biblios Johor can't free-cool697.93 C85j

Front endpaper, combed from the call number. No two volumes share one.

Infrastructure · Explainer 697.93 C85j

Johor can't free-cool

In a decade of hourly readings at Senai, the outside air never once got dry enough to cool a server. Warm water can do the job, and it brings back the water question.

Written
and drawn by Asvin
Extent
5 signatures · 4 min
Plates
3
Edition
First · 1.X.2026
  1. AJohor can't free-cool
  2. BNot one hour
  3. CWetter than every class
  4. DWarm water fits
  5. EThe catch

Climate · Senai

Not one hour dry enough

Free cooling lets outside air, or water cooled by it, do the chillers' work. It only works when the air already fits the server: ASHRAE recommends inlet air at 18 °C to 27 °C with a dew point no higher than 15 °C. At Senai, across 86,644 hourly readings from 2015 to 2024, the dew point met that ceiling in 0 h. Frankfurt's air sat inside the envelope 91.4% of the time.

0hSenai hours at or under the dew-point ceiling
91.4%of Frankfurt's hours inside the envelope

Sources — [1]NOAA National Centers for Environmental Information. Global Hourly (Integrated Surface Database), stations 48679099999 Senai and 10637099999 Frankfurt, 2015 to 2024; [2]ASHRAE TC 9.9. 2011 Thermal Guidelines for Data Processing Environments: Expanded Data Center Classes and Usage Guidance.

Bar chart: Senai, Johor 0%; Frankfurt 91.4%.

Bar chart: Senai, Johor 0%; Frankfurt 91.4%.
Fig. B1 Share of hourly readings, 2015 to 2024, with outside air inside ASHRAE's recommended envelope: dry bulb at or under 27 °C and dew point at or under 15 °C. Senai is Johor's airport station. Fidelity 5 · MeasuredNOAA hourly, 2015–24Senai, JohorFrankfurtMeasured, airport stationsUpper limits only; dry air can be humidified
Data
QuantityValueSource
Senai hours inside the recommended envelope0%NOAA National Centers for Environmental Information
Frankfurt hours inside the recommended envelope91.4%NOAA National Centers for Environmental Information
Recommended inlet air, upper bound27 °CASHRAE TC 9.9
Recommended ceiling on dew point15 °CASHRAE TC 9.9

Standard · ASHRAE

Wetter than the looser classes allow

The allowable classes let the dew point climb: 17 °C for class A1, 21 °C for A2, 24 °C for A3 and A4. Senai met the A1 ceiling in 3 h of the decade and the A2 ceiling in 0.5% of its hours. Its median dew point, 24.5 °C, sits above all of them. Every hour of outside air needs a cold coil to wring it out first.

24.5°Cmedian dew point at Senai
3hhours at or under the class A1 ceiling in a decade

Sources — [1]NOAA National Centers for Environmental Information. Global Hourly (Integrated Surface Database), stations 48679099999 Senai and 10637099999 Frankfurt, 2015 to 2024; [2]ASHRAE TC 9.9. 2011 Thermal Guidelines for Data Processing Environments: Expanded Data Center Classes and Usage Guidance.

Bar chart: Recommended, 15 °C 0 h; Class A1, 17 °C 3 h; Class A2, 21 °C 452 h; Classes A3 and A4, 24 °C 39,771 h; Every hour on record 86,644 h.

