Gas Safe ACS - Accredited Certification Scheme Meters and Regulators Questions and Answers — Questions and Answers
Question 1: An engineer is installing a new U6 diaphragm meter in a purpose-built surface-mounted meter box on the external wall of a domestic property. According to BS 6400-1, what is the minimum required horizontal clearance between the meter box regulator vent and an opening window?
- 100 mm
- 300 mm (Correct answer)
- 500 mm
- 1000 mm
Correct answer: 300 mm
BS 6400-1:2016 specifies the installation standards for low-pressure gas meters. To prevent any vented gas from entering the property, a minimum horizontal clearance of 300 mm must be maintained between the regulator vent and any opening, such as a window or door.
Question 2: What is the primary function of an Over-Pressure Shut-Off (OPSO) device fitted within a domestic gas meter regulator assembly?
- To reduce the mains pressure to the required appliance operating pressure.
- To shut off the gas supply if the downstream pressure rises to an unsafe level. (Correct answer)
- To shut off the gas supply if the downstream pressure drops too low.
- To act as a secondary, finer filter for the gas supply.
Correct answer: To shut off the gas supply if the downstream pressure rises to an unsafe level.
The Over-Pressure Shut-Off (OPSO) is a critical safety device. Its sole purpose is to detect if the regulator fails and allows excessive pressure into the installation pipework. If the downstream pressure rises above a pre-set safe limit, the OPSO will activate (trip) and completely stop the flow of gas, protecting appliances and occupants.
Question 3: An engineer is assessing an existing gas meter installation in a domestic property and finds the Emergency Control Valve (ECV) is located in a kitchen cupboard, behind a fixed shelf stacked with tins and jars. According to the Gas Safety (Installation and Use) Regulations 1998, why is this positioning non-compliant?
- The ECV must be located within 2 metres of the property's main entrance.
- The ECV is not painted bright yellow for easy identification.
- The ECV is not in a readily accessible position for operation. (Correct answer)
- The ECV must be fitted inside a purpose-built, ventilated housing.
Correct answer: The ECV is not in a readily accessible position for operation.
Regulation 13 of GSIUR 1998 mandates that an emergency control must be provided and maintained in a readily accessible position. Placing it behind a fixed shelf and obstructing it with other items means it cannot be quickly and easily operated in an emergency, making the installation non-compliant.
Question 4: While checking the working pressure at a meter test point, you record a reading of 18.5 mbar with all appliances operating. The nominal working pressure for Natural Gas is 21 mbar. According to the Gas Industry Unsafe Situations Procedure (GIUSP), how should this situation be classified and managed?
- Immediately Dangerous (ID) - Disconnect the supply and report to the Gas Transporter.
- At Risk (AR) - Turn off the supply at the ECV, apply a warning notice, and advise the customer to contact the Gas Transporter. (Correct answer)
- Not to Current Standards (NCS) - Note the reading on the job sheet and advise the customer it is slightly low.
- Acceptable - The pressure is within a safe operating tolerance.
Correct answer: At Risk (AR) - Turn off the supply at the ECV, apply a warning notice, and advise the customer to contact the Gas Transporter.
Under GIUSP, a working pressure between 18.0 mbar and 18.9 mbar (i.e., less than 19 mbar) is classified as 'At Risk' (AR). The engineer must not leave the installation operating. The correct procedure is to turn off the gas at the Emergency Control Valve (ECV), attach a 'Danger Do Not Use' warning notice, explain the situation to the responsible person, and advise them to immediately contact the gas supplier or Gas Transporter, as the fault lies on the network side.
Question 5: Before an engineer begins to physically remove an existing gas meter for replacement, what is the most critical safety check that must be performed immediately after closing the Emergency Control Valve (ECV)?
- A full tightness test of the entire installation.
- A visual inspection of all downstream appliances for signs of corrosion.
- A check to ensure the ECV is not passing gas (let-by test). (Correct answer)
- A continuity test of the main equipotential bonding.
Correct answer: A check to ensure the ECV is not passing gas (let-by test).
Before breaking any gas seal downstream of a valve, it is a fundamental safety requirement to verify that the valve is holding tight and not allowing gas to pass. This is often called a 'let-by' test. If the ECV is passing gas, attempting to remove the meter would cause a significant and dangerous gas escape. This check must be completed before any union is loosened.
Question 6: Which of the following describes a key responsibility of a Gas Safe registered engineer when commissioning a new SMETS2 smart gas meter installation?
- Setting the customer's monthly budget on the In-Home Display (IHD).
- Configuring the customer's home Wi-Fi router to connect to the communications hub.
- Demonstrating the functionality of the In-Home Display (IHD) to the customer. (Correct answer)
- Providing the customer with a comparison of different energy tariffs.
Correct answer: Demonstrating the functionality of the In-Home Display (IHD) to the customer.
A crucial part of the smart meter installation process is customer handover. The engineer is responsible for commissioning the meter and associated equipment, including the In-Home Display (IHD). They must then explain and demonstrate to the customer how the IHD works, how to read it, and how it can be used to monitor their gas consumption. The engineer is not responsible for financial settings, the customer's IT equipment, or sales.
Gas Safe ACS - Accredited Certification Scheme Meters and Regulators Questions and Answers
An engineer is installing a new U6 diaphragm meter in a purpose-built surface-mounted meter box on the external wall of a domestic property.
According to BS 6400-1, what is the minimum required horizontal clearance between the meter box regulator vent and an opening window?