recovery level for Type II systems over 200 lb of R-22 refrigerant (post-Nov 15, 1993)
0 psig.
Refrigerant cleaned for reuse without meeting ARI-700 standards
Recovered refrigerant.
Reason why reclaimed refrigerants are classified as hazardous materials
They may contain corrosive or carcinogenic chemicals.
Self-contained recovery device
Does not rely on the system from which the refrigerant is being recovered for its operation.
Special methods for recovering from Type III systems
Most of these systems utilize toxic chemicals.
Pressure change in a nonpressurized container after refrigerant addition
Increase in proportion to the amount of refrigerant added.
Connection for push-pull liquid recovery system
The liquid valve on the refrigerant recovery cylinder.
Recovery level for Type II systems over 200 lb of R-22 refrigerant (pre-Nov 15, 1993)
10 in Hg vacuum.
Importance of Title VI, Section 608 of the Clean Air Act for technicians
It regulates refrigerant emissions.
Legal framework regarding ozone-depleting refrigerants
Title VI of the Clean Air Act.
Condition of refrigerant removed and stored without processing
Recovered refrigerant.
Reason to recover liquid refrigerant first from chillers
To prevent the removal of refrigerant oil with the refrigerant.
Method for recovering into a receiver
Add the trunk duct length, branch duct length, and equivalent lengths of all fittings used from blower to register.
Normal operational refrigerant release example
Venting refrigerant to correct an overcharge.
Difference in recovery levels for Type III equipment
They require lower vacuums than for other types.
Sealing method for round sheet metal ductwork
Fastened with sheet metal screws and sealed with mastic.
Required spacing for supporting flex duct over long distances
Every 10 ft.
Common air leak point in sheet metal duct systems
At joints between ducts.
Standard 181 B covers
Methods of connecting and sealing flexible duct.
Joining method for rectangular sheet metal ducts
Flanges and bolts.
Sealing method for rectangular sheet metal ducts
Mastic.
Material used for commercial flexible duct that has spiral seams
Steel sheet metal duct.
Hanging material width requirement for flexible duct
At least 2 inches wide and spaced no further than every 5 ft.
Duct type that undergoes the most rigorous testing
Galvanized sheet metal duct.
Duct system maximum location for efficiency
Inside the insulation envelope.
Maximum installed length for a flexible air connector
10 ft.
Major disadvantage of metal duct compared to other materials
Requires more support hangars than other material.
Leakage rate for a system with 100 CFM leakage and 1,200 CFM design flow
100 CFM/1,200 CFM = 8% leakage rate.
Types of fittings available for sheet metal duct
Weld-on stubs, preformed stubs.
Maximum spacing for hangers on metal duct
5 ft.
Heating airflow divisor for a heating load of 28,000 BTUH and airflow of 800 CFM
35 BTU per CFM.
Basis for air distribution in duct systems
The heat load of the rooms.
Equivalent length of duct determination method
Add the trunk duct length to takeoff, branch duct length, and equivalent lengths of all fittings used from blower to register.
Total available static pressure calculation
0.1 in WC (sum of all losses).
Formula for available duct static
Available duct static = total available static - total fixed static losses.
Common methods for duct design
Static regain and equal friction.
Function of duct calculator
It shows how much air can travel through a particular duct size at a given static pressure.
Reason to limit air velocity in branch ducts
To minimize air noise.
Adjusted friction rate for duct with design rate of 0.1 in WC and equivalent length of 75 feet
0.10 × (75/100) = 0.075 in WC.
Common standards for duct design
The ASHRAE method and ACCA Manual D.
Data points needed for duct calculators to provide design values
Two points of data.
Duct systems designed to provide conditioned air that matches
The needs of the structure.
Typical equivalent length of runs in a residential house
10 ft or greater.
Distance air travels before slowing to terminal velocity in a register
Throw.
Recovery level for Type II systems over 200 lb of R-22 refrigerant (post-Nov 15, 1993)
0 psig.
Refrigerant cleaned for reuse without meeting ARI-700 standards
Recovered refrigerant.
Reason why reclaimed refrigerants are classified as hazardous materials
They may contain corrosive or carcinogenic chemicals.
Self-contained recovery device
Does not rely on the system from which the refrigerant is being recovered for its operation.
Special methods for recovering from Type III systems
Most of these systems utilize toxic chemicals.
