Main Switch Keeps Tripping. Why and What to do?

1) Why does my Main Switch Keep Tripping? 

The answer is that there is an electrical fault with your wiring system. The photograph above shows three different consumer units and each contains a Main Switch that is designed to trip when there are electrical problems. The reasons for the Main Switch tripping could be any of the following:

• Main Switch is Faulty
• Water in electrical system
• Short Circuit 
• Earth Fault
• Appliance Fault
• Damaged Wiring
• Damaged Outlets
• Damaged Lights
• Burnt Out Connections
• Too much electrical demand

Despite the way in which these are listed, this does not relate to how common each issue occurs. For instance, a Main Switch does generally not become faulty unless there are other electrical problems first. It is far more likely that tripping is occurring from damaged wires or appliances than the switch itself going faulty.

2) Main Switch is Faulty

Whilst it is not one of the most common reasons for electrical circuits tripping or power loss, it can happen. A Main Switch can go faulty over time. These Main Switches that are designed to trip are RCD devices and will trip when they become very old due to failing internal components making the device become too sensitive. 

These devices are designed to be tested every 6 months by pressing the test button and further tested by an electrician every ten years or so to ensure that, not only are they tripping, but they are tripping within the required time to prevent injury and electrical shock. 

It is not a job that you can carry out yourself with a stop watch, this requires specialist electrical test equipment as these devices are designed to trip incredibly quickly! With a specialist RCD tester, the electrician can inject a fault current, record the trip time, and ensure that it complies with the BS7671 wiring regulations. 

3) Water in Electrical System

Most of us will definitely have some outdoor electrical bits and bobs. In fact, we probably don’t even think about it anymore. Outdoor porch light, security light for the garden, outdoor socket outlet for the occasional party or for mowing the grass. Then there is the pond pump which we always forget about.

The issue is, water is the worst enemy of an electrical system. When water enters electrical wiring or electrical accessories it acts as a bridge between electrical connections and allows electrical current to flow where it shouldn’t. The result is that the Main Switch thinks there are people receiving electric shocks as there is some electricity missing from the system. 

This electricity or electrical current, actually flows to earth. Either through a human body or from the Line/Neutral conductors to the earth connections.

Water can seep in over time to electrics. Silicone and other sealants can fail and allow water into outdoor electrical enclosures, pond pumps and garden lights seals can fail and allow water to pass into the electrical workings and this can trip the electrical supply to an entire system. 

4) Short Circuit

When I say short circuit, I must be specific. Technically a short circuit is a direct connection of low or negligible resistance between Line and Neutral. When a short circuit occurs there is a very large fault current that flows around the electrical circuit and without a switch to operate and disconnect the electricity supply there is likely to be a fire.

Most types of Main Switch will not trip at all. RCD types of Main Switch will trip when there are small amounts of current missing or leaking from Line or Neutral to Earth. 

Only a circuit breaker will trip if there is a short circuit. If the Main Switch happens to be a specific type of circuit breaker, then it will trip for short circuit faults.

5) Earth Fault

When there is an unwanted connection to earth, electrical current can leak away from an otherwise healthy electrical circuit and disappear to earth. This causes an imbalance in the electrical current flowing in the circuit. 

Let’s get scientific for a moment. 

There is a healthy 1 amp of electrical current flowing in a circuit. This should be exactly the same flowing down the LINE conductor and back through the NEUTRAL conductor. Everything is fine and all switches are happy. The MAIN SWITCH senses no imbalance and will not trip. 

NOW THEN…..

Water enters the cable and bridges the connections allowing a very small amount of electrical current to leak away. Water is not a great conductor of electrical current so not much current can leak away but sometimes enough can. 

The MAIN SWITCH senses that there is 1 amp flowing down the LINE conductor but only 0.97 amps flowing back through the NEUTRAL. This missing 0.03 amps (or 30 milli amps) is enough to trip the 30 milli amp RCD device.

6) Appliance Fault

Just as with an EARTH FAULT appliances can go bad and begin leaking electrical current to earth. Electrical appliances have many internal electrical components that can fail such as circuit boards, wiring looms, heating elements and more. Appliances containing water are a common source of electrical problems as water enters the electrical system and causes havoc. 

In this article we talk about what to do when an RCD or Main Switch RCD is tripping and how to solve the problem. If the article doesn’t help then you will need an electrician to come and assist. 

It may be difficult to pin down a faulty appliance electrical problem as there are certain cycles that appliances run through making it difficult to determine if it is the appliance or not. For instance, a washing machine may fill with water before it spins the drum. It may then heat the water up and rotate again.

If the heating element of the washing machine is faulty, it won’t necessarily trip the electrical supply until the heating element is turned on a few minutes into the washing machine cycle. This is how faulty components in appliances can be a problem to diagnose. 

7) Damaged Wiring

Most cables are installed in such a manner as to prevent accidental damage but nevertheless we receive many calls each year to attend properties and repair wiring where DIY mishaps have caused wires to become damaged. 

Drilling the walls to install shelves or other furniture is a common cause of electrical problems. Where there are electrical accessories installed, great care should be taken drilling above, below or in the general vicinity of these. 

If you are unsure of where it is likely to be safe to drill, consult an electrician. Newer homes should be wired in accordance with the most recent building regulations and wiring regulations but older homes may have electrical cables hidden in places where one may not assume they are. 

