HHS5–HHS12 High-Bay Sprinkler Design

Warehouses with 5–12 m storage heights are the standard form of today's e-commerce, logistics and distribution buildings. ESFR, or CMSA plus in-rack? The roof condition, the commodity class, the available water capacity and the insurer's preference together decide the answer.

At one e-commerce warehouse the racking was planned at 11 m. The first tender proposed CMDA with three in-rack levels — very complex and the most expensive option. The second proposed ESFR K360 — a simple ceiling-only system, cheaper overall but with a costly pump. The third proposed CMSA at ceiling plus two in-rack levels, sitting between the two. ESFR was chosen with the insurer: the roof was flat concrete, the commodity was Class III, and the town main pressure was adequate. The logic behind choosing ESFR is consistent — least complexity, fastest control, least maintenance.

HHS storage height table

Category	Storage height	Recommended mode
HHS1	≤ 4 m	CMDA OH3 sufficient
HHS2	4–5 m	CMDA plus single in-rack level
HHS3	5–6 m	CMDA plus in-rack, or CMSA at ceiling
HHS4	6–7 m	CMSA at ceiling or ESFR
HHS5	7–8 m	CMSA plus in-rack, or ESFR
HHS6	8–9 m	ESFR common
HHS7–8	9–10 m	ESFR K360
HHS9–10	10–11 m	ESFR K360 with a suitable roof
HHS11–12	11–12 m	ESFR K480, or CMSA plus three in-rack levels

Water demand comparison (Class III)

Storage height	ESFR flow	CMSA plus in-rack flow	Pump pressure
5 m (HHS3)	3500 L/min for 60 min	3000 L/min for 90 min	5–6 bar
7 m (HHS5)	4500 L/min for 60 min	4000 L/min for 90 min	6–7 bar
9 m (HHS6)	5500 L/min for 60 min	4500 L/min for 90 min	8 bar
11 m (HHS9)	6500 L/min for 60 min	5500 L/min for 90 min	10 bar

Selecting the ESFR K-factor

Storage height	K-factor	Pressure
≤ 7.6 m	K200	5.2 bar
≤ 9.1 m	K240	4.1 bar
≤ 10.7 m	K280	3.5 bar
≤ 12 m	K360	4 bar
≤ 13.7 m	K480	3.5 bar

Deciding the number of in-rack levels

• Storage ≤ 6 m: a single in-rack level at about 3 m
• 6–9 m: two levels, at about 3 m and 6 m
• 9–12 m: three levels, or ceiling ESFR as the alternative
• ST1–ST3 (open racking): in-rack heads at 3 m horizontal spacing
• ST4–ST6 (palletised block stacks): in-rack heads at 2.4 m horizontal spacing

Field error — future storage growth was never planned

One logistics warehouse was designed at HHS3 (6 m). Eighteen months later the racking was raised to 9 m (HHS6). The existing CMDA plus single in-rack level was no longer adequate; two additional in-rack levels and a pump upgrade were required. Storage height should be documented as a five-year plan at the outset, and the mode decision taken with the manufacturer and insurer on that longer horizon.

Planning the pump room

• For HHS5–12, a duplicated electric plus diesel pump set is standard
• Tank volume 300–700 m³ (60–90 min of supply duration)
• Pump room at least 50 m² for a duplex set plus control panels
• Tank located below ground or above ground with freeze protection
• Redundant town main connection from two separate inlets

Note on hydraulic calculation

For HHS5–12 designs a full hydraulic calculation is mandatory; pre-calculated tables are not adequate. Insurers ask for a report showing the balance at the most remote and highest sprinkler. Mains are typically DN150–DN200, with DN50–DN65 at the most remote point.

Turkish regulation and local practice

BYKHY does not split out the HHS categories individually; it defines "high-hazard storage" and refers to EN 12845. Newer Turkish distribution centres are being built as standard with ESFR under flat concrete roofs, while older facilities continue with CMSA plus in-rack. Automated storage and retrieval systems reaching 20–30 m require a dedicated insurer study.

Quick check list

• Storage height documented as a five-year plan.
• HHS category correctly identified from the table.
• Mode selection justified in writing (roof, commodity, water).
• K-factor checked against the listing for the storage height.
• Number of in-rack levels matches the storage height.
• Pumps duplicated (electric plus diesel).
• Tank sized for 60–90 min of duration.
• Hydraulic report issued to the insurer.

Frequently Asked Questions

At what storage height does ESFR become the usual choice?

From around 8 m (HHS6) upwards, provided the roof is flat and within slope limits and the commodity is listed. Below 6 m, CMDA with in-rack heads is often simpler and cheaper.

Which ESFR K-factor suits 11 m of storage?

K360 is the common selection for storage up to 12 m, typically at around 4 bar. K480 extends the range to about 13.7 m at a lower operating pressure.

How many in-rack levels are needed?

One level up to 6 m, two levels for 6–9 m, and three levels for 9–12 m — unless ceiling ESFR replaces in-rack protection entirely.

Is a hydraulic calculation mandatory at these heights?

Yes. Pre-calculated tables do not cover HHS5–12. Insurers expect a full calculation demonstrating the balance at the most remote and highest sprinkler.

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