Immersion Heater Is Not Working

immersion heater

You are feeling excited and well deserved after a day of hard work. It can be frustrating when the hot water tap only lets out a small amount of warm water! If you have to wait a long time to get hot water, you have some issues in the system.

You are wondering why my immersion heater is not working? The likely causes of immersion heater issues may be anything from a limescale buildup to a faulty thermostat.

Is your hot water not reaching the temperature you expect it to? Then read on for insight into what could be causing this issue. We will give you few tips on what can you look out for.

Why I have cylinder immersion heaters

The old water heater that used a gas burner to warm the water was replaced with a storage tank and immersion heater.

First, you should have a hot water cylinder in the airing cupboard or the loft. Inside the storage tank, you can find the cylinder immersion heaters. You can have two immersion heaters, one at the top and one at the bottom. The immersion heater is heating your water inside the steel tank providing you with hot water. The immersion heater replaces the gas water heaters, which is not manufactured anymore.

The upper heating element is just for a boost. You can turn it on and you will receive hot water in less than 10 minutes.

How does my heating element works?

heating element

The immersion heaters are heating the cylinder directly. In simple terms, this means that the element is slid inside the water tank.

The heating element is a small metal coil that is inside the cylinder. An electric current will pass through this thin wire. And the element will heat the water.

Your kettle in the kitchen is working the same as an immersion heater in the cylinder. The water heater is working the same too.

The immersion heater is connected with the main electrical supply through an isolating switch that you can find next to the cylinder. You can turn on and of the cylinder with a switch. The electricity flowing through this wire, which will be heating the heating element which heats the hot water.

Also, you can find external and internal safety devices, this can be a thermostat that regulates the water temperature.

How do I get hot water?

When you start to use your hot water, you open the tap and the hot water start to flow out. Meantime the cold water (what should be high pressure) will enter the cylinder. This will push out the hot water from the tank, thus you have good pressure at the taps.

When you using a lot of water the temperature in the cylinder drops. The thermostat will sense the drop and turn on the immersion heater heating your water.

The process between the hot and cold water mixing in the cylinder are the following:

When the hot water heats up, it will start to rise to the top of your cylinder, leaving the cold water at the bottom. This heated water then will flow out to your taps.

Make sure your cylinder temperature is set to at least 55°C so you can avoid legionella bacteria.

Read more about how can you avoid the dangerous legionella bacteria in your storage tank.

My immersion heater stopped working

The reason behind this can be a few things. Limescale build-up can be an issue. Or the constant use of the immersion heater. If you have also a gas boiler that heats your cylinder, try to use that instead. The immersion heater consumes a lot of electricity.

The average immersion heater will last up to 6000 hours. Manufacturers will give a 5-year warranty. But most of the storage tanks in the UK are over 20 years old.

Why is my immersion heater not working?

The most Common Immersion Heater Faults

In the next few minutes, we explain the most common problems that can cause the immersion heater to fail. But remember not to carry out any work if you are not competent or not confident. We will explain how to investigate the source of your problem starting with the basic immersion heater faults.

1.Check if your circuit breaker tripped

circuit breaker

For the immersion heater to work, it needs electrical power. If there is no power going to the heating element there will be no hot water supply. The immersion heater electrical panel breaker could be tripped.

This is to protect your circuit from overloading. If your circuit overloads this can cause a fire.

All you have to do is to go to the electrical panel and check if the breaker is tripped and turn back on. If you are lucky it could work again. But if not then you have an issue with the heating element.

If you are an advanced DIY homeowner, you can test if the immersion heater has a 220-240 volt supply.

If you start to work on any electrical device, the first turn of all the circuit breakers, remove the immersion heater plastic top and don’t touch any wiring. After you remove the lid, turn back on the power and check if there is 240 Volt.

Stay safe, stay alive. Do not rush.

Get more advice from our experienced plumber and check out our services!

Read more about how can an immersion heater be tested with a voltmeter.

