How many seconds it took to consume the volume above.
Please enter valid numerical values greater than zero.
Gas Flow Rate:–
Gross Heat Input:–
Net Heat Input (approx):–
// Initialize labels on load
window.onload = function() {
updateLabels();
};
function updateLabels() {
var type = document.getElementById("meterType").value;
var cvLabel = document.getElementById("cvLabel");
var cvInput = document.getElementById("calorificValue");
var cvHint = document.getElementById("cvHint");
var volLabel = document.getElementById("volLabel");
var volInput = document.getElementById("volumeUsed");
if (type === "metric") {
cvLabel.innerText = "Calorific Value (MJ/m³)";
cvInput.value = "39.0";
cvHint.innerText = "Standard metric CV is approx 38-40 MJ/m³.";
volLabel.innerText = "Volume Measured (m³)";
volInput.placeholder = "e.g. 0.010 (common test volume)";
} else {
cvLabel.innerText = "Calorific Value (BTU/ft³)";
cvInput.value = "1040";
cvHint.innerText = "Standard imperial CV is approx 1030-1050 BTU/ft³.";
volLabel.innerText = "Volume Measured (ft³)";
volInput.placeholder = "e.g. 1.0 (1 revolution)";
}
}
function calculateGasRate() {
var type = document.getElementById("meterType").value;
var cv = parseFloat(document.getElementById("calorificValue").value);
var vol = parseFloat(document.getElementById("volumeUsed").value);
var time = parseFloat(document.getElementById("timeSeconds").value);
var errorDiv = document.getElementById("errorMsg");
var resultsDiv = document.getElementById("results");
// Validation
if (isNaN(cv) || isNaN(vol) || isNaN(time) || time <= 0 || vol <= 0 || cv <= 0) {
errorDiv.style.display = "block";
resultsDiv.style.display = "none";
return;
}
errorDiv.style.display = "none";
resultsDiv.style.display = "block";
var flowRatePerHour;
var grossInputKW;
var grossInputBTU;
var unitDisplay;
if (type === "metric") {
// Metric Calculations
// Flow Rate (m3/hr) = (Volume / Seconds) * 3600
flowRatePerHour = (vol / time) * 3600;
// Heat Input (kW) = Flow Rate (m3/hr) * CV (MJ/m3) / 3.6
grossInputKW = (flowRatePerHour * cv) / 3.6;
unitDisplay = " m³/hr";
document.getElementById("flowRateResult").innerText = flowRatePerHour.toFixed(3) + unitDisplay;
document.getElementById("grossInputResult").innerText = grossInputKW.toFixed(2) + " kW";
document.getElementById("netInputResult").innerText = (grossInputKW * 0.9).toFixed(2) + " kW";
} else {
// Imperial Calculations
// Flow Rate (ft3/hr) = (Volume / Seconds) * 3600
flowRatePerHour = (vol / time) * 3600;
// Heat Input (BTU/hr) = Flow Rate * CV
grossInputBTU = flowRatePerHour * cv;
// Convert BTU/hr to kW for reference (1 kW = 3412.14 BTU/hr)
grossInputKW = grossInputBTU / 3412.14;
unitDisplay = " ft³/hr";
document.getElementById("flowRateResult").innerText = flowRatePerHour.toFixed(2) + unitDisplay;
document.getElementById("grossInputResult").innerText = Math.round(grossInputBTU).toLocaleString() + " BTU/hr (" + grossInputKW.toFixed(2) + " kW)";
document.getElementById("netInputResult").innerText = Math.round(grossInputBTU * 0.9).toLocaleString() + " BTU/hr";
}
}
Understanding Gas Rate Calculations
Accurately calculating the gas rate (heat input) of an appliance is a critical skill for gas engineers and HVAC technicians. It ensures that boilers, furnaces, and water heaters are burning the correct amount of fuel required for safe and efficient operation. An incorrect gas rate can indicate a blocked injector, incorrect gas pressure, or a faulty metering device.
Why Measure Gas Rate?
Every gas appliance has a manufacturer-specified heat input rating, usually expressed in kilowatts (kW) or British Thermal Units per hour (BTU/hr). By performing a gas rate check at the meter, you can verify if the appliance is actually consuming the energy it claims to be.
Under-gassing: If the rate is too low, the appliance may not reach the desired temperature, leading to efficiency loss and condensation issues in non-condensing units.
Over-gassing: If the rate is too high, it can cause dangerous overheating, excessive carbon monoxide production, and damage to the heat exchanger.
How to Perform the Test
Preparation: Turn off all other gas appliances in the property to ensure the meter is only measuring the appliance under test.
Appliance Operation: Turn the appliance on to its maximum setting (full load). Allow it to stabilize for a few minutes.
Measurement:
For Metric Meters (E6): Observe the decimal dials. It is common to time 0.010 m³ or 0.1 m³ depending on the appliance size.
For Imperial Meters (U6): Observe the dial measuring 1 cubic foot per revolution. Time one full revolution.
Timing: Use a stopwatch to record exactly how many seconds it takes to consume the specific volume of gas.
Calculation: Input the Volume, Time, and Calorific Value (CV) into the calculator above to determine the heat input.
Metric vs. Imperial Formulas
The math differs slightly based on the meter type:
Metric: Heat Input (kW) = (Volume in m³ ÷ Time in Seconds × 3600) × Calorific Value ÷ 3.6
Imperial: Heat Input (BTU/hr) = (Volume in ft³ ÷ Time in Seconds × 3600) × Calorific Value
Note: The standard Calorific Value is approximately 39.0 MJ/m³ for natural gas in metric regions and 1040 BTU/ft³ in imperial regions, though this can vary slightly by supplier.