INSTANTLY MEASURE & GAS RATE APPLIANCES
Free Gas Rate Calculator
GAS RATE
M3/HR
0.00
GROSS
KW
0.00
NET
KW
0.00
How to use this Gas Rate Calculator
Getting started:
- Select the gas type.
- Toggle between the 1 or 2 minute timer, depending on your preference.
- Select the measurement system.
- Turn off all other gas appliances.
- Allow the appliance you are testing to warm up for at least 10 minutes
Then, depending on metric or imperial gas rating:
Metric Gas Rate Calculator:
- Take an initial meter reading and enter it in the calculator.
- Start the timer.
- When the timer finishes, take and enter a final reading.
- Record your results.
Imperial Gas Rate Calculator:
- Start the timer.
- When the meter test dial completes one full revolution, stop the timer.
- Record the results.
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How gas rates are calculated
Gas rating an appliance is a fairly simple calculation, but there are a few different things that need to be taken into account. Whether you’re gas rating an imperial or metric boiler using natural gas or LPG will all change your resulting figures, for example.
Here is how our calculator works:
The constant values used:
- The calorific value* (CV) for natural gas: In our calculator, we use a value of 10.76 kW/m³ (1040 BTU/ft³)
- The calorific value* (CV) for LPG: In our calculator, we use a value of 26.39 kW/m³ (2516 BTU/ft³)
- The gross to net conversion rate: 1.11
- ft³ to m³ conversion rate: 0.0283
- BTU to kW conversion rate: 3412
*Note that calorific values will vary slightly based on the gas supplier and location.
Metric gas rating calculations:
Gas rate:
3600 (seconds in 1 hour) * (final reading - initial reading)(m³) / test time (s)
e.g.
3600 * 0.053 / 120 = 1.59m3/hr
Gross
Gas rate * CV (kW/m³)
e.g. (using the CV of natural gas):
(3600* 0.053 * 10.76) / 120 = 17.11kW
Net
Gross / net conversion rate
e.g.
((3600* 0.053 * 10.76) / 120) / 1.1 = 15.41kW
Imperial gas rating calculations:
Gas rate:
3600 (seconds in 1 hour) * ft³ to m³ conversion rate / timer (seconds)
e.g.
(3600 * 0.0283) / 45 = 2.26m³/hr
Gross:
3600 (seconds in 1 hour) * CV (BTU/ft) / timer (seconds) * BTU to kW conversion rate
e.g. (using the CV of natural gas)
(3600* 1040) / (45*3412) = 24.38 kW
Net:
Gross / net conversion rate
e.g.
((3600* 1040) / (45*3412))/1.1 = 21.97 kW
Metric gas rating calculations:
Gas rate:
3600 (seconds in 1 hour) * (final reading - initial reading)(m³) / test time (s)
e.g.
3600 * 0.053 / 120 = 1.59m3/hr
Gross
Gas rate * CV (kW/m³)
e.g. (using the CV of natural gas):
(3600* 0.053 * 10.76) / 120 = 17.11kW
Net
Gross / net conversion rate
e.g.
((3600* 0.053 * 10.76) / 120) / 1.1 = 15.41kW
Imperial gas rating calculations:
Gas rate:
3600 (seconds in 1 hour) * ft³ to m³ conversion rate / timer (seconds)
e.g.
(3600 * 0.0283) / 45 = 2.26m³/hr
Gross:
3600 (seconds in 1 hour) * CV (BTU/ft) / timer (seconds) * BTU to kW conversion rate
e.g.
(3600* 1040) / (45*3412) = 24.38 kW
Net:
Gross / net conversion rate
e.g.
((3600* 1040) / (45*3412))/1.1 = 21.97 kW
Why are there different calorific values (CVs)?
Every type of fuel has a calorific value, which is a way of measuring how much potential energy is contained within it. As it is combusted in a boiler, this energy is released.
There will be some natural variation amongst the CV of gas supplies due to differences in the chemical makeup and concentrations of gases.
Here in the UK, gas engineers can use a standard CV for their gas rate calcuations and not worry about minute differences.
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