Water Heater / Geyser Symbol

The Water Heater / Geyser schematic symbol. Standard-specific details are listed below where available.

Definition: The Water Heater / Geyser symbol represents an electric storage water heater in residential and commercial wiring diagrams, depicted as a cylindrical or rectangular tank block with supply terminals (L, N, GND) and a thermostat control terminal, indicating a resistive heating-element load requiring dedicated circuit protection, as recognised in IEC 60617 wiring diagram conventions and ANSI/NFPA 70 (National Electrical Code) load symbols; the load designator is WH.

Also known as: water heater, geyser, electric geyser, storage water heater, hot water cylinder, electric water heater, immersion heater tank, hot water system.

What the Water Heater / Geyser symbol means

The Water Heater / Geyser symbol denotes an electrically powered appliance that heats and stores a volume of water using one or more resistive immersion heating elements controlled by a thermostat. The symbol in a wiring diagram identifies the appliance as a high-wattage, continuously-rated load (typically 1.5 kW to 6 kW) that requires a dedicated circuit, appropriate overcurrent protection, and an isolation switch accessible for maintenance without shutting down the entire distribution board.

In a wiring or load schedule diagram, the Water Heater symbol communicates circuit requirements to the electrician: the L (live/line) and N (neutral) supply terminals carry the heating element current, the GND terminal connects to the protective earth for safety, and the Thermostat terminal indicates the connection point for the temperature-sensing control switch that cycles the heating element on and off to maintain the set-point temperature. In South African and Australian practice, the device is universally called a 'geyser'; in North American NEC practice it is a 'water heater'; in British IEE/IET practice it is an 'unvented hot water storage unit' or 'immersion heater'.

How to identify the Water Heater / Geyser symbol

The Water Heater / Geyser symbol is drawn as a tall rectangular or cylindrical block labelled 'WH', 'GEYSER', or 'HWC' (hot water cylinder). Three supply pins enter from the left: L (live) at the top, N (neutral) in the middle, and GND (earth) at the bottom. A fourth terminal labelled 'Thermostat' exits from the right side, representing the control connection. Some representations add a wavy line inside the block to represent the heating element, or show a temperature sensor symbol at the thermostat pin.

Function and usage boundary

The Water Heater heats water by passing current through a sheathed resistive heating element (nichrome or incoloy) immersed in the tank. The thermostat senses water temperature and interrupts power to the element when the set temperature is reached (typically 55–65°C), then restores power when temperature drops. The earthed metal tank and element sheath provide a low-resistance fault path to trip the RCD/GFCI if element insulation fails, which is why the GND terminal is safety-critical.

Standards: IEC vs ANSI

IEC 60617	IEC 60617 does not define a unique glyph for a water heater; the symbol is drawn as a functional load block per IEC 60617-11 (wiring of buildings). The applicable product standard is IEC 60335-2-21 (household electric storage water heaters — safety). The thermostat sub-component follows IEC 60730 (automatic electrical controls).
ANSI/IEEE 315	ANSI Y32.2 / IEEE 315 does not define a specific water heater glyph. In NFPA 70 (National Electrical Code) load calculations and riser diagrams, the water heater appears as a labelled box with NEC Article 422 (appliances) governing circuit requirements. The standard designator is WH.
Key difference	Both IEC and ANSI/NEC use a labelled load-block rectangle for the water heater. The primary regional difference is in circuit requirements: NEC Article 422.13 mandates a dedicated 125% rated-current circuit for water heaters; IEC/AS/NZS 3000 (Wiring Rules) specifies a dedicated circuit of at least 20 A. Thermostat cut-out temperature requirements also differ: IEC 60335-2-21 mandates a non-self-resetting high-limit thermostat above 90°C.

The displayed SVG is the live editor implementation, not a licensed reproduction or certification of an IEC or IEEE database glyph. Verify the exact official entry and project edition before issuing work.

