Understanding the Importance of Correct Sizing for Tankless Water Heaters
Groundwater Temperature and Its Impact
The temperature of incoming water plays a crucial role in determining the appropriate size of a tankless water heater. The groundwater temperature, which varies by location, affects how much a water heater needs to increase the water temperature to reach your desired level of hot water output. To find your local US groundwater temperature, consult a regional temperature map or check local resources to use as a reference in the sizing equation.
The Reality of Tankless Water Heater Performance
While tankless water heaters offer efficient, on-demand hot water, understanding their limitations is crucial to avoid dissatisfaction. The performance of these units is often misunderstood due to marketing exaggerations. For example, a common feature advertised like “Provides up to 4GPM” typically represents a best-case scenario and might not reflect the actual performance you’ll experience.
Factors Influencing Tankless Water Heater Sizing
- Incoming Water Temperature: Knowing the groundwater temperature for your area helps determine how much heating is required.
- Desired Output Temperature: This is the temperature you want for your usage, such as for showers or dishwashing.
- Flow Rate Requirements: Calculate based on the number of shower heads, faucets, and other hot water demands in your home.
Example: Sizing in a Cold Climate
Take Boston, MA, for instance, where the average groundwater temperature is around 47°F. If you desire a shower temperature of 105°F, you’ll need a temperature rise of 58°F (105 – 47 = 58). It’s essential to select a tankless water heater that can handle this temperature rise at your desired flow rate.
For a practical example, consider the Bosch 1600P-NG, which advertises a 4 GPM flow rate. However, in Boston, the effective flow rate at a 58°F temperature rise would be closer to 3.3 GPM. Such a unit might suffice for a single bathroom but would be inadequate as a whole-house solution in a colder climate.
Choosing the Right Tankless Water Heater
For whole-house applications, especially in larger or multi-bathroom homes, consider a larger unit or multiple tankless water heaters to meet the higher demand. It’s important to consult with a professional to assess your specific needs based on the factors mentioned above.
Need Professional Advice?
If you’re considering a tankless water heater or need help sizing one for your home, contact GAC Plumbing Company at 707-538-8000. Our experts can provide tailored advice and installation services to ensure optimal performance and satisfaction.
