Does a Surge Protector Prevent a Circuit Breaker from Tripping?

Definitely not because it all depends on the time frames involved. Surges occur in microseconds. Circuit breakers operate in seconds or milliseconds when faults are considered. Therefore, the time domain is different, and that is one of the reasons why connecting a power strip has never solved the problem of circuit breakers interrupting.

It is very important to mention that what surge protection systems do is mostly misinterpreted as such devices being bought to serve the purpose of protection.

Brief answer: A surge protective device is capable of limiting electrical surge voltage that lasts for a short period of time (picoseconds) but has no ability to deal with overloads, short circuits and earth faults, which is what breakers respond to. A failed SPD may cause a breaker to trip: the most common failure modes of SPD are connecting to the ground, which is equivalent to short-circuiting.

Why the Two Devices Cannot Sub for Each Other

A surge protection device is a voltage-operated switch. It is almost always in the open state and invisible to the circuit because its switch is activated only when the voltage exceeds the rated value for a fraction of a second. The surge protection device passes this excess voltage to the ground and then resets after the voltage temporarily goes below the acceptable level. The surge protection value is expressed as the voltage level measured in kilovolts and the current passed through the device in kiloamps.

A circuit breaker is a current-controlled switch. It can switch the maximum rated current indefinitely, but if it carries such current for a long time, it starts getting hot and opens when too much current flows through the switch and it reaches the magnetic threshold. Current rating for a circuit breaker is expressed in amperes and kiloamps.

The two are totally different devices; one works on voltage (the SPD), and another on current (the circuit breaker). Thus, a 20-amp circuit breaker cannot clamp a transient of 6 kV, and a Type 2 SPD will not interrupt the work of a 60-amp circuit. The construction of the current-sensing device is described in this single-pole MCB specification, and there is no voltage element in it at all.

What Actually Trips a Breaker

There are four different root causes but surge is not one among them.

• Overload – the current exceeds the value for the rating for a sufficient period of time to warm up the bimetal; the duration can be seconds to hours.
• Short circuit – the current is a multiple of the rating and opens the equipment magnetically almost instantaneously.
• Earth fault – the current returns through an unintended route and causes an RCD or GFCI to trip in 30 milliseconds or less at 30 mA.
• Arc fault – there is an intermittent parallel or series arcing, which can be picked by an AFCI over seconds to minutes.

Take heed to the units. The fastest among them, earth fault, has milliseconds as the measurement unit, but it gets triggered as a result of a persistent unbalanced current, not because of a spike lasting milliseconds. A fifty-microsecond surge would neither heat the bimetal, keep a solenoid functioning, nor create an imbalance of 30 mA for thirty milliseconds.

When a circuit breaker trips during a storm, the surge usually serves not as a cause but rather as a consequence of some issue: it damaged the control system board and as a result, it consumes too much current; it deteriorated the winding of the electric motor and therefore the motor is leaking to the earth; or it damaged a capacitor making the initial current of the compressor change.

How an SPD Can Cause Tripping

The majority of surge protective devices (spds) use metal oxide varistors. At the end of its service life, having absorbed a sufficient amount of power energy or one very strong event, the element suffers a short-circuit breakdown, rather than an open one. This means a malfunction stage at the electrical panel, which causes an upstream circuit breaker to trip.

This is why quality spds have the so-called status window or remote signalling contact, and “main circuit breaker tripping after the thunderstorm” is a typical failure signature of spds or a failure detected. If the surge protective device is equipped with its own breaker or fuse, then the symptom is localised; if it is directly connected to busbars, then the whole surge protective device is tripped.

Thus, choosing a device that has a visible indicator of the end of life cycle and disconnector is strongly recommended. A Type 2 SPD rated 40 kA for distribution boards is the usual residential choice, and the 40 kA figure is the maximum discharge current per pole, which sets how much energy it can absorb before it fails.

