4B is one of two papers required for a 4th Class Power Engineer's Certificate of Competency, alongside 4A. It is 100 multiple-choice questions, a 3-hour time limit, and you need 65% of the total marks to pass. Like 4A, it is sold and sat on its own, so you can study and write 4B without having already passed 4A, or come back for it later.
For the other paper, see the SOPEEC 4A exam guide to mechanics, thermodynamics, legislation and plant safety. For the certification path itself, see how to become a 4th Class power engineer, and for what the ticket is worth, 4th Class power engineering salary.
What the syllabus actually says is on 4B
4B covers 55 chapters, and unlike 4A it is almost entirely applied. It opens with rotating equipment (lubrication, bearings, pumps and compressors), moves into a long run of boiler fittings, safety controls, startup, operation and shutdown, then boiler maintenance and cleaning, then the water treatment chapters that sit under every wet system in the plant. From there it covers prime movers, building services, refrigeration, HVAC, and closes with two chapters on how these systems come together differently depending on the industry.
On section weighting: the syllabus states the format, the duration and the 65% pass mark, and nothing about how the 100 questions are divided across 55 chapters. Anyone quoting you an exact split for 4B is estimating, not citing a published figure. Study the breadth of the paper rather than someone's guess at where the marks concentrate.
Grouped into eight areas, the 55 chapters become manageable.
Lubrication, bearings, pumps and compressors
Six chapters of rotating equipment fundamentals: lubrication principles, types of bearings and lubrication, types of pumps, pump operation and maintenance, an introduction to compressors, and compressor operation and maintenance.
What trips people up here
Lubrication regime. Boundary lubrication and full hydrodynamic film lubrication protect a bearing surface by different mechanisms, and questions test which regime a given condition (startup, low speed, high load) puts you in.
Journal versus rolling element bearings. Different construction, different lubrication needs, different failure signs, and the syllabus separates bearing types from lubrication for exactly that reason.
Centrifugal versus positive displacement, in both pumps and compressors. A centrifugal pump can be throttled or even deadheaded briefly against a closed valve; a positive displacement pump cannot, and needs a relief path or it will burst piping or blow a seal. The same logic separates dynamic from positive displacement compressors. This distinction is tested directly and it is also assumed knowledge in later maintenance questions.
Boiler fittings, safety controls, startup, operation and shutdown
Eleven chapters, the backbone of the paper: pressure relief valves, combustion safety, water level safety controls, boiler fittings, firing rate controls, boiler plant startup, boiler startup, boiler operation, operational checks, shutdown procedures, and boiler plant monitoring and reporting.
What trips people up here
Safety control versus operating control. Water level safety controls (the low water fuel cutoff, for instance) exist to shut the boiler down; feedwater regulation exists to run it. The syllabus lists them as related but distinct chapters, and candidates who treat every water-level device as the same one lose marks on both.
Boiler plant startup versus boiler startup. These are two separate chapters for a reason: bringing the wider plant systems, feedwater, fuel supply, auxiliaries, online is a different sequence from the firing and warm-up sequence of the boiler itself, and exam questions distinguish plant-level readiness from boiler-level ignition.
Combustion safety and firing rate controls are not the same system. Combustion safety covers purge sequences, flame failure detection and ignition interlocks that prevent an unsafe firing condition. Firing rate control modulates how much fuel and air are delivered once firing is already safe. Questions rely on candidates conflating the two.
Emergency shutdown versus planned shutdown. Shutdown procedures cover both, and they are not interchangeable: what you do, and the order you do it in, changes when the shutdown is a response to a fault rather than a scheduled event.
Boiler maintenance and cleaning
Four chapters: energy plant maintenance I and II, boiler maintenance, and boiler cleaning.
What trips people up here
General plant maintenance versus boiler-specific maintenance. Preventive and corrective maintenance principles apply plant-wide; boiler maintenance is where those principles get applied to a specific, high-consequence piece of equipment, and the exam expects both levels.
Fireside versus waterside cleaning. Boiler cleaning covers both, and they address different deposits (soot and scale, respectively) with different methods. Naming the wrong side of the boiler for a given deposit is a common wrong answer.
Water treatment across boiler, condensate and cooling systems
Five chapters, and the section candidates most often study as one undifferentiated topic when the syllabus clearly does not: external boiler water treatment, internal boiler water treatment, condensate treatment, cooling tower and condenser water treatment, and recirculating system water treatment.
What trips people up in water treatment
External versus internal boiler treatment. External treatment (softening, deaeration and similar processes) happens to makeup water before it ever reaches the boiler. Internal treatment is chemical dosing inside the boiler itself, phosphates, sulfites, amines and similar, to manage what external treatment did not fully remove. Questions describe a chemical or a process and ask which side of the boiler wall it belongs on.
Condensate treatment is its own problem, not boiler water treatment repeated. Condensate corrosion is mostly a carbon dioxide and dissolved oxygen problem picked up in the steam and return lines, and the controls used there differ from what you'd dose into the boiler.
Cooling tower and recirculating water treatment share concerns that boiler water does not. Concentration cycles, scale control, and biological growth are cooling-water problems, and they get confused with boiler-side treatment simply because both involve chemical dosing. They are answering different questions about different water.
