Solar Panels Tripping the Fuse Box? What It Means and What to Do

If the solar circuit in your consumer unit, or an RCD protecting it, keeps tripping, something is letting current go where it shouldn’t, or the protective device isn’t suited to the inverter. Common causes are moisture getting into connectors or cables, a fault in the inverter, damaged wiring, or the wrong type of RCD. A single trip in a storm can be a one-off. Repeated tripping needs an electrician or solar engineer to find the cause.

Key points

• Reset a tripped device once. If it trips again, leave it off and get it checked.

• Tripping after rain, or in the early morning, often points to moisture and an insulation fault on the solar side.

• Many inverters need a specific type of RCD. The wrong type can trip, or fail to protect properly.

• An inverter alarm about insulation or leakage at the same time is an important clue.

• Never open the inverter, isolator covers or the consumer unit, and don’t switch DC isolators unless an engineer has told you to.

What is actually tripping?

In most homes the solar inverter is connected to the consumer unit through its own circuit breaker, often labelled “PV” or “solar”. That circuit is usually protected by an RCD, either a separate device covering several circuits or a combined device (an RCBO) for the solar circuit alone.

• An RCD trips when it detects current leaking to earth. That points to an insulation or earth leakage problem somewhere on the protected circuits.

• A circuit breaker trips when the current is too high, from an overload or a short circuit.

Which device has tripped, and whether it takes out other circuits too, is useful information for whoever investigates.

The common causes

Moisture in the solar side. Water in a cable connector, a damaged cable on the roof or a failing panel can lower the insulation between the solar wiring and earth. It often shows up after rain, in damp mornings or in winter, and may clear as things dry out. Inverters usually log this as an insulation or leakage alarm at the same time. Our guides to Solis and FoxESS fault codes list the alarm names.

The wrong type of RCD. UK wiring rules for solar installations say the RCD protecting the inverter’s AC circuit must be a Type B device unless the inverter provides the necessary separation, or the manufacturer states that a Type B device isn’t required. A Type AC or Type A RCD where Type B is needed can be affected by the inverter in ways it wasn’t designed for. It can turn up on older installations, or after a consumer unit has been replaced without the solar system being taken into account.

A fault in the inverter. Internal faults can cause trips, particularly in older inverters. If the inverter shows an internal fault or trips the circuit as it starts up in the morning, it may need repair or replacement.

Leakage adding up. An RCD covering several circuits sees the combined leakage from everything on them. Solar and battery inverters, EV chargers and some appliances all contribute a little, and together they can be enough to trip a shared RCD.

Something that isn’t the solar at all. If the RCD covers other circuits, the cause may be an appliance or wiring elsewhere in the house that happens to share it.

What you can safely check yourself

1. Reset once. If the device stays on, keep an eye on it.

2. If it trips again, leave it off. Don’t keep resetting it.

3. Note when it happens. After rain, early morning, when the sun comes up, or when a particular appliance is switched on are all clues.

4. Look at the inverter screen or app. Note any alarm and the time it appeared.

5. Check which circuits went off. Only the solar, or other circuits too?

6. Photograph the consumer unit labels and the inverter label.

Electrical Safety First’s advice is that an RCD that keeps tripping is likely to mean a fault that needs investigating, and that you should get a registered electrician to look at it. With solar, that means someone who understands both the house wiring and the DC side of the system.

What not to do

• Don’t keep resetting a device that trips straight away.

• Don’t open the inverter, the battery, isolator covers or the consumer unit.

• Don’t switch the rooftop or DC isolators on a guess. Solar panels produce voltage whenever there is daylight, and the switching order matters.

• Don’t swap the RCD for a less sensitive one, or move the solar to an unprotected circuit, to stop the tripping. That removes the protection rather than fixing the fault.

If you smell burning, see scorch marks or hear crackling, switch off at the consumer unit if you can reach it safely, keep away from the equipment and call an engineer.

What an engineer will do

A solar engineer will check the consumer unit arrangement and the type of RCD, read the inverter’s fault history, and test the insulation of each string of panels to find where the leakage is. The fault may be in a single connector or cable run. Where the inverter is at fault, the options include repair or inverter replacement. Our solar servicing team handles these investigations whoever installed the system.

Frequently asked questions

Is it safe to leave the solar switched off?

Yes. With the solar circuit off, the house runs from the grid as normal. You lose generation until it’s fixed, but that’s better than repeated tripping.

Why does it only trip when it rains?

Rain and damp often reveal an insulation fault on the solar side, such as water in a connector. As things dry out the problem can disappear, which is why it needs testing rather than ignoring.

Can a battery cause tripping?

It can, through a fault in the battery inverter or the way it is connected. The same approach applies: note when it happens and have it investigated.

My RCD trips in the morning when the panels start up. What does that mean?

It often points to an insulation fault that shows up when the inverter starts its checks, or to an RCD type that doesn’t suit the inverter. Either way, it needs an engineer.

Book a solar system inspection. If your solar keeps tripping, we’ll find the cause and fix it properly.