Does A Water Heater Need A Disconnect? Amp, Height, Size Explained

water heater disconnect

Many electricians will tell you that any heater you want to install requires a disconnect. But is that true? What purpose does the disconnect serve? Why do you need one in your home? Better yet, what happens if you don’t have a water heater disconnect?

Does a Water Heater Require a Disconnect?

A water heater requires a disconnect because it protects your life and the lives of all the people in your home. Additionally, it eases electrician work. On top, it is not only essential but the law doesn’t give you as much of a choice as you think.

Don’t forget; disconnects are supposed to immediately cut the power. Water heaters are heavy-duty items that use a lot of electricity.

If a water heater malfunctions, the amount of electricity it uses is more than capable of causing lasting harm or killing the occupants of your home.

This is why disconnects are so important. You can use the switch to shut the power supply off, rendering the water heater harmless. This gives you time to call a professional.

Speaking of professionals, an electrical contractor needs to know that you have a disconnect in place that will keep the power off while they perform repairs on your water heater.

Most electricians have no interest in repairing devices and appliances on a live circuit. ETP expects contractors to secure an energized work permit before they repair energized equipment.

A disconnect makes energized work permits unnecessary because it de-energizes the heater, making repairs so much safer.

Don’t forget the law. If your local code expects you to pair a water heater with a disconnect, you must comply.

As you can see, water heater disconnects are not only essential but the law doesn’t give you as much of a choice as you think. Though, the legal regulations surrounding this issue are not as strict were the type of disconnect is concerned.

If you want to stay within your inspector’s good books, try to keep the following in mind:

  • The only thing you need to do to comply with the law is to install an electrical panel within the line of sight of the water heater. This has to be the same electrical panel that serves the water heater.
  • If you have this electrical panel in place, you don’t have to worry about installing a separate disconnect for the water heater.
  • Inspectors will give you grief over the absence of a disconnect within the line of sight of a hard-wired water heater. But they don’t have anything to say about water heaters with a cord that plugs into a wall outlet.
  • Water heaters with cords are somewhat rare these days. But they exist. The plug is very important in this scenario because it acts as a disconnect. You can cut the power by simply pulling the plug out. That being said, just like the panel, the plug should be within the water heater’s line of sight.
  • Wall switches are frowned upon. You can still use a switch as a disconnect (30 amps). But it is risky because anyone can flip the switch without realizing what it does. You should add a label that says ‘Water Heater’ to prevent people from mistaking it for a light switch.

How To Look At A House mentions an interesting device called a lockout device that you should consider. A lockout device is a metal tool with a hasp and a hole.

You install it on the water heater’s circuit breaker. Then, you pass a padlock through the hole to keep the circuit breaker in the ‘Off’ position. You should think about getting a lockout device if you are worried about random passersby flipping the water heater circuit breaker to the ‘On’ position while you or your contractor perform repairs.

The ‘Line of Sight’ component of a water heater disconnect is very important. It isn’t enough for you to ensure that you can see the switch from the water heater. You should be able to see the water heater while standing at the switch. Otherwise, you may incur a penalty from a, particularly strict inspector.

What is a Disconnect for a Water Heater?

A disconnect is simply a switch. Some people call it ‘Safety’.

As the name suggests, the objective of a disconnect is to disconnect a device or appliance from its power supply. When things go wrong, you need a way of immediately cutting the power. This is the role the disconnect/switch plays.

What Size Disconnect Do I Need For A Water Heater?

The average water heater runs on a 240V circuit. It requires a 30A double-pole breaker and 10-2NM cable.

You have to make sure that the rating of the disconnect matches the voltage of the water heater. The disconnect should also include an ‘ON/OFF’ label.

What Amp Disconnect Do I need For A Water Heater?

If the water heater’s wattage rating is 4500, you will need a 25 or 30-amp breaker. In other word, if you have a 30A breaker, the disconnect should be at least 30A. 

To find the right amp rating for the disconnect, you need two things, namely: voltage and wattage.

1). Wattage

Every water heater has a wattage rating that reveals the power and capacity of that heater. The wattage of a heater is normally written on the heater. Look for it near the panel hiding the heating element. The wattage will affect the cost of the water heater.

2). Voltage

A water heater will either run on 120V or 240V.

SFGATE says that water heaters that run on 120V have one heating element. They are not very appealing because their recovery time is far too long.

Water heaters that run on 240V use two elements. If your water heater runs on 240V, the label will reveal a wattage rating for each element. You don’t have to add the two wattage ratings of a 240V water heater together to determine the amount of power the heater consumes.

Doing so would suggest that the heating elements operate at the same time, which isn’t the case. If your 240V water heater has two elements with a rating of 4500 watts each, the water heater’s wattage rating is 4500. It would be inaccurate to multiple 4500 by 2.

3). Amperage

Once you know the wattage and voltage ratings, you can find the amperage. It is a simple matter of dividing the wattage by the voltage. In other words, 4500/240. The answer is 18.75A.

Is 18.75A the right amp rating for a water heater disconnect?

No, it is not. You have to multiply that figure by 125 percent. This gives you 23.43A. You don’t have to get a breaker with an amp rating of 23.43A.

Aim for a disconnect whose amp rating comes close to this figure. A 25 or 30-amp breaker should do nicely for a 4500W water heater. For the most part, you cannot go wrong with a disconnect whose amp rating is equal to or greater than the rating of the breaker.

You don’t want to install a disconnect with a lower amperage than you need. The heater will cause incessant tripping. This isn’t just a source of irritation. The sudden loss of power can damage the heater in the long run.

This is why you are encouraged to hire a professional contractor to install your water heater disconnect. You can trust them to select a disconnect of the right amp rating.

What Height Disconnect Do I Need for a Water Heater?

Though there is no minimum height for a disconnect switch, the switch cannot be more than six feet seven inches from the floor. You have to measure from the center of the operating handle’s grip to the floor or working platform.

You can ignore this rule if the switch or circuit breaker is next to the equipment it serves. You can mount it at a higher point.

Water Heater Disconnect Code

The NEC does not directly address water heaters and disconnects. However, the regulations expect homeowners to pair water heaters with disconnects because Article 422.31(b) mentions permanently connected appliances whose rating exceeds 300 volt-amps.

Water heaters fit the bill. The NEC says that appliances in this category can use an overcurrent device as a disconnect if you can see the overcurrent device from the appliance. You can also use an overcurrent device as a disconnect in this situation if you can lock it in the OFF position. For instance, by using a lockout device.

How Do You Hookup a Water Heater to a Disconnect?

1). Go to the electrical panel and switch the power off.

2). Identify a suitable spot for the disconnect.

3). Place the disconnect on the spot you chose and secure it with screws.

4). Start wiring the disconnect. You need one set of wires to run from the power supply to the line side of the disconnect, and another set of wires to run from the load side to the heater.

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