Gas rating tells you how much gas an appliance is actually burning, so you can compare it against what the data plate says it should be. Mucka does the sums for you. You put in what you read off the meter and the clock, and it gives you the gas rate and the heat input.
You need the Gas Calculators skill installed. It sits alongside Gas & Oil Certs.
Where to find it
There are four ways in, and they all do the same sum.
- Calculators in the menu, under Trade, then pick Gas rate off the board. This is the one to use when you are fault finding and there is no certificate open.
- From a certificate. On any appliance with a heat input field, tap Work it out next to it. When you are done, one tap puts the figure straight onto the certificate.
- Ask Mucka. Type or say it: "gas rate this boiler, meter went from two three oh point six six to two three oh point seven six over two minutes fourteen".
- With no signal. Open the offline screen and tap Calcs, next to New certificate. Meters live in cellars, so this one matters.
Doing the test
Get the appliance running at maximum output and leave it about ten minutes. Turn every other gas appliance in the property off, or you will be measuring those too.
On a metric meter (a modern one with digits), note the reading, run it for two minutes, then keep timing until the next whole digit appears. Put the total time in, including those extra seconds. So two minutes and fourteen seconds is 134 seconds, not 120. There is a stopwatch in the calculator if you want to use it.
On an imperial meter (an older one with a test dial), pick the size of the dial off the meter face — 1, 2, 5 or 10 cubic feet per revolution — and time one complete turn.
Then pick your gas, natural or LPG, and read the answer.
What it gives you
- Gas rate in cubic metres an hour, plus cubic feet an hour and litres a second.
- Gross heat input in kilowatts.
- Net heat input in kilowatts. This is the one that goes on a certificate.
Under Calorific value and data plate you can put in two more things. The calorific value off the customer's gas bill gives you a more accurate answer than the standard figure. And the appliance's data plate rating tells you how far off it is running.
If you put a data plate figure in, check whether it is the gross or the net rating and set it accordingly. Comparing a net measurement against a gross plate figure makes a perfectly good appliance look about ten percent under.
Why it does not say pass or fail
You will see the percentage difference from the data plate, and nothing else. That is deliberate.
The plus or minus five percent people quote comes from the BS EN standards for approving and factory testing appliances. There is no tolerance set for gas rating an appliance at commissioning. So Mucka gives you the number and leaves the judgement where it belongs, with you and the manufacturer's instructions.
Saving the working
Tap Save to a job under the results and pick the job. The readings, the time and the answer all get kept, so months later you can show what you measured and when. You can ask Mucka to do it too, while you are talking about a job.
If there is no job for it yet, New job on that screen makes one and puts the working straight on it.
With no signal
Saving works down there as well. Pick the job from the list and the figures sit on your phone until you are back in range, then go on the job by themselves. The screen tells you that is what has happened, so you know it is not on the job yet.
You will not see New job while you are offline, because making one needs a connection. Saving onto a job you already have is the bit that matters at a meter, and that works.
A note on LPG
Most domestic LPG installations have no meter to rate against. Where there is no meter, check combustion instead. If there is a meter, switch the gas to LPG and it works the same way.