• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer
DIY Doctor
MENUMENU
  • DIY Doctor menu logo
  • Home
  • DIY Projects
    • All Projects
    • Brick, Block, Marsonary and Concrete
    • Damp, Condensation, Rot and Woodworm
    • Doors, Windows and Conservatories
    • Electrical
    • Fencing, Decking, Paving and Patios
    • Floors, Walls, Ceilings and Lofts
    • Garages, Sheds and Outbuildings
    • Gardening and Landscaping
    • General Building, Self Build and Renovation
    • General Repairs and Cleaning
    • Green Living and Eco DIY
    • Ground work, Foundations and Drainage
    • Heating, Central Heating and Boilers
    • Joinery and Carpentry
    • Materials, Fixings and Fixing
    • Painting, Decorating and Finishing
    • Planning Regs, Project Management and Safety
    • Plastering, Plasterboard and Rendering
    • Plumbing
    • Roofing and Gutters
    • Tiling and Tiles
    • Tools, Appliances and Access
    • DIY Tips
  • UK DIY Forums
  • DIY Videos
    • Bathroom DIY Videos
    • Building Foundation Videos
    • Building Videos
    • Carpentry and Woodworking Videos
    • Damp and Damproofing Videos
    • Decorating Videos
    • Electrical Videos
    • Fitting Blinds Videos
    • Flooring Videos
    • Gardening Videos
    • Green and Eco Friendly Videos
    • Hand and Power Tools Videos
    • Heating and Central Heating Videos
    • Kitchen Videos
    • Plastering and Drylining Videos
    • Plumbing Videos
    • Security Videos
  • Find Tradesmen
    • Find a Tradesman
    • Contract Download
    • Working with Tradesmen - Ultimate Guide
    • Home Improver Protection
    • Price Doctor
  • Tool Store
    • Tool Store
    • Bookstore
    • Tool Reviews and Product Reviews
  • Blog
    • Blog
    • DIY Competitions
  • About us
    • About DIY Doctor
    • What we do
    • Trade Shows and Exhibitions
    • Master Classes
    • Contact Us

Home > DIY How To Projects and Tutorial Guides > How to Wire an Immersion Heater and How to Replace an Immersion Heater Thermostat

How to Wire an Immersion Heater and How to Replace an Immersion Heater Thermostat

Wiring an immersion heater safely and making sure you have the correct cables. In this project guide we show you how to wire an immersion heater and include and also how to replace your immersion heater thermostat if it breaks and causes your water to become very hot.

Don't want to do this job yourself? Let us help you find a tradesman local to you

TwitterFacebookPin ItBuffer
Project MenuProject Menu
  • How to Tutorial
  • Video
  • Find Tradesmen
  • Help

Warning: To complete electrical works you must comply with Electrical Regulations – Click here for more information.

Diagram of immersion heater wiring

Diagram of immersion heater wiring

Immersion heaters are usually rated at 3KW which, under normal circumstances would qualify them for being wired into a ring main. However, because immersion heaters can be left on indefinitely, taking 3kw from a ring circuit would reduce the circuits capacity immensely so immersion heaters are placed on their own radial circuit.

Cable Sizes for an Immersion Heater

The mains cable for an immersion heater is a two core and earth 2.5mm cable. This cable should run to a 20amp double pole isolator switch (With neon indicator light) from where a heat resistant 16amp cable or flex should run to the heater. Since April 2004 new and replacement immersion heaters must be protected by an overheating safety cut out.

Availabel Sizes of Immersion Heaters

Immersion heaters are available in the following lengths:

  • 27 inches
  • 18 inches
  • 11 inches
  • 7 inches

How to Replace an Immersion Heater Thermostat

Replacing the thermostat is not a difficult operation. The immersion heater operates just like a kettle with the element in the water heating up to the required temperature which, in turn, heats the water.

If the element breaks or malfunctions the fault will usually short circuit the mains box and you will need to change the immersion heater. Any other fault is likely to be the thermostat. See our project on chaning an immersion heater for more information on this.

Please remember to make tight all electrical connections. Loose connections can cause fires.

To replace the thermostat in the immersion heater should your water get scalding hot all of a sudden, make sure the electricity to the immersion is off and the fuse in the isolator switch is out.

Undo the top screw’s of the thermostat cover and you will usually see a cable clamp holding the mains flex in place. You will usually need to undo this cable clamp before the lid can be lifted clear.

The wire going in to the thermostat from the flex, and the wire coming out to the probe can be removed by undoing the small retaining screws and the thermostat rod can be lifted free. Please reme,ber to make a note or take a picture showing where each wire goes so that wiring the replacement back in is as easy as possible.

Replacing the thermostat is the operation in reverse.

Many replacement parts for your immersion heater and heating system can be purchased from a variety of sources including online and your local DIY stores.

All project content written and produced by Mike Edwards, founder of DIY Doctor and industry expert in building technology.

TwitterFacebookPin ItBuffer

Video

Back to the Top

Apologies, but we don't seem to have a video for this project yet, but we will do our best to get one up soon

Find a Reliable Local Tradesman

Back to the Top
Don't fancy doing this project yourself? We work with the industries best to ensure that we recommend only reliable and trustworthy tradesmen.
Let DIY Doctor help you find a tradesman

Find a tradesman now!


More Help

Back to the Top
Related Projects That May Help You:
  • Fixing an Immersion Heater – How to Replace an Immersion Heater Yourself
  • Electric Cable Sizes and Amp Ratings for the UK – Electrical Resistance and Cable Rating Tables
  • Stripping Cables – How to Strip Electrical Wire, Cable or Flex
  • Electrical Safety – How to do Electrical Jobs Safely
  • Electrical Cables – How are Electrical Flexes and Electrical Wires Made up and What Cables and Wires you Should use for Certain Jobs
Give us Some Feedback!
Was this page useful:
We read and respond to all feedback by email. To allow us to do so you will be added to our email list, however you can unsubscribe at any time using the links at the bottom of any of our emails. Find out more in our privacy policy. Any DIY questions should be posted to our Forum
Sign me up to the DIY Doctor Newsletter:

Primary Sidebar

DIY Doctor deal of the week

DIY Utility Kit:

Build your own work bench!

RRP Price: £49.99

Special Price: £39.95

Get it here now

See our other deals now!

Master Basic DIY - By DIY Doctor

Our Book - Master Basic DIY

Grab your copy now for all the DIY help you need right at your finger tips!

Buy it Here!

Signup for our Newsletter

Keep up to date with our DIY projects, tips and latest deals

Sign Me Up!

Our Sponsors

Find out about advertising on DIY Doctor

Advert

Other Similar Projects
  • How To Check You Are Using The Right Cable For The Right Job
  • How To Choose The Right Electric Cable For The Right Job
  • How To Be Safe With The Electricity In Your Home
  • How To Replace An Immersion Heater In Your Central Heating System
  • How To Safely Strip And Prepare Electrical Cables For Wiring

Footer

DIY Doctor

Site Menu

  • About Us
  • Contact Us
  • Blog
  • Media/Press
  • Community Work
  • DIY Projects
  • DIY Videos
  • Superstore
  • DIY Tips
  • DIY Suppliers
  • UK DIY Forum
  • DIY Webinars

Other Stuff

  • Advertise
  • Competitions
  • T and Cs
  • Privacy Policy
  • Cookies
  • NHIC
  • Sitemap

DIY Doctor Social Channels

Follow us on Facebook
Follow us on Twitter
Follow us on YouTube
Follow us on Pinterest
Follow us on Tumblr

DIY Doctor are members of:

© DIY Doctor Ltd 2021 All Rights Reserved