NSW Gasfitting common mistakes
NSW Gasfitting · Understand the traps and how to avoid them.
When a flued appliance is installed in a room with an openable window or mechanical exhaust, the candidate checks only the room volume against the minimum and skips the ventilation opening calculation, or treats an openable window as a permanent ventilation opening.
Study notes often present room-volume tables in isolation, and candidates memorise the minimum room volume figure without learning that effective ventilation area, permanent openings, and the interaction with exhaust fans are assessed separately.
What to do instead
For every appliance, work through a fixed sequence: determine appliance type and flue category, find the minimum room volume, calculate required permanent ventilation area if the volume is insufficient, then check that any exhaust fan cannot depressurise the space below the appliance's allowance. Practise with three worked examples where the window is and is not counted.
The candidate calculates a gas pipe size from a rule-of-thumb table without first converting the appliance input to a gas rate at the actual delivered pressure and heating value, and without adding the pressure drop of each fitting and the meter outlet.
Pipe sizing tables in training material are indexed by MJ/h and equivalent length, and candidates skip the conversion step because it feels like arithmetic rather than gasfitting; they also forget that the allowable pressure drop is shared across the whole run.
What to do instead
Build a one-page sizing worksheet: convert each appliance's rated input to actual gas flow using the local heating value and specific gravity, sum loads downstream of each section, measure equivalent length including fittings, and subtract each section's drop from the total allowance until the last appliance. Redo it until the sequence is automatic.
During commissioning the candidate records the operating pressure at the meter or regulator outlet rather than at the appliance test point, and accepts a reading taken with other appliances running.
The test point location is easy to confuse with the regulator adjustment point, and candidates take the easiest accessible reading under time pressure, especially in exam scenarios describing a multi-appliance installation.
What to do instead
State explicitly in every answer where the gauge is connected and what is isolated: appliance test point, appliance operating, all other appliances off unless the standard requires otherwise. Practise writing the full test procedure in order, including the warm-up and the allowed tolerance.
The candidate describes a leak test as 'pressurise and watch the gauge' without specifying the test medium, test pressure, stabilisation period, duration, and acceptable drop for the pipe volume involved.
Leak testing is often learned on site by imitation, so the numeric criteria are fuzzy, and exam questions reward the specific values that on-site habit omits.
What to do instead
Memorise a leak-test template with blanks: medium (air or inert gas, never oxygen or gas), test pressure relative to operating pressure, stabilisation time, test duration, and permissible pressure drop, plus the requirement to isolate the meter and appliance. Write it out from memory weekly.
The candidate classifies an appliance as room-sealed or open-flued from its brand or appearance rather than from the flue and combustion air path, then applies the wrong clearance and ventilation rules.
Appliance categories are visually similar, and candidates rely on recognition memory from familiar models instead of tracing where combustion air enters and where products exit.
What to do instead
For every appliance in a practice question, draw the air-in and products-out path before answering, then state the category and the rule set that follows. Drill with mixed sets of appliance descriptions rather than photos, since the exam is text-based.
The candidate answers a compliance question with what is physically safe or common practice, ignoring the specific obligation to notify, obtain consent, or hold the correct licence class before work begins.
Experienced candidates reason from trade practice, and regulatory content is studied last and least, so the administrative preconditions are the first thing forgotten under exam pressure.
What to do instead
Create a compliance checklist covering who may perform which class of work, what must be notified before and after, what certification or notice must be given to the consumer, and record-keeping timeframes. Answer regulation questions by naming the obligation and who bears it, not by describing the safe outcome.
When a fault is described, the candidate jumps to replacing the most commonly failing component instead of following a structured diagnostic sequence that confirms the fault before any part is disturbed.
Real-world experience rewards pattern recognition, and candidates transfer that shortcut into exam answers that ask for the logical test sequence and the evidence that confirms the diagnosis.
What to do instead
Use a fixed diagnostic frame for every fault question: confirm the reported symptom, verify supply and pressure, check the safety devices in order, isolate to a section, then test the suspect component. Write the sequence and the confirming measurement, not just the part name.
The candidate treats carbon monoxide risk as a combustion-quality issue only, and omits spillage testing, flue integrity checks, and the effect of depressurisation when answering safety questions.
CO is taught alongside gas analysis, so candidates focus on the analyser reading and forget that a correctly burning appliance can still spill products into the room because of pressure or flue faults.
What to do instead
For every safety scenario, list four checks: combustion analysis, flue flow and spillage, ventilation and pressure interaction, and the presence and location of alarms. Answer with the test that proves the products are leaving the space, not only the reading that shows they are clean.
The candidate ignores consumer protection duties, giving an answer that covers technical compliance but not the requirement to provide clear information, a compliant contract or notice, and a pathway for complaints.
Consumer protection is treated as peripheral reading, and candidates do not connect it to everyday jobs such as quoting, variations, and explaining defects to a customer.
What to do instead
Prepare short scripts for three situations: quoting and disclosing costs, reporting an unsafe appliance and the action taken, and handling a complaint. For each, name the obligation, the document or notice involved, and the timeframe.
The candidate disposes of or handles refrigerant, LPG cylinders, combustion condensate, or asbestos-containing flue materials using general waste practice, and does not identify the environmental or hazardous-material obligation in the answer.
Environmental requirements are rarely practised on site, so candidates default to the nearest bin or drain and cannot recall the specific handling and documentation requirements.
What to do instead
Build a short table of materials encountered on gas jobs with the correct handling route, storage requirement, and record. Include LPG cylinder exchange and testing, condensate disposal, and the stop-work rule for suspected asbestos in flue or lagging.