8) Damaged Outlets

A damaged electrical outlet can easily cause an RCD Main Switch to trip. When plug sockets become broken, they deviate from the very tight tolerances to which they were manufactured. Internal parts can touch and cause earth faults or short circuits and this will lead to a blown fuse, tripping circuit breaker or even a burning smell and possible fire risk. 

There is also the risk of electric shock from a damaged electrical outlet. Even if an outlet is cracked it can easily fall apart with another knock or accidental impact. Cracked Socket outlets are a definite danger to the electrical system and those using the electrics. 

9) Damaged Lights

Poorly fitted light fittings are a cause for an RCD or Main Switch RCD to trip. If a circuit breaker keeps tripping, then ask yourself if you have carried out any DIY or light fitting swaps recently. Connections can move with time, heat and vibration and touch earthed parts causing electrical hazards and circuit breaker trips. 

Light fixtures have very little room in the ceiling cup and as such it is often very difficult to install modern lights into older properties which tend to have several different wires in the ceiling position. The source of the problem can often be a loose connection causing intermittent tripping. 

Light fixtures are best installed by a qualified electrician as despite appearing to take only a few simple steps, the installation of light fixtures can present many unforeseen problems. 

If the light fitting is very old then there could be internal problems with the wiring leading to a main switch trip.

10) Burnt Out Connections

When connections burn out, it may initially trip a circuit breaker rather than the Main Switch. In most cases, the RCD Main Switch will trip before anything else as these devices tend to be the most sensitive. The photograph shows a Main Switch that has burnt out along with all the Neutral connections in the electrical panel. 

The RCD was tripping off and despite this, the homeowners did not have the issue investigated until it would no longer turn on. By this point, the whole consumer unit needed replacing and this could very well of caused a serious electrical fire beyond the situation seen here.

Connections also commonly burn out in plug sockets , shower switches or pull cords, cooker circuits and Electric Vehicle Charging circuits. The common theme is that all of these electrical circuits typically require a large electrical demand and, combined with connection loosening over time, will burn out quickly once they start. 

11) Too Much Electrical Demand

An overloaded circuit or overloaded electrical installation will lead to problems. If each individual circuit is not overloaded but as a whole, the installation is overloaded then the breaker panel will likely take the brunt of this and burn out. 

If an individual circuit is overloaded then it may not trip immediately. In fact, it may be continually slightly overloaded without ever tripping. This can create a situation where things get hot, melt and catch fire without any intervention from the electrical system.

Modern electric circuits are designed by electricians to take account of the existing power supply and electrical loading including any specific appliance that may draw large loads like electric showers. They are also designed to ensure that the different circuits are capable of supplying the current flow that will likely be demanded of them under most operating conditions. 

12) Does every Main Switch Trip?

If we look at the photograph, we can see that this consumer unit has a Main Switch also. Nearly every consumer unit will have a Main Switch but not every Main Switch will trip! 

This switch is simply an on / off switch that isolates the electrical supply to the other switches inside the unit. There is an RCD / GFCI trip switch here that we can see. It has the yellow test button on it. This is the only Electric Shock Protection device installed in this particular fuse box / consumer unit.

There are a variety of different trip switches and safety switches that are installed in modern consumer units. There are two installed in the one above and we discuss more about these in our article on consumer units, the internal parts, and their specific jobs.

13) Common Questions

13.1) How long do Main Breakers Last?

Generally speaking, a Main Breaker will last anywhere from 20 to 40 years. This depends upon the use of the electrical installation and the load placed upon the main switch. A switch that powers a small home where only two people live is likely to be under much less stress than a commercial property where maximum power demand is placed upon the switch continually due to commercial activities. 

Electrical installations in a Domestic property should be inspected on a regular basis every ten years to ensure that there are no hidden defects, loose wiring, earthing problems or deteriorating cables and circuits. Only a licensed electrician can competently check for faulty wiring, issues in the main fuse box and the safe operation of Ground Fault Circuit Interrupters or RCD devices. This is especially important if your Main Switch is an RCD breaker. 

13.2) What are the warning signs of an overloaded circuit?

Any particular circuit, if overloaded will generally manifest as a tripped circuit breaker in most instances. Intermittent power outage on that specific circuit will also occur if the circuit is overloaded. Also beware if any of the following are occurring:

• Burning Smells
• Flickering Lights 
• Regular tripping of any electrical device
• Electrical accessories feeling warm or hot
• Power Outage without tripping switches

13.3) Do I need an Electrician to replace a circuit breaker?

YES, is the answer. There are several requirements that cannot be met without the Electricians knowledge of testing and inspection.

Without an electrician to replace a circuit breaker or residual current devices there is no guarantee that the device is correctly installed, to the right torque, has been sufficiently tested, the circuit resistance is sufficient to operate such a device or that the device will perform safely as required. 

13.4) How do I know if My RCD Switch is Faulty?

If your RCD safety switch trips regularly then it could well be faulty. It could also indicate that there are other problems occurring in the wiring installation. 

The only way to know if an RCD is GENUINELY faulty is to have an electrician carry out a variety of tests. These tests include:

• Insulation resistance testing of the circuits that the RCD protects
• Testing the sensitivity of the RCD device
• Checking for excessive Earth Leakage that the device may be seeing
• Checking the trip times for the device

Generally, the most common reasons for an RCD tripping are NOT a faulty RCD. It is more common that appliances, wiring, electrical accessories, water ingress or burnt connections are to blame.