2.Faulty thermostat

immersion heater thermostat

If you start to investigate the fault, turn off the power first. On some systems, there should be a red reset button on the thermostat that you can press. This will restart your immersion heater and everything will be back to normal.

If you have an older system the steps are the following:

Switch off the circuit breaker in your electrical panel.

On the immersion heater, there is a plastic cover which you have to remove.

Do not touch any wire with your bare hand!

On the thermostat, you can press the simple reset button. This could be a small round red button.

Put back the plastic cover and check the system by turning on the power.

If it’s still not working, you can change the thermostat yourself after you checked there is no power going into it with a voltmeter. But if you are not confident to do so book one of our professional plumbers who can investigate the fault.

3.Your heating elements is damaged

You can’t investigate your fault yourself but just think about the past week’s cylinder performance.

Does the storage water tank take a while or quick to heat up? Usually, a 150Liter cylinder would take between 1-3 hours.

What is happening here, is that the element inside the cylinder corroded. It will still survive a few weeks but when a hole appears on the element, the water will leak inside. In a case like this, the element will turn trip the circuit breaker.

We do not encourage you to change any faulty elements. Only a professional plumber or brave electrician can do this work.

This is serious plumbing work involving closing the water that supplies the tank. Draining down the cylinder and taking out the immersion heater with special tools. Also, if an airlock will build up in the pipes, the plumber can deal with that and know how to resolve the upcoming situation.

Even for a professional plumber is hard work, because sometimes the immersion heater is not moving.

Also, it can happen while the plumber taking out the immersion heater the cylinder can crack and this needs replacing. This is a rare occasion, but if the cylinder is over 30 years old it could happen.

4.Limescale inside your cylinder

This could happen in hard water areas. And we can say that part of North London is falling into this category.

If limescale builds up in your water tank, this can damage the heating element and also you can have less water in the tank.

Again, only a professional plumber can clean out a cylinder. For this work, the cylinder needs to be washed with a high-pressure jet.

The best way to avoid limescale buildup is to call a plumber who can install a limescale reducer. This reducer will be installed onto the cold water pipe before the cold water enters the cylinder.

Cylinder Insulation

hot water cylinder insulation

The insulation is not a fault, but it can reduce heat loss. But if the insulation starts to come off from the water heater then the cylinder will takes double the time to heat up. And even after the cylinder heats up, will lose a lot of heat because of a lack of insulation.

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Frequently asked questions about immersion heater faults

Q. How much does it cost to replace a cylinder immersion heater?

To replace an immersion heater would take around 2-4 hours for the plumber depends on the circumstances. If there will be no complications it will be quick work.

What we mean by plumbing complication:

  • An airlock will be trapped in the pipes.
  • The immersion heater cylinder thread can crack. In this case, the cylinder needs replacing.
  • There will be no draincock in the system to drain the cylinder and the plumber needs to improvise.

Q. Who can change an immersion heater?

A plumber or gas engineer can replace your immersion heater. The best is to get a gas engineer because they can work on gas boilers too. And most likely your water tank will also be heated with the boiler. Or you have a water heater which you need a gas engineer.

Q. What are the different types of immersion heaters?

The copper cylinder has two common sizes which are 11 inches and 27 inches.

There are many types of the cylinder on the market so we advise you to search or buy the immersion heater specially made for your cylinder.

Q. How do you reset an immersion heater?

You should follow the instruction we give above and press the reset pin!

Q. How do you know if the immersion heater is working?

You can’t test it. But if you leave the immersion heater on for a maximum of 3 hours, you should have hot water by then.

Q. How long should the immersion heater last?

It should last at least 5 years or 6000 hours.

Q. Why is the water heater warm and not hot?

Check the temperature settings first. Make sure it is set to at least 55°C.



Do you have hot water by now?

We hope by now, you know the basics of how to investigate some of the immersion heater faults. If you still don’t have any success contact us today for advice! Our expert plumber will help you sort out your problems.

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