Do not use autogas to run appliances – it is dangerous and illegal. Australian gas appliances have been designed to run on 100% propane and not on autogas (a propane/butane mixture). The proportion of butane in autogas can range from 60% to virtually zero, but there is no way of determining what the ratio is. Under Australian regulations, it is only legal to use autogas in a tank that is used to propel a vehicle and it is not legal to fill gas cylinders with autogas.
On the rare occasions when there is very little butane in the autogas mixture, there may not be a noticeable difference in how appliances operate. However, in the common circumstance of a 50% propane/50% butane mix, appliances may not operate normally due to improper combustion of the gas.
Gas is stored in a cylinder in liquid form under pressure, and to use this gas it must vaporise and pass through a regulator before being piped to appliances. Propane and butane vaporise at different temperatures: propane will vaporise down to -42ºC but butane will vaporise only down to 0ºC or -1ºC.
Rather than worrying about what would happen if you were camped in extremely cold conditions, it is more reasonable to discuss what happens in more normal temperatures. Propane is the more volatile gas, and in this form it will always flow much more freely than butane. At 20ºC, the vapour pressure of butane is about one-third the pressure of propane so only a small amount of butane will flow with the propane. As you use gas from the cylinder, the proportion of butane being supplied to appliances will increase, making them even less efficient.
The injectors (or jets) in Australian stoves are designed to operate on propane and to release the appropriate amount of gas for combustion. If the gas contains a significant proportion of butane, the appliance is likely to operate poorly. Improper combustion is likely to produce excessive levels of carbon monoxide that can reach dangerous levels in an enclosed space.
A stove burning butane-rich gas may produce lower levels of heat due to small flames at the burner, and the flames will be yellowish compared with the clear blue flames produced by propane. There is likely to be a black sooty residue.
When only butane remains in the cylinder it is likely that it will not vaporise easily, particularly in cold weather. You will be left with a cylinder that is part full of gas that you cannot use.
Legal implications of using autogas in appliances – It is not legal to either fill an LPG cylinder with autogas or to draw gas from a vehicle gas tank to run appliances. Either practice could have serious insurance implications. Any accident, death or injury that may occur as a result of using autogas in an illegal manner could invalidate an insurance policy.
Because autogas in its usual butane/propane mixture is not efficient in appliances, there is little cost saving unless you could guarantee it was 100% propane, and this is not possible. Additionally, you are faced with a health risk and legal and insurance implications. It is simply not worth the risk.
Autogas in vehicle engines - Autogas is piped in liquid form to a vehicle engine so the problem of vaporising at different pressures does not arise. Butane is used as a component of autogas because Australia has good supplies of butane as well as propane, and vehicle engines are designed to use a range of autogas mixes. Household appliances installed in Australian campervans and motorhomes are designed to use 100% propane.
Gas cylinders – Propane is stored in cylinders capable of withstanding the high pressure required to maintain propane in a liquid state, and it remains in liquid form only while under pressure. When released it expands into gas at a ratio of 270:1 and usually passes through a regulator to control the pressure supplied to appliances.
Gas cylinders are available with a variety of surface finishes, and this is indicated by a single numeral within a circle stamped into the shield at the top of the cylinder.
- #1 cylinders - galvanised steel. Considered the premium quality surface finish.
- #2 cylinders - steel with a polyester epoxy coating, usually powder coated. Very robust.
- #3 cylinders - steel treated with a zinc rich paint and finishing coats.
- #4 cylinders - steel painted conventionally using approved metal primer and finishing coats. A #4 cylinder should remain out of the weather.
- Fibre reinforced polymer cylinders are very corrosive resistant, but are several times the price of a steel cylinder. Popular with yacht owners.
For marine craft, clause 6.3.2.2 of the Australian Standard AS5601 requires that ‘the protective coating on a cylinder be suitable for the conditions of use. Cylinders bearing the coating identification mark ‘4’ are unlikely to have the corrosion resistance required for marine applications’. The Australian Standard does not specify any particular type for use in motorhomes or campervans, although cylinders of #2 quality are the most commonly used. Most exchange cylinders have a #4 surface finish, and are quite legal and safe to use in your motorhome. Do not believe anyone who tells you otherwise and tries to sell you a new cylinder.
Installing gas cylinders - Gas cylinders must be carried outside the accommodation area of the motorhome and should be housed in an enclosure (or fully open recess) within the framework of the vehicle (or on a caravan drawbar). The installation of LPG cylinders must comply with AS 5601.
Clause 6.2.3.2 of the Australian Standard requires a gas compartment to -
(a) Be designed to -
(i) house the cylinder(s) and associated equipment only;
(ii) allow the cylinder(s) to be positioned in the compartment without obstructing the drain; and
(iii) not have access from the inside of the caravan to a cylinder installed in a compartment.
(iv) permit easy removal of the cylinder(s) and the operation of the cylinder valve(s).
(b) Be constructed of material that is water and corrosion resistant.
(c) Be capable of securing the filled cylinder(s).
(d) Be sealed to prevent gas vapour from entering the caravan.
(e) The access door or opening shall be openable without the use of tools.
NOTE: A key is not regarded as a tool.
Clause 6.2.3.1 of the Australian Standard requires that the compartment must be identified with an approved durable red label with white lettering ‘LP Gas Storage’ and a ‘Flammable Gas 2’ logo. For full details refer to AS5601. Consumer instruction labels in accordance with clause 6.2.8.2 must be displayed near cylinders, and labels in accordance with clause 6.2.8.3 must be displayed near an appliance.
Cylinders are fitted with a safety relief valve designed to release gas should a high pressure build-up occur as a result of very high temperatures. If the cylinder is installed in the open, it should be shaded from the sun on hot days to prevent heat build-up.
Cylinders must be installed upright and securely fastened with the valve uppermost to ensure the inlet to the safety valve always remains in the vapour space clear of the liquid content of the cylinder.
Any work carried out on gas lines or equipment can only be done by a qualified gas fitter.
Gas hose alert – Recently there have been reports regarding loss of gas supply associated with the use of integral two-stage pressure regulators and hose connections, particularly where a flexible hose is installed between the cylinder and the regulator. Gas vapour can condense and strip plasticiser from the interior of the hose. This material can attack the rubber components, block supply and, in some cases, distort or rupture the diaphragm. If you have experienced gas supply problems, have a gas fitter check the hoses and regulator.
Gas regulator – A regulator controls and lowers the pressure at which gas flows from a cylinder to the appliances. Never attempt to use gas from a cylinder that is not fitted with a regulator unless that appliance is designed to use propane at high pressure, such as some small camping stoves and small camping lights. The fittings used on high pressure appliances are not compatible with fittings used on regulated pressure appliances.
For additional practical information relating to motorhomes and campervans as well as travelling in general, refer to 'The Ultimate Travelling Companion'.
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