Heater shows E10 and will not start; often associated with low or no water flow.

Safety: Turn off power before opening any water connections.

• 1. Check supply valves: Ensure the cold-water isolation valve feeding the heater is fully open.
• 2. Clean inlet filter: Close the inlet valve, relieve pressure by opening a hot tap, then remove and clean the inlet filter/strainer at the heater’s cold-water connection.
• 3. Check downstream restrictions: Clean or replace clogged faucet aerators and shower heads that may be restricting flow.
• 4. Inspect flow sensor: Remove the cover and locate the flow sensor in the hydraulic block. Check for scale or debris; clean gently with descaling solution if accessible.
• 5. Flow test: With valves open, measure flow rate at a hot tap (using a container and stopwatch). Compare to the minimum flow specified by Kospel. If household plumbing cannot provide sufficient flow, consult a plumber.