3-Phase AC CircuitsElectrical DesignElectrical WiringHow ToHVACMeasuring Instruments

How to Wire 3-Phase Non-Simultaneous Water Heater Thermostat?

Three Phase Non-Continues Unbalanced Dual Element Electric Water Heater Thermostat Wiring

In our today post, we will be showing three phase non-simultaneous and unbalanced electric water heater thermostats and dual heating elements wiring (480V and 400V AC) in electric water heater wiring and installation series.

We already know the difference between balance and  unbalance (imbalance) three phase water heater wiring discussed in three phase simultaneous water heater wiring, so we will stick to the three phase non-continuous water heater wiring only.

Related Posts:

3-Phase Non-Simultaneous and Unbalanced  Water Heater Thermostat Wiring

Non-simultaneous or non-continuous means that only one heating element and related thermostat operates at a time either lower or upper. In other words, the upper and lower thermostats and heating elements are wired in such a way where both are dependent on each other. When the upper heating element does its job, the wiring configuration automatically disconnects the upper thermostat as well as heating element and connects the lower thermostat and 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, the Line 1 (Black) is connected to the upper thermostat terminal L1 and latter L3 terminals of lower thermostat via terminal T4 of upper thermostat. Line 2 (Red) is connected to the L3 terminal of the upper thermostat and Line 3 (Blue) is directly connected to the L1 of lower thermostat.

Upper heating element is connected via T2 and T4 of the upper thermostat while the lower heating element is connected to the L4 and T2 terminals of the lower thermostat.

The same wiring diagram can be used for three phase 480V AC (US – NEC) or any other three phase supply like 3-Phase 400 – 415 V 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 (see below section).

Click image to enlarge

3-Phase Non-Simultaneous and Unbalanced  Water Heater Thermostat Wiring


Related Posts:

Circuit Breaker & Wire Size for 3-Phase Water Heater

A 6 gauge wire should be used for each line as this is non-simultaneous wiring (for simultaneous, we have used 6 gauge for each line). You may use the appropriate cable / wire and circuit breaker according to the heater rating. Check the user manual and nameplate data printed on thermostat and heating elements. The following table shows the suitable cable / wire size and fuse / circuit breaker protection size.

Wire Gauge Size and Amperage for Fuse - Circuit Breaker for Watts

Related Posts:

3-Phase Wiring Color Codes – IEC & NEC

You may use the local area codes instead of NEC or IEC wiring color codes when applicable to your region. 


120V, 208V & 240 AC (1 & 3-P):

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


Three Phase 400 to 415V AC:

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

Related Posts:

General Precautions


  • 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.

Related Water Heater Wiring Tutorials

Electrical Technology

All about Electrical and Electronic Engineering & Technology. Join us on WhatsApp at Electrical Technology Official Channel, to receive the latest content, articles, and updates. You can also like and follow our social media networks below, or subscribe with your email to receive premium engineering articles in your mailbox.

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button