Electrical work near gas installations
Energy Safety has increasing concerns about electrical equipment (e.g. external heat pump units) being located too close to some gas installation equipment.
Typically the gas installation will include two 45 kg LPG cylinders supplying the installation (a “twin pack”) and it will be found that the external unit of a heat pump has been placed too close to the cylinders. Heat pumps have also been found installed too close to natural gas meters.
Electrical workers are reminded that there is a hazardous area classification around 45 kg LPG cylinders and there should be no electrical equipment installed in this area, unless it has the appropriate hazardous area protection.
The hazardous area classification from AS/NZS 60079.10.1 is shown above. This classification is repeated in both the gas installation code (AS/NZS5601.1) and is referred to in the LPG storage and handling code (AS/NZS1596).
The change over regulator connected to a twin pack may vent gas if it fails. AS/NZS 60079.10.1 states that a pressure relief discharge point will describe a cylindrical Zone 2 area of 1 metre diameter along the axis of discharge extending 1.5 metres in front of the point of discharge and 0.5 metres behind it.
Another area where electrical workers may encounter LPG in the home is where there is a 9 kg cylinder installed under the kitchen bench to supply a gas hob. The gas installation code requires such cupboards to be vented to the outside of the hous and to have no electrical equipment in it.
Natural gas meters
The New Zealand standard for gas distribution systems (NZS 5258) also specifies hazardous areas around gas meters (in Appendix J). For a natural gas meter with a venting regulator the interior of the enclosure is Zone 1 and an area of at least 0.8 m horizontally from the service riser (inlet pipe) centre line, and at least 1.5 m vertically from the finished ground level should be classified as Zone 2.
If the metering system has a regulator with an automatic shut-off the device the zoning of the enclosure remains the same but the external dimensions are reduced to 0.4 m and 0.8 m respectively. (There are also classifications for LPG gas meters).