How do electric tankless water heaters work?

An electric tankless water heater is a water heating system that heats water as it flows through the unit rather than storing heated water in a tank. For example, when you turn on the hot water faucet, cold water enters the tankless heater and is heated by either a heating element or a gas burner. The heated water then flows out to the tap, replacing the cold water that was just drawn off. Because there is no storage tank, you can use as much or as little hot water as you need at any given time without running out. And since there’s no standby heat loss from a storage tank, you’ll save energy dollars too.

The installation process for electric tankless water heaters can be tricky, so it is essential to hire a professional to do the job. The first step is to identify where you will be installing the unit. The best place is usually near the water main, ensuring the water is heated quickly.

Once you have identified the installation location, you will need to cut a hole in the wall and run the appropriate wiring. Again, follow the manufacturer’s instructions carefully, as each unit has specific requirements.

Once the wiring is in place, you can install the tankless water heater. Be sure to seal any gaps around the unit with caulk or insulation, as this will help keep your energy bill low.

Picking the Perfect Breaker Size

1. Refer to the manual

The best way to discover the right size for your water heater amp circuit breaker is by checking your tankless water heater’s manual. You can look at what kind of wiring it has and how many breakers are required for optimal performance.

The model you have will determine whether it is a 3 x 50 or 4 x 40. Remember that more circuit breakers with higher amperage means more significant electrical current. For example, electric tankless heaters can draw a maximum of 42 to 167 amps. However, if you can’t find the manufacturer’s manual, you can always use the mathematician’s method.

1. Use the Power formula.

Use the Power equation, P = I x V, from which you can derive the formula to get the specific amp breaker size: I = P ÷ V (I = Amps, P = Watts, and V = Volts). ETWHs operate on 240 Volts, so you’ll need to find the wattage of your device either in its spec sheet or inside the water heater itself.

You will need several variables to calculate the breaker size for a tankless water heater. Here is an example: Let’s say that a heating element needs 7600 watts from a 240-volt circuit. To find the amperage, divide 7,600W by 240V:

The result reveals that 31.7 amps are required for this heating element to operate appropriately. However, using the same calculated amperage as your final breaker size for a tankless water heater is dangerous. Using the same amp amount could lead to accidents if you do not have protection against power surges.

The National Electric Code (NEC) has established that an amp circuit breaker shouldn’t be used for more than 80% of its total capacity to avoid potential fires. To discover what size breaker for electric tankless water heater you require, multiply 1.25 or 125% by the rated amps of your device – in this example, 31.7 amps.

ased on the final answer of 39.62 amps, get the closest breaker size possible. So, for a safe maximum continuous load on our sample heating element, buy a 40-amp breaker.

This example only featured one circuit breaker for one heating element. However, as I’ve mentioned earlier, there are water heaters that need multiple circuit breakers for each heating element they have. So, make sure to take into account other heating elements as well.

Can my breaker panel handle an electric tankless water heater?

Before buying a new electric tankless water heater, ensure you have enough space in your main pole breaker panel. Each heating element has its own double circuit breaker, so it’s essential to have a spacious and safe panelboard. To determine if you need an upgrade, ask yourself: “Do I need a panelboard upgrade?”

100-amp panels might have been enough in the past for energy-consuming appliances like dishwashers and air conditioners. However, technology has rapidly changed, making many devices outdated. The latest ETWH cannot work under that minimal amperage due to insufficient power.

Three breakers power three heating elements, each carrying 40 to 50 amps for 120+amps. Therefore, your 100-amp panel is useless when an emergency thermal shutoff occurs. Calculate 125% of the heater’s continuous load to size your main pole breaker panel.