Recirculation can outpace a tankless heater’s minimum flow

If a dedicated return line were already available, I’d lean toward using it so cooled water returns through that line rather than the cold pipe. A crossover seems more appealing when adding a return line would be impractical. I’d still treat either choice as separate from the cycling question: the heater’s manual or installer needs to confirm that specific recirculation setup is supported.

Demand-based recirculation may limit how long the pump runs compared with continuous circulation, but that alone doesn’t tell us whether the heater will cycle frequently. It depends on how that particular model handles recirculation and whether the flow through it meets its firing requirements. I’d check whether its documentation specifies minimum-flow behavior for the supported recirculation mode - not just whether the pump can move water through the loop.

A crossover’s convenience has a possible everyday trade-off: while it moves cooled water back through the cold pipe, a nearby cold tap could briefly run lukewarm, depending on the layout and when the pump runs. That might matter more in a bathroom where someone expects cold water immediately; a dedicated return avoids using the cold line for that return path.

I’d lean toward demand-based control to limit pump runtime, especially if saving electricity matters. But that doesn’t establish whether the heater will fire smoothly during a circulation cycle. That still depends on the model’s behavior in that mode and its flow requirements.

I’d treat those checks as one compatibility question, not separate boxes to assume are interchangeable: does this model support the proposed dedicated-return or crossover piping, which recirculation mode and pump control are approved with it, and how does the heater handle firing flow during that mode? A pump’s rated flow alone doesn’t answer whether the heater will run smoothly. If the manual leaves that unclear, the installer should confirm the specific arrangement before it’s chosen.