Quick answer
A burning smell from your consumer unit when the heating starts is most commonly caused by a loose or overloaded circuit connection arcing under the surge of current. This is a serious fire hazard. Turn off the heating circuit breaker immediately, do not use the heating until the cause is found, and call a registered electrician the same day. Never ignore a burning smell near your consumer unit as it can indicate imminent electrical failure.
When your boiler or central heating fires up, it draws a surge of electrical current through your consumer unit. If anything inside the unit is loose, corroded, or struggling to handle that surge, it can overheat and produce a burning smell. Here is what is likely going on and what you should do about it.
The most common causes are a loose terminal on the circuit breaker or busbar, a circuit breaker that has weakened internally after years of use, or wiring that is undersized for the load being placed on it. Heating systems, especially modern combi boilers with pumps, fans, and controls, can draw more current than older wiring was designed for.
There is also a possibility that the smell is not from inside the consumer unit at all, but from the boiler itself or from old cable insulation near a heat source. However, if the smell is clearly coming from the consumer unit area, treat it as an electrical fault until proven otherwise.
What you can safely do yourself:
1. Switch off the heating at the consumer unit by turning off the relevant circuit breaker.
2. Let the area cool for a few minutes, then carefully get close to the consumer unit and check whether the smell is strongest there or elsewhere.
3. Look for any visible discolouration, scorch marks, or melting around the front of the consumer unit or on any visible wiring.
4. Do not open the consumer unit cover. This exposes live parts and is dangerous to anyone who is not a qualified electrician.
5. If you see scorch marks, smell burning plastic, or the circuit breaker feels hot to the touch on its outside face, do not restore power to that circuit.
When to call an electrician urgently:
If you can see any scorch marks or melting, call someone today. If the smell recurs every time the heating fires up, that is a pattern telling you there is a fault that will get worse. A registered electrician will be able to open the consumer unit safely, inspect every connection, and test the circuits properly. Look for someone registered with NICEIC, NAPIT, or a similar competent person scheme. This is not a job to leave until next week.
⚡ North London Electrician
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