ACS Appliance Installation 2 — Questions and Answers
Question 1: What is the maximum permissible length for a bayonet hose connector on a domestic gas cooker?
- No limit, as long as it is BS-approved
- 2 metres as specified by BS 669 and GSIUR 1998 (Correct answer)
- 5 metres
- 0.5 metres
Correct answer: 2 metres as specified by BS 669 and GSIUR 1998
BS 669 and GSIUR 1998 limit the length of a bayonet flexible hose for domestic gas cookers to 2 metres to minimise the risk of damage, leakage, and excessive pressure drop.
Question 2: When installing a gas fire in a pre-existing fireplace, what must the engineer check first?
- That the customer has planning permission for the installation
- The flue integrity, draw, and cross-sectional area to ensure it can safely remove products of combustion from the appliance (Correct answer)
- That the fireplace is made of stone or brick only
- That the room is greater than 30 m³ in volume
Correct answer: The flue integrity, draw, and cross-sectional area to ensure it can safely remove products of combustion from the appliance
Before installing any gas fire, the engineer must conduct a flue draw test (smoke test) and verify the flue is clear, adequately sized, and correctly terminates to ensure safe removal of combustion products.
Question 3: What does the 'gas rate' of an appliance measure?
- The cost per unit of gas consumed
- The volume of gas consumed per unit time, used to verify the appliance is operating within its design range and not overfiring or underfiring (Correct answer)
- The pressure of gas at the appliance inlet
- The thermal efficiency of the appliance
Correct answer: The volume of gas consumed per unit time, used to verify the appliance is operating within its design range and not overfiring or underfiring
Gas rate (cubic metres or cubic feet per hour) is measured using the meter and timing the gas consumed; it is compared to the manufacturer's data to confirm correct gas input and safe operation.
Question 4: Which type of gas valve controls the main burner gas flow and is required to close safely in the event of a fault?
- A cock valve
- A solenoid valve controlled by the appliance's safety circuit, which closes if a fault is detected (Correct answer)
- A manual isolation valve only
- A pressure governor
Correct answer: A solenoid valve controlled by the appliance's safety circuit, which closes if a fault is detected
Solenoid valves in the gas train are normally closed and require energisation to open; if the appliance detects a fault (no flame, overheat), the solenoid closes, stopping the gas supply safely.
Question 5: When must an engineer carry out a spillage test on an open-flued gas appliance?
- Only on new installations, not during servicing
- After installation, servicing, or any work that could affect flue performance, to confirm combustion products are being safely evacuated (Correct answer)
- Only when the customer complains of fumes
- Only on appliances older than 10 years
Correct answer: After installation, servicing, or any work that could affect flue performance, to confirm combustion products are being safely evacuated
A spillage test (using a smoke match or detector) is required after any work on an open-flued appliance to confirm the flue is drawing correctly and combustion products are not spilling into the room.
Question 6: What is the purpose of a thermocouple or flame supervision device (FSD) in a gas appliance?
- To control the room temperature
- To detect whether a flame is present and shut off the gas supply if the flame is extinguished, preventing unburned gas release (Correct answer)
- To regulate the gas pressure at the burner
- To activate the boiler pump
Correct answer: To detect whether a flame is present and shut off the gas supply if the flame is extinguished, preventing unburned gas release
The flame supervision device (thermocouple, ionisation probe, or UV sensor) confirms flame presence; if the flame goes out, it signals the gas valve to close within seconds, preventing a dangerous build-up of unburned gas.
ACS Appliance Installation 2
What is the maximum permissible length for a bayonet hose connector on a domestic gas cooker?