Meter installation, housings and positioning

Installing or exchanging a primary meter is meter work, arranged through the meter asset manager (see 4.1). But you'll work at meters every day: tightness testing, checking pressures, connecting new pipework. You need to recognise a correct meter installation, and know when one isn't safe.

This lesson follows BS 6400-1:2016, for low pressure supplies (75 mbar or less) and meters of up to 6 m³/h.

What's in a meter installation

A typical low pressure installation, in the order the gas flows:

1. The ECV, at the end of the service pipe (see 4.2).
2. A pliable connector: a short flexible connection from the ECV to the regulator. Its length can noticeably affect pressure loss.
3. The meter regulator, as close as practicable to the ECV outlet, and just upstream of the meter (see 4.4).
4. The meter, on a meter bracket.
5. The meter outlet, with a pressure test point in the outlet boss or liner. This is the test point you use for the operating pressure check.

The main protective bonding is connected to the installation pipework as near as practicable to where it enters the building, before any branch (see 7.2).

These parts can come as a meter installation kit made to IGEM/GM/PRS/41: a regulator, flexible connector, washers and fixings. The meter isn't part of the kit.

Across the whole meter installation, the pressure loss must be no more than 4 mbar at the meter's full rated flow. That leaves the pipework downstream its own 1 mbar (see 3.4).

Where a meter can go

A meter installation must be sited so that:

• the regulator and meter can be installed, serviced and exchanged, and the meter can be read and inspected easily
• it is not exposed to temperatures outside the meter's range, accidental damage, damp or corrosive air (unless it's in a semi-concealed box), or flooding
• it doesn't cause an obstruction or a danger to anyone, and isn't in an unventilated space
• it is far enough from electrical equipment (below)
• it isn't in contact with any wall, cement or a floor that might get wet.

Meters shouldn't be installed where food is normally stored. Coin-operated meters must be out of reach of unauthorised people.

The usual places are a purpose-made meter housing outside, a garage or outbuilding, inside the building, or a housing at the property boundary. Inside a building, the meter goes as near as practicable to where the service pipe enters.

For design purposes, a meter in a home, whether inside or in a meter housing, is treated as being in a Zone 2 hazardous area. The meter, and any electrical equipment in the meter housing, must be suitable for that zone.

Means of escape in a fire

GSIUR requires a meter to be sited so it doesn't make it harder to escape from the building in a fire (reg. 12(1)). Before installing a meter, check the escape route.

Meter housings

Most meters outside are in a meter box. BS 6400-1 lists five types of housing:

• semi-concealed boxes, partly below ground
• surface-mounted boxes, fixed to the outside of a wall
• built-in boxes, set into the wall
• universal boxes, which fit to the wall
• purpose-built housings for low pressure meters.

The gas transporter approves the type of housing and agrees its location. New boxes are made to BS 8499, and are marked with a "G". A space of about 550 × 550 × 300 mm holds a typical 6 m³/h meter. Only meters the manufacturer says are suitable can go in a semi-concealed box (see 4.3 for how to spot one from the serial number).

Also for meter boxes:

• If the box or compound locks, the consumer must have a labelled key (GSIUR reg. 13(3)–(4)).
• Nobody may knowingly store combustible materials in a meter box or compound (reg. 13(2)). HSE gives household waste such as paper and cardboard as an example.
• A purpose-built housing must be gas-tight to the wall and building, protect against weather and vandalism, and resist the spread of flame. It needs permanent ventilation of at least 2% of its plan area above ground (half high, half low), or 6% at high level where it's partly below ground.

Fitting the meter

When a meter is installed or exchanged, BS 6400-1 expects the installer to:

• assess the site first: confirm there's no smell of gas, check for signs of gas theft, and check exposed metalwork for stray voltage with a non-contact voltage detector
• check for signs of tampering with the meter, seals or service pipe. Report tampering to the supplier's theft team, and any smell of gas to the National Gas Emergency Service
• confirm the supply is low pressure (75 mbar or less)
• keep diaphragm meters upright at all times, and their connections capped until fitted
• fit a temporary continuity bond before disconnecting anything (see 7.3). It must not bridge an insulation joint upstream of the ECV
• support the meter so there's little strain on its connections. Inside, it's on a bracket, inlet on the left and index facing away from the bracket, upright and level. The bracket unions shouldn't come off without a tool
• fit the regulator so it doesn't touch the wall
• use only one pliable connector, not bent so tightly that its corrugations close up. Two are allowed only on a semi-concealed installation with a meter box outlet adaptor
• fit new meter washers whenever a meter union is undone.

GSIUR requires the meter and its fittings to be tightness tested and purged straight after installation (reg. 12(6)), see 6.3 and 6.6. A meter with soldered-on bosses must never have rigid pipe connections (reg. 12(5)).

Notices at the meter

• The emergency notice goes on or near every primary meter (GSIUR reg. 15(1)). It tells the consumer to shut off the gas, ring 0800 111 999 if gas keeps escaping, not to turn the gas back on until it's repaired, and gives the date it was first displayed.
• Where the ECV isn't next to the meter, a notice at the meter says where it is (reg. 15(2)).
• Where one service feeds more than one primary meter, each meter has a notice saying so. The gas transporter normally fits it (reg. 16(2)).
• Where there are secondary meters, there's a "SECONDARY METER" label and a line diagram (reg. 17).
• A meter housing carries a label from its maker, including its ventilation, hazardous zone and maximum operating pressure.

Several meters in one place

Where meters for several homes are grouped together, for example in a block of flats, BS 6400-1 expects that:

• every meter is accessible at all times, in a lockable housing, with a labelled key for each occupier
• each meter or box is marked with the home it serves
• each home has an AECV near where the gas enters it.

Sources: BS 6400-1:2016 6.1, Figure 1zone, arrangement BS 6400-1:2016 6.2–6.8, Figure 6pressure loss, components BS 6400-1:2016 6.9, 7location, housings BS 6400-1:2016 8.1–8.3fitting BS 6400-1:2016 11notices IGEM/GM/PRS/41installation kits GSIUR 1998 regs 12, 13, 15–17meters, housings, notices HSE L56 paras 162–171escape routes, sleeving IGEM/G/11 Ed. 2 Table 1situations 2.8–2.10 CCN1 Issue 16 §5, §9assessed

▸Tutor notes

• Use photos of real meter installations, good and bad. Ask learners to spot the problems: a meter touching a wet floor, a damaged built-in box, an unsealed sleeve, a meter under the only staircase in a three-storey house, a meter 100 mm from the consumer unit.
• Ask: why is only one pliable connector allowed, and why mustn't it be bent tightly?
• CCN1 §5 assesses disconnecting and reconnecting a meter with a temporary continuity bond, and the restrictions on making and sealing holes in meter boxes.
• Medium pressure supplies are outside this lesson. Note for learners that IGEM/G/11 treats a medium pressure meter inside a home, or pipework or a bonding cable leaving a medium pressure meter box through its rear spigot, as At Risk.