.calc-section { background: #fff; padding: 20px; border-radius: 8px; box-shadow: 0 2px 4px rgba(0,0,0,0.1); margin-bottom: 30px; }
.calc-header { text-align: center; margin-bottom: 25px; }
.calc-header h2 { color: #2c3e50; margin-bottom: 10px; }
.input-group { margin-bottom: 15px; }
.input-group label { display: block; font-weight: bold; margin-bottom: 5px; color: #444; }
.input-group input, .input-group select { width: 100%; padding: 10px; border: 1px solid #ccc; border-radius: 4px; box-sizing: border-box; font-size: 16px; }
.calc-btn { width: 100%; padding: 12px; background-color: #27ae60; color: white; border: none; border-radius: 4px; font-size: 18px; cursor: pointer; transition: background 0.3s; }
.calc-btn:hover { background-color: #219150; }
#gas-results { margin-top: 20px; padding: 15px; border-radius: 4px; background: #e8f5e9; display: none; }
.result-item { display: flex; justify-content: space-between; padding: 8px 0; border-bottom: 1px solid #c8e6c9; }
.result-item:last-child { border-bottom: none; }
.result-label { font-weight: bold; }
.result-value { color: #2e7d32; font-weight: bold; }
.article-content h2 { color: #2c3e50; margin-top: 30px; }
.article-content h3 { color: #34495e; margin-top: 20px; }
.article-content ul { padding-left: 20px; }
.example-box { background: #f0f4f8; border-left: 5px solid #3498db; padding: 15px; margin: 20px 0; }
function updateVolumeDefault() {
var type = document.getElementById("meterType").value;
var volumeInput = document.getElementById("gasVolume");
var volumeLabel = document.getElementById("volumeLabel");
var cvInput = document.getElementById("calorificValue");
if (type === "metric") {
volumeInput.value = "0.01";
volumeLabel.innerText = "Volume Measured (m³)";
cvInput.value = "39.5";
} else {
volumeInput.value = "1";
volumeLabel.innerText = "Volume Measured (ft³)";
cvInput.value = "1040";
}
}
function calculateGasRate() {
var type = document.getElementById("meterType").value;
var volume = parseFloat(document.getElementById("gasVolume").value);
var seconds = parseFloat(document.getElementById("gasSeconds").value);
var cv = parseFloat(document.getElementById("calorificValue").value);
var resDisplay = document.getElementById("gas-results");
var resGasRate = document.getElementById("resGasRate");
var resHeatInput = document.getElementById("resHeatInput");
if (isNaN(volume) || isNaN(seconds) || isNaN(cv) || seconds <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
var gasRatePerHour;
var heatInputKW;
if (type === "metric") {
// Formula: (Volume / Seconds) * 3600 = m3/hr
gasRatePerHour = (volume / seconds) * 3600;
// Heat Input (kW) = (Gas Rate m3/hr * CV) / 3.6 (to convert MJ/hr to kW)
heatInputKW = (gasRatePerHour * cv) / 3.6;
resGasRate.innerText = gasRatePerHour.toFixed(4) + " m³/hr";
resHeatInput.innerText = heatInputKW.toFixed(2) + " kW";
} else {
// Formula: (Volume / Seconds) * 3600 = ft3/hr
gasRatePerHour = (volume / seconds) * 3600;
// Heat Input (kW) for Imperial is usually: (ft3/hr * CV) / 3412 (Btu to kW)
// CV usually ~1040 Btu/ft3
heatInputKW = (gasRatePerHour * cv) / 3412.14;
resGasRate.innerText = gasRatePerHour.toFixed(2) + " ft³/hr";
resHeatInput.innerText = heatInputKW.toFixed(2) + " kW";
}
resDisplay.style.display = "block";
}
How to Calculate Gas Rate: A Professional Guide
Calculating the gas rate is a vital procedure for heating engineers and homeowners looking to verify if a gas appliance, such as a boiler or hob, is operating at its correct design specification. This process ensures safety, efficiency, and longevity of the appliance.
Why Calculate the Gas Rate?
The "gas rate" measures the volume of gas consumed by an appliance over a specific period. By comparing this rate against the manufacturer's data plate, you can determine if the appliance is "under-fired" or "over-fired." Over-firing can lead to overheating and dangerous levels of carbon monoxide, while under-firing results in poor performance and inefficiency.
The Metric Calculation (U6/G4 Meters)
Most modern smart meters and digital meters are metric. They measure gas in cubic meters (m³). To calculate the rate:
- Step 1: Ensure all other gas appliances in the property are turned off.
- Step 2: Run the appliance you are testing at full rate.
- Step 3: Use a stopwatch to time how long it takes for 0.01m³ (one digit change on the far right) to pass through the meter.
- Step 4: Apply the formula.
Metric Example:
If it takes 120 seconds for 0.01m³ to pass, and the Calorific Value (CV) is 39.5:
1. Gas Rate = (0.01 / 120) × 3600 = 0.3 m³/hr.
2. Heat Input = (0.3 × 39.5) / 3.6 = 3.29 kW.
The Imperial Calculation (E6 Meters)
Older meters measure gas in cubic feet (ft³). Usually, engineers time one full revolution of the "1 cubic foot" dial.
- Step 1: Time one revolution (1 ft³).
- Step 2: Formula: (3600 ÷ Seconds) = Gas Rate in ft³/hr.
- Step 3: Convert to Heat Input (kW) by multiplying the rate by the calorific value (usually ~1040 Btu) and dividing by 3412.
What is Calorific Value (CV)?
The Calorific Value is the amount of energy contained in the gas. This value fluctuates slightly depending on the gas supply in your region but generally sits between 39.0 and 40.0 MJ/m³ for natural gas in the UK. You can find the exact CV on your gas bill.
Safety Considerations
Gas rating should ideally be performed by a qualified professional (such as a Gas Safe registered engineer). If you notice that your gas rate is significantly higher than the manufacturer's instructions indicate, turn off the appliance immediately and seek professional assistance, as this may indicate a fault with the gas valve or burner.