Earthing in normal and rocky soil

Retrofit Vertical Earthing Installation

Vertical protective earthing using deep earth ground rods is applicable for standard soil and other porous ground types. Depending on soil hardness, site dimensions, and soil resistivity, a grounding system can be created using one or more interconnected deep earth ground rods driven into the earth.

Horizontal Earthing Installation in Rocky Soil

Horizontal earthing using stainless steel flat conductor (sometimes referred as earthing strap) is prioritized in locations where rocky soil makes it physically impossible to drive earth ground rods. This is typical in areas like Budapest’s 2nd District, where rocks similar to those in the Pál-völgy Cave can be expected directly beneath the surface.

What is a Good Earth Resistance Value?

A unfortunate misconception in the electrican world is that an earth resistance value just below 10 Ω is "good" and qualifies for a "compliant" rating. While this is the currently accepted value for commissioning solar panels, the reality is much more nuanced.

The recommendation for an earth resistance value below 10 Ω spread in the country due to Section 4.4.2 of the Hungarian National Standard MSZ 447:2019, which states: "the potential of the operational PEN protective conductor in the main distribution board or unmetered distribution board must be fixed to an independently significant earthing (preferably no greater than 10 Ohms)."

Note that the standard says "preferably" below 10 Ω, not strictly mandatory.

However, while international standards IEC 60479-1 and IEEE 80 use a nominal body resistance of 1000 Ohms for substation calculations, this data—theoretically based on a statistical worst-case scenario—applies to an adult male.

A woman's resistance is roughly 64–75% of a man's up to the "let-go" current threshold. Resistance for elderly people and children is even lower.

In wet environments (e.g., jacuzzis or saunas), these values drop to a fraction, increasing the danger.

For the optimal operation of modern surge protection, a value below 2 Ω is required.

For true safety, an earth resistance below 2 Ω is considered full-value protection.

Residential Earthing – Vertical Methodology

A family home can be earthed using earting ground rods installed in one or multiple locations.

Think of the "sphere of influence" of an earth ground rod as an inverted 45-degree cone. If placed too close together, efficiency drops; if too far apart, space is wasted and extra labor is required to dig the 1-meter-deep connecting trench.

In the sketch below, Installation "A" shows rods too close together, causing their effects to cancel each other out in the overlapping area (green line). Installation "B" is optimal: they are far enough apart to utilize space efficiently without reducing each other's effectiveness.

Determining the optimal distance is crucial.

For vertical grounding, we use:

• Extendable earth ground rod or rod electrodes
• Single-piece earth ground rod, or rod electrode
• Cross-profile earth ground rods

After digging the inspection pit, the deep-earth rod (also known as rod electrode) is driven in:

After driving in the V4A stainless steel earthing rod, we secure it to the 10 mm² round steel conductor using a deep-earth connector clamp.

In multi-point systems, we use this method to connect the rods. For single-point installations, the 10 mm² V4A stainless round steel is led directly into the earth test/junction box inside a protective conduit.

The conduit is vital: if a fault current causes voltage on the earthing conductor, the conductive part remains untouchable, preventing electric shock. Practically, if recessed into a wall during a residential earthing system installation, the conduit makes future maintenance or repairs much easier.

Horizontal Grounding in Rocky Soil

Horizontal earthing technology differs significantly from deep-earth grounding. It must be preceded by a comprehensive soil resistivity measurement to determine the optimal path.

After defining the path, we dig the trench and place spacers to ensure the stainless steel flat earthing conductor is laid on its edge. Although called sometimes as "strip", "strap" or "tape," it is robust and impossible to bend or twist along its edge.

The acid-resistant V4A flat earthing conductor is then fitted into these spacers.

Next, the 10 mm² round steel is secured to the flat earthing conductor using a cross-connector clamp.

The installation concludes—before final testing—by leading the 10 mm² round steel into the prepared earth test/junction box, which connects the earthing system to the electrical network.

When designing the system, the MSZ HD 60364-5-54:2012 standard guidelines for grounding arrangements and protective conductors are applied regarding routing, connection points, and material selection.

Earthing System Installation – The Full Process

1) Preliminary Assessment

We start the implementation of an earthing system by mapping the physical characteristics of the site to determine where earthing can be installed and where digging is possible.

