The short answer
A plastic consumer unit in an existing installation does not automatically cause an EICR to be rated 'Unsatisfactory'. However, it is commonly coded as either a C2 (potentially dangerous) or a C3 (improvement recommended) depending on the inspector's assessment of its condition, age and context. The 18th Edition of BS 7671 requires new consumer unit installations to have a non-combustible (typically metal) enclosure, but this requirement is not retrospectively applied to all existing plastic boards — an EICR assesses the installation against the standard in force when it was installed as well as current practice. A plastic board that is in poor condition, shows signs of heat damage, or is in a domestic property without adequate fire safety provisions is more likely to receive a C2 code.
The 18th Edition's metal-enclosure requirement causes understandable confusion. Here is what it actually means for an existing plastic board inspected under an EICR.
Plastic boards and EICR
- 18th Edition ruleMetal enclosure required for NEW installations (from Jan 2019)
- Existing plastic boardsNot automatically failed — assessed on condition and context
- Typical EICR codeC3 (improvement recommended) to C2 (potentially dangerous)
- C2 meaningRequires remedial action for satisfactory report
- C3 meaningDoes not fail the EICR; improvement advised
What the 18th Edition metal-enclosure requirement says
Amendment 3 to BS 7671 — incorporated into the 18th Edition and effective from January 2019 — introduced Regulation 421.1.201, which requires consumer units in domestic premises to have a non-combustible enclosure. In practice, this means a metal enclosure for any new consumer unit installation or replacement carried out from that date.
The rationale is fire safety: in a fault condition, a plastic enclosure can melt or ignite, spreading fire into the building fabric. A metal enclosure contains any fault-induced heat and fire within the board itself, giving more time for protective devices to operate and for occupants to evacuate.
Critically, this requirement applies to new work. It does not retrospectively require every existing plastic board to be replaced immediately. However, an EICR inspector assessing an existing installation against current standards will note a plastic consumer unit and code it according to the risk it presents in its specific context.
How inspectors typically code a plastic consumer unit on an EICR
EICR coding categories are defined in BS 7671 as follows:
- C1 — Danger present: risk of injury or death; immediate remedial action required.
- C2 — Potentially dangerous: urgent remedial action required for the report to be rated Satisfactory.
- C3 — Improvement recommended: does not cause the report to be rated Unsatisfactory; remedial action is advised but not urgent.
- FI — Further investigation needed.
For an existing plastic consumer unit, the most common EICR coding is:
- C3 — where the board is a relatively modern plastic unit in good condition with sound protective devices (RCDs/MCBs present and operating), no signs of damage, and the installation otherwise satisfactory. The non-compliance with the current enclosure standard is noted as an improvement recommendation.
- C2 — where the plastic board shows signs of heat damage, discolouration, or deterioration; where it is in a higher-risk location (e.g., a property with a combustible structure close to the board); or where the inspector considers the risk of fire from the plastic enclosure in the context of the specific installation to be more than a theoretical future concern. A C2 code requires remedial action for the report to be rated Satisfactory.
There is genuine inspector discretion in how a plastic board is coded, and different inspectors may reach different conclusions on the same board. If you receive an EICR with a C2 code on a plastic consumer unit, the remedial action is typically replacement with a metal-enclosure unit.
The distinction between the 18th Edition requirement and an EICR assessment
A common source of confusion is the difference between what BS 7671 requires for new work and what an EICR concludes about existing work:
- For new or replacement work carried out from January 2019, a metal enclosure is required. An electrician who fits a plastic consumer unit on a new installation from that date is not complying with BS 7671, and the EIC cannot legitimately be issued.
- For an EICR on an existing installation, the inspector assesses the installation's condition and safety, noting where it does not meet current standards. Regulation 644.1.2 of BS 7671 states that the inspector should compare the installation against the edition of the wiring regulations in force at the time of installation as well as current standards, noting divergences. A plastic board installed before January 2019 is technically not in breach of the regulations under which it was installed — but it does not meet current standards for new work, which is why it appears on the EICR.
This distinction matters because it affects the urgency of the remedial recommendation. An installation that was compliant when installed but no longer meets the current standard is a different assessment from one that was never compliant.
| Scenario | EICR code | Effect on report |
|---|---|---|
| Plastic board, good condition, sound protective devices | C3 (typically) | Report may still be Satisfactory |
| Plastic board with heat damage or discolouration | C2 (typically) | Report rated Unsatisfactory; remedial action required |
| Plastic board, no RCD protection, older installation | C2 (likely — for the protection gap) | Report rated Unsatisfactory |
| New plastic board installed post-January 2019 | C2 or C1 (non-compliant installation) | Significant deficiency — immediate remediation |
Indicative EICR coding scenarios for plastic consumer units. Actual coding depends on inspector judgement and full installation context.
Should you replace a plastic consumer unit before an EICR?
There is no obligation to replace a plastic consumer unit before an EICR. The EICR assesses the installation as-is and gives you a documented picture of its condition. If the board receives a C3 code and the rest of the installation is Satisfactory, you have an accurate baseline and a clear improvement recommendation but no urgent legal obligation.
If you are in a position to replace the board — for example, if you are having other electrical work done, or if the board is old and lacks RCD protection — doing so before the EICR will naturally remove that element from the report. But replacing a sound plastic board solely to avoid a C3 annotation on an EICR is not necessary; the EICR is a condition report, not a pass-or-fail exam on a single item.
The considerations that genuinely push toward replacing a plastic board promptly are: a C2 code on the EICR; signs of heat damage or deterioration on the existing board; the absence of RCD or RCBO protection; or a scheduled sale of the property where the buyer's survey may flag an Unsatisfactory EICR.
Frequently asked questions
Does having a plastic consumer unit mean my EICR will fail?
Not automatically. A plastic consumer unit is typically coded C3 (improvement recommended) if it is otherwise in good condition and the installation has sound protective devices. It is more likely to be coded C2 (requiring remedial action) if the board shows heat damage, if it lacks RCD protection, or if the inspector considers the specific installation context to represent a more serious risk. Only a C2 or C1 code makes the overall EICR report Unsatisfactory.
Was it legal to fit a plastic consumer unit before 2019?
Yes. The metal-enclosure requirement came in with the 18th Edition amendments effective from January 2019. Plastic consumer units installed before that date were compliant with the edition of BS 7671 in force at the time. An EICR notes the divergence from current standards but cannot fairly code it as a defect that existed at the time of installation.
If my EICR gives a C2 for a plastic board, do I have to replace it?
A C2 code requires remedial action for the EICR to be rated Satisfactory. For a private landlord, an Unsatisfactory EICR must be remedied within 28 days (or the specified shorter time) under the Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020. For owner-occupiers there is no legal deadline, but the work should be carried out as a matter of safety.
Sources & further reading
- IET — BS 7671 18th Edition wiring regulations overview
- Electrical Safety First — replacing a consumer unit (best practice guide)
- NICEIC — EICR coding guidance
Figures on this page are typical UK ranges drawn from published sources and depend on your specific property and installation. They are guidance, not a quotation.