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  • Alan Beard

RCD's tripping what might be the cause

Updated: Nov 14, 2022

The cause of the RCD tripping could be a genuine fault which must be investigated and resolved as it could lead to a fire or electric shock but it may also be down to the design of your installation and some simple changes may resolve the problem.

Which type of RCD do you have AC, A or maybe B

MK Type A RCD protecting circuits
Typical RCD in a consumer unit

Most homes will have type a 30mA type AC RCD but with modern electrical equipment these can cause nuisance tripping.

Modern equipment can cause electrical noise that upsets type AC RCD's; washing machines with spin speed selection, light dimmers, computer equipment, etc.

It's now recommended that with the proliferation of this type of equipment the RCD is changed from a type AC to type A. This is a quick and relatively cheap change

Hager provide a great explanation of RCD types and symbols

Many electronic devices now have filters inside to prevent interference with other equipment, these filters create earth leakage current, with larger amounts of equipment this can build up to trip a 30mA RCD.

If this is the case and there are multiple circuits on single RCD the simplest solution is to have separate RCD's for each circuit and split the leakage current over them. Depending on which consumer unit you have it may be possible to achieve this in the existing consumer unit or a modern replacement may be required.

Conversely if there is an electric car charger it can stop a type A or AC RCD working properly. In these cases it's essential that circuits for many EV chargers are equipped with a type B RCD.

If you don't have significant electrical knowledge and experience please don't try to resolve these problems on your own, please call in a professional.

I can help resolve these problems with a site survey, I have an insulation tester and clamp meter which allows me to measure the leakage current to help understand the likely cause and best solution for the problem.

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