We consider future plans: if an area will be paved or concreted, it affects water retention, which in turn affects earth resistance.

2) Soil Resistivity Measurement

The measurement of soil resistivity (ρ) is the foundation for designing an earthing system. Through this measurement, we determine how well the soil conducts electricity at various depths, such as 1, 2, 3 meters, and below.

Based on the resistivity values measured at specific depths, we don't just get information on the quantity of earthing materials needed to achieve the desired result; we also learn how and where it is worth starting the installation.

For example:

• A higher value, around 400–500 Ωm, may indicate stony, gravelly, or limestone soil. In such cases, it is better to consider a multi-point earthing system, as there is a high probability that ground rods cannot be driven deeper than 3 meters.
• Similarly, if one part of the property has much better soil characteristics for earthing, it is clearly logical to begin the installation there.

Measurement results are influenced by soil moisture content, temperature, mineral content, and, naturally, the soil type itself.

Groundwater maps of Hungary can also provide useful preliminary information.

The measurement of soil resistivity is conducted according to Annex L1 of the MSZ EN 50522:2011 standard.

Average Soil Resistivity Values

Soil Type	Resistivity (Ωm)	Typical Hungarian Locations
Silty, cultivated soil, wet/compact fill	50	River floodplains (Danube, Tisza), embankments
Wet peat	5-100	Hanság, Kis-Balaton, Zala valley
Clayey sand	50-500	Homokhátság, Nyírség, Transdanubian hills
Soft limestone	100-300	Sóskút, Budapest area, Fertőrákos, Mecsek
Cracked limestone	500-1000	Karst regions (Bakony, Vértes, Pilis, Bükk)
Lightly cultivated, gravelly fill	500	Upper Danube valley (Szigetköz), Dráva valley
Stony soil	1500-3000	Budapest Dist. II, Bükk, Mecsek, Velence hills
Bare stony ground, dry sand	3000	Karst plateaus, Bükk plateau, Nyírség sand

Source: MSZ HD 60364-5-54:2012, Hungarian geological and soil science literature

3) Excavating the Working or Inspection Pit

The excavation of a 1-meter deep and 1 x 1-meter wide inspection pit serves a triple purpose:

1. Utility Detection: As the name suggests, digging this pit allows us to scout and verify that there are no underground utilities or other elements in the target area that could be damaged when driving the earth ground rod. It is important to be cautious during excavation; rather than using high-force pickaxe strikes, a careful and deliberate exploration is more effective.
2. Frost Line Considerations: The frost line is below 70 cm, and earthing is only considered effective below this depth. The soil above this level can dry out in the summer or freeze in the winter, which continuously degrades the earth resistance value. I generally place the top of the rod between 90–100 cm deep to ensure the achieved resistance value remains stable and permanent.
3. Work Space: A pit of at least 1 x 1 meter is necessary to provide a physically suitable environment for the work. It ensures there is enough room for the specialist to stand and move while driving the rod and connecting it to the round steel conductor.

4) Installation and Construction of the Earthing System

The installation of the earthing system typically takes place near the metering point (electric meter).

The detailed procedure for this work depends on whether vertical earth ground rods are being driven into the earth or if a horizontal stainless steel flat conductor is being applied. These methodologies have been explained in detail in the relevant sections above.

5) Entry and Connection to the Earth Test/Junction Box

Once the earthing is established, it must be led into a dedicated test/junction box using a 10 mm² cross-section, V4A-grade acid-resistant round steel conductor. The earth inspection box must have a minimum size of 100 x 100 mm.

The connection is made using a specialized clamp or screw terminal designed for this purpose. The purpose of the box is to ensure that the termination point remains easily accessible for future inspections or maintenance.

It allows the earthing system to be temporarily disconnected from the entire electrical installation, enabling the safe measurement of earth resistance. Because of this function, the inspection box is also frequently referred to as a "disconnect box".

6) Connecting the Grounding from the Inspection Box to the Distribution Board (Electrical Panel, Fuse Box or Meter Box)

Starting from the test/junction box, a green/yellow copper conductor with a cross-section of at least 16 mm² must be used for the direct connection to the electrical distribution board—whether it is the electrical distribution board or the meter cabinet.

