QMED Cheat Sheet 2026: One-Page Review of Must-Know Facts

What This Cheat Sheet Covers (and What It Doesn't)

This page is a compressed review of the National QMED: Electrician/Refrigerating Engineer endorsement, formally the QMED02 rating. It is built directly from the topic lists the U.S. Coast Guard National Maritime Center publishes for the Q802 Electrician and Q803 Refrigerating Engineer examinations. If you want the full narrative walk-through, our QMED Study Guide 2026: How to Pass on Your First Attempt goes deeper. Use this sheet as the page you print, tape inside a locker, and re-read the night before sitting down to test.

One identity note up front, because it trips people up: this is not the Junior Engineer, Oiler, Boiler Technician-Watertender, or Machinist-Pump Technician rating. Those are separate QMED endorsements with their own exam topic lists. Material written for those ratings will not cover the electrical and refrigeration depth that Q802 and Q803 demand. If you are still sorting out the terminology, What Is QMED? and What Does QMED Stand For? give the background.

The Two Modules at a Glance

The published structure for this endorsement is simple: two examination modules, each with its own topic list. The Coast Guard does not publish percentage weights for these headings, so do not trust any source that claims a specific "Q802 is 60% of the exam" breakdown. Treat each module as a body of knowledge you must be able to work through in full.

For a structural breakdown of how the two content areas fit together, see QMED Exam Domains 2026: Complete Guide to All 2 Content Areas.

Q802 Electrician: The Must-Know Facts

The Electrician module is where the endorsement earns its name. Expect the electrical block to be the heart of your review, with the general engine-room subjects layered around it.

Circuit Fundamentals: A/C and D/C

• D/C circuits: Be fluent in Ohm's law, series versus parallel resistance, and power relationships. Know how to read a simple schematic and predict what happens to current and voltage when one element changes.
• A/C circuits: Understand frequency, phase, reactance, impedance, and the idea of power factor. Know why inductive loads (motors, transformers) behave differently from resistive loads.
• Calculations: This is a named topic. Practice the arithmetic by hand until the relationships feel automatic, since you should not rely on memorizing answers.

Machines and Power: Generation, Distribution, Motors, Controllers

• Generation equipment: Shipboard generators, their basic operating principles, and the factors that govern output.
• Distribution systems: How power gets from the source to the load, including switchboards, protective devices, and the logic of circuit protection.
• Motors: Types, characteristics, starting behavior, and common failure modes.
• Motor controllers: Starters, contactors, overload protection, and control circuit logic. Be able to trace a basic control circuit and explain what each component does.

Batteries, Electronics, Communications

• Batteries: Types, charging, maintenance, hazards, and safe handling.
• Electronic principles: The basics of semiconductors and electronic components as they appear in marine control and monitoring gear.
• Communication devices: Shipboard communication equipment and its electrical basis.

Measuring and Troubleshooting

Two named topics reward practical judgment: measuring devices (what each instrument reads, how to connect it, and what a reading means) and troubleshooting (isolating a fault methodically). Questions in this area tend to describe a symptom and ask for the most likely cause or the safest next step, so think like a person standing at the equipment.

Q803 Refrigerating Engineer: The Must-Know Facts

The Refrigerating Engineer module shifts the emphasis from electrons to heat. You still need electrical competence (motors, controllers, and troubleshooting are on this list too), but the signature content is thermodynamic and mechanical.

Refrigeration Principles and Systems

• Understand the basic refrigeration cycle: compression, condensation, expansion, and evaporation, and what each component does in that loop.
• Know how heat moves, why refrigerant changes state, and how pressure and temperature relate during those changes.
• Be ready to reason about system behavior: what a low-side or high-side pressure change tells you about the system's condition.

Air Conditioning and Heating/Ventilation

Both appear as named shipboard systems in the Q803 list. Review how conditioned air is produced and distributed, how heating and ventilation are controlled, and how these systems relate to the underlying refrigeration plant.

Heat Exchangers, Hydraulics, Pipes, Fittings, and Valves

• Heat exchangers: Purpose, construction types, and what degrades performance.
• Hydraulic principles: Pressure, force, fluid behavior, and basic hydraulic circuits.
• Pipes, fittings, and valves: Identification, function, and proper use. Know which valve type suits which job.
• Lubrication principles: Why lubrication matters in compressors and rotating equipment, and what goes wrong without it.

Shared Topics Both Modules Test

A large share of the published topic lists overlaps between Q802 and Q803. That overlap is good news: one solid pass through the shared material pays off twice. The common "general subjects" block includes:

• Auxiliary machinery
• Basic safety procedures
• Bearings
• Care of equipment and machine parts
• Drawings and tables
• Instrumentation principles
• Maintenance procedures
• Measuring instruments
• Pollution prevention
• Pumps, fans, and blowers
• Remote control equipment
• Use of hand/power tools

Note that a few items are module-specific. Deck machinery appears on the Q802 list, while heat exchangers, hydraulic principles, lubrication principles, and pipes, fittings, and valves appear on the Q803 list. Also notice that both modules include the electrical heading's motors, motor controllers, troubleshooting, and safety topics.

Safety and Environmental Protection Block

Both modules carry an identical safety and environmental protection group. Do not skip it because it feels less technical; it is a reliable place to secure points.

• Communications and damage control
• Elementary first aid and emergency equipment
• Environmental awareness and pollution prevention
• Fire prevention, firefighting equipment, and firefighting principles
• General safety and hazardous materials

Anyone with prior sea service will have lived much of this material, but wording on a formal exam can differ from shipboard habit. Review the underlying principles rather than relying on "how we do it on my vessel."

Quick-Reference Comparison Table

Sequencing Your Review Around the Two Modules

Because the two modules overlap heavily, the order you study them matters more than the total hours. Here is a QMED-specific sequence that front-loads the shared material so it carries into both modules.

Electrical goes before refrigeration because motors, controllers, and troubleshooting are shared and the circuit logic transfers directly to compressor and fan control. If you already work in refrigeration, flip weeks 2 and 3 and spend the extra time on circuit calculations, which tend to be the harder gap for mechanically oriented candidates.

Common Traps for QMED Electrician/Refrigerating Engineer Candidates

• Studying the wrong QMED rating. Generic QMED or Oiler material will not cover A/C circuit theory or refrigeration cycles. Make sure everything you study maps to the Q802 and Q803 topic lists.
• Assuming percentage weights exist. The two headings are modules. Do not allocate time based on invented percentages.
• Neglecting the shared general subjects. Bearings, pumps, drawings, and instrumentation are easy to dismiss as "basic," yet they appear in both modules.
• Skipping hand calculations. Calculations is a named Q802 topic. Familiarity with formulas is not the same as being able to apply them.
• Treating safety as common sense. The safety block is large and formal. Know the principles as written, not just as practiced on your vessel.

For a realistic view of difficulty, read How Hard Is the QMED Exam? Complete Difficulty Guide 2026. To confirm whether you are eligible to sit the exam in the first place, check QMED Requirements 2026: Eligibility, Prerequisites & How to Qualify. For scoring thresholds, see QMED Passing Score 2026: Exactly What You Need to Pass, and for scheduling mechanics, QMED Exam Dates 2026: Testing Windows, Deadlines & Scheduling.

Frequently Asked Questions