Loose or broken wires, a faulty outlet, a faulty plug and a temporary power cut are all possible reasons why an outlet might stop working then start again. This post aims to give you a few ideas why this is happening (from an electrician’s perspective) so you can decide what to do next.
To find out what is wrong with the outlet let’s look at how an outlet is wired.
Outlet Wiring & Fault Finding
A power outlet can be wired to other outlets on a single circuit.
A power outlet in the home will be wired with a cable containing a phase (live red) wire, a neutral wire and an earth wire.
The cable will go from the outlet to another outlet or straight to the switchboard where it will be connected to a circuit breaker.
A household outlet is required to be protected from short circuits, overloads and earth leakage faults. A short circuit is an explosive type of fault that occurs when the red wire (phase) crosses the black wire (neutral). Lots of heat is generated which can cause a fire if power isn’t shut off in time. An MCB will trip when a short circuit happens.
An overload occurs when too much electrical current is drawn from the outlet due to hungry appliances. This causes cables to heat up and cause a fire. Overload protection for an outlet is typically 16 amps or 20 amps depending on the size of the cable. An MCB will trip when an overload happens.
Finally, earth leakage is another way of saying electric shock. An RCD will trip when someone gets a shock or a shock is about to happen. The RCD exists to prevent permanent damage or electrocution from an electric shock. RCDs are mandatory on all domestic power outlets but might not be present in homes with older plug in circuit breakers.
An MCB will be labelled at the switchboard as ‘power’ or something more specific such as ‘bedroom’. A RCD will simply be labelled as ‘Residual Current Device’ or something similar.
Outlet Stops Working Then Starts Again? – Reason #1
Loose Wire
Likelihood: Low But Possible
If a phase (hot wire) or neutral wire is loose then the outlet will work intermittently. This is because the wire only has a weak or temporary connection causing the circuit to open and break.
A loose wire could be located in three places.
1. Loose Wire In Appliance
Firstly, the loose wire could be located inside of an appliance plugged into the outlet. To check if this is the cause plug a different appliance into the outlet to see if the problem persists.
2. Loose Wire In Outlet
Next the loose wire might be in the outlet itself where either the phase or neutral wire coming into the outlet is loose.
3. Loose Wire In Breaker
Lastly, the phase wire going into the circuit breaker could be loose. The neutral wire in the RCD neutral bar could also be loose.
Outlet Stops Working Then Starts Again? – Reason #2
Broken Wire
Likelihood: Moderate – if rodents are present or a tripped breaker keeps getting reset.
A broken wire will have a weak connection causing the outlet to stop then start. The wire with this weak connection would either be a phase or neutral wire. Here are some common reasons why a wire might be broken.
Firstly, rodents are known to chew and break wires. If there is evidence of rodents in the ceiling then this could be the reason.
Secondly, if the outlet has a circuit breaker which is too big (such as a 32 amp or larger breaker) then a fault in the cable is likely to burn through the wires. This will either burn them apart entirely or leave a weak electrical connection. This could occur in either the wall or ceiling cavity out of sight and hard to find. To find these type of faults use a insulation resistance test.
Outlet Stops Working Then Starts Again? – Reason #3
Appliance Plug Pins Are Loose, Dirty Or Damaged
Likelihood: Moderate – depending on the condition of the appliance.
Loose, short or dirty plug prongs on an appliance could cause power to come on and off. Loose or damaged plug prongs can happen due to wear and tear or damage. If the phase prong or neutral prong loses connection then it could make it seem like the outlet is not working when there actually is no problem.
Inspect if the plug pins are the cause of the problem by tugging them to check if they are loose. If the pins are dirty use a cloth to remove. Loose prong pins can also be an electric shock hazard.
Outlet Stops Working Then Starts Again? – Reason #4
Temporary Power Cut
Likelihood: Low – depending on local power situation.
A temporary power cut could be why this has happened. Check if other appliances are working and that your power meter is turning or has lights (if digital).
Outlet Stops Working Then Starts Again? – Reason #5
Failing Outlet
Likelihood: Moderate
A failing outlet is quite common. This is usually due to heavy use and overloading the outlet with too many appliances. A failing outlet can also be caused by being too rough when plugging in and removing appliances. An outlet is typically rated at 10 amps, but we commonly see people draw 10 amps or even more by plugging multi boards (which can handle several appliances) into the outlet.
Electricians Perspective
The most likely cause in my experience is either a broken or loose wire located inside the appliance, outlet or even the breaker. Damaged or dirty plug pins (from an appliance) and a failing power outlet are the next most common reasons why this occurs.
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