Bar chart: Recommended, 15 °C 0 h; Class A1, 17 °C 3 h; Class A2, 21 °C 452 h; Classes A3 and A4, 24 °C 39,771 h; Every hour on record 86,644 h.
Fig. C1 Hours at Senai, 2015 to 2024, when the outside dew point was at or under each ASHRAE ceiling, against every hour on record. Only the loosest classes are met in any real share. Fidelity 5 · MeasuredNOAA hourly, 2015–24Recommended, 15 °CClass A1, 17 °CClass A2, 21 °CClasses A3 and A4, 24 °CEvery hour on recordMeasured, one airport stationDew point only; temperature limits not applied
Data
QuantityValueSource
Senai hours with dew point at or under 15 °C0 hNOAA National Centers for Environmental Information
Senai hours with dew point at or under 17 °C3 hNOAA National Centers for Environmental Information
Senai hours with dew point at or under 21 °C452 hNOAA National Centers for Environmental Information
Senai hours with dew point at or under 24 °C39,771 hNOAA National Centers for Environmental Information
Hourly readings at Senai, 2015 to 202486,644NOAA National Centers for Environmental Information
Recommended ceiling on dew point15 °CASHRAE TC 9.9
Class A1 allowable maximum dew point17 °CASHRAE TC 9.9
Class A2 allowable maximum dew point21 °CASHRAE TC 9.9
Classes A3 and A4 allowable maximum dew point24 °CASHRAE TC 9.9

Liquid · The way out

Warm water fits outside

A cold plate on the chip doesn't need dry air. It needs facility water under a class ceiling, and ASHRAE names each class by that ceiling. Most cold plates today, it says, live easily on W32 water, supplied at 32 °C or less. A cooling tower works against the wet bulb, and Senai's stayed at or under 28.5 °C in all but the wettest hundredth of hours. The hottest reading of the decade, 37 °C, leaves 8 °C under the W45 ceiling: room for a dry cooler, which evaporates nothing.

28.5°CSenai wet bulb, all but the top hundredth of hours
8°C, marked * in Fig. D1headroom from the hottest hour to the W45 ceiling

Sources — [1]NOAA National Centers for Environmental Information. Global Hourly (Integrated Surface Database), stations 48679099999 Senai and 10637099999 Frankfurt, 2015 to 2024; [3]ASHRAE TC 9.9. Emergence and Expansion of Liquid Cooling in Mainstream Data Centers (white paper, 2021).
Method — own derived.

A horizontal temperature scale with three lanes. Top: air into a server, a red bar up to the recommended dew-point ceiling of 15 °C, dashed on to the loosest class at 24 °C, and a red arrow dragging Senai's median dew point down to the ceiling. Middle: Senai's outdoor dew point as a gilt band from 22 °C to 27 °C, median 24.5 °C, with markers for the wet bulb, 28.5 °C, and the hottest hour, 37 °C. Bottom: water to a cold plate, a blue bar to the W32 ceiling at 32 °C, dashed on to W45 at 45 °C, with brackets showing 3.5 °C of headroom over the wet bulb and 8 °C over the hottest hour.

A horizontal temperature scale with three lanes. Top: air into a server, a red bar up to the recommended dew-point ceiling of 15 °C, dashed on to the loosest class at 24 °C, and a red arrow dragging Senai's median dew point down to the ceiling. Middle: Senai's outdoor dew point as a gilt band from 22 °C to 27 °C, median 24.5 °C, with markers for the wet bulb, 28.5 °C, and the hottest hour, 37 °C. Bottom: water to a cold plate, a blue bar to the W32 ceiling at 32 °C, dashed on to W45 at 45 °C, with brackets showing 3.5 °C of headroom over the wet bulb and 8 °C over the hottest hour.
Fig. D1 One temperature scale, three lanes. The air limits sit below Senai's outdoor dew point, so a chiller coil must dry every hour of air; the warm-water classes sit above its wet bulb and its hottest hour.* 8 °C applies at the headroom under the W45 ceiling. Fidelity 3 · SourcedNOAA data, ASHRAE limitsMeasured weather, one airport stationTower and dry-cooler approach not drawnPercentiles, not extremes, for the dew point
Data
QuantityValueSource
Recommended inlet air, upper bound27 °CASHRAE TC 9.9
Recommended ceiling on dew point15 °CASHRAE TC 9.9
Classes A3 and A4 allowable maximum dew point24 °CASHRAE TC 9.9
Senai dew point, 1st percentile22 °CNOAA National Centers for Environmental Information
Senai median dew point24.5 °CNOAA National Centers for Environmental Information
Senai dew point, 99th percentile27 °CNOAA National Centers for Environmental Information
Senai wet bulb, 99th percentile28.5 °CNOAA National Centers for Environmental Information
Hottest hourly dry bulb at Senai, 2015 to 202437 °CNOAA National Centers for Environmental Information
Class W32 facility water supply ceiling32 °CASHRAE TC 9.9
Class W45 facility water supply ceiling45 °CASHRAE TC 9.9
W45 ceiling above Senai's hottest hour8 °Cown derived
W32 ceiling above Senai's 99th-percentile wet bulb3.5 °Cown derived

