How to Wire a 120V Simultaneous Water Heater Thermostat?

How to Wire a 120V Simultaneous Water Heater Thermostat? . Wiring a 120V simultaneous water heater thermostat might seem challenging, but with the right tools and guidance, it becomes a straightforward task. Simultaneous systems allow both heating elements to work at the same time, providing faster heating. This guide will walk you through the wiring process safely and efficiently.

Understanding a 120V Simultaneous Water Heater System

How It Works

A 120V simultaneous system uses two heating elements that function together, unlike non-simultaneous systems where only one element operates at a time. This setup ensures quicker water heating but may consume more electricity.

Key Components

Upper Thermostat – Manages the upper heating element.
Lower Thermostat – Controls the lower heating element.
Heating Elements – Two resistive heating elements located inside the water tank.

Single Phase 120V Continues Dual Element Water Heater Thermostat Wiring

In our previous water heater wiring and installation post, we discussed the non-continuous (non-simultaneous) water heater wiring connection. In today’s post, we will be showing the continuous or simultaneous 9kW dual element water heater thermostat wiring.

Simultaneous or Continuous Operation of Water Heater

Continuous or simultaneous heating elements are not dependent on each other i.e. both elements are “ON” at the same time. In other words, both the upper heating element and lower heating element will turn “ON” at once and this operation is needed at more conservation and hot water consumption points like restaurants. This is the automatic process due to the thermostat wiring connection where the lower thermostat / element and upper thermostat / element is fed up by the separate power supply.

This way, both elements operate at the same time. Keep in mind that the same thermostats can be wired for non-simultaneous or non-continuous operation where both elements are not operational at the same time in case of low hot water consumption.

Simultaneous 120V AC Single Phase Dual Element Water Heater Thermostat Wiring

In simultaneous water heater thermostat wiring, the phase or Hot “L” line is connected to the left terminal L₁ of the upper thermostat and a second wire is outgoing from T₂ to the heating element. The Neutral “N” is connected to the right terminal of thermostat L₃ and outgoing from L₄ to the heating element.

The lower thermostat and heating element is powered up separately through a 50A double pole (you can use single pole) circuit breaker same as the above thermostat heating element wiring. In short, a separate 120V supply wires (from the main 120/240V panel via breaker) are connected to the lower thermostat i.e. Line to thermostat terminal L₁ and to heating element via T₂ and Neutral wire to thermostat terminal L₃ and to heating element via L₄.

Since there are two heating elements each rated about 4500 watts, the total wattage rating of this heater is 9000 watts. We will be using the breaker and switch sizes for full rating i.e. 9kW as both elements are operational at once.

Now in case of 120V AC, a 50A circuit breaker is suitable for both wires having 10 gauge size according to the following calculations.

Total wattage = 9000 Watts.
Load Current = 9000 / 120V = 75A.

We have used separate circuit breaker for each heating element, the breaker rating size for single element would be:

Wattage: = 9000W / 2 = 4500 Watts.
Load Current = 4.5kW / 120V = 37.5A

37.5A x 1.25 = 46.875A

Another way, the safe limit of circuit breaker is 80% (0.8), this way 50A x 0.8 = 40 Amp which is safe for load current.

This way, a 50A circuit breaker for over current protection is suitable in case of a 9kW dual element continuous water heater circuit for 120V AC.

120V-AC-9kW-Electric-Water-Heater-Dual-Elements-Simultaneous-Wiring

Note: Red color illustrates the Line or Phase wire and Black color shows the Neutral Wire in the above figures. You may follow your regional wiring color codes i.e. IEC or NEC.

Tools and Materials Required

Before you start wiring, ensure you have the following:

Screwdrivers (flathead and Phillips)
Voltage tester
Wire strippers
Electrical tape
Thermostat wiring diagram (specific to your model)
Safety gloves

Tips:

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.

Safety Precautions Before Wiring

Turn Off the Power: Shut off the circuit breaker supplying power to the water heater. Use a voltage tester to confirm.
Wear Safety Gear: Always wear insulated gloves and goggles.
Follow Local Codes: Adhere to local electrical codes to ensure safety and compliance.

Identifying the Thermostat and Heating Elements

The thermostat setup generally consists of:

Upper Thermostat: Includes a reset button and terminals for wiring.
Lower Thermostat: A simpler device with fewer connections.
Mark the connections to avoid confusion during wiring.

Understanding Thermostat Wiring Diagrams

A wiring diagram is essential for understanding which wires connect to specific terminals. It typically includes:

Line wires (from the power source)
Load wires (to heating elements)
Ground wires

Refer to the manufacturer’s wiring diagram to avoid errors.

Step-by-Step Guide to Wiring

1. Turning Off the Power

Turn off the water heater’s circuit breaker and double-check with a voltage tester to ensure no power is present.

2. Accessing the Thermostat

Remove the access panels on the water heater using a screwdriver.
Unscrew the protective cover over the thermostat and heating elements.

3. Wiring the Upper Thermostat

Connect the line wires from the power source to the designated terminals on the upper thermostat.
Link the load wires from the upper thermostat to the upper heating element.
Attach the ground wire securely to the grounding screw.

4. Wiring the Lower Thermostat

Connect the wires from the lower thermostat to the lower heating element, following the diagram.
Ensure all connections are tight and secure.

How to Wire a 120V Simultaneous Water Heater Thermostat?

Common Mistakes to Avoid

Not Cutting Power: Never work on live circuits.
Incorrect Wiring: Mismatched wires can cause short circuits or damage.
Loose Connections: Poor connections lead to overheating and potential hazards.

Testing the Thermostat and Heater

Restore Power: Turn on the circuit breaker.
Check Functionality: Use a multimeter to test the voltage at the thermostat terminals.
Monitor Heating: Verify that both elements heat simultaneously.

Troubleshooting Wiring Issues

If the water heater isn’t working correctly:

Check Connections: Re-inspect wiring for loose or misplaced wires.
Test Heating Elements: Use a multimeter to measure resistance and identify faulty elements.
Verify Thermostat Settings: Ensure the thermostats are set to the desired temperature.

Maintaining Your 120V Water Heater

Regular Cleaning: Flush the tank annually to remove sediment buildup.
Inspect Connections: Check wiring and thermostats periodically for wear or corrosion.
Monitor Energy Use: Adjust thermostat settings to balance comfort and efficiency.

Energy Efficiency Tips for Water Heaters

Lower the thermostat setting to 120°F to save energy.
Install insulation blankets around the tank to retain heat.
Use water-saving fixtures to reduce hot water demand.

Read More : How to Wire a Three-Phase Meter?

FAQs

1. Can I wire a water heater without turning off the power?
No, it’s extremely dangerous. Always shut off the power before starting any wiring work.

2. What happens if I miswire the thermostat?
Mismatched wiring can cause the heating elements to malfunction, potentially leading to overheating or electrical hazards.

3. Do I need special tools for wiring a thermostat?
Basic tools like screwdrivers, wire strippers, and a voltage tester are sufficient.