When half the house has no power while other lights and sockets are still working, the problem may involve a tripped circuit, a faulty protective device, a loose connection or an interruption affecting part of the electrical supply.
Before attempting to switch anything back on, check whether there is a burning smell, unusual heat, buzzing sound or visible damage around the DB box. Avoid touching the equipment if any warning signs are present.
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Why Does Only Part of the House Have Power?
A house is divided into several electrical circuits. Lights, sockets, air conditioners, water heaters and other appliances may be protected by different MCBs inside the DB box.
If one circuit trips or develops a fault, only the area connected to that circuit may lose power. Other parts of the house can continue operating normally.
Common causes include:
- An MCB has tripped because of an overload or short circuit.
- A faulty appliance is affecting a particular circuit.
- A loose or overheated connection is interrupting the supply.
- An RCCB or another protective device is faulty.
- One phase of a three-phase supply has been interrupted.
- There is a problem with the incoming electrical supply.
If the electricity frequently trips before part of the house loses power, refer to why home electricity keeps tripping for related warning signs.
Check the MCB Position in the DB Box
Look at the breaker positions without removing the DB box cover or touching any internal wiring. A tripped MCB may appear lower than the other breakers or remain between the ON and OFF positions.
If there is no burning smell, heat or visible damage, switch off the appliances connected to the affected area before resetting the MCB once. Do not repeatedly force the breaker back on if it trips again.
A breaker that trips immediately usually indicates a fault that requires proper testing. Repeated resetting can increase the risk of overheating or further damage.
Could the DB Box Be the Cause?
Yes. A worn breaker, loose terminal, damaged busbar connection or overheated component inside the DB box can interrupt electricity to one or more circuits.
Warning signs may include:
- The DB box feels unusually warm.
- A buzzing or crackling sound can be heard.
- There is a burning smell near the DB box.
- A breaker appears discoloured or damaged.
- The same circuit keeps losing power.
Do not open the internal deadfront or tighten electrical terminals yourself. Testing should be carried out using suitable instruments after the supply has been made safe.
An old or damaged distribution board may require component replacement or a complete DB box upgrade service, depending on its condition and available circuit capacity.
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Can a Three-Phase Supply Cause Partial Power Loss?
In a property with a three-phase supply, different circuits may be distributed across separate phases. If one phase is interrupted, some rooms or appliances may stop working while circuits connected to the remaining phases continue to receive electricity.
The interruption may originate from the property’s main switch, DB box, incoming cable, meter panel or the external electricity supply. Testing is needed to determine where the voltage is lost.
A contractor should check the incoming supply and internal distribution before deciding whether the issue needs to be referred to TNB.
When Should You Contact TNB?
Check whether neighbouring properties are experiencing the same interruption. If several nearby premises have lost power, the issue may involve the external electricity network.
You may report a suspected supply interruption through the myTNB application or TNB CareLine at 15454. If the problem only affects your property, arrange an internal electrical inspection first.
What Will an Electrical Contractor Check?
The inspection depends on the symptoms and type of electrical installation. It may include:
- Checking voltage at the incoming supply and main switch.
- Testing the RCCB, MCBs and affected circuits.
- Inspecting accessible connections for overheating or looseness.
- Identifying faulty appliances connected to the affected circuit.
- Checking phase distribution for a three-phase installation.
- Confirming whether the fault is internal or supply-related.
Our electrical troubleshooting service can be used when the cause cannot be identified through basic checks.
Frequently Asked Questions
Why are the lights working but some sockets have no power?
The lights and sockets may be connected to different circuits. A tripped MCB or a fault on the socket circuit can interrupt the sockets without affecting the lights.
Can I reset the MCB myself?
You may reset it once after switching off the appliances on the affected circuit, provided there is no heat, burning smell or visible damage. Stop if it trips again.
Does partial power loss mean the house needs rewiring?
Not necessarily. The fault may involve one breaker, appliance, connection or circuit. Rewiring should only be considered after testing confirms that the existing wiring is damaged or no longer suitable.
Should I contact TNB or an electrical contractor?
Contact an electrical contractor when the problem only affects your property. Contact TNB if the interruption involves the incoming supply or also affects nearby premises.
Restore the Electrical Supply Safely
Partial power loss should not be ignored, especially when the breaker keeps tripping or the DB box shows signs of heat. Proper testing helps identify the affected circuit and prevents unnecessary replacement work.
For related installation and upgrading services, visit our electrical wiring services page.
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