Does anyone have experience or advice about using a tankless water heater to boost a traditional tanked water heater? We are thinking about installing a small- to mid-size electric thermostatic tankless water heater downstream of an electric 85-gallon traditional tank water heater. We are trying to maximize the availability of hot water for numerous low-flow showers in quick succession when we have guests in our north Florida vacation condo. Our thinking is that the tanked heater would do most of the work, with the tankless only kicking in, as needed, to pick up the slack as the hot water from the tanked heater is depleted.
The condo is in a 30-year-old mid-rise building. Natural gas is not available and our existing 150-amp box only has the capacity to handle another 50 to 60 amps in addition to the existing 30-amp circuit for the tanked water heater. Increasing our electrical capacity is not feasible due to the distance and the way the service cable was routed. For that reason, using a larger whole-house tankless, or multiple point-of-use tankless heaters is out of the question.
Will this set-up work? Will the tankless heater reduce or restrict the flow or pressure of the hot water in any way? Is there anything else we should be thinking about? Thanks for any help.
The water heaters we are considering are the following (or similar models):
Eemax “SERIES TWO” Model EX144TC (Twin Module) With Single Thermostat
Hot or cold water feed
Turns on in stages based on hot water demand- (showers, etc.).
Min. flow, 0.7 GPM.
Adjustable, Precise Temperature Setting +/– 0.5°F
Anti Scald Protection
Ideally suited for any booster type application or as solar backup
Volts kW Amps Recommended Wire Size
240V 15kW 64 (2x32)A 8AWG per module
Temperature Rise (degrees Fahrenheit)
65 @ 1.5
51 @ 2.0
39 @ 2.5
34 @ 3.0
Rheem/Ruud – Marathon – 85 Gallon Electric – Model MR85245
First Hour Rating – 90
Recovery in GPH @ 90 degree rise - 21