Sizing a commercial water heater accurately is crucial for ensuring a reliable and efficient hot water supply for your business needs. While various factors influence the final selection, a key aspect involves calculating the necessary hot water storage tank size.
According to the provided reference from September 3, 2019, one method to estimate the hot water tank size your business requires involves the following calculation:
Estimating Hot Water Tank Size for Commercial Use
To determine the estimated hot water tank size, you'll need to consider your business's peak hot water demand, the water heater's recovery rate, and the duration of your peak usage period.
Here's the formula:
Estimated Hot Water Tank Size = (Peak Hourly Hot Water Demand - Water Heater's Recovery Capacity) × Duration of Peak Demand
Let's break down the components of this calculation:
Key Variables for Calculation
| Variable | Description |
|---|---|
| Peak Hourly Hot Water Demand | This refers to the highest volume of hot water your business uses in a single hour (measured in Gallons Per Hour, or GPH). This can be estimated based on the type of business, number of fixtures, and specific processes requiring hot water. For example, a restaurant might have peak demand during lunch or dinner service. |
| Water Heater's Recovery Capacity | This is the rate at which your water heater can heat a fresh supply of water to the desired temperature, typically measured in Gallons Per Hour (GPH) at a specific temperature rise (e.g., heating water by 100°F). A higher recovery capacity means the heater can replenish hot water more quickly. |
| Duration of Peak Demand | This is the number of hours during which your business experiences its maximum daily water usage or peak hourly demand. Identifying this peak period is essential for ensuring sufficient storage. |
Step-by-Step Calculation
- Identify Your Peak Hourly Hot Water Demand: Determine the maximum amount of hot water (in gallons) your business consumes during its busiest hour. This might involve tracking usage or using industry-specific guidelines.
- Determine the Water Heater's Recovery Capacity: Find the Gallons Per Hour (GPH) recovery rate of the water heater you are considering. This specification is typically provided by the manufacturer.
- Calculate the Hot Water Deficit: Subtract the water heater's recovery capacity from your peak hourly hot water demand. This difference represents the amount of hot water demand that the heater cannot meet instantaneously during the peak hour.
Hot Water Deficit (GPH) = Peak Hourly Hot Water Demand (GPH) - Water Heater's Recovery Capacity (GPH)
- Multiply by the Duration of Peak Demand: Take the hot water deficit calculated in Step 3 and multiply it by the total number of hours your business experiences this peak demand. This final figure provides an estimate of the hot water tank size (in gallons) needed to cover the peak demand that exceeds the heater's recovery rate.
Estimated Hot Water Tank Size (Gallons) = Hot Water Deficit (GPH) × Duration of Peak Demand (Hours)
Practical Example
Let's consider a small hotel with the following hot water requirements during its morning peak:
- Peak Hourly Hot Water Demand: 150 gallons per hour (GPH)
- Water Heater's Recovery Capacity: 100 gallons per hour (GPH)
- Duration of Peak Demand: 3 hours
Using the formula:
- Hot Water Deficit:
150 GPH (Peak Demand) - 100 GPH (Recovery Capacity) = 50 GPH - Estimated Hot Water Tank Size:
50 GPH (Deficit) × 3 Hours (Peak Duration) = 150 Gallons
In this example, an estimated 150-gallon hot water storage tank would be required to supplement the water heater's recovery rate during the busiest period.
