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Completion Certificate No. 3 (Alterations)

The Irish Electrical Completion Certificate No. 3 is issued when a Safe Electric registered contractor carries out alterations to an existing electrical installation — such as adding new socket circuits, upgrading a consumer unit, or rewiring a room extension. It documents the existing installation's condition and supply characteristics, lists only the altered circuits with their test results, and certifies that the alterations comply with ET 101 and have not impaired the safety of the existing installation.

ET 101:2018 (National Rules for Electrical Installations), Safe Electric schemeValid: No fixed expiry — attached to the altered installation

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Sample Completion Certificate No. 3 certificate

Sample Completion Certificate No. 3 (Alterations) certificate created with CertBox, showing the professional PDF layout with description of the alterations carried out, existing installation earthing system and supply characteristics, condition assessment of the existing installation (satisfactory / unsatisfactory)

Sample Completion Certificate No. 3 with fictional data. All personal details shown are fake.

What it covers

  • Description of the alterations carried out
  • Existing installation earthing system and supply characteristics
  • Condition assessment of the existing installation (satisfactory / unsatisfactory)
  • Consumer unit details including RCD protection status
  • Altered circuits with cable sizes, protective devices, and full test results
  • Confirmation that alterations do not impair the existing installation
  • Safe Electric registration number and contractor signature

Who needs a Completion Certificate No. 3?

Safe Electric registered contractors carrying out partial rewires
Electricians upgrading consumer units
Contractors adding circuits for extensions or outbuildings
Any contractor altering an existing Irish electrical installation

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Frequently asked questions about Completion Certificate No. 3

When should I use a No. 3 certificate instead of a No. 1?
Use a No. 3 when adding to or altering an existing installation — for example, a new socket circuit, consumer unit replacement, or additional lighting in an extension. A No. 1 is for entirely new installations or full rewires. The No. 3 only covers the circuits you have altered.
Do I need to test the whole installation for a No. 3 certificate?
No. You only need to include the circuits that were altered or newly added in the circuit schedule and test results. However, you must assess the condition of the existing installation and confirm that your work has not adversely affected it.
Does a consumer unit upgrade require a No. 1 or No. 3 certificate?
A consumer unit upgrade — where the board is replaced but the existing circuits remain largely unchanged — is typically documented on a No. 3 certificate, as it is an alteration rather than a wholly new installation. However, if you are fully rewiring all circuits at the same time, a No. 1 would be more appropriate.

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