OFTEC Commissioning and Servicing 4 — Questions and Answers
Question 1: What is the purpose of checking the system water pressure during an oil boiler service?
- Low pressure indicates possible leaks or expansion vessel failure affecting boiler operation (Correct answer)
- Water pressure has no relevance to oil boilers
- High pressure indicates the boiler is efficient
- It is only checked during commissioning
Correct answer: Low pressure indicates possible leaks or expansion vessel failure affecting boiler operation
System pressure should typically be 1-1.5 bar when cold on a sealed system. Low pressure may indicate water leaks or a failed expansion vessel. High pressure could indicate a failed pressure relief valve or waterlogged expansion vessel.
Question 2: What controls should be checked for correct operation during an oil boiler service?
- Room thermostat, programmer/timer, cylinder thermostat, TRVs, and boiler thermostat (Correct answer)
- Only the on/off switch
- Only the room thermostat
- Controls are not checked during a service
Correct answer: Room thermostat, programmer/timer, cylinder thermostat, TRVs, and boiler thermostat
All heating controls must be verified: room thermostat operation and setting, programmer/timer functions, cylinder thermostat (if applicable), thermostatic radiator valves, boiler thermostat, and any zone valves. Faulty controls waste energy and reduce comfort.
Question 3: What is the significance of the CO alarm in a property with an oil-fired appliance?
- It provides an additional layer of safety by detecting CO leaks that visual inspection might miss (Correct answer)
- CO alarms are not needed for oil appliances
- CO alarms only work with gas appliances
- They are decorative only
Correct answer: It provides an additional layer of safety by detecting CO leaks that visual inspection might miss
While not a substitute for proper maintenance, a CO alarm provides vital early warning of carbon monoxide leaks from any fuel-burning appliance including oil boilers. Building Regulations now require CO alarms in rooms with combustion appliances.
Question 4: What should a technician check regarding the boiler's expansion vessel during a service?
- The pre-charge pressure and whether the diaphragm is intact by checking the Schrader valve (Correct answer)
- Only that it is still physically attached to the boiler
- Expansion vessels never need checking
- Only the colour of the vessel
Correct answer: The pre-charge pressure and whether the diaphragm is intact by checking the Schrader valve
The expansion vessel pre-charge pressure should be checked using a tyre pressure gauge on the Schrader valve (typically 0.75-1.5 bar). If water comes from the Schrader valve, the diaphragm has failed and the vessel needs replacing.
Question 5: Why is it important to run the boiler through a complete heating cycle during commissioning?
- To verify all components function correctly together, including controls, safety devices, and circulation (Correct answer)
- It is not important — a short test is sufficient
- Only to warm up the house
- To use up old oil in the tank
Correct answer: To verify all components function correctly together, including controls, safety devices, and circulation
A full heating cycle tests the entire system: burner operation, heat distribution, thermostat response, zone valve operation, pump circulation, cylinder heating (if applicable), and safety device activation. Problems only reveal themselves under real operating conditions.
Question 6: What is the importance of checking the flue condensate drain on a condensing oil boiler?
- A blocked drain causes acidic condensate to back up, potentially corroding the heat exchanger (Correct answer)
- Condensing boilers do not produce condensate
- The drain only needs checking every 5 years
- Condensate is harmless and can be ignored
Correct answer: A blocked drain causes acidic condensate to back up, potentially corroding the heat exchanger
Condensing oil boilers produce acidic condensate that must drain freely. A blocked condensate drain causes the condensate to back up into the boiler, corroding the heat exchanger and potentially causing the boiler to lock out or fail.
OFTEC Commissioning and Servicing 4
What is the purpose of checking the system water pressure during an oil boiler service?