January 21, 2020 Bradford White
When sizing for a tankless water heater there are several pieces of information that are needed to make the product selection:
* Remember to be realistic. While the application may have two showers, five sinks, a dishwasher and a washing machine in a house it does not mean they are all going to be running at one time.
Take the known GPH recovery and multiply by known temperature rise. Divide this by your desired temperature rise.
Example for sizing a tankless water heater (refer to the chart below):
1) 2 showers (2.5 GPM each) + 1 lavatory sink (0.5 GPM) = 5.5 GPM
2) 110°F - 40°F = 70°F deltaT
3) 5.2 (GPM) x 75 (°F) = 390
4) 390/70 (°F) = 5.57 GPM at a 70°F deltaT
In this example, one Model B would satisfy the demand.