A 16 mm² green/yellow copper conductor is also the minimum requirement for surge protection devices. This conductor ensures the proper bonding of the earthing system to the electrical network and fixes the potential of the PEN conductor.

Note: PEN (Protective Earthing Neutral) means that the protective conductor (PE) and the neutral conductor (N) are combined into a single common conductor. During potential fixing, this directs both the operating current (N) and the fault current (PE) to the ground.

During installation, the main terminal block or other connecting elements must be tightened to the torque specified by the manufacturer using a certified electrician’s torque screwdriver.

Since the 16 mm² green/yellow copper conductor originates outdoors, it must be rated for that environment. The commonly used MKH (H07V-K) type wire is not suitable for this; instead, H07RN-F (heavy-duty rubber cable) must be used for the earthing connection.

7) Earth Resistance Measurement

The measurement of earth resistance is the "crowning" of the work performed so far and is an essential part of commissioning any new or renovated electrical system.

This measurement may only be carried out by a qualified Electrical Safety Inspector using a certified and calibrated earth resistance meter. The results determine whether the installed earthing meets shock protection and operational safety requirements.

It is important to note that the measured value immediately after installation is not yet final. When a rod is driven, the soil "vibrates out" (loosens), and the backfilled soil over a horizontal stainless steel flat earthing conductor needs time to settle.

The earliest truly relevant result can be measured approximately three weeks later. In the case of horizontal earthing, it is worth re-measuring after two to three months, as the natural compaction time for the soil is significantly longer.

Inspection is conducted based on the MSZ HD 60364-6:2007 standard (Low-voltage electrical installations – Verification).

8) Issuing the Measurement Certificate

The measurement certificate issued by the electrical safety inspector is considered an authentic official document with legal force. With this document, the customer gains the authorization to—among other things—connect a solar power system to the electrical grid.

Earthing Material: V4A Acid-Resistant Stainless Steel (NIRO)

Hot-dip galvanized steel is widely used, yet its suitability for earthing is highly questionable from several perspectives. While it may be a good choice for lightning protection above ground, it is not recommended for earthing components in direct contact with the soil.

Hot-dip galvanizing is merely a surface treatment. Consequently, it can be damaged or flake off under high impact or mechanical stress. When driving a rod electrode—especially into rocky ground—this protective layer is inevitably compromised by intense friction, causing the rod to lose its corrosion resistance.

Furthermore, we usually lack specific information regarding the soil’s pH level (whether it is acidic, neutral, or alkaline). Measuring this can sometimes cost nearly as much as the total price of V4A stainless steel components—not to mention that a laboratory analysis might reveal that an acid-resistant system was necessary from the start.

It is also crucial to consider that soil pH is unpredictable over time due to changing weather patterns, such as acid rain.

Soil acidification can occur for many reasons: the use of fertilizers, decomposition of organic matter (e.g., plant remains), nutrient uptake by plants (especially calcium and magnesium), the natural leaching of basic cations by precipitation, air pollution, or the influence of the parent rock on soil formation.

Conversely, alkalinity is caused by basic (alkaline) substances in the soil. Most Hungarian soils formed on calcareous parent rock, making them slightly alkaline or neutral. Other causes of alkalinity include salinization—due to dry, warm climates or poor drainage—and irrigation with water high in salt or lime content.

From a gardening perspective, most plants thrive in a slightly acidic or neutral environment (pH 6.0–7.5), where nutrients are most easily absorbed. Therefore, considering future landscaping and planting plans, an acid-resistant system is a much better investment.

Perhaps the only thing worse than a known lack of earthing is living with a false sense of security provided by an inadequate system. In that case, we wouldn't even know that action is required.

For these reasons, I personally only install V4A acid-resistant components for earthing purposes. A further advantage of V4A elements is that connection points do not require anti-corrosion tape, and electrochemical corrosion—which can occur when joining different metals like copper conductors—is avoided.

People often ask me: "If these other products aren't ideal, why are they sold?" I usually answer with a question of my own: "When you walk into a grocery store, do you only see healthy food on the shelves?"

Protective Earthing Installation Prices

Earthing installation price (labor): from 67,500 HUF.

