Example 1: quick document cross-check
Open the page next to a drawing, datasheet or marking when you need to confirm what a specific symbol, contact, protection code or table entry means before reading the full source document.
SpecCalc Hub
Grounding System Types Reference
TN-C, TN-S, TN-C-S, TT and IT educational diagrams.
Preliminary estimate only. Not a code-compliance document, not installation approval, not final engineering design. Verify with qualified professional and local codes.
Reference data
TN-C
N and PE functions combined as PEN
TN-S
N and PE separate throughout
TN-C-S
PEN upstream; N and PE separated downstream
TT
Source earth and installation electrode are distinct
IT
Source isolated from earth or connected through impedance
Earthing arrangements
| Type | Conductor arrangement | Important distinction |
|---|---|---|
| TN-C | N and PE functions combined as PEN | Combined throughout the arrangement being described |
| TN-S | N and PE separate throughout | Neutral is not the protective conductor |
| TN-C-S | PEN upstream; N and PE separated downstream | Separation must follow the actual approved design |
| TT | Source earth and installation electrode are distinct | Protection requires checks beyond electrode resistance alone |
| IT | Source isolated from earth or connected through impedance | Insulation monitoring and fault procedures are important |
What this page helps with
Distinguish source earthing from the protective connection of exposed conductive parts and compare TN-C, TN-S, TN-C-S, TT and IT.
Grounding System Types Reference is a public SpecCalc Hub reference page for technical reference lookup, symbol reading and standards-oriented context. TN-C, TN-S, TN-C-S, TT and IT educational diagrams.
The page is meant for transparent early-stage comparison: you can see the working inputs, the result context and the limitations without relying on a black-box answer. Professional verification is required before real-world use.
Formula or method
The page is structured as a practical reference: start with the visible table, diagram and labels, then compare them with the exact connector, device, enclosure or symbol set in front of you.
Use the listed sources to confirm revision, naming and application context. Similar labels can hide different electrical limits, pin functions or test conditions, so the page should be treated as a guided reference rather than a universal standard text.
How to use
- Identify the exact symbol, connector, protection code or table entry you want to verify.
- Match the visible diagram and table with the label on the product, datasheet or drawing instead of assuming a familiar shape means the same thing.
- Check the current manufacturer document and local rules if the reference affects procurement, wiring or installation work.
Practical examples
Example 2: procurement or connection check
A familiar label can still hide a different revision or function. Use the page as a fast filter, then verify the exact document revision before you buy, connect or specify the real part.
Common mistakes
- Using the page without checking units, document revision or the real operating context.
- Treating a preliminary result or reference table as a final engineering decision.
- Ignoring the source links, limitations and related tools needed for the next validation step.
Limitations
- PEN, PE and N are not freely interchangeable conductors. These comparisons do not authorize combining or separating them in an existing installation; verify the supply arrangement and approved design.
- The page does not replace official manufacturer documentation, local rules or site measurements.
- Separate professional verification is required for safety, protection, cable or installation decisions.
FAQ
What does the Grounding System Types Reference page help with first?
It gives a transparent first pass for tn-c, tn-s, tn-c-s, tt and it educational diagrams. and shows which inputs, assumptions or references should be checked before you move into a real decision.
Can I treat the result as a final decision?
No. This is a preliminary estimate or reference aid, not a final design, code-compliance check or installation approval.
What should I verify next?
Check the cited sources (Schneider Electric — characteristics of TT, TN and IT systems), the related tools and the real equipment or site data that will govern the final decision.
Related tools
Explanation updated: 2026-09-15
This calculator provides an estimate for informational purposes only. It is not a certified engineering design, electrical safety approval, or professional installation recommendation. Always verify final decisions with a qualified professional and applicable local codes.