What a Surge Protector Is For

This device protects the machinery against transient overvoltages due to switching or inductive kickback from motors inside the building or shocks due to the impact of lightning nearby.

Both the NEMA and insurance companies agree that most damage is caused by transients generated inside the building instead of any lightning discharge; hence, SPDs are designed to protect from transients even where thunderstorms are never seen. A number of switching operations, like running a compressor, hitting an arc by a welder or opening the contactor, all create transients in the electrical system feeding electronics.

This type of protection comes in layers. SPDs are divided according to the following classification: Type 1 or Type 2 at the service level and Type 3 at the equipment level. A simple power strip without the upstream SPD falls under Type 3 devices, which is true for many small events leading to small damage.

If the service is located outside and in a highly thunderstorm-prone area, the use of more powerful devices pays off.A Type 1+2 device with a 50 kA maximum discharge current covers both the service entrance and the distribution board in one unit.

Coordinating the SPD With the Protection

The interaction between a surge protective device (SPD) and the RCD must be specifically planned and can be tested. Some SPDs may allow a small amount of current to leak into earth due to aging, and this can eventually result in a nuisance trip of the 30 mA RCD. Some SPD types are designed to be installed upstream of the RCD specifically for that reason.

There is also a rule regarding the wiring that determines whether the SPD can work at all: the leads have to be short and direct. Every 10 cm of additional wiring will introduce some inductance, hence increasing the voltage supplied to the equipment. In case a SPD is installed with large loops, it may end up not functioning properly. The coordination rules, including the lead length and the RCD arrangement, are set out in this note on coordinating SPD and RCCB protection in LV boards.

What to Do About a Breaker That Keeps Tripping

A surge protector will not make a difference, nor will introducing a larger unit make it better. This is a matter of load and faults.

If you disconnect the circuit and the problem does not reoccur, the problem is with an appliance. If it trips when there is nothing plugged in, then the wiring is to blame. If it trips at intervals, it means there has been an overload. If the issue appears only during wet conditions, that is due to humidity. In each case, there is a solution to the issue, but they are not related to surge protection. The full procedure is in our breaker troubleshooting FAQ.

A surge protector serves to protect electronic devices from malfunctioning and causing damage to them. These two things have very different objectives and technology, but it is more cost-effective to do both jobs at once and avoid replacing the control boards every summertime.

FAQ

What should never be plugged into a surge protector?

High-wattage appliances with heating and/or motor function include heaters, steam irons, kettles, hoovers, microwave ovens, and refrigerators. These devices draw current beyond the strip’s rating, and in this case, the strip’s breaker or the thermal cutout will be the weak element in the system.

How do you prevent a breaker from tripping?

In order to mitigate tripping, it is necessary to take a few steps, which includes eliminating the load from the circuit, connecting large appliances on separate circuits, fixing appliances that are heavy draw, and changing over the equipment that causes tripping even with a legitimate fault.

Why does my 20-amp circuit breaker keep tripping even though there’s nothing plugged in?

The fault is related to either fixed wiring or the appliance itself. An electric circuit could be isolated because a wiring problem could arise with the wire itself (e.g. a damaged wire), a nail penetrating through it, etc.

Do you leave a surge protector plugged in all the time?

Yes. It is operational when connected and does not provide protection when turned off. Change it after an event of considerable magnitude or when its light indicates that protection is lost.

References

• NEMA — Surge Protective Devices and Their Ratings
• UL Solutions — UL 1449 Surge Protective Devices
• U.S. Department of Energy — Power Quality and Surge Protection
• This Old House — Whole-House Surge Protection
• Bob Vila — Surge Protector vs Circuit Breaker

Conclusion

While Surge Protectors are built to protect against small amounts of over voltage, Breakers protect against excessive current for longer periods of time. As such, buying one to take the place of the other would mean that you would be buying the wrong product twice.

Reach out to us for advice on the SPD with info on the panel and its exposures. If you reach out to us with the trip pattern, we will be able to help you identify what caused the breaker to trip.