The electrical surge can burn electrical and electronic devices and these surges can occur due to lightning strikes that fall on the electrical network, starting of large electric motors and other anomalies that can occur in electrical installations. That’s why we should always use a DPS, which is the surge protection device!

The correct use of a residential DPS provides adequate protection against outbreaks that occur in the electrical network, but there arises some very common doubts, where to install DPS and which one to choose? There are several brands on the market: DPS Clamper, DPS Siemens, DPS Schneider, DPS Abb, DPS Altronic, DPS Alumbra, DPS Fame, DPS Lukma, DPS Exatron, DPS Soprano and others! These devices are separated by DPS type 1, DPS type 2, and DPs type 3.

Thinking about these doubts, we prepared a very complete article that will explain everything about the installation position of the DPS. See if you should install DPS before or after the general circuit breaker?

How does DPS work?

Regarding the DPS, it is important to understand that when an outbreak occurs, the DPS diverts this outbreak to the grounding system, this occurs in a fraction of seconds and is usually so fast, that the circuit breaker does not even detect this leakage to ground. Exactly why the DPS is a connected phase on one side and ground on the other.

It really looks like you are closing a short circuit between phase and ground, and in fact when the DPS detects an outbreak, it does close a short between phase and ground, but this happens in an extremely short period so that it is not harmful to the installation.

The big problem is when the DPS reaches the end of its useful life, that is, when its internal circuit is no longer able to make this quick closing to earth. In some cases when the DPS burns it closes a permanent short between phase and ground and then we have a huge problem. To solve this, the NBR 5410 standard regulates the use of protective devices for the DPS, even circuit breakers to protect the DPS, these circuit breakers are called disconnecting devices. Then, in the event of a permanent short due to the burning of the DPS, the circuit breaker will trip and prevent the earth leakage.

Where to install DPS?

The position of the DPS and the general circuit breaker has to do with this disconnecting device because the general circuit breaker can be used as a disconnecting device. The standard provides for cases in which the DPS itself has a device internally that allows disconnection, that is, for these cases, the standard says that there is no need for a circuit breaker to protect the DPS.

The DPS can be installed before the general circuit breaker as shown in image 14 of NBR 5410, in item a), in this case, a disconnect circuit breaker is used, or that the DPS itself can disconnect preventing a permanent short, see the image below.

Example of DPS installation positioning before the circuit breaker

In this first positioning option, continuity of service is ensured, that is, in the event of a DPS failure, the system continues to function as shown in the image below. On the other hand, this also means that there is a lack of protection against any new outbreak that may occur.

Operation of a system with DPS installed before the circuit breaker after an outbreak

In the second positioning option, as shown in image 14 of NBR 5410, in item b), a system is used that the circuit breaker protects circuits and the DPS, being interpreted as the DPS installed after the general circuit breaker, see the image below.

Example of DPS installation positioning after the circuit breaker

In this positioning, the failure of the DPS activates the circuit breaker that interrupts the supply of the circuit, as shown in the following image. This disconnected circuit situation will continue until the DPS is correctly replaced.

Operation of a system with DPS installed after the circuit breaker after an outbreak

For those who do not know what an electrical surge is and how to choose the correct DPS, we will leave you with a video suggestion from the Mundo da Elétrica channel, where you can follow all this explanation we did in a very didactic way and still have access to 3 others videos that talk exclusively about DPS, its uses and installations.

Finally, let’s make it clear what the NBR 5410 standard says about installing DPS! According to the NBR 5410 standard, the DPS must be installed in all electrical installations in order to prevent electrical surges in the network! The standard allows the installation of the DPS to be done both before and after the general circuit breaker. Therefore, it is up to the user to observe the positive and negative points of each installation placement, but what should never be done is to keep the installation running without using a DPS.