Grounding of the ventilation system: what elements need to be grounded and how to do it correctly

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Have you ever experienced electric shocks while touching the metal enclosures of your home appliances? One of the reasons for the threat of electric shock is the absence or improper grounding of the ventilation system in a private house. Its device is required for the safe use of electrical equipment.

Agree that even weak impulses do not evoke positive emotions. And for people with pacemakers, the consequences of such touching can be especially unfortunate.

It is not difficult to check the correctness and integrity of the grounding. It is not necessary for this very often to invite electricians. We will help you deeply understand all the intricacies of electrical safety control of the home ventilation system.

The content of the article:

  • The physical essence of the grounding process
  • What does grounding consist of?
  • Classification and types of grounding
  • Differences between the protective and working system
  • How to make grounding of air ducts?
  • Installation of protective circuit earthing switches
  • Typical mistakes of home craftsmen
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  • System check by technical services
  • Why do you need to ground air ducts?
  • Conclusions and useful video on the topic

The physical essence of the grounding process

Electrical wiring beautifully mounted and tucked into walls or channels, as well as a complete absence electrical devices in the ventilation system, do not guarantee against injury from contact with its metal parts. Only a reliable connection of conductive external structures of ventilation equipment with grounding will provide you with confidence in safety.

Parts of air ducts, fan casings made of metal and other electrically conductive materials that are not energized in operation must be grounded. Such requirements are spelled out in the Electrical Installation Rules (PUE).

An electrical charge on touchable elements can appear from damage to the insulation of nearby wires, devices, or from the accumulation of static electricity. Grounding means that if an accidental electricity charge occurs, it will leak from the duct into the ground.

Grounding a circular duct

The touch of a person to a grounded air duct becomes injury-safe. But only if the electrical resistance of your body (approximately 1 kΩ) is higher than that of the metal grounding conductor

We all know from the school physics course that electric current follows the path of least resistance. If we compare, for example, with the free flow of accidentally spilled water, then the analogy is this - the water will not flow up or sideways, but according to the force of gravity it will rush down. So it is with an electric charge, accidentally hitting a grounded air duct, it will leak deep into the ground to the ground electrodes of the house circuit.

Human electrical conductivity can be reduced by additional insulation from earth and other electrical conductors. To do this, use special protective clothing, shoes. Or it can be increased due to the moist unprotected area of ​​the skin.

A person with an embedded metal medical device is at greater risk. Or hung with various metal decorations. The resistance to current also decreases in people under the influence of alcohol.

What does grounding consist of?

The ground loop is a simple circuit of two elements - conductors and grounding electrodes.

Throughout the air ducts located inside and outside the house, their external electrically conductive parts that are not energized in normal operation must be connected into a single electrical chain. At least at two points, this bundle is firmly attached to the ground loop.

Fastening of grounding elements

For efficiency, there must be good contact between the individual elements of the circuit. The connection of the air duct housing parts with conductors to the grounding system should be done at least every 40-50 meters

It is necessary to ground the ventilation ducts in accordance with the rules of the PUE. The rules prescribe the use of steel strips, copper wires or direct connection to grounded pipelines and other structural elements. It is common practice to combine duct grounding with the common grounding system of the house.

Classification and types of grounding

These elements ground loop of any type are located directly in the ground. Grounding ensures the drainage of electric charge into the ground from housings and other non-working conductive parts of ventilation equipment.

Earthing switches are of two types - natural and artificial. According to the PUE standards, it is preferable to use natural grounding conductors.

In a private home, these include:

  • metal pipelines, armor of power cables;
  • buried reinforced concrete columns, foundations;
  • metal outdoor structures, such as a fence.

It is forbidden to use water and sewer pipes as natural grounding conductors.

Before joining the permitted types of natural grounding conductors, their conductivity should be determined. The provisions of the PUE regulate the maximum value of the spreading resistance of ground electrodes. For three-phase / single-phase current sources with a voltage of 380 / 220V, its value should be no more than 4 ohms.

Measurement of resistance to spreading of the ground loop

Artificial ground electrodes are used after determining the spreading resistance of natural ground electrodes. In the event that the values ​​measured by a special device exceed the norms of the PUE

To order measurements, you need to contact any certified electrical laboratory. You should be given a protocol with the result of measurements and copies of certified documents certifying the admission of specialists, the compliance of instruments with metrological requirements.

Differences between the protective and working system

The grounding conductors from the air ducts can be connected to the main grounding bus (GZSH) or to the protective grounding bus in electrical panels. Provided that this equipment is available in the house, where the ground loop has already been installed, if necessary.

Main grounding bar

Usually GZSh is located in technical rooms, garages, workshops. They can be easily used in the ventilation system grounding scheme.

If you have already decided which air ducts in the house must be grounded according to the rules, then do not confuse the connection points. The fact is that there is a working grounding bus in the electrical panels. It is intended for a working function, not a protective one.

The working neutral conductor (N) is the fourth core of the power supply cable, where three phase conductors (L) are present. It is connected to the neutral of the power supply. In the electrical panel, this neutral conductor is connected to the panel body and the working ground bus.

There are cables with a special insulated conductive braid, armor, which can serve as a natural ground electrode. Or with a protective earth conductor (PE).

It also connects to the shield body and to another grounding bus, but not a working one, but a protective one. It is not a fact that in your house such a reinforced expensive cable is used in the power supply circuit.

Electrical board diagram with protective and working and grounding

The grounding conductors from the ventilation equipment must be connected to the protective ground PE. Do not confuse with the working zero bus N

With the help of a working neutral conductor, all devices with a voltage of 220 V are connected to the power supply. That is, the socket has two contacts "phase" and "zero". All home craftsmen are aware of this.

