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Key Facts: RSES CMS Controls Exam

100

Practice Questions

OpenExamPrep

80%

Passing Score

RSES

CM required

Prerequisite

RSES

MCQ

Exam Format

RSES

Controls

CMS Specialty

RSES

6 areas

Control Content Domains

OpenExamPrep

The RSES Certificate Member Specialist (CMS) — Controls exam is one of the Refrigeration Service Engineers Society's specialty certifications, available only to technicians who already hold the RSES Certificate Member (CM) credential. It is a multiple-choice exam requiring 80% to pass, focused specifically on HVACR controls: control circuits and ladder diagrams, thermostats and sensors, relays, contactors and sequencers, electronic and DDC/BAS controls, safety and limit controls, and sequence of operation and troubleshooting. RSES does not publicly post the exact question count or time limit for the Controls specialty exam, and CMS specialist exams are known to be rigorous. This free prep includes 100 research-based practice questions with explanations and an AI tutor.

Sample RSES CMS Controls Practice Questions

Try these sample questions to review concepts for the RSES CMS Controls exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1In an HVAC ladder (line) diagram, what do the two vertical lines on the left and right represent?
A.The neutral and ground conductors
B.The two power-supply rails (L1 and L2 or hot and neutral) of the control circuit
C.The high-voltage line and low-voltage line
D.The supply air and return air paths
Explanation: A ladder diagram is drawn with two vertical lines that represent the power source 'rails' (such as L1 and L2 or hot and neutral). Each horizontal 'rung' between them is a separate control circuit containing loads and switches.
2On a ladder diagram, loads (such as relay coils and motors) and switching contacts should be arranged so that the:
A.Loads are on the left rail and switches on the right rail
B.Switches/contacts are placed before the load and the load connects to the other rail
C.Load is always wired directly across both rails with no switch
D.Switches are placed only after the load
Explanation: Standard ladder-diagram convention places switching devices (contacts) on the line side and the load (coil, motor, relay) on the rung so that the load connects to the opposite rail. This places the load at a known potential and the controlling contacts upstream of it.
3A set of normally open (N.O.) contacts in a control circuit will:
A.Conduct when the controlling coil/device is de-energized and open when energized
B.Be open until the controlling coil/device is energized, then close to complete the circuit
C.Always remain closed regardless of coil state
D.Open and close at a fixed time delay only
Explanation: Normally open contacts are open in their resting (de-energized) state and close when the relay coil or controlling device is energized. They are shown open on the ladder diagram and complete the rung only when actuated.
4Most residential and light-commercial HVAC control circuits operate at what nominal voltage?
A.12 VAC
B.24 VAC
C.48 VAC
D.120 VAC
Explanation: Low-voltage HVAC control circuits operate at 24 VAC, produced by a step-down control transformer. 24 VAC is a NEC Class 2 voltage, which limits current and reduces shock and fire hazard for field-wired thermostat circuits.
5A control transformer with a 120 V primary and 24 V secondary rated at 40 VA can supply a maximum secondary current of approximately:
A.0.33 A
B.1.67 A
C.2.4 A
D.40 A
Explanation: Secondary current equals VA divided by secondary voltage: 40 VA / 24 V = 1.67 A. Knowing the VA rating prevents overloading the transformer when adding relays, contactors, or accessories on the 24 V circuit.
6When two control transformers are connected in parallel to increase available VA, you must ensure that they are:
A.Different voltages so they share load
B.Connected with matching secondary voltage and correct phasing (in phase)
C.Connected with one secondary reversed to cancel ripple
D.Wired with the primaries in series
Explanation: Paralleling control transformers requires identical secondary voltages and correct phasing so their secondaries are additive rather than opposing. Out-of-phase secondaries create a dead short across the windings and will fail the transformers.
7In HVAC thermostat terminal designations, what does the 'C' terminal provide?
A.The cooling call to the compressor
B.The 24 VAC common (return) connection from the transformer
C.The condenser fan signal
D.The changeover signal for a heat pump
Explanation: The 'C' terminal is the 24 VAC common, the return side of the transformer secondary. It completes the circuit and is required to continuously power electronic and smart thermostats. 'R' supplies the hot side of the 24 VAC.
8On a conventional cooling thermostat, which terminal carries the call for the compressor (cooling)?
A.W
B.Y
C.G
D.O
Explanation: The 'Y' terminal carries the cooling call and energizes the compressor contactor (and typically the outdoor fan). 'W' is heat, 'G' is the indoor fan, and 'O' is the reversing valve on a heat pump.
9The heat anticipator in a mechanical (bimetal) heating thermostat is best described as a:
A.Mercury bulb that tilts to make contact
B.Small resistor in series with the heat contacts that adds heat to shut off the burner early
C.Capacitor that delays the cooling call
D.Magnet that holds the contacts closed
Explanation: A heat anticipator is a small resistance heater wired in series with the heating (W) contacts. It warms the bimetal slightly, opening the contacts before the room actually reaches setpoint, which reduces overshoot and sets the cycle rate.
10If a heat anticipator is set with too low an amperage value (lower than the actual circuit current), the typical result is:
A.Longer burner cycles with greater temperature swing (overshoot)
B.Faster, shorter burner cycles and possible short cycling
C.No effect on cycling
D.The burner will fail to ignite
Explanation: A heat anticipator setting that is too low (under the actual current) adds too little anticipating heat, so the burner runs longer before the contacts open. This produces fewer, longer cycles and more temperature overshoot. Setting it too high causes short cycling.

