Under Pressure: Why Your Oven Trips the Electrics

⚠️ SAFETY FIRST: EXTREME DANGER

If your oven is tripping the electrics, it is doing so because it has detected a potentially lethal fault. The Residual Current Device (RCD) or circuit breaker is acting as a life-saver. Never bypass a fuse or keep resetting a breaker without identifying the fault, as this is a major fire and electrocution risk.

as usual work safe do safely isolate the electricity supply before working on any appliances.

This is quite a common complaint and can be caused by many different issues the more common ones i find are detailed below but some issues can take quite a bit of diagnostics to find the cause of the electric tripping , and some you need to use insulation testers to pin point the faults.

Directs shorts from Positive to Neutral will blow the fuse or trip the MCB breaker as will a direct short to earth, RCDs can trip when any earth leakage current reaches a set threshold usually in domestic anyway 30ma of current. A 30 mp cooker circuit upon short shorth can have currents in the thousands of amps range for a fraction of  second prior to it operating whereas an RCD with detect milliamps of leakage current.

If  turning on a certain function say for instance the grill blows the fuse or trips the MCB breaker RCD you can usually assume that this circuit is the issue and focus your testing in this area.

But other times it may trip as soon as turning on the oven so more thorough examination is required to find the issues.

In this case i usually start by looking at the wiring itself from the plug inside the connectors and at the connection to the cooker are they tight safe and secure and is the wire intact through out its whole length terminated correctly and using the correct insulation sleeving. You could also at this point if working on oven disconnect the oven wiring t oven terminals  and insulation resistance test from electrical distribution board to the end of the wiring cable. If its a cooker does the breaker reset and stay on with cooker unplugged to check integrity of the electric instillation wiring.

Next check the terminal wiring inside the oven/cooker i have known these to be wired wrong from the factory so well worth checking if you are just installing  new oven and it blows fuses also check for links in the ovens terminals as often manufacturers use links these days and if fitted they are incorrectly problems will occur.

Check terminals for any signs of burning as this will signal loose connections.

If the power blows when you turn on a certain function then you need to be looking at components within that circuit. These could include and all need to be eliminated, Selector switches, Thermostat, Safety thermal cut offs, Cooling and cooking fan motors and any control thermostats, all oven heating elements and any light bulbs or indictor lamps and of course the timer/clock PCB board. 

Switches are a common problem here as they are very often used part and high wear and tear will take place you can often see signs of arcing or burning or just damage to a switch you can do a basic test on switches and thermostats buy testing them for continuity with a multimeter see our post here . Elements re common problems causing tripping on electrics and are the main power consumers in the oven you need to test these to ensure they are safe this will need to be insulation resistance tested to ensure that they are not leaking to much current to earth especially if the RCD is tripping. 

To test elements you need to continuity test them as seen in photo below and insulation resistance test them as seen in video below.

See video below on how to testing the installation wiring to the cooker for insulation resistance 

Fan motors are the next to be checked as the winding can be damaged or they can overheat we have  few posts dedicated to fans here is one here .

In high-end modern ovens, the mechanical selector switch is replaced by a Printed Circuit Board (PCB) and electronic sensors. This "electronic brain" allows for far more precise temperature control and energy efficiency than old-school mechanical systems.

The Role of the PCB

The PCB uses relays and microchips to orchestrate the oven's functions.

Diagnosis: Many boards will display error codes to help identify faults. However, if the board itself is dead, it cannot communicate.

Cost Factor: Replacing a PCB is often expensive. A common rule for engineers is to test every other component first—elements, fans, and sensors—and only replace the board if everything else tests perfect.

The NTC Sensor: The Digital Thermometer

Instead of a gas-filled capillary tube, modern ovens use an NTC (Negative Temperature Coefficient) sensor.

Operation: It’s a semiconductor where resistance decreases as the temperature increases. The PCB monitors this resistance to decide when to cycle the heating elements.

Testing: Using a multimeter set to Ohms, you can measure the sensor's resistance. It’s best to test at room temperature against the manufacturer’s specifications. You can also test its responsiveness by placing it in hot water and watching the resistance drop.

Failure: If the sensor reads "OL" (Open Loop), it has failed internally and will likely trigger an error code or prevent the oven from heating.

Buy cooker oven spares on Ebay UK here 

Buy a good Multimeter on Ebay UK here