Annex P is one of the shortest annexes in TS EN 12845+A2:2026: two clauses on a single page. This article reproduces those two clauses in full, shows that the annex is normative, and opens up numerically the addresses it refers to (EN 12845-2 and EN 17451). Source: TS EN 12845+A2:2026, Annex P, TS p.167 / EN p.164 and TS EN 12845-2:2025 (EN 12845-2:2024).
Not a single K-factor, pressure or distance is attributed to Annex P in this article, because none of them appears in the annex.
Annex P is normative
The heading of the annex is written in the standard on three lines (TS p.167 / EN p.164):
Annex P
(normative)
ESFR sprinkler protection
It is listed in the table of contents in the same way, as "Annex P (normative) ESFR sprinkler protection" (TS p.12 / EN p.9). For comparison: in the same list Annex Q appears as "(informative)" and Annex N as "(normative)". The two sentences of Annex P are therefore binding provisions.
The full content of Annex P
The annex consists of two clauses.
P.1 General
The standard says two things:
- For ESFR sprinkler systems, EN 12845-2 shall be applied in connection with this document.
- For the water supply of ESFR sprinkler systems, it is recommended that three 50% pump sets in accordance with EN 17451 be used.
The difference in language matters: the first sentence uses "shall", the second uses "recommended". Applying EN 12845-2 is mandatory; the triple 50% pump arrangement is a recommendation.
P.2 Class conversion
Because the hazard classification systems of the two documents differ, the standard states that EN 12845-2:2024 Annex A shall be applied: either the conversion Table A.1 or the flow chart in Figure A.1.
Table A.1 in Annex A of EN 12845-2 (TS p.62 / EN p.59) is as follows:
| EN 12845 class | EN 12845-2 equivalent |
|---|---|
| LH | FH1 |
| OH1 | FH1 |
| OH2 | FH2 |
| OH3 | FH2 |
| OH4 | FH3 |
| HHP1 | FH4 |
| HHP2 | FH4 |
| HHP3 | FH5 |
Clause 6.2 of EN 12845-2 (TS p.36 / EN p.33) gives the practical consequence of this conversion: ESFR and CMSA protection do not apply to FH3 to FH5 occupancies. In other words, OH4, which falls into FH3 in the conversion table, and the HHP classes, which fall into FH4/FH5, cannot be protected by ESFR.
What Annex P does not say here
None of the following appears in Annex P; any text that attributes them to Annex P is wrong:
- A K-factor list or a K-factor / ceiling height table
- Minimum operating pressure values
- The 12 sprinkler rule or the shape of the area of operation
- Deflector distance, sprinkler spacing, roof slope or skylight criteria
- Provisions for dry ESFR, foam water or CE marking
- History, edition comparison or a manufacturer/model list
Note: the skylight criterion does exist in EN 12845, but not in Annex P. It is in Clause 12.4.5 (TS p.75 / EN p.72): skylights with a volume greater than 1 m³ measured above the normal ceiling level shall be protected by sprinklers; the exceptions are where the distance from the normal ceiling level to the top of the skylight does not exceed 0.3 m, or where there is a close fitting frame and glazing flush with the roof or ceiling.
Where the numbers Annex P points to actually are
The values below are not in Annex P but in EN 12845-2. Annex P brings them into force normatively.
Dry system prohibition
EN 12845-2 Clause 4 (TS p.9 / EN p.6): ESFR sprinklers shall only be used in wet installations; CMSA sprinklers may be used in wet and dry installations. Clause 6.5 (TS p.38 / EN p.35) repeats the same point: this ESFR concept has no dry installation option; where dry pendent ESFR sprinklers are used, the installation is considered to be wet.
Design number of sprinklers, supply duration and area shape
EN 12845-2 Table 6 (TS p.37 / EN p.34):
| Number of ceiling sprinklers in the design | Supply duration (min) | Shape of the area of operation (sprinklers × range pipes) |
|---|---|---|
| 9 | 60 | 3 × 3 |
| 10 | 60 | 3 × 2 + 4 × 1 |
| 12 | 60 | 4 × 3 |
| 15 | 90 | 5 × 3 |
| 16 | 90 | 5 × 3 + 1 × 1 |
| 20 | 120 | 5 × 4 |
| 24 | 120 | 6 × 4 |
| 25 | 120 | 6 × 4 + 1 × 1 |
| 30 | 120 | 7 × 4 + 2 × 1 |
According to the table, the shape of the widely known "12 sprinkler" scenario is 4 × 3 and the supply duration is 60 minutes.
Minimum operating pressures
EN 12845-2 Table 7 (TS p.39 / EN p.36) gives the minimum operating pressures for a ceiling-only HHS design with at least 12 ESFR sprinklers. A few of the HHS1 to HHS3 rows of the table (P = pendent):
| Max. ceiling height (m) | Max. storage height (m) | K200 (P) | K240 (P) | K320 (P) | K360 (P) |
|---|---|---|---|---|---|
| 7.6 | 6.1 | 3.4 bar | 2.4 bar | 1.7 bar | 1.0 bar |
| 9.1 | 7.6 | 3.4 bar | 2.4 bar | 1.7 bar | 1.0 bar |
| 10.7 | 9.1 | 5.2 bar | 3.6 bar | 2.4 bar | 1.4 bar |
| 12.2 | 10.7 | - | 3.6 bar | 2.8 bar | 1.7 bar |
| 13.7 | 12.2 | - | - | 2.8 bar | 2.8 bar |
The last two rows of the same table give K400 and K480 values for ceiling heights of 15.2 m (max. storage 13.3 m) and 16.8 m (max. storage 14.9 m); those rows are tied to footnotes on minimum aisle width (1.8 m and 2.4 m).
