A Domestic Hot Water Coil System heats potable water using a copper/stainless heat-exchanger coil coupled to a heat source (biomass/gas stove jacket, boiler, or solar preheater). Water is stored in an insulated tank and delivered at safe temperature via a thermostatic mixing valve. The build demonstrates heat transfer, thermosyphon/forced circulation, plumbing safety, and basic control.

Parts Used:

1. Heat Exchanger Coil – Ø10–12 mm copper or SS coil (≈ 8–12 m length) with brazed/compression fittings.
2. Storage Tank (25–80 L) – Food-grade liner, PUF insulation, cold-in/hot-out dip tubes.
3. Heat Source – Stove/boiler jacket, flue wrap, or solar flat plate (preheat); electric immersion backup (optional).
4. Hydraulics – Ball valves, non-return/check valve, air vent, drain cock, Y-strainer.
5. Safety – T&P relief valve, expansion tank (2–5 L), thermostatic mixing valve (set 48–50 °C), pressure gauge.
6. Pump & Control (optional) – Circulation pump (12/24 V or 230 V), Arduino/ESP32, NTC sensors, relay/SSR.
7. Plumbing – PEX-a/CPVC/copper lines, insulation sleeves, unions, mounting brackets.
8. Instrumentation (optional) – Flow sensor, energy meter, data logging display.