In euro samples of sockets, there is also a grounding contact. You should never confuse these two completely different concepts - grounding and zeroing. The consequences can be sad for both the victim and the owner of a private house. After all, it is the homeowner who is responsible for the safe operation of all equipment.

How to make grounding of air ducts?

Flexible copper bridging jumpers must be installed between the flanges if there are no factory-supplied ones on the air ducts. A bolted connection, even without gaskets, is unlikely to comply with regulations.

Since the contact resistance must be less than 0.1 Ohm. It is allowed to join joints of metal structures by welding steel staples.

Grounding conductors are connected:

  • through adapter bars to bolts of flanges or other detachable connections;
  • crimp clamp, cleaned and treated with conductive grease;
  • by welding or reliable detachable connections to the supporting frame.

Visible grounding must be done at the beginning and at the end of the duct. Copper lugs can be used as adapter bars.

Air duct grounding in a private house

The rules require mandatory grounding of air ducts, regardless of other protective measures taken, including against static electricity

The cross-section of the steel grounding conductors must be at least 75 mm2. For a copper conductor, the cross-sectional thickness is allowed from 10 mm2.

The conductive parts of the fan housings with the loop must be grounded with separate conductors. Series connection of fans with duct grounding is not allowed, there should only be a parallel circuit.

Installation of protective circuit earthing switches

When reconstructing or building a private house, the missing grounding device can also be done by hand. The effectiveness of the circuit depends on the selected connection scheme, the type and resistivity of the soil.

Examples of schemes for the ground loop of a house

The location and number of electrodes can be carried out according to any of the proposed schemes. The required resistance is achieved by increasing either the length of the electrode, or the number of ground electrodes

The resistance of the grounding device, used exclusively to protect a person from static electricity in the duct, can be increased to 100 ohms. It will acquaint you with the methods of measuring resistance next article, which we recommend to read.

It is advisable to photograph all stages of hidden work during the installation of the grounding loop. Store printed paper photographs, hand-drawn diagrams with exact dimensions and specified materials with the test reports.

These are serious documents called a grounding device passport. With their help, you can control changes in the contour, plan repairs and even reduce the rates of the insurance company when applying for a home policy.

Typical mistakes of home craftsmen

Self-earthing can be performed flawlessly. But sometimes carelessness, haste, low practical skills lead to errors in the installation.

The most common common flaws and flaws:

  • Poor contact due to protective coating of detachable connections;
  • Non-compliance with the norms of the dimensions of grounding conductors;
  • Rapidly decaying material of the elements of the grounding system;
  • Connection of neutral working and protective conductors.

For some reason, many advise placing ground electrodes away from home, choosing the distance figures from the depths of their consciousness. All these settings are advisory, but optional. The contour does not pose any danger to a person, there are no restrictions in the rules for distance.

Lightning hits a private home

Connection of the grounding of air ducts to the grounding circuit of lightning rods is not allowed. The huge current flowing through the ground during a lightning strike can damage the entire ventilation system

Some "experts" advise to pour salt into the ground to the ground electrodes for better conductivity. No need to listen to amateurs, consult with professionals.

Indeed, at the beginning, due to an increase in humidity, a slight decrease in the resistance to spreading of the ground loop is possible. But metal elements in such an environment will quickly collapse due to the acceleration of the corrosion processes of ground electrodes.

System check by technical services

It is recommended to inspect the grounding of home ventilation equipment 2 times a year in spring and autumn. Found breaks, corrosion, other defects in visible external connections must be eliminated as soon as possible.

Installation of ground electrodes in the ground

The performance check of the protective device with selective soil opening is carried out at least once every 12 years. At the same time, the resistances of the contacts of the air duct with grounding, the resistance to spreading of the ground loop are measured

It is better to carry out measurements with the involvement of electricians in dry summer weather or in winter frosts. Under these conditions, the specific resistance of the soil increases. This means that the value of resistance to spreading of the grounding circuit will be maximum. That will ensure its reliability, compliance with the norm in all other seasons.

Why do you need to ground air ducts?

Ignoring proper design and installation of grounding ventilation systems owners of private houses explain most often by their unwillingness to spend extra money. For some reason, people who do not have special knowledge in this area believe that electrical safety can be neglected here.

Ventilation system grounding installation

Before thinking about false cost savings, you need to get acquainted with the possible tragic consequences of a lack of grounding. Only the most irresponsible homeowner can not take care of the mandatory protection of ventilation equipment.

In Russia, electrical injuries are the cause of death in 2.7% of accidents. Behind these dry numbers there are concrete human sacrifices. The bottom line is that the electric current overtakes unexpectedly. It has no smell, no color, you cannot see or feel it until you touch it or determine it with the help of instruments.

The process of connecting metal parts of ventilation equipment to grounding devices requires special care. Observe safety measures when working at height, with welding equipment, with electrical appliances.

Conclusions and useful video on the topic

Installation of a ground loop in a private house:

The composition of the exhaust ventilation system of the building:

The fan casing, air ducts and other elements, which may be electrically charged, must be safe for accidental human contact.

All grounding conductors, electrodes, natural grounding conductors have electrical characteristics normalized by the rules. A well-calculated circuit and properly mounted protective elements will serve you for many years. It is only important to periodically carry out maintenance and measure the electrical parameters of the grounding parts.

What do you think - is it worth doing grounding on your own or is it better to invite specialists? In the form below for comments, share your opinion, ask questions to our expert, leave a review.

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