Why there is a minimum size gas bottle for each situation.


We get asked a lot of the same questions over and over again, so its time we started a blog.

One I hear weekly is, why can't I use a 9kg gas bottle to run my heating and cooking?

Basically, gas bottles all have an evaporation rate. The rate in which the LPG (Liquid Petroleum Gas) gas turns from a liquid to a vapor. This is determined by a number of factors such as temperature, pressure etc. The most basic and easy to calculate factor is the surface area of the gas bottle, the bigger the surface area the higher the evaporation rate.

The lower the temperature the lower the evaporation rate. The more gas you draw off the bottle quickly the colder the bottle gets, the lower the evaporation rate.

At around 18deg and 30% full a standard 45kg bottle can produce around 180mj/h. A 9kg at the same temperature can produce around 70mj/h or enough to run 5 burners on your 6 burner bbq safely.

A standard Rinnai B26 continuous flow unit runs at around 200mj/h under maximum load. Or more than a single 45kg bottle can handle, and let's hope you're not running the stove, heater, bbq, and oven at the same time. But because you don't spend hours in the shower and the bottle gets quick short breaks you don't burn your house down.

So what happens if I ran that system off a 9kg bottle? The bottles would eventually run out of vapor and pump liquid down the lines. What happens next? The regulator might stick open and allow extra pressure down the line, the lines might block, the regulator might block and everything stops. Worst case scenario the liquid makes it to the water heater, the solenoid sticks open, you turn the tap off and the heater keeps running. No water running to cool the heater down, and it catches fire and the story goes on.

Gas is generally very safe, in sensible hands. Don't let your gasfitter tell you 9kg bottles are fine unless it's just for a stove, bbq or small space heater.

When you decide to make the switch to gas give us a call and we will run through your options. 9kg is not cheaper than 45kg bottles, do the ring around, find a good deal and look after your family.