Gas cookers and hobs

Freestanding cookers

A freestanding gas cooker is normally connected with a bayonet fitting and an approved flexible connection. Three details matter and all three get missed:

• The hose must be the right one. An approved gas cooker hose of the correct length and rating, within its date, and orientated so the bayonet points downwards where the fitting requires it. A hose that is too short is pulled taut when the cooker is moved to clean behind it, which is exactly when connections fail.
• The stability device is not optional. A chain or bracket that prevents the cooker tipping forward when an oven door is opened and loaded. Without it, a cooker can tip – which is a burn risk in its own right and puts direct strain on the gas connection.
• The bayonet must be accessible. The whole point is that the appliance can be disconnected quickly and safely. A bayonet behind a fitted unit defeats it.

Wall clearances also matter. Cookers have specified minimum distances to adjacent surfaces and to anything above, and a cooker installed too close to a combustible surface or under an inadequately spaced extractor is a fire risk rather than a technicality.

Built-in hobs

A built-in hob is a rigid connection with an accessible isolation valve – normally in the adjacent cupboard, reachable without dismantling anything. It also needs:

• Correct worktop cut-out and clearances, including to any adjacent wall or upstand, and the specified gap beneath to any drawer or oven.
• The manufacturer’s own fixing and sealing. The seal between hob and worktop keeps spills out of the cabinet and is part of the installation, not a finishing touch.
• Compatibility with the oven below, if there is one. Not every hob and oven combination is permitted in the same cabinet, and the manufacturers specify it.
• Correct jet set for the gas type. LPG and natural gas need different injectors, and conversion kits exist for a reason. An appliance running on the wrong jets burns badly.

Ventilation, which applies to both

A gas hob consumes air and produces combustion products directly into the room – unlike a boiler, there is no flue. Kitchens therefore have ventilation requirements: an openable window, and mechanical extraction at a specified rate, with permanent ventilation required in some circumstances depending on the total appliance input.

The common failures are a blocked-up airbrick, an extractor that recirculates rather than ducts to outside, or a kitchen that has been sealed up as part of a refurbishment. All three are easy to create during a kitchen fit and none of them look like gas work.

LPG, which is common in rural Norfolk

Plenty of properties in this county are on bottled or bulk LPG rather than natural gas. It is not interchangeable: LPG runs at a different pressure and needs different injectors, so an appliance must either be supplied for LPG or correctly converted with the manufacturer’s kit.

LPG is also heavier than air, which changes where a leak accumulates – at low level, in cellars, ducts and voids, rather than dispersing upwards. That affects installation requirements and it affects where you site a detector. The regulator, the changeover valve and the hose on a bottled installation are all consumables with dates on them, and they are commonly found long out of date.

If you are moving an appliance between properties, check which gas it is set up for before assuming it will work.

What you should get

1. The appliance connected with the correct fitting, at the correct pressure for the gas type.
2. An accessible isolation valve.
3. A stability device on a freestanding cooker, actually fitted rather than left in the box.
4. A tightness test on the installation, carried out and recorded.
5. The appliance commissioned – burners lit, flame picture checked, flame supervision devices tested.
6. A record of the work, and notification where the work is notifiable.