The fee above includes the professional placement, laying, and interconnection of the earthing elements according to regulations.

The cost of earthing materials is added/separate to the labor fee. This expense can only be determined after an on-site assessment and measurement of the soil, as it is the only way to accurately estimate the requirements for a successful installation.

Earthing Measurement Prices

• Earth resistance measurement: 25,000 HUF / occasion.
• Soil resistivity measurement: from 35,000 HUF.

Why is Earthing Important?

Earthing ensures the safety of electrical systems (life protection and protection against electric shock) and provides vital defense for our appliances.

If a device fails—for example, if the metal casing of a washing machine becomes live due to an insulation fault—the current takes the path of least resistance through the earthing conductor into the ground, protecting the human body from electric shock.

Since the RCD (Residual Current Device), also known as a safety switch, trips based on current difference, earthing serves as its reference point. Therefore, proper installation is essential for this life-saving device to function effectively during serious network faults, such as a PEN conductor break.

For high-value equipment—such as electric vehicle chargers, the cars themselves, laptops, and computers—surge protection is of paramount importance. In a well-designed system, sudden excess current from lightning or grid surges is safely diverted toward the ground.

Additionally, good earthing plays a fundamental role in:

• Dissipating electrostatic charges.
• Reducing electrical noise (EMC): It helps decrease electromagnetic interference by providing a stable reference point to the ground. This is why it is often referred to as potential-fixing earthing, as it anchors the electrical system to zero potential.

The guidelines for designing protective earthing to ensure it functions as a proper part of the shock protection system are regulated by the MSZ HD 60364-5-54:2012 standard (Earthing arrangements and protective conductors).

The system becomes complete by bonding auxiliary elements, such as gas pipe earthing and Equipotential Bonding for buildings (EPB), into this supplementary network.

Myths and Reality Regarding Earthing

Myth	Reality
Earth resistance just slightly below 10 Ω is already "good."	It does not perform full-scale life-safety functions; based on common practice, it merely secures a "compliant" qualification on paper.
It is enough to drive a few iron bars into the ground starting from the surface.	Only the portion of the earthing system that lies below the frost line is considered significant, regardless of its orientation (vertical or horizontal), as it must withstand environmental impacts.
For foundation earthing, it is sufficient to connect the electrode to the reinforced concrete structure without further action.	Concrete foundation earthing requires serious engineering. Due to improper calculations of distances and connections, lightning current can literally cause the concrete to explode from the voltage accumulated at specific focal points. However, properly embedded local foundation earthing can be highly effective for device and system protection due to its extent.
Retrofitting an earthing system is a simple task—it is enoght to drive in a few rods.	Building a truly effective earthing system that actually serves life-safety goals requires significant experience, specialized expertise, and professional instrumentation.
Earth resistance values are only important for connecting solar panels.	The adequate value serves both life-safety and equipment protection. The value obtained during measurement indicates the strength and quality of the protection against electric shock.
Earth resistance measurement can be performed by anyone.	Due to the inherent hazards, electrical measurements must only be performed by qualified professionals with the appropriate certifications, such as an Electrical Safety Inspector.
Earth ground rod installation can be handled with manual tools.	While 2–3 rods can sometimes be driven by a hammer, it is an extremely time-consuming and exhausting process. In harder soils, driving them without a power demolition hammer is not a realistic goal.
Soil-embedded earthing is only installed for residential or commercial properties.	There is also operational earthing, which stabilizes the operation and voltage levels of the power supply system. This is implemented at transformer stations and at the connection points of consumer networks.
Soil-related measurements provide a perfect, definitive guide.	Initial measurements provide a sufficiently accurate direction to start the electrical work. The final implementation is always determined by practice; preliminary estimates and plans often need to be modified due to obstacles encountered during the process, such as hitting solid rock.

Glossary of Terms

• MSZ HD: The "MSZ" prefix denotes Hungarian National Standards, while "HD" signifies that the document is part of European harmonization (HD – Harmonization Document). This means the substantive requirements of the European standard have been integrated into domestic regulations.
• MSZ EN: This indicates that a European Standard (EN) is being introduced within the framework of the Hungarian National Standards. In these cases, the Hungarian standardization body adopts and naturalizes the European standard in its entirety, making it legally binding within the country.