How do I determine the peak demand flow and rise for my Bradford White tankless heater? (BRADFORD WHITE Tankless Heater Instruction Manual)

Answer

manuals.plus

Mar 13, 2025 - 12:47 AM


To determine the peak demand flow and rise for your tankless heater, you can follow these steps:

1. Determine which fixtures will be used simultaneously. The total flow rate is the peak demanded flow. Determine the flow rate of each of these fixtures and total them. For example, each sink will flow approximately 1 GPM, each shower will flow approximately 2 GPM, and each bath/garden tub will flow between 3.5-4.5 GPM.

2. To determine the flow rate, determine the length of time required to fill a known volume. Using the fill time and the container volume, calculate the peak flow rate. For example, if it takes 20 seconds to fill a 1-gallon container, the flow rate would be 3 GPM.

3. Using a thermometer, run a cold water fixture until the room temperature water is purged from the cold water line. The rise is the difference between the demanded setpoint and this cold water temperature. For example, if the inlet water is 58°F and the setpoint is 120°F, the rise would be 62°F.

4. Multiply the rise by the peak flow rate to calculate the peak BTU demand. For example, if the rise is 62°F and the peak flow rate is 5 GPM, the peak BTU demand would be 525 * 62 * 5 = 162,750 BTU/hr.

Please note that these are general guidelines, and it is always recommended to consult the installation manual or contact the manufacturer for specific application needs and to ensure compliance with local building codes.