Policy · Johor

The catch is water

A cooling tower makes W32 water by evaporating some of it, and Johor wants that water to come from somewhere else. On 27 November 2025 the state's housing and local government committee chairman said data centres must use reclaimed water rather than supplies from Syarikat Air Johor.

The chips push the other way. ASHRAE expects falling case temperatures to drag facility water down toward W27, and Senai's wet bulb sits above 27 °C in 13.2% of hours, before a tower's approach is counted. Warm water is Johor's way out of the chiller, but only while the chips can take it.

13.2%Senai hours with the wet bulb above the W27 ceiling

Sources — [4]New Straits Times. Johor shuts door on water-guzzling data centres, tightens approval rules (27 November 2025); [3]ASHRAE TC 9.9. Emergence and Expansion of Liquid Cooling in Mainstream Data Centers (white paper, 2021); [1]NOAA National Centers for Environmental Information. Global Hourly (Integrated Surface Database), stations 48679099999 Senai and 10637099999 Frankfurt, 2015 to 2024.

Endmatter

Sources

Every number in this volume is stored once, with where it came from.

  1. 1

    NOAA National Centers for Environmental Information. Global Hourly (Integrated Surface Database), stations 48679099999 Senai and 10637099999 Frankfurt, 2015 to 2024. Accessed 30.IX.2026.For Hourly readings at Senai, 2015 to 2024 86,644; Senai hours with dew point at or under 15 °C 0 h; Senai hours with dew point at or under 17 °C 3 h; Senai hours with dew point at or under 21 °C 452 h; Senai hours with dew point at or under 24 °C 39,771 h; Share of Senai hours at or under the A2 dew-point ceiling 0.5%; Senai dew point, 1st percentile 22 °C; Senai median dew point 24.5 °C; Senai dew point, 99th percentile 27 °C; Senai hours inside the recommended envelope 0%; Frankfurt hours inside the recommended envelope 91.4%; Senai wet bulb, 99th percentile 28.5 °C; Senai hours with wet bulb above 27 °C 13.2%; Hottest hourly dry bulb at Senai, 2015 to 2024 37 °C

  2. 2

    ASHRAE TC 9.9. 2011 Thermal Guidelines for Data Processing Environments: Expanded Data Center Classes and Usage Guidance. Accessed 30.IX.2026.For Recommended inlet air, lower bound 18 °C; Recommended inlet air, upper bound 27 °C; Recommended ceiling on dew point 15 °C; Class A1 allowable maximum dew point 17 °C; Class A2 allowable maximum dew point 21 °C; Classes A3 and A4 allowable maximum dew point 24 °C

  3. 3

    ASHRAE TC 9.9. Emergence and Expansion of Liquid Cooling in Mainstream Data Centers (white paper, 2021). Accessed 30.IX.2026.For Class W27 facility water supply ceiling 27 °C; Class W32 facility water supply ceiling 32 °C; Class W45 facility water supply ceiling 45 °C

  4. 4

    New Straits Times. Johor shuts door on water-guzzling data centres, tightens approval rules (27 November 2025). Accessed 30.IX.2026.

Own work

  • W32 ceiling above Senai's 99th-percentile wet bulb3.5 °Cderived
  • W45 ceiling above Senai's hottest hour8 °Cderived

End of volume · 697.93 C85j

Shelved beside it

biblios is read along the shelf, not down a feed. These volumes stand either side of this one by class number, whatever their date.

  1. How biblios draws, 001.4226 F69h 2026
  2. Johor can't free-cool, 697.93 C85j 2026, this volume

  3. The 600s end here. Nothing is shelved after 697.93 C85j yet.