7 components coveredField manual · Water Heater
EcoSmart ECO 11, 18, 24 and 27 electric tankless water heaters: quick sheet
Covers: EcoSmart whole-house electric tankless ECO 11, ECO 18, ECO 24 and ECO 27 (240 V, self-modulating, digital setpoint); ECO 36 uses the same element type. Not covered: ECO MINI and POU point-of-use units (120 V, different internals) and SmartPool. Search terms: EcoSmart ECO 27 not heating, ECO 18 lukewarm, ECO 11 breaker, EcoSmart element replacement, HA-P005, HE 90240.
Slim wall-hung units with copper screw-in elements in one to three heating chambers, a flow sensor, and an electronic board that modulates power to an 80-140 F setpoint. Larger models need several 40 A double-pole breakers, one per chamber. Most calls are undersized flow capacity for the season, one dead circuit or element, flow below the 0.3 GPM activation, anti-scald valves set too low, or crossed hot and cold lines.
Safety first
- Several separate 240 V circuits feed one unit: lock out all and verify every terminal dead
- Live checks only with insulated probes and hands clear of the board and terminals
- Never apply power with air in the chambers (dry fire)
- Outlet temperature can exceed setpoint at very low flow or if a switching device fails shorted: scald risk; shut power if water overheats with no demand
- Breaker, wire and service size must follow the rating plate and local code
How it works
Water flow above about 0.3 GPM trips the flow sensor and the board starts heating. It compares inlet and outlet temperature and modulates power so only as much energy as needed is used. There is no storage, so when flow stops heating stops.
Each heating chamber has its own element and circuit. The ECO 11 runs on a single 60 A breaker; ECO 18 on two 40 A breakers; ECO 24 and ECO 27 (the 21-27 kW frame) use three chambers and three 40 A breakers. Every circuit must go to its own double-pole breaker. If one is off or one leg is crossed or loose, the unit runs but heats weakly.
Output is a fixed temperature rise for a given flow. EcoSmart's own FAQ points out that exceeding the mapped flow lowers the rise, so a tub filler or two showers in winter can outrun even an ECO 27. The setpoint cannot be raised above 140 F.
The elements are rated for 240 V; on lower voltage they deliver less heat (the ECO 11 is marketed as 13 kW at 240 V and about 11 kW at 220 V). Outlet temperature can run above setpoint at very low flow or with warm inlet water.
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Always confirm values against the tech sheet for the exact model.
OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Main electrical panel beside a subpanel with its cover removed by Gvolk, CC BY-SA 3.0
