on video QDC assembly and questions for GRAU Técnico students.

 QDC assembly and questions for GRAU Técnico students.

In this video I show how to assemble a two-phase distribution board, in addition to properly sizing and choosing the protection components and the power cables of the circuits. All done in light of NBR-5410.

Can I do 02 different TYPES of GROUNDING in the same QDC?

Speak my dears!!! All pasta???

Every day we receive hundreds of messages with questions from our subscribers on our social networks. Some are common questions and the answers, for the most part, are right here on the channel. But today's one is so interesting that we decided to share it with you. Can I have two grounding schemes in the same QDC?

Well, whenever we talk about electrical installations, to remove any doubt, we need to refer to the electrician's bible, the famous NBR 5410, and check if there is any item that addresses this subject.

We researched a lot, but we did not find an explicit reference in the standard that says that the grounding scheme in the building must be unique. However, the concept of single grounding is present in several points of the standard, such as in item 5.1.2.2.3.3, which deals with equipotentialization.

In short, this item of the standard mentions that “All the masses of the installation located in the same building must be linked to the main equipotential of the building for protection against shocks and/or electromagnetic compatibility”.

Translated, it is important that there is only one grounding scheme in the entire electrical system to avoid potential differences that could lead to electrical shocks.

“Ah André, and the TN-C-S? Aren't there two groundings?”

Not really my dear, the TN-C-S grounding scheme has only one grounding system, which is the neutral grounded in the input pattern.

What happens is that the PEN conductor, which is the name given to the neutral conductor along with the standard ground, is separated in the QDC, and from there the neutral and ground conductors come out separately, but they are equipotentialized within the QDC.

Okay André, but what about when the QDC is very far from the standard, and I decide to do a TT grounding close to the QDC, then I have two schemes, the TNC that comes with the neutral grounded from the standard and the TT that I did, I can do it like this ?

Power can, but in my opinion it shouldn't!

I have already shown countless works in the last seasons of the direct work here on the channel that we chose to do a grounding near each QDC. But we always connect these TT systems to what we call a BEP, a main equipotential bus, and on this same bus we connect the neutral that comes from the standard. In this way we have a TN-C-S system, because everything arrives together at the BEP and separates into different neutral and ground cables for the circuits from then on. In short, I don't have 2 different grounding systems there, I have a BEP that puts everything together and originates a new system just the TN-CS and I repeat, I will always opt for TN systems when possible, TT only for specific cases.

And another curiosity, there will be a situation where the building will have two different grounding systems, which is in the case of hospital facilities where the medical IT system is required.

In this case, part of the hospital has a type of grounding (usually TN-S), and rooms such as the ICU, CTI and operating rooms will have IT-type grounding, requiring the use of a specific transformer for this.

Therefore, my dear, although the standard does not have a specific item that says that the grounding scheme must be unique, this is one of the recommended measures to guarantee the safety of building users against electric shocks.

 QDC assembly and questions for GRAU Técnico students.

In this video I show how to assemble a two-phase distribution board, in addition to properly sizing and choosing the protection components and the power cables of the circuits. All done in light of NBR-5410.

Can I do 02 different TYPES of GROUNDING in the same QDC?

Speak my dears!!! All pasta???

Every day we receive hundreds of messages with questions from our subscribers on our social networks. Some are common questions and the answers, for the most part, are right here on the channel. But today's one is so interesting that we decided to share it with you. Can I have two grounding schemes in the same QDC?

Well, whenever we talk about electrical installations, to remove any doubt, we need to refer to the electrician's bible, the famous NBR 5410, and check if there is any item that addresses this subject.

We researched a lot, but we did not find an explicit reference in the standard that says that the grounding scheme in the building must be unique. However, the concept of single grounding is present in several points of the standard, such as in item 5.1.2.2.3.3, which deals with equipotentialization.

In short, this item of the standard mentions that “All the masses of the installation located in the same building must be linked to the main equipotential of the building for protection against shocks and/or electromagnetic compatibility”.

Translated, it is important that there is only one grounding scheme in the entire electrical system to avoid potential differences that could lead to electrical shocks.

“Ah André, and the TN-C-S? Aren't there two groundings?”

Not really my dear, the TN-C-S grounding scheme has only one grounding system, which is the neutral grounded in the input pattern.

What happens is that the PEN conductor, which is the name given to the neutral conductor along with the standard ground, is separated in the QDC, and from there the neutral and ground conductors come out separately, but they are equipotentialized within the QDC.

Okay André, but what about when the QDC is very far from the standard, and I decide to do a TT grounding close to the QDC, then I have two schemes, the TNC that comes with the neutral grounded from the standard and the TT that I did, I can do it like this ?

Power can, but in my opinion it shouldn't!

I have already shown countless works in the last seasons of the direct work here on the channel that we chose to do a grounding near each QDC. But we always connect these TT systems to what we call a BEP, a main equipotential bus, and on this same bus we connect the neutral that comes from the standard. In this way we have a TN-C-S system, because everything arrives together at the BEP and separates into different neutral and ground cables for the circuits from then on. In short, I don't have 2 different grounding systems there, I have a BEP that puts everything together and originates a new system just the TN-CS and I repeat, I will always opt for TN systems when possible, TT only for specific cases.

And another curiosity, there will be a situation where the building will have two different grounding systems, which is in the case of hospital facilities where the medical IT system is required.

In this case, part of the hospital has a type of grounding (usually TN-S), and rooms such as the ICU, CTI and operating rooms will have IT-type grounding, requiring the use of a specific transformer for this.

Therefore, my dear, although the standard does not have a specific item that says that the grounding scheme must be unique, this is one of the recommended measures to guarantee the safety of building users against electric shocks.