Copper tube erected on the premises for a Nevada C-21 refrigerant circuit shall be which product?
Piping
Question · Easy
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Short
While brazing a copper ACR joint on a C-21 split-system line set, a dry nitrogen purge is used primarily to:
Field-erected refrigerant pipe joints on a C-21 system shall be:
Question · Medium
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Per UMC 2018 Chapter 11, a positive-displacement C-21 system containing more than 6.6 pounds of refrigerant shall have stop valves:
A field-erected C-21 refrigeration system shall be pressure-tested on:
Six feet: a hard-hat anthem
Copper and copper-alloy refrigerant piping shall not be used with which refrigerant?
Under the 2018 UMC, field joints in copper C-21 refrigerant piping may be made by:
Refrigerant suction lines are insulated primarily to prevent condensation and heat gain. Where must the vapor retarder be placed?
Insulation
Per 2018 UMC Table 313.3, horizontal copper or copper-alloy pipe 1-1/2 inches and smaller shall be supported at intervals not exceeding:
Hangers And Supports
What is the maximum horizontal support spacing for 1/2-inch steel fuel-gas pipe under NFPA 54 2012 / UMC 2018 Table 1310.3.5.1?
How should insulated refrigerant or chilled-water piping be supported at hangers so the specified thickness is not lost?
A rooftop condensing unit in a Nevada seismic-design category must be restrained. Which statement is correct?
Question · Hard
Sound and vibration from a C-21 compressor or air handler are controlled first by which combination?
Sound Vibration Seismic
One refrigeration ton is defined as a heat-removal rate of:
Heating And Cooling Principles
A gas furnace delivers 60,000 Btu/h output. The measured temperature rise is 50°F. Using CFM = Btu/h ÷ (1.08 × ΔT), the circulating airflow is closest to:
Which set of standard air-side load equations is correct?
A 5-ton comfort cooling coil is selected at the common 400 cfm per ton rule. What supply airflow should the C-21 designer start with before Manual N or manufacturer data refine it?
Evaporator superheat is which temperature difference?
Refrigerants And Refrigeration
A TXV comfort system has a suction pressure whose saturation temperature is 40°F. The suction-line temperature at the bulb is 52°F. Evaporator superheat is:
A condenser saturation temperature converted from liquid-line pressure is 110°F. The liquid-line temperature leaving the condenser is 95°F. Subcooling is:
Compared with an R-22 comfort system of the same capacity, an R-410A system typically operates at:
When a C-21 system is opened for repair, used refrigerant shall be:
A C-21 comfort unit with a thermostatic expansion valve is normally charged by:
Per UMC 2018 Chapter 11, the accepted medium for pressure-testing field-erected refrigerant piping is:
Under UMC 2018 Chapter 11, a signed certificate of field test shall be provided for refrigeration systems containing:
Conductive heat gain through a wall or roof is calculated as which product?
Load Calculations
A west wall is 40 feet long by 12 feet high. The assembly U-factor is 0.10 Btu/h·ft²·°F. Design indoor temperature is 75°F and outdoor design is 105°F. The conductive cooling load through that wall is:
Internal cooling load from occupants and lights is handled in a commercial (Manual N) calculation by:
Outdoor-air ventilation load on a cooling coil is primarily a function of:
A calculated total cooling load is 42,000 Btu/h. The nearest nominal equipment size, and the starting supply airflow at 400 cfm/ton, are:
The PSI C-21 study list includes ACCA Manual N. Manual N is used to:
A zone has 24,000 Btu/h sensible and 6,000 Btu/h latent cooling load. Total load and the sensible-heat ratio (SHR) are:
A duct traverse for testing, adjusting, and balancing is performed with which primary instrument pair?
Testing Adjusting Balancing
A 12-inch round duct has a measured average velocity pressure of 0.04 in. w.c. Using V = 4005 × √VP and area = π(D/2)², the airflow is closest to:
In a duct, total pressure equals:
After a Pitot traverse shows a branch is 20 percent high, the C-21 balancer should first:
Most residential and light-commercial C-21 thermostats switch the contactor and gas valve on which control voltage?
Controls
A high-pressure cutout on a C-21 condensing unit opens the control circuit when:
On a reversing-valve heat pump, heating mode is created by:
An anti-short-cycle (lockout) timer on a C-21 condensing unit is provided to:
A dry-bulb economizer on a packaged rooftop unit should modulate outdoor air toward 100 percent when:
A low-pressure or loss-of-charge switch on a comfort condensing unit typically opens when:
UMC 2018 1106.2.5.1 sizes machinery-room emergency exhaust for A1 and most other groups as Q = 100√G, with Q in cfm and G the refrigerant mass (lb) in the largest system. For a 400-pound R-410A charge, the required emergency airflow is:
Machine Room
In cooling mode a split-system air conditioner uses the indoor coil as the:
Ac And Heat Pump Equipment
An air-source heat pump initiates defrost primarily because:
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