Minimum area of operation
EN 12845-2 Clause 6.6.1.2 (TS p.41 / EN p.38): for ESFR designs with special requirements, the minimum area of operation (number of sprinklers × spacing) shall be 71 m²; the exception is where a sprinkler is required in every channel formed by obstructed construction. The same clause also states that a 9 sprinkler design shall consist of 3 sprinklers on each of 3 adjacent range pipes.
Tyre storage: the chain from Annex C to Annex P
In TS EN 12845+A2:2026 Annex C, Table C.1 (TS p.138 / EN p.135) tyres stored horizontally are classified as Category IV, and the remarks column states that tyres stored horizontally are covered by Annex P. Since Annex P brings EN 12845-2 into play for ESFR, the designer is directed to Table 8 of EN 12845-2, which is dedicated to tyre storage (TS p.40 / EN p.37). That table gives tyre storage pressures for a 12 ESFR sprinkler design; for example, for STC3/STC4.1/STC4.2 tyres stored on tread or on side, with a storage height of 7.6 m or less and a ceiling at 10.7 m, the values are 5.2 bar for K200 pendent, 3.6 bar for K240 pendent, 2.4 bar for K320 and 1.7 bar for K360.
Field note
Because Annex P is a two clause referral annex, writing the specification language of an ESFR project as "in accordance with EN 12845-2 as required by EN 12845 Annex P" rather than "in accordance with EN 12845 Annex P" leaves no doubt about which table the calculation rests on. In the same way, stating both the EN 12845 class and its EN 12845-2 Table A.1 equivalent in the class declaration makes reviews that move between the two documents easier to read. (This paragraph is engineering commentary, not the text of the standard.)
Frequently Asked Questions
Is EN 12845 Annex P normative or informative?
It is normative. In TS EN 12845+A2:2026 the heading of the annex reads 'Annex P (normative) ESFR sprinkler protection' (TS p.167 / EN p.164). It is also listed as 'Annex P (normative)' in the contents (TS p.12 / EN p.9). Its provisions are therefore binding and cannot be read as a recommendation.
How many clauses does Annex P contain and what do they say?
Two. P.1 General: 'For ESFR sprinkler systems, EN 12845-2 shall be applied in connection with this document' and 'it is recommended that three 50% pump sets in accordance with EN 17451 be used for the water supply of ESFR sprinkler systems'. P.2 Class conversion: 'Because of the different hazard classification systems, EN 12845-2:2024 Annex A shall be applied; either the conversion Table A.1 or the flow chart in Figure A.1.' (TS p.167 / EN p.164)
Does Annex P contain a K-factor or pressure table?
No. Annex P contains no K-factor, no minimum operating pressure, no spacing distance and no area of operation value. All of these are in EN 12845-2: Table 7 for ceiling-only ESFR protection (TS p.39 / EN p.36), Table 6 for the design number and supply duration (TS p.37 / EN p.34), and Clause 6.6.1.2 for the 71 m² minimum area of operation (TS p.41 / EN p.38).
What do the three 50% pump sets recommended by Annex P mean?
Clause 10.2 of TS EN 12845+A2:2026 (TS p.60 / EN p.57) requires that where three pumps are installed, each pump shall be capable of delivering at least 50% of the specified flow at the specified pressure. Annex P recommends this triple arrangement for the ESFR water supply and requires the pump sets to comply with EN 17451. Under the same clause, in a superior or duplicate water supply not more than one of the pumps may be electric motor driven.
Why are horizontally stored tyres referred to Annex P?
In TS EN 12845+A2:2026 Annex C, Table C.1 (TS p.138 / EN p.135) the row 'Tyres stored horizontally' is given category IV with the remark that tyres stored horizontally are covered by Annex P. Since Annex P points to EN 12845-2 for ESFR, the chain leads to Table 8 of EN 12845-2, which is dedicated to tyre storage (TS p.40 / EN p.37).
References
- TS EN 12845+A2:2026 Annex P (normative), P.1 and P.2 (TS p.167 / EN p.164)
- TS EN 12845+A2:2026 Contents, Annex P and Annex Q rows (TS p.12 / EN p.9)
- TS EN 12845+A2:2026 Clause 10.2 Multiple pump set arrangements (TS p.60 / EN p.57)
- TS EN 12845+A2:2026 Clause 12.4.5 Skylights (TS p.75 / EN p.72)
- TS EN 12845+A2:2026 Annex C, Table C.1, "Tyres stored horizontally" row (TS p.138 / EN p.135)
- TS EN 12845-2:2025 (EN 12845-2:2024) Clause 4 General (TS p.9 / EN p.6)
- TS EN 12845-2:2025 Clause 6.2 (TS p.36 / EN p.33)
- TS EN 12845-2:2025 Clause 6.4, Table 6 (TS p.37 / EN p.34)
- TS EN 12845-2:2025 Clause 6.5 (TS p.38 / EN p.35)
- TS EN 12845-2:2025 Clause 6.6.1.1, Table 7 (TS p.39 / EN p.36)
- TS EN 12845-2:2025 Table 8, tyre storage (TS p.40 / EN p.37)
- TS EN 12845-2:2025 Clause 6.6.1.2 (TS p.41 / EN p.38)
- TS EN 12845-2:2025 Annex A, Table A.1 (TS p.62 / EN p.59)
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Download MEP Calc on the App StoreTS EN 12845+A2:2026 (EN 12845:2015+A2:2026) Fixed firefighting systems — Automatic sprinkler systems — Design, installation and maintenance; TS EN 12845-2:2025 (EN 12845-2:2024) ESFR and CMSA sprinkler systems. Every figure in this article is taken from the published standard text; clause, table and page references are listed under References. General information only, not a substitute for the standard or for a design review.