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100+ Free RSES CMS Commercial AC Practice Questions

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Key Facts: RSES CMS Commercial AC Exam

100

Exam Questions

RSES

80%

Passing Score

RSES

$35

Exam Fee

RSES

CM Required

Prerequisite

RSES

1 of 8

CMS Specialties

RSES

100

Free Practice Questions

OpenExamPrep

The RSES Commercial Air Conditioning Specialist exam is one of eight RSES Certificate Member Specialist (CMS) credentials and is open only to RSES Certificate Members (CM) in good standing. It is a proctored, 100-question multiple-choice written exam that requires a score of 80% or better to pass, and the exam fee is $35. Official categories include air conditioning principles, air distribution, fans, filters, cooling towers and condensers, refrigerants, instruments, controls, electrical, compressors, absorption machines, chilled water systems and reciprocating chillers, the pressure-temperature chart, service and troubleshooting, and the psychrometric chart. This free prep includes 100 research-based practice questions with explanations and an AI tutor.

Sample RSES CMS Commercial AC Practice Questions

Try these sample questions to test your RSES CMS Commercial AC exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1In commercial air conditioning, what is the standard rate of heat removal represented by one ton of refrigeration?
A.6,000 Btu/h
B.12,000 Btu/h
C.3.5 kW only
D.500 Btu/h
Explanation: One ton of refrigeration equals 12,000 Btu/h, derived from the 288,000 Btu absorbed when one ton (2,000 lb) of ice melts in 24 hours (288,000 / 24 = 12,000). Commercial AC equipment is rated in tons, so a 20-ton rooftop unit removes 240,000 Btu/h.
2Sensible cooling load in a commercial space refers to heat that:
A.Changes the moisture content of the air
B.Changes the dry-bulb temperature of the air without changing moisture
C.Is removed only by the cooling tower
D.Comes solely from the refrigeration compressor
Explanation: Sensible heat changes the dry-bulb temperature of air without changing its moisture content. Sources include solar gain, lights, equipment, and conduction through walls. Latent load, by contrast, involves moisture (people, infiltration, ventilation), and total load is the sum of both.
3The sensible heat ratio (SHR) of a cooling coil is defined as:
A.Latent load divided by total load
B.Sensible load divided by total (sensible plus latent) load
C.Total load divided by sensible load
D.Sensible load divided by latent load
Explanation: Sensible heat ratio equals sensible load divided by total load (sensible + latent). A typical comfort-cooling coil runs an SHR around 0.70-0.80, meaning most of the load is sensible. A lower SHR means more dehumidification is required.
4Using the standard sensible-heat equation Qs = 1.08 x CFM x deltaT, how much sensible cooling is supplied by 4,000 CFM of air with a 20 degF drop?
A.43,200 Btu/h
B.86,400 Btu/h
C.21,600 Btu/h
D.8,640 Btu/h
Explanation: Qs = 1.08 x 4,000 x 20 = 86,400 Btu/h. The constant 1.08 combines air density, specific heat, and 60 min/h for standard air. This equation is fundamental for sizing supply airflow to meet a sensible load.
5A common design supply-air temperature difference (delta-T off the coil) for a comfort cooling system is approximately:
A.5 to 8 degF
B.18 to 22 degF
C.40 to 45 degF
D.60 degF
Explanation: Comfort cooling systems are typically designed for an 18 to 22 degF drop between return and supply air, often cited as a nominal 20 degF. Larger drops risk cold-draft complaints; smaller drops require excessive airflow to meet the load.
6The rule of thumb of approximately 400 CFM per ton of cooling applies to:
A.Condenser water flow
B.Standard comfort-cooling supply airflow
C.Cooling tower makeup water
D.Outdoor ventilation only
Explanation: Standard comfort air conditioning is designed around roughly 400 CFM of supply air per ton (range about 350-450 CFM/ton). Lower airflow per ton increases dehumidification (lower SHR); higher airflow favors sensible cooling.
7Which factor is a LATENT cooling load rather than a sensible load in a commercial building?
A.Solar gain through windows
B.Heat from electric lighting
C.Moisture from occupants and ventilation air
D.Conduction through the roof
Explanation: Moisture introduced by occupants, infiltration, and outdoor ventilation air is latent load because it adds water vapor that the coil must condense. Solar gain, lighting, and roof conduction are sensible loads that only raise dry-bulb temperature.
8ASHRAE Standard 55 generally defines the summer comfort zone for occupants as approximately:
A.62-66 degF and 80% RH
B.73-79 degF with about 30-60% relative humidity
C.85-90 degF and 70% RH
D.55-60 degF and any humidity
Explanation: ASHRAE Standard 55 places the summer comfort zone near 73-79 degF operative temperature with relative humidity roughly between 30% and 60%. Maintaining humidity in this band prevents both clammy and overly dry conditions.
9On a packaged rooftop unit nameplate, an EER of 11.0 means the unit delivers:
A.11 Btu/h of cooling per watt of electrical input at rated conditions
B.11 tons of cooling
C.11% efficiency
D.11 kW of cooling per ton
Explanation: Energy Efficiency Ratio (EER) is cooling output in Btu/h divided by electrical input in watts at a single rated condition (95 degF outdoor). An EER of 11.0 means 11 Btu/h of cooling per watt; higher EER means more efficient operation.
10On the psychrometric chart, the curved line forming the upper-left boundary represents:
A.Constant dry-bulb temperature
B.100% relative humidity (saturation)
C.Constant enthalpy
D.Zero humidity ratio
Explanation: The curved upper-left boundary of the psychrometric chart is the saturation curve, representing 100% relative humidity. Air on this line is fully saturated; its dry-bulb, wet-bulb, and dew-point temperatures are all equal.

