How to Wire 3-Phase Simultaneous Water Heater Thermostat?

Electrical Technology

Three Phase Continues Unbalanced Dual Element Electric Water Heater Thermostat Wiring

In our popular electric water heater wiring installation series, we will show three phase unbalanced and simultaneous electric heater thermostats and heating element wiring (480V or any other three phase voltage – NEC and 400V to 415V AC – IEC) in today’s post.

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Difference Between 3 Phase Balanced and Unbalanced Water Heater

Balanced 3 Phase Water Heater:

In balanced three phase wiring, all the hot wires (lines) carry equal supply (same magnitude of current and voltage). In case of star connection, the neutral carries zero current acting as a return path for current.

Unbalanced 3 Phase Water Heater:

In this wiring, a single hot wire (line) provides supply to both heating elements through heater thermostat. The sum total of Neutral point is not zero i.e. it carries the net unbalanced current.

3-Phase Unbalanced Simultaneous Water Heater Thermostat Wiring

Simultaneous or continuous means both the upper and lower thermostats and heating elements are operational at the same time and doesn’t depend on each other as separate three phase supply has been provided to each heating element.

Keep in mind that both the lower and upper thermostats are ECO-protected i.e. both are the same. In this wiring connection from a three phase main panel, the Line 1 (Black) is connected to the L₁ and L₃ terminals of upper and lower thermostats respectively. Line 2 (Red) and Line 3 (Blue) are connected to the L₃ of the upper thermostat and L₁ of the lower thermostat respectively.

Upper heating element is connected through L₄ and T₂ terminals of the upper thermostat and the lower heating element is connected through L₄ and T₂ terminals of the lower thermostat.

This way, both heating elements are operational at the same time. The same wiring diagram can be used for three phase 480V AC or any other three phase voltage (US – NEC) or any other three phase supply and 3-Phase 400 – 415V AC (UK & EU – IEC). Note that we have used red, black and blue for three phase hot lines for illustration purposes only. You may follow your regional electrical codes and wiring colors.

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Wire and Breaker Size for Three Phase Electric Heaters

In our wiring tutorial, we have used 6 gauge wire for each hot wire. You may use the appropriate size cable / wire and right sized circuit breaker according to the heater rating. Check the user manual and nameplate data printed on thermostat and heating elements.

Element Wattage	Phases	Circuit Breaker Size (Amp)				Copper Wire Size in Gauge
Element Wattage	Phases	208V	240V	277V	480V	208V	240V	277V	480V
3000W	1	20 A	20 A	15 A	15 A	12	12	14	14
	3	20 A	20 A	–	15 A	12	12	–	14
3800W	1	25 A	20 A	–	–	10	10	–	–
	–	–	–	–	–	–	–	–	–
4000W	1	25 A	25 A	20 A	15 A	10	10	12	14
	3	25 A	25 A	–	15 A	10	10	–	14
4500W	1	30 A	25 A	25 A	15 A	10	10	10	14
	3	30 A	25 A	–	15 A	10	10	–	14
5000W	1	30 A	30 A	25 A	15 A	10	10	10	14
	3	30 A	30 A	–	15 A	10	10	–	14
5500W	1	35 A	30 A	25 A	15 A	8	10	10	14
	3	35 A	30 A	–	15 A	8	10	–	14
6000W	1	40 A	35 A	30 A	20 A	8	8	10	12
	3	35 A	30 A	–	15 A	8	10	–	14
8000W	1	50 A	45 A	40 A	25 A	8	8	8	10
	3	45 A	40 A	–	20 A	8	8	–	12
9000W	1	–	50 A	45 A	25 A	–	8	8	10
	3	50 A	45 A	–	25 A	8	8	–	10
10000W	1	–	–	50 A	30 A	–	–	8	10
	3	–	50 A	–	25 A	–	8	–	10
11000W	1	–	–	50 A	30 A	–	–	8	10
	3	–	50 A	–	25 A	–	8	–	10
12000W	1	–	–	–	35 A	–	–	–	8
	3	–	–	–	30 A	–	–	–	10

Three Phase Wiring Color Codes – NEC & IEC

Other than NEC or IEC wiring color codes, you may use the local area codes applicable to your region.

NEC:

120V, 208V & 240 AC:

Black = Phase 1 or Line 1, Red = Line 2, Blue = Line 3, White / Gray = Neutral and Green/Yellow = Ground Wire

277V & Three Phase 480V

Brown = Phase 1 or Line 1, Orange = Line 2, Yellow = Line 3, Gray = Neutral and Green or bare conductor = Ground Wire

IEC:

Three Phase 400 to 415 AC:

Brown = Phase 1 or Line 1, Black = Line 2, Gray = Line 3, Blue = Neutral and Green = Earth Conductor

Warning:

Disconnect the power before replacing, repairing, troubleshooting, maintenance and installation electrical appliances and equipment.
Use the suitable voltage and ampere rating of switch with appropriate wire size and proper size of breaker according to the load rating.
Failure to do so can result in electrical shock, serious injury, fire or even death.
Please follow the manual instruction, local area codes or contact a licensed electrician for proper installation.
The author will not be liable for any losses, injuries, or damages from the display or use of this information or if you try any circuit in the wrong format. So please! Be careful because it’s all about electricity and electricity is too dangerous.

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