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What is an RCD, and what should you do when it trips?
An RCD, or residual current device, sits in your consumer unit and cuts the power when it detects a fault, which helps protect people from electric shock [S1]. If it keeps tripping, Electrical Safety First says there is likely to be a fault with an appliance or the wiring, and a registered electrician should investigate [S2].
Last reviewed:What is an RCD?
An RCD, short for residual current device, is a safety switch in the consumer unit, the box many people still call the fuse box. Electrical Safety First describes it as a life-saving device that cuts out the power when it detects a fault and helps prevent you getting an electric shock [S1]. It is not the same thing as an ordinary circuit breaker, although the two can sit side by side in the same box, and some devices combine both jobs.
You do not need to know how it works inside to use this page. What matters is what it tells you. When an RCD trips, it has switched a set of circuits off on purpose. That is the device protecting the house, not a nuisance to be worked around.
How can you tell whether your consumer unit has one?
Electrical Safety First says to look for a button marked "Test" or "T" on the consumer unit. Pressing it switches off the power to the areas of the home the device protects [S1]. If there is no RCD, or it is not working, the same page says to use plug-in RCDs for the sockets [S1].
Older consumer units may have no RCD at all, or may cover only some circuits. If you are buying an older house in Cheshire, or simply moving in, the age and layout of the consumer unit is a fair thing to ask an electrician about when you book a check. This page does not say what your box should contain, because that depends on the installation.
Why does an RCD keep tripping?
Electrical Safety First says that if the RCD in your fuse box keeps tripping, there is likely to be a fault that needs investigating, either with a particular appliance or with the wiring itself, and that a registered electrician should investigate [S2].
That is as far as this page goes. We do not give steps for unplugging, swapping or testing circuits, and we do not suggest opening the consumer unit. Electrical fault finding is regulated, skilled work. If the power keeps going off, write down when it happens and what was switched on at the time, then pass that to the electrician. A simple note like "it trips when the outside light comes on in the rain" saves a lot of guessing on the day.
Who should you call about an RCD?
Call a registered electrician. You can look one up through the official registers:
Electrical Safety First: find a registered electrician; NICEIC; NAPIT. QuoteZila is not affiliated with this organisation.
The Planning Portal says an installer registered with a competent person scheme can self-certify compliance with the building regulations [S3]. Whether a given job is notifiable is a question for the electrician, not for this page. Ask them to say in the quote whether it is, and what certificate you will get at the end.
What should you tell an electrician when you ask for a quote?
A clear description makes quotes easier to compare:
- what trips, and how often
- whether it happens at a particular time, in wet weather or with one appliance on
- the rough age of the consumer unit, if you know it, and a photo of the closed front
- whether you want only the tripping looked at, or a wider check of the installation
- your postcode, and when the electrician can get access
Ask each electrician to say what the first visit covers, and how they will price any further work once they have found the cause.
Jobs you might post
These are examples, not taken from real job posts. "The RCD in our consumer unit trips two or three times a week, usually in the evening. Please find the cause." Or: "We have just moved into a house in Nantwich and the consumer unit looks old. We would like an electrician to look at it and tell us what it needs." Or: "The kitchen circuit goes off whenever the kettle and the washing machine run together."
Get help from a local electrician
Post the job with your postcode and a short description of what trips. Up to five matched local businesses can reply [QZ2]. QuoteZila is free for customers and local businesses [QZ1]. QuoteZila is starting in Cheshire, with Crewe, Nantwich and Sandbach among the first towns, and anyone in the UK can post or register.
Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.
Posting a job is not open yet
See the electricians page for what the work covers, or the electrician cost guide for what goes into an electrician's quote.
Questions about RCDs
What does RCD stand for?
RCD stands for residual current device. Electrical Safety First describes it as a life-saving device in your consumer unit that cuts out the power when it detects a fault and helps prevent you getting an electric shock.
How do I know if my consumer unit has an RCD?
Electrical Safety First says to look for a button marked 'Test' or 'T' on the consumer unit, and that pressing it switches off the power to the parts of the home that the device protects. If you are not sure what you are looking at, ask a registered electrician to check it for you.
Why does my RCD keep tripping?
Electrical Safety First says a repeatedly tripping RCD is likely to mean a fault that needs investigating, either with a particular appliance or with the wiring itself, and that a registered electrician should look at it. This page does not give fault-finding steps, because finding an electrical fault is a job for an electrician.
Can I just bypass an RCD that trips a lot?
No. The RCD is doing its job when it cuts the power on a fault. Removing or defeating it takes away protection against shock. Leave the consumer unit closed and book a registered electrician to find out why it is tripping.
Does QuoteZila check the electricians who quote?
No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.
This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.
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Sources
- QZ1: QuoteZila product fact. QuoteZila home and jobs-for-tradesmen copy.
- QZ2: QuoteZila product fact. QuoteZila terms and matching notes.
- S1: Electrical safety advice for older and vulnerable people, Electrical Safety First. Accessed 2026-10-25. https://www.electricalsafetyfirst.org.uk/safety-advice/home-and-people/older-and-vulnerable-people/
- S2: If my RCD keeps tripping, what action is required?, Electrical Safety First. Accessed 2026-10-25. https://www.electricalsafetyfirst.org.uk/safety-advice/your-questions-answered/
- S3: Building Regulations: general information, electrics, Planning Portal. Accessed 2026-10-25. https://www.planningportal.co.uk/permission/common-projects/electrics/building-regulations-general-information/