Geyser Not Heating? Common Causes and What to Do

You turn on the hot tap and the water stays cold. A geyser not heating is one of the most common calls Pretoria homeowners make to an electrician, and the cause is usually one of a handful of electrical faults. Some you can check yourself in a few minutes. Others need a qualified electrician with the right test equipment. This guide explains the common causes, what you can safely check, and when it is time to call for help.

First, safe checks you can do yourself

Before you assume the worst, rule out the simple things. None of these checks involve opening the geyser or touching wiring.

• Check the DB board. Look for a geyser breaker that has tripped to the off position, or an earth leakage unit that has dropped. If the geyser breaker trips again as soon as you switch it on, leave it off. That is a sign of a fault, not bad luck.
• Check the geyser timer or controller. Many homes have a geyser timer, a smart controller or a switch in the passage. A power failure or load shedding can reset the clock, so the geyser may simply be switching on at the wrong time.
• Check the isolator switch. Some geysers have an isolator near the unit in the roof or outside. Make sure nobody has switched it off.
• Give it time. After a power failure, a full 150 or 200 litre geyser can take several hours to heat from cold. If you have been using a lot of hot water, it may just be catching up.

If everything is switched on, the timer is right and the water is still cold after a few hours, the fault is most likely inside the geyser’s electrical parts or in the circuit that feeds it.

The most common causes of a geyser not heating

1. A failed heating element

The element is the part that actually heats the water. Over time, scale from hard water builds up on it and it can burn out. A burnt-out element often makes the earth leakage trip, because water gets into the element and leaks current to earth. In other cases the element simply goes open circuit and the geyser stays cold with no tripping at all. An electrician confirms this by testing the element’s resistance and its insulation to earth, rather than guessing.

2. A faulty thermostat

The thermostat switches the element on and off to keep the water at the set temperature. If it sticks open, the element never gets power and the water stays cold. Most thermostats also have a safety cut-out that trips if the water gets too hot. Once that safety cut-out has tripped, it stays off until it is reset, and if it keeps tripping there is a reason that needs to be found.

3. Burnt or loose wiring

A geyser draws a lot of current for long periods. Loose terminals at the thermostat, the isolator or the breaker heat up, discolour and eventually burn through. Signs include a burning smell in the roof, scorch marks on the isolator or a breaker that feels warm. This is a fire risk, so switch the geyser off at the DB board and get it looked at.

4. A tripping breaker or earth leakage

If your geyser breaker or earth leakage trips every time the geyser switches on, the geyser circuit is very often the culprit. Water in the element, a damaged cable or a failing thermostat can all cause it. Our guide on why your DB board or earth leakage keeps tripping explains how to narrow it down, and our tripping and earth leakage service covers how we find the real fault.

5. Damage after a power surge

Pretoria’s summer thunderstorms and the surges when power returns after load shedding can damage geyser controllers, timers and thermostats. If the geyser stopped heating straight after a storm or a power cut, a surge is a likely cause. Surge protection at the DB board helps protect the geyser and the rest of your home.

Water only lukewarm? Here is what that can mean

A geyser that heats a little, but never properly hot, points to different problems:

• The thermostat is set too low or is drifting out of calibration.
• The element is heavily scaled and heats slowly.
• The timer only runs the geyser for a short window each day.
• Hot water is being used faster than the geyser can recover, for example several showers back to back.

If water is leaking from the geyser, the drip tray or the overflow pipe, that is usually a plumbing problem with the tank or valves. Switch the geyser off at the DB board until it has been repaired, because water and electricity do not mix.

Why you should not repair a geyser element yourself

Replacing a geyser element or thermostat means working on a 230 V circuit that carries a heavy load, in a hot, cramped roof space, next to a tank full of water. Wrong connections, a missing earth or a poorly tightened terminal can lead to shocks, fires or a geyser that overheats. Electrical work in your home also needs to comply with SANS 10142, and work done by an unqualified person can cause problems with insurance claims.

A qualified electrician tests the element, thermostat, wiring and earth leakage properly, finds the real fault and fixes it neatly the first time, instead of swapping parts until something works.

How Electrician Worx helps with geysers that are not heating

Electrician Worx has looked after homes and businesses across Pretoria and Centurion since 2014. When we come out for a geyser that is not heating, we test the circuit from the DB board to the geyser, check the element, thermostat, isolator and wiring, and explain what we found before we repair it. All work is done neatly and to SANS 10142. Read more about our geyser repairs or see all our electrical services in Pretoria.

If you are thinking about solar water heating or a solar system to keep your geyser running during load shedding, see our solar power page.

Frequently asked questions

Why is my geyser not heating but the breaker is on?

Check the geyser timer, controller and any isolator switch first. If they are all on, the most likely causes are a failed element, a faulty thermostat or a tripped thermostat safety cut-out. An electrician can test each part to find which one has failed.

How long should a geyser take to heat up?

It depends on the size of the geyser and the element, but a full geyser heating from cold can take several hours. If the water is still cold the next morning with the power on, there is a fault.

Can a geyser element cause the earth leakage to trip?

Yes. When an element burns out, water can get inside it and leak current to earth, which trips the earth leakage. It is one of the most common reasons for an earth leakage that trips at night or early in the morning, when the geyser switches on.

Is it safe to keep resetting the geyser breaker?

No. A breaker or earth leakage trips to protect you and your home. If it trips again after one reset, leave the geyser switched off and have the circuit tested by a qualified electrician.

Geyser still cold? Call Electrician Worx

Our qualified electricians go out to homes across Pretoria and Centurion, Monday to Friday from 08:00 to 16:00. We test properly to find the real fault and do neat, quality work. Call 012 383 2011 to make an appointment, or visit our contact page.