When it comes to choosing the right tankless electric water heater for your home, proper sizing is crucial for ensuring adequate hot water supply to meet your household's demands. Stiebel Eltron's Tempra Trend and Tempra Plus series offer reliable, efficient solutions for whole-house water heating, but selecting the correct model requires understanding your specific needs and local conditions.
Understanding Ground Water Temperature Impact
The foundation of proper water heater sizing begins with understanding your local ground water temperature. This baseline temperature directly affects how much energy your unit needs to heat water to your desired temperature. Ground water temperatures vary significantly across different regions, typically ranging from 42°F in colder northern climates to 72°F in warmer southern areas.
All maximum flow rates are calculated for 105°F water. Ground water temperature average shown - use actual local information for more accurate results.
Tempra Model Specifications and Electrical Requirements
The Tempra Trend and Plus series includes six different models, each designed for specific household demands and electrical service requirements:
Understanding Fixture Flow Rates
To properly size your water heater, you need to understand the typical flow rates of various fixtures in your home:
- Shower: 1.5 GPM (typical range: 1.5-2.5 GPM)
- Kitchen Sink: 1.5 GPM (typical range: 1.0-2.2 GPM)
- Bathroom Sink: 0.5 GPM (typical range: 0.5-1.0 GPM)
These flow rates are crucial for determining how many fixtures can operate simultaneously with your chosen water heater model.
The Three-Step Sizing Process
Follow this straightforward three-step process to select the right Tempra model for your home:
Step 1: Determine Your Ground Water Temperature
Use local climate data or contact your water utility to find your approximate ground water temperature. This information is essential for accurate sizing calculations.
Step 2: Check Simultaneous Fixture Capacity
Check the column on the table with your ground water temperature to see how many fixtures can be supplied at the same time with hot water.
Step 3: Match Your Needs to Model Capacity
Using your ground water temperature and simultaneous fixture requirements, select the appropriate model from the sizing table. For instance, if you have 52°F ground water and need to supply two showers simultaneously (3.0 GPM total), you would need at least a Tempra 24 model, which can supply 3.1 GPM at that ground water temperature.
Voltage Considerations
All recommendations are correct if unit is installed with 240V service. Increase one model size if unit will be installed with 208V service.
Temperature Rise Performance Charts
Understanding how temperature rise varies with flow rate helps fine-tune your selection and ensures optimal performance across different usage scenarios.
The PDF shows there are temperature rise charts for both 240V and 208V service on the next page.
These charts demonstrate how each model's temperature rise capability decreases as flow rate increases. This relationship is crucial for understanding real-world performance under varying demand conditions.
Optimizing Your Selection
When selecting your Tempra model, consider these additional factors:
Future Needs: If you're planning home additions or bathroom renovations, factor in potential increased demand.
Usage Patterns: If your household has predictable usage patterns with limited simultaneous demand, you might be able to select a smaller model.
Flow Rate Variations: If you know your specific fixture flow rates differ from standard assumptions, use your actual measurements for more accurate sizing.
Climate Considerations: In areas with seasonal ground water temperature variations, consider the coldest expected ground water temperature for year-round performance.
Installation Planning
Remember that proper sizing extends beyond just selecting the right model. Ensure your electrical service can handle the unit's current draw with adequate safety margin. Professional installation is recommended to ensure proper electrical connections, safety compliance, and optimal performance.
The Tempra Trend and Plus series represents reliable, efficient tankless water heating technology. By following this comprehensive sizing guide and understanding your specific household needs, you can select the ideal model to provide consistent, on-demand hot water for your home.