How to Wire 120V Simultaneous Water Heater Thermostat?
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.
Related Water Heater Wiring:
- How to Wire 120V Water Heater Thermostat – Non-Simultaneous?
- How to Wire a Single Element Water Heater and Thermostat?
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.
Related Posts:
- How to Toggle Electric Water Heater Between 120V and 240V?
- How to Control Electric Water Heater using Switches?
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
Breaker Size should be 1.25 (125%) of the load current:
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.
Related Water Heater Wiring:
- How to Wire 240V Simultaneous Water Heater Thermostat?
- How to Wire 240V Water Heater Thermostat – Non-Continuous?
Click image to enlarge
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.
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