Fluctuating high voltages, a lost phase, and a hot water control relay in the ‘off’ position are three different reasons why a water heater won’t work after an outage.
A power outage due to a fault with the electricity network can be caused by many things.
The best thing to do is to contact your local electricity power lines company for details about the power outage. This post will show you three reasons why the water heater isn’t working from an electrician’s perspective.
Water Heater Wiring & Fault Finding
A water heater can be powered by electricity, gas or other systems. Understanding what hot water system you have is the first step to finding out what is wrong.
For example, electric hot water heaters are often controlled by relays which turn the hot water on or off automatically. This won’t be present with gas hot water systems.
In general, an electric hot water system uses a lot more electrical power than gas hot water and is harsher on your power bill.
The unit for a gas hot water heater is normally plugged into a standard wall socket while an electric hot water cylinder is hard wired with a bigger cable to compensate for the larger amount of current it draws.
A domestic electric hot water heater is typically sized at 2-3 kilowatts of power but can be larger. Larger cylinders may have more than one heater element and be powered by more than one electrical feed.
An electric hot water heater will have at least one element, a thermostat, an isolating switch, potential relays and contactors turning it on and off.
The cable at the switchboard for the hot water heater will be connected into a miniature circuit breaker (MCB) or fuse which protects the circuit from overloading and short circuits.
Water Heater Not Working After Power Outage – Reason #1
High Voltage Surge
Likelihood: High – commonly accompanying power outages in my opinion. Contact your local lines company for more information on the electrical fault.
Fixable? Yes, may require replacement of the water cylinder element, thermostat or switch.
A power outage isn’t usually the reason why a water heater wont work. Instead it is the voltage surges preceding the outage that can cause components to not function properly.
A water heater is designed to work at a standard voltage.
For America this is 120 or 240 volts at 60 Hertz and for AUS/UK/NZ it is 230 volts at 50 Hertz. The components in the water heater including the element, thermostat, switch contacts are all rated to work at a specific voltage.
When this voltage gets too high even if it is only momentarily these components start to get damaged. If the voltage surge gets very high it can cross the insulation barrier (‘jump’ through the insulation) on a cable and short out against something.
The solution to voltage surges is to install surge protection which to protect a water heater would be installed at the switchboard.
Water Heater Not Working After Power Outage – Reason #2
An Electrical Feed Is Still Offline
Likelihood: High – if the water heater is powered by more than one electrical feed (phase). Contact your lines company to find out if an electrical feed is still out.
Fixable? Yes, wait for the electrical feed to come back online.
If your property has three phase power it could be possible that one phase is offline. This phase would normally be powering your hot water heater. A lost electrical feed is a common occurrence when a nearby powerline is down, for example. Waiting for this electrical feed to come back online will resolve the problem.
Water Heater Not Working After Power Outage – Reason #2
Hot Water Control Relay Is Off
Likelihood: High – this relay can trip off when power is lost.
Fixable? Yes, the hot water relay should automatically reset after a set amount of time.
Electric hot water systems are often controlled by automatic relays that turn the hot water on and off. These automatic relays are controlled by the power companies and are used for managing the load on the electrical network because hot water cylinders use a lot of power.
When the power is shut off due to an outage, sometimes the relay is also shut off. When the power is returned, the relay often doesn’t immediately reset and may take some time to turn back on. This could be 20 minutes. Waiting for it to come back online should work.
The hot water control relay can be found in a few places. Usually it is in the switchboard or with the electrical meter.
Surge Protectors
Surge protectors will help ensure that high surge voltages are diverted away from appliances thereby protecting them from damage.
A surge protector is a small circuit breaker sized device that lives in your switchboard. Its job is to take surges and send them to your earthing system.
Multiboards can also contain surge protection however they will only protect whatever appliance is plugged into it. Surge protectors located in the switchboard will protect all appliances in the home.
Electrician’s Perspective
A high voltage surge damaging a critical part of the water heater such as the thermostat is the most likely reason why it isn’t working.
Luckily replacing a damaged element, thermostat or switch is possible without having to replace the whole heater unit.
A hot water relay in the off position is also a possibility. Waiting for the relay to turn back on will resolve the problem.
We Fix Faults is an electrician blog looking to find and solve common electrical problems in the home. If you have any topics you’d like us to cover send us a message above.