Pressure change in a nonpressurized container after refrigerant addition
Increase in proportion to the amount of refrigerant added.
Connection for push-pull liquid recovery system
The liquid valve on the refrigerant recovery cylinder.
Recovery level for Type II systems over 200 lb of R-22 refrigerant (pre-Nov 15, 1993)
10 in Hg vacuum.
Importance of Title VI, Section 608 of the Clean Air Act for technicians
It regulates refrigerant emissions.
Legal framework regarding ozone-depleting refrigerants
Title VI of the Clean Air Act.
Condition of refrigerant removed and stored without processing
Recovered refrigerant.
Reason to recover liquid refrigerant first from chillers
To prevent the removal of refrigerant oil with the refrigerant.
Method for recovering into a receiver
Add the trunk duct length, branch duct length, and equivalent lengths of all fittings used from blower to register.
Normal operational refrigerant release example
Venting refrigerant to correct an overcharge.
Difference in recovery levels for Type III equipment
They require lower vacuums than for other types.
Sealing method for round sheet metal ductwork
Fastened with sheet metal screws and sealed with mastic.
Required spacing for supporting flex duct over long distances
Every 10 ft.
Common air leak point in sheet metal duct systems
At joints between ducts.
Standard 181 B covers
Methods of connecting and sealing flexible duct.
Joining method for rectangular sheet metal ducts
Flanges and bolts.
Sealing method for rectangular sheet metal ducts
Mastic.
Material used for commercial flexible duct that has spiral seams
Steel sheet metal duct.
Hanging material width requirement for flexible duct
At least 2 inches wide and spaced no further than every 5 ft.
Duct type that undergoes the most rigorous testing
Galvanized sheet metal duct.
Duct system maximum location for efficiency
Inside the insulation envelope.
Maximum installed length for a flexible air connector
10 ft.
Major disadvantage of metal duct compared to other materials
Requires more support hangars than other material.
Leakage rate for a system with 100 CFM leakage and 1,200 CFM design flow
100 CFM/1,200 CFM = 8% leakage rate.
Types of fittings available for sheet metal duct
Weld-on stubs, preformed stubs.
Maximum spacing for hangers on metal duct
5 ft.
Heating airflow divisor for a heating load of 28,000 BTUH and airflow of 800 CFM
35 BTU per CFM.
Basis for air distribution in duct systems
The heat load of the rooms.
Equivalent length of duct determination method
Add the trunk duct length to takeoff, branch duct length, and equivalent lengths of all fittings used from blower to register.
Total available static pressure calculation
0.1 in WC (sum of all losses).
Formula for available duct static
Available duct static = total available static - total fixed static losses.
Common methods for duct design
Static regain and equal friction.
Function of duct calculator
It shows how much air can travel through a particular duct size at a given static pressure.
Reason to limit air velocity in branch ducts
To minimize air noise.
Adjusted friction rate for duct with design rate of 0.1 in WC and equivalent length of 75 feet
0.10 × (75/100) = 0.075 in WC.
Common standards for duct design
The ASHRAE method and ACCA Manual D.
Data points needed for duct calculators to provide design values
Two points of data.
Duct systems designed to provide conditioned air that matches
The needs of the structure.
Typical equivalent length of runs in a residential house
10 ft or greater.
Distance air travels before slowing to terminal velocity in a register
Throw.
Recovery level for Type I systems over 200 lb of R-22 refrigerant (after Nov 15, 1993)
0 psig.
Refrigerant that has been partially cleaned and meets ARI-700 standards
Recycled refrigerant.
Reason why reclaimed refrigerants can be dangerous
They may contain unknown contaminants.
Type of recovery device that relies on external power sources
System-dependent recovery device.
Why is it essential to handle Type III systems with care?
They may contain unsafe refrigerants such as ammonia.
Effect on pressure in a pressurized container after refrigerant is added
Increases with the amount of refrigerant added.
Connection needed for vapor recovery system
The vapor valve on the refrigerant recovery cylinder.
Recovery level for Type I systems over 200 lb of R-22 refrigerant (before Nov 15, 1993)
10 in Hg vacuum.
Significance of Title VI, Section 608 for environmental protection
It establishes regulations to reduce ozone depletion.
Legal classification of ozone-depleting refrigerants
Controlled substances under the Clean Air Act.