About the RSES CMS Commercial AC Exam

The RSES Commercial Air Conditioning Specialist exam is one of eight RSES Certificate Member Specialist (CMS) credentials. It is a 100-question multiple-choice written exam requiring 80% to pass, open only to RSES Certificate Members (CM) in good standing. It validates advanced knowledge of commercial AC systems, cooling loads, psychrometrics, chillers, cooling towers, controls, and troubleshooting.

Assessment

100 multiple-choice questions covering AC principles, psychrometrics, air distribution, fans, filters, cooling towers, condensers, refrigerants, compressors, controls, electrical, chillers, and absorption; 80% required to pass. This practice bank is 100 selected-response items.

Time Limit

Proctored written exam (no fixed published time limit)

Passing Score

80%

Exam Fee

$35 per CMS exam (Refrigeration Service Engineers Society (RSES))

RSES CMS Commercial AC Exam Content Outline

22%

AC Principles, Loads & Psychrometrics

Tons of refrigeration, sensible/latent load, sensible heat ratio, CFM per ton, comfort conditions, and reading the psychrometric chart (dew point, mixed air, apparatus dew point, bypass factor)

20%

Air Distribution, Fans & Filters

Equal-friction duct design, static/velocity/total pressure, Pitot traverses, VAV, diffuser throw, fan laws and fan types, brake horsepower, and MERV filtration

18%

Cooling Towers, Condensers & Refrigerants

Cooling-tower approach, range and blowdown, water/air-cooled condensers, GPM per ton, EPA 608, ASHRAE 34 safety groups, R-410A, and chiller refrigerants

20%

Compressors, Controls & Economizers

Reciprocating and scroll compressors, cylinder unloading, DDC/pneumatic controls, ladder diagrams, economizer and enthalpy free cooling, DCV, and freezestats

10%

Electrical & Instruments

Ohm's law, three-phase power, voltage imbalance, locked rotor amps, capacitors, contactors, VFDs, clamp ammeters, micron gauges, anemometers, and megohmmeters

10%

Chillers, Absorption & Troubleshooting

Chilled-water temperatures and flow, kW per ton, primary-secondary pumping, flooded coolers, lithium-bromide absorption, crystallization, evacuation, and superheat/subcooling

How to Pass the RSES CMS Commercial AC Exam

What You Need to Know

  • Passing score: 80%
  • Assessment: 100 multiple-choice questions covering AC principles, psychrometrics, air distribution, fans, filters, cooling towers, condensers, refrigerants, compressors, controls, electrical, chillers, and absorption; 80% required to pass. This practice bank is 100 selected-response items.
  • Time limit: Proctored written exam (no fixed published time limit)
  • Exam fee: $35 per CMS exam

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

RSES CMS Commercial AC Study Tips from Top Performers

1Get fluent with the psychrometric chart: locate dry-bulb, wet-bulb, dew point, humidity ratio, mixed-air points, and the apparatus dew point
2Memorize the core formulas: Qs = 1.08 x CFM x deltaT, Q = 500 x GPM x deltaT, 1 ton = 12,000 Btu/h, and the fan laws (CFM~RPM, SP~RPM squared, BHP~RPM cubed)
3Know the design rules of thumb: about 400 CFM/ton supply air, 3 GPM/ton condenser water, and 2.4 GPM/ton chilled water with a 10 degF range
4Understand cooling-tower approach (vs wet-bulb) and range, and why a rising condenser approach means fouled tubes
5Practice systematic troubleshooting with superheat and subcooling: link low suction and high superheat to a starved coil, and high head with high subcooling to overcharge or a dirty condenser
6Complete all 100 practice questions and review every miss with the AI tutor before sitting the exam

Frequently Asked Questions

How many questions are on the RSES Commercial Air Conditioning Specialist exam and what score do I need?

The RSES Commercial Air Conditioning Specialist (CMS) exam has 100 multiple-choice questions and requires a score of 80% or better to pass. It is a proctored written exam administered through RSES chapters, regional events, or the annual conference.

What does the CMS Commercial Air Conditioning exam cost?

The RSES CMS exam fee is $35 per test. You must already be an RSES Certificate Member (CM) in good standing, so current RSES membership dues are also required to be eligible.

Who is eligible to take the RSES CMS Commercial Air Conditioning exam?

Only RSES Certificate Members (CM) in good standing may sit a CMS specialty exam. You must first pass the core RSES CM examination before attempting the Commercial Air Conditioning Specialist exam or any of the other seven specialties.

What topics does the Commercial Air Conditioning Specialist exam cover?

Official RSES categories include air conditioning principles, air distribution, fans, filters, cooling towers and condensers, refrigerants, instruments, controls, electrical, compressors, absorption machines, chilled water systems and reciprocating chillers, the pressure-temperature chart, service and troubleshooting, and the psychrometric chart.

How is the RSES CMS Commercial AC exam different from the Commercial Refrigeration specialty?

The Commercial Air Conditioning specialty focuses on comfort cooling: cooling loads, psychrometrics, air distribution, chillers, cooling towers, and economizers. The Commercial Refrigeration specialty focuses on low-temperature systems, rack/parallel systems, defrost, and EPR/CPR valves instead.

Is this free RSES CMS Commercial AC practice as good as paid prep?

Our 100 practice questions span the official RSES Commercial Air Conditioning categories with a teaching explanation for every answer plus free daily AI tutor interactions. All content is free forever and updated for 2026.