About the RSES CMS Controls Exam

The RSES Certificate Member Specialist (CMS) — Controls exam is a multiple-choice specialty test for HVACR technicians who have already earned the RSES Certificate Member (CM) credential. It validates advanced knowledge of HVACR control circuits, ladder diagrams, thermostats and sensors, relays/contactors/sequencers, electronic and DDC/BAS controls, safety and limit controls, and sequence of operation. A score of 80% is required to pass.

Exam sponsor: Refrigeration Service Engineers Society (RSES). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Multiple-choice specialty exam (Controls) requiring 80% to pass; candidates must already hold RSES Certificate Member (CM) status. This practice bank is 100 selected-response items covering all six control content areas.

Time Limit

Proctored session (length not published)

Passing Score

80%

Exam / Certification Fees

RSES member specialty-exam fee (set by RSES); requires current CM membership

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

18%

Control Circuits & Ladder Diagrams

Ladder and wiring diagrams, power rails and rungs, N.O./N.C. contacts, series (AND) and parallel (OR) logic, control transformers and VA, holding contacts, and pilot-duty ratings

17%

Thermostats & Sensors

Thermostat terminals, heat anticipators and cycle rate, thermistors, RTDs, thermocouples, pressure transducers, humidistats, CO2 sensors, and control differentials

17%

Relays, Contactors & Sequencers

Electromechanical and solid-state relays, contactors and coil voltages, potential and current relays, electric-heat sequencers, time-delay relays, and troubleshooting

18%

Electronic, DDC & BAS Controls

Direct digital control, BACnet/Modbus and RS-485 networks, analog/binary I/O, PID and proportional control, VAV and economizer control, VFDs, ECM motors, and actuators

15%

Safety & Limit Controls

High-limit, rollout, draft-proving and pressure switches, freeze-stats, high/low-pressure cutouts, oil-safety and phase-monitor relays, flame-safeguard and lockout controls

15%

Sequence of Operation & Control Troubleshooting

Heating, cooling, heat-pump and defrost sequences, staging, pump-down, voltage-drop and hopscotch troubleshooting, ignition lockout diagnosis, and DDC commissioning

Preparing for the RSES CMS Controls Exam

What You Need to Know

  • Passing score: 80%
  • Assessment: Multiple-choice specialty exam (Controls) requiring 80% to pass; candidates must already hold RSES Certificate Member (CM) status. This practice bank is 100 selected-response items covering all six control content areas.
  • Time limit: Proctored session (length not published)
  • Exam / certification fees: RSES member specialty-exam fee (set by RSES); requires current CM membership Official sources

Using Our Practice Resources

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

RSES CMS Controls: Suggested Study Strategy

1Get fluent with ladder diagrams: practice tracing each rung, identifying N.O. vs N.C. contacts, and recognizing series (AND) and parallel (OR) safety strings
2Memorize thermostat terminals (R, C, Y, W, G, O/B) and how 24 VAC control circuits and control transformers (VA = volts x amps) are sized
3Know the relay family cold: potential relay (N.C., opens on start-winding voltage) vs current relay (N.O., closes on inrush), contactors, and electric-heat sequencers
4Study modern electronic and DDC/BAS controls: PID action, BACnet/Modbus on RS-485, analog vs binary I/O, VAV, economizer changeover (dry-bulb vs enthalpy), and VFD/ECM operation
5Practice systematic troubleshooting using voltage-drop and hopscotch methods: full voltage across an open device, near zero across a closed one
6Complete all 100 practice questions and review every miss with the AI tutor before sitting the exam

Frequently Asked Questions

What is the RSES CMS Controls exam and who can take it?

It is one of the Refrigeration Service Engineers Society's Certificate Member Specialist (CMS) specialty exams, focused on HVACR controls. You must already hold the RSES Certificate Member (CM) credential before sitting any CMS specialty exam, including Controls.

What score do I need to pass the RSES Controls specialty exam?

You need 80% to pass. CMS specialist exams are known to be rigorous, so balanced study across control circuits, sensors, relays, DDC/BAS controls, safeties, and sequence of operation is important.

How many questions are on the RSES CMS Controls exam?

RSES does not publicly post the exact question count or time limit for the Controls specialty exam; it is a multiple-choice exam requiring 80% to pass. For reference, the core CM exam is 150 questions. Confirm current details directly with RSES.

What topics does the RSES Controls exam cover?

It covers control circuits and ladder diagrams, thermostats and sensors, relays/contactors/sequencers, electronic and DDC/BAS controls, safety and limit controls, and sequence of operation and control troubleshooting.

Do I need to pass the RSES CM exam first?

Yes. The CMS specialty exams, including Controls, are only available to technicians who already hold RSES Certificate Member (CM) status. Earning the CM is the prerequisite step.

Is this free RSES Controls practice as good as paid prep?

Our 100 practice questions cover the same control content domains the specialty exam tests, with a teaching explanation for every answer plus free daily AI tutor interactions. All content is free forever and updated for 2026.