Gas Safety Bulletin: Reducing Gas Rating Time to 1 Minute

Gas Safety Bulletin: Reducing Gas Rating Time to 1 Minute

Reducing Gas Rating Time

Gas Safe Register has released a new technical bulletin (TB 162) that advises on the rationale behind a change to the 2-minute gas rate (heat input) check for domestic installations with metric (ultrasonic and diaphragm) gas metres.

Traditionally, gas engineers have conducted gas rating checks over a 2-minute period. However, Gas Safe Register has now stated that this can be completed in just 1 minute, reducing the time and cost of the check for both engineers and customers.

The bulletin explains that the 2-minute gas rate was introduced in 1995 and has become the industry recognised procedure for carrying out a gas rate. However, it can be difficult to accurately carry out a 2 minute test with larger appliances installed with a smaller heat load requirement. As such, a trial was set up to test a 1 minute test duration.

Several trials by British Gas and Gas Safe Register were carried out using a 1 minute test time duration. The trials proved that the reduction in time did not negatively affect the accuracy of the test, and in many cases gave a heat input nearer that given by the manufacturer.

In addition to saving time and money, the 1-minute gas rate check also has environmental benefits. The bulletin estimates that the reduction in test time could save up to 3.5 million cubic metres of gas per year, which would reduce CO2 emissions by 6,000 tonnes.


How to conduct a 1-minute gas rate check


To conduct a 1-minute gas rate check, follow these steps:

  • Ensure all other appliances are turned off.
  • Set the appliance up for a gas rate (heat input) check as detailed in the manufacturer’s instructions.
  • Note the initial metre reading.
  • Operate the appliance for 1 minute, plus any additional seconds that it takes for the display to change after 1-minute.
  • After 1-minute, take the final metre reading.
  • Subtract the initial metre reading from the final metre reading. This is the amount of gas used.
  • To calculate the gas rate in kW, use the following formula:
  • Gas rate (kW) = 3600 x [m3] x 10.80 [CV (kW/m3)] / [time taken in seconds] + additional seconds for digit change

The CV (calorific value) used in this calculation is used as an example only. It may be acceptable to use a different number to this in the calculation.


The introduction of the 1-minute gas rate check is a positive development for both gas engineers and their customers. It is a quicker, more efficient, and more environmentally friendly way to conduct gas rating checks. Engineers who are not already doing so should switch to the 1-minute test at their earliest convenience.


Benefits of the 1-minute gas rate check

  • Quicker and more efficient for engineers and customers
  • More environmentally friendly
  • Saves time and money
  • Reduces CO2 emissions


How to switch to the 1-minute gas rate check

To switch to the 1-minute gas rate check, simply follow the steps outlined in the bulletin. Engineers should also ensure that they have the necessary equipment and training to conduct the test accurately.

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