Logical terminals

Logical ID	Editor terminal name
l	L
n	N
gnd	GND
tstat	Thermostat

Where the Water Heater / Geyser symbol is used

Residential electrical wiring diagrams showing the dedicated water heater circuit from the distribution board
Commercial and industrial load schedules listing water heater capacity, circuit breaker rating, and cable size
Solar thermal and heat-pump hybrid system schematics showing the electric backup element wiring
Smart-home energy-management system diagrams where the water heater is a demand-response load
Off-grid renewable energy system designs showing water heater control via a diversion relay or immersion controller
Bathroom and kitchen electrical plans in building services drawings indicating hot water supply points

Key facts

The Water Heater / Geyser symbol is drawn as a labelled load-block rectangle with terminals L (line), N (neutral), GND (earth), and Thermostat, per IEC 60617-11 wiring diagram conventions.
The designator for a water heater in wiring diagrams is WH; the IEC product standard is IEC 60335-2-21 (household electric storage water heaters).
Electric water heaters require a dedicated circuit — NEC Article 422.13 requires 125% of the rated load ampacity for the circuit conductors and overcurrent device.
The Thermostat terminal on the symbol represents the internal temperature-sensing switch that interrupts heating element current when the water reaches the set-point temperature, typically 55–65°C.
A non-self-resetting high-limit thermostat (cut-out at 90–95°C) is mandatory under IEC 60335-2-21 to prevent scalding and tank overpressure if the primary thermostat fails.
The GND (earth) terminal is safety-critical: it provides a low-impedance fault current path to trip the 30 mA RCD/GFCI if the immersion element's insulation breaks down and water becomes energised.
In South Africa and Australia, the water heater is universally called a 'geyser'; in North America it is a 'water heater'; in the UK it is an 'unvented cylinder' or 'immersion heater unit'.
Solar geyser and heat-pump hybrid systems retain the water heater symbol for the backup electric element, with additional symbols for the solar collector or heat-pump compressor on the same schematic.

Diagrams that use this symbol

Frequently asked questions

What does the Water Heater / Geyser symbol mean in a wiring diagram?

The Water Heater / Geyser symbol represents an electric storage water heater appliance. It identifies a high-wattage load (1.5 kW to 6 kW) requiring a dedicated circuit, with supply terminals L (live), N (neutral), GND (earth), and a Thermostat control terminal for the internal temperature switch.

What does the water heater symbol look like on a schematic?

The water heater symbol is a labelled rectangular block marked 'WH' or 'GEYSER', with three supply pins on the left (L at top, N in the middle, GND at the bottom) and a Thermostat terminal on the right. Some versions include a wavy heating-element line inside the rectangle.

What circuit protection does a water heater require?

An electric water heater requires a dedicated circuit with a circuit breaker rated at 125% of the heater's full-load current (NEC Article 422.13) or at the ampacity specified by the wiring rules (IEC/AS/NZS 3000). A 30 mA RCD/GFCI is required for shock protection in most IEC and NEC residential installations.

What is the thermostat terminal on the water heater symbol?

The Thermostat terminal on the water heater symbol represents the connection to the internal temperature-sensing switch that cycles the heating element on and off to maintain the set-point temperature. A separate non-self-resetting high-limit thermostat (set at 90–95°C) provides a safety cut-out if the primary thermostat fails.

What is the designator for a water heater in a schematic?

The water heater is designated WH in wiring diagrams and load schedules, following NFPA 70 (NEC) and common IEC wiring diagram practice.

What standard governs electric water heaters?

IEC 60335-2-21 governs household electric storage water heaters for safety requirements including thermostat ratings and insulation. Circuit wiring is governed by IEC 60364 (IEV) or NFPA 70 NEC Article 422 in North America. Schematic symbol representation follows IEC 60617-11 for building wiring diagrams.

Why is the earth (GND) terminal important on a water heater symbol?

The GND (earth/ground) terminal ensures the metal tank and heating element sheath are bonded to the protective earth. If the element insulation fails and water becomes energised, the earth connection provides a low-impedance fault path that trips the 30 mA RCD/GFCI before shock current through a person reaches a dangerous level.

Related symbols

Physical breadboard, PCB, and panel mapping

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