Prime movers: turbines, condensers and internal combustion engines
Five chapters: heat engines and prime movers as an overview, steam turbines, condensers and cooling towers, gas turbines, and internal combustion engines. Note that construction detail on turbines is 2nd Class 2B1 territory; 4B's treatment is operational, how these machines run and what they need to keep running, not their internal design.
What trips people up here
Open versus closed cycle gas turbines. A straightforward distinction that still costs marks when it hasn't been reviewed directly.
Two stroke versus four stroke IC engines. Questions ask which configuration suits a given application and why, not just how many strokes are in the cycle.
Condensers grouped with prime movers, not with water treatment. The syllabus places condensers and cooling towers next to steam turbines because the two are operationally linked. Studying condensers only in a water-treatment mindset misses the vacuum and heat-rejection half of the picture.
Building systems: lighting, water and drainage
Three chapters, easy to treat as filler and not tested that way: lighting systems, building water systems, and drainage systems.
What trips people up here
Sanitary versus storm drainage. Different systems, different code requirements, and the exam does not merge them just because both are "drainage."
Treating this block as non-core. It is three full chapters on the syllabus. Skipping it because it feels less like power engineering than boilers or turbines is exactly the assumption the paper is built to catch.
Refrigeration
Seven chapters: refrigeration basics, compression refrigeration systems, refrigeration system control and operation, refrigeration system operation and maintenance, absorption refrigeration systems, refrigeration plant safety, and ammonia refrigeration safety.
What trips people up in refrigeration
Compression versus absorption refrigeration are different cycles, not different brands of the same one. Compression refrigeration uses a mechanical compressor to raise refrigerant pressure. Absorption refrigeration replaces the compressor with a heat-driven absorber and generator pair. Questions ask which cycle is being described from its components, and swapping "compressor" language into an absorption question is a common distractor.
Ammonia refrigeration safety is named separately from general refrigeration plant safety for a reason. Ammonia is toxic at concentrations well below where most refrigerants become a problem, and it carries its own PPE, detection and leak-response requirements. Treating it as "just another refrigerant" is the most consequential mistake this section can expose.
HVAC and plant configurations
Fourteen chapters closing the paper: conditioning the air, humidification, fans for air distribution systems, ventilation and air filters, HVAC duct systems, types of coils and operation, steam heating, hot water heating, other heating systems, cooling systems and combination systems, heat gains and losses and heat recovery methods, HVAC control strategy, and finally common plant configurations in hydrocarbon-centric industries and in energy-intensive industries.
What trips people up here
Sensible versus latent load. Conditioning the air and humidification both deal with moisture and temperature together, and the exam tests whether you know which process is changing temperature, which is changing moisture content, and which does both.
Coil type versus the system it serves. A chilled water coil, a DX coil and a heating coil are named separately because they are plumbed and controlled differently, and questions ask which coil type fits which system.
Steam heating versus hot water heating. Distribution, control and the failure modes each system produces are different, and the syllabus treats them as separate chapters for that reason.
Plant configurations as the paper's own summary. These last two chapters exist because a hydrocarbon-centric plant and an energy-intensive industrial plant assemble the same boiler, refrigeration and HVAC building blocks differently. It is the syllabus asking you to see the whole plant, not just its parts, at the very end of the paper.
How to sequence your study for 4B
- Lubrication, pumps and compressors first. Short, mechanical, and it sets up vocabulary used throughout the rest of the paper.
- Boiler fittings, safety controls, startup, operation and shutdown as the core block, and give it the most time. Eleven chapters, and it is where the paper concentrates.
- Water treatment right after boiler operation, not separately. The distinctions between external, internal, condensate and cooling water treatment make more sense once you already know where each fits in the system you just studied.
- Prime movers, refrigeration and HVAC as three parallel tracks. They don't depend heavily on each other, so short daily sessions across all three beat finishing one before starting the next. Use active recall rather than re-reading.
- Plant configurations last, as a review. By the time you reach it you already know every system it references; treat it as confirmation that the pieces connect.
- Timed full papers once every area has had a first pass. 100 questions in 3 hours is a pacing problem as much as a knowledge one. See exam time management and what to expect on exam day.
For total time to budget, see how long it takes to prepare for a power engineering exam, and watch for the distractor patterns that repeat across every SOPEEC paper in the guide to SOPEEC multiple-choice traps.
How Full Steam Ahead covers 4B
4B's question bank on the platform runs to 1,693 questions, the deepest of any paper Full Steam Ahead teaches, ahead even of 4A's 1,566 and well beyond the 254 to 631 questions behind each 2nd Class paper. Fifty-five chapters of applied plant systems is a lot to test properly, and the size of the bank is built to match that, not to make 4th Class look like the lighter of the two certificates.
Each objective across all eight areas above has its own lesson, its own practice questions and a chapter quiz. When you miss a question, the lesson for that objective plays inside the results screen, and the AI tutor takes follow-up questions on the spot, which matters most on 4B's water treatment and refrigeration chapters, where the confusion is usually about which system a term belongs to rather than the term itself.
4B is $99 per paper per year, non-renewing, and sold separately from 4A, so you can study and sit one paper at a time. If you just want the source material, the power engineering textbook library on this site is free and ungated.