A faulty water heater element is the most common reason why a water heater will trip a breaker. The fault could also originate inside the heater thermostat, switch, cable, or switchboard.
This post will discuss where the fault could be occurring and why the breaker will trip from an electrician’s perspective.
Why A Breaker Trips?
Circuit breakers are designed to automatically shut off power when an electrical fault occurs.
They are designed to prevent faults from developing into situations that can harm people or property.
For example, a short circuit or overload fault has the potential to cause a fire while a ground fault could deliver a fatal electric shock or damage property. In both cases it’s essential that power is shut off before any of these faults cause major damage.
There are several types of breakers each with a specific purpose. For this post I will mainly talk about MCB’s and RCD’s.
MCB’s or miniature circuit breakers are the most common type of circuit breaker. They are designed to interrupt short circuits and overload faults. As mentioned above, these faults have the potential to cause fires.
A water heater must be protected against both short circuit and overload. Therefore there should be a MCB in the switchboard for it (unless the property has an old switchboard with plug in fuses).
Water Heater Overload?
A water heater should be on its own dedicated circuit.
This means that it isn’t sharing the same circuit with outlets, appliances or anything like that. For this reason, if the water heater was installed properly it shouldn’t be overloading the cable.
There should be enough capacity on the circuit to handle the water heater.
We have seen water heaters getting replaced with larger units without checking the current capacity of the cable. If this happens it is easy to overload the circuit and trip the breaker.
Does A Water Heater Need An RCD?
Next, we have RCD’s. These circuit breakers are designed to trip power if a ground fault occurs.
A ground fault occurs when someone receives an electric shock or current leaks to earth.
RCD’s are a requirement in modern homes but they might not be on the water heater circuit depending on how it was installed.
If the water heater is plugged into a wall socket it probably will be on RCD. If it is hardwired it may not be on RCD.
In most cases, there won’t be an RCD on the water heater circuit but that isn’t guaranteed.
With this in mind, a water heater will most likely trip a breaker due to a short circuit located somewhere in the circuit (unless you’ve installed a new water heater which is overloading the existing circuit).
5 Places Where A Water Heater Fault Could Occur
Water Heater Tripping Breaker? – Reason #1
Faulty Water Heater Element
Likelihood: Most common reason why it’ll trip a breaker in our opinion
The water heater is responsible for heating the water.
It is the main current drawing component of the water heater.
It is also the only component which is immersed in water.
Over the long term, it is exposed to the corrosive and oxidising effects of water.
The element is also used daily and one of the main electricity consumers in the home. This use generates wear and tear.
This eventually causes the element to fail, short circuit, then trip the breaker.
Replacing a water heater element is a common job of an electrician.
Voltage at the element but no current being drawn indicates a faulty element.
Water Heater Tripping Breaker? – Reason #2
Faulty Thermostat
The thermostat is responsible for switching the element on or off according to a set temperature.
The thermostat won’t typically short circuit but it is worth checking the condition of the thermostat to ensure that there is nothing shorting out the live contacts.
Things that could short out the live contacts include ant nests, water intrusion, or something physical shorting out the contacts.
Water Heater Tripping Breaker? – Reason #3
Faulty Water Heater Switch
The water heater switch is responsible for switching a relatively high current.
For this reason it can fail over a period of time. A symptom of this is a switch that is either stuck or too soft to press.
It may even short against the neutral cable located behind the switch. There may also be ant or other bug nests in the switch cavity. Bug nests are a common cause of short circuits tripping breakers.
Water Heater Tripping Breaker? – Reason #4
Faulty Cable
The cable between the water heater and switchboard could also be damaged.
As the cable likely goes up a wall and then through a ceiling cavity or underfloor it is difficult to check the physical condition of the cable. For this reason the cable is generally tested with an insulation resistance tester or ‘megger’ to check for any shorts in the cable.
The cable can become damaged due to rodents, physical damage and many other reasons.
Water Heater Tripping Breaker? – Reason #5
The Switchboard
A fault in the switchboard such as a loose cable or short circuit could be causing the fault. Sometimes we find burnt rodents in switchboards which are shorting out cables. It is unlikely in most cases but is always a possibility.
Electricians Perspective
A faulty element is the most likely reason why the water heater is tripping a breaker. Replacing the element will fix the problem.
Checking the general condition of the circuit is also important to rule out any other reasons or faults. We Fix Faults is an electrician blog. If you have any information you’d like to share send us a message here.