OFTEC Commissioning and Servicing 4

Question 1

What is the purpose of checking the system water pressure during an oil boiler service?

Accepted Answer

Low pressure indicates possible leaks or expansion vessel failure affecting boiler operation

Answer

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?

Accepted Answer

Room thermostat, programmer/timer, cylinder thermostat, TRVs, and boiler thermostat

Answer

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?

Accepted Answer

It provides an additional layer of safety by detecting CO leaks that visual inspection might miss

Answer

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?

Accepted Answer

The pre-charge pressure and whether the diaphragm is intact by checking the Schrader valve

Answer

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?

Accepted Answer

To verify all components function correctly together, including controls, safety devices, and circulation

Answer

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.

OFTEC Practice Test

OFTEC Practice Test

OFTEC Commissioning and Servicing 4