For hyperscale and colocation white-space cooling, the working solenoid valves are predominantly 2-way normally-closed pilot-operated bodies in brass or 304/316 stainless steel, ported 1/4" through 2" NPT, with 24 VDC coils rated for continuous duty and an IP65 minimum enclosure for condensation exposure at the CRAH row [S2][S3].
What the cooling loop actually demands from the solenoid
Three flows matter: chilled water (7-12 °C, often with 25-35% propylene glycol freeze protection), hot-water return to the CDU (45-65 °C in liquid-to-liquid AI racks), and condensate/drain on the CRAC units [S2]. Each of these puts a different stress on the same solenoid part number.
Direct-acting valves are used on small or zero-pressure-differential circuits (drain, sample, makeup) because they open without a minimum line pressure; pilot-operated valves are used on the larger mains because they handle higher Kv with smaller coils, but they need a minimum differential — typically 0.5-2.0 bar — to open [S2]. Specifying a pilot-operated valve on a dead-head pump is a classic commissioning failure.
Seal material is where most data-center jobs get burned. EPDM handles chilled water and glycol up to roughly 120 °C, but swells in mineral oil; FKM (Viton-class) handles higher temperatures and many oils but is not the first pick for plain water; NBR is the cheapest but ages fastest in hot-glycol service. For the hot-side CDU return above 60 °C, EPDM or PTFE seals are the conservative default [S2].
Voltage, coil and enclosure: 24 VDC vs 110/220 VAC
Modern data-center valve coils are 24 VDC, 50/60 Hz rectified to DC, or true 24 VDC, for two reasons: the BMS output is already 24 VDC, and a DC coil holds lower continuous wattage for the same pull-in force, which reduces heat soak into the coil class — a real concern inside a CRAC unit where the surrounding air can already be 35-40 °C [S3][S5].
Coil insulation class F (155 °C) or H (180 °C) is the right pick above the CRAC; class B (130 °C) is the false economy. IP65 is the minimum for any valve inside or above the cold-aisle; valve terminals in the under-floor plenum see wash-down water during slab work and routinely fail at IP54 [S2].
Explosion-proof (ATEX/IECEx) coils are not the default in a data-center white space — there is no flammable atmosphere in the cold aisle — but they are routinely required in the generator-yard fuel-gas train and in any on-site gas-insulated switchgear room, where an air solenoid valve controlling instrument air must be Ex d or Ex e marked [S6]. Specifying ATEX on every valve in the hall is over-spend; omitting it on the fuel-gas train is a non-compliance.
Body material: brass, stainless, or engineered plastic
Brass bodies are the default for indoor chilled-water and air-service lines up to roughly 80 °C and 16 bar, and they cost less than stainless by a factor of 2-3 [S1][S3]. Stainless 304 is the step up when the loop is deionized water (DI rinse in semiconductor-adjacent halls) or when the chemistry includes corrosion inhibitors that attack copper alloys.
316 stainless is the right call for any chemistry above 5% chloride, for outdoor condenser-water loops, and for any valve on the seawater or glycol side of a water-source heat pump. Engineered plastics (PA66, PPS) appear in condensate drain valves and in 2/2 Nylon-body irrigation-pattern valves such as the ZCS-06PM and ZCS-08P families, but plastics do not belong on the pressurized mains [S1].
The practical body comparison: brass costs least and fits 80% of indoor chilled-water duty; 304 SS handles DI and slightly hotter return; 316 SS is mandatory outdoors, on chloride-bearing glycol, and on any makeup-water line downstream of an unfiltered city supply. Plastic bodies are acceptable only on drain and low-pressure sample lines.
Solenoid vs motorized ball: pick by duty cycle
A solenoid is binary. It is fully open or fully closed in 50-300 ms, it draws power only while shifting (or continuously if held), and it cycles cleanly several times per hour for years. A ball valve with an electric actuator is the right part when the loop needs slow open/close to prevent water hammer, when the valve must stay in a mid-position for hours, or when the BMS is calling for a modulating flow setpoint [S2][S3].
For the chilled-water isolation valve on a CRAH unit, the standard 2-way or 3-way solenoid valve is the correct part. For a chilled-water bypass that has to track a leaving-water-temperature PID loop, you want a modulating control valve with a 0-10 V or 4-20 mA actuator, not a solenoid — a solenoid will either full-open or full-close and the loop will hunt.
The cross-reference for the data-center spec sheet: 2-way NC pilot-operated brass, 1" NPT, EPDM seals, 24 VDC class-F IP65 coil is the default CRAH isolation valve; 3-way brass diverter with the same coil is the default for changeover between primary and secondary loops; a 2-way stainless proportional valve sized on Kv replaces the solenoid wherever a BMS PID output is present.
Selection checklist for the procurement engineer
Run this list against any vendor data sheet before signing the PO. (1) Function: 2-way NC, 2-way NO, or 3-way; (2) Port size and thread — NPT vs BSP matters, BSP into an NPT fitting will leak; (3) Body and seal material matched to the loop chemistry and temperature; (4) Coil voltage, wattage, insulation class, IP rating and duty cycle; (5) Minimum operating differential for pilot-operated types; (6) Kv or Cv value at the actual working pressure; (7) Certifications relevant to the loop — potable water (NSF/ANSI 61 in some jurisdictions), gas (UL 125 or EN 161 for fuel-gas), Ex rating for hazardous areas [S2][S3][S5].
Two practical shortcuts from the field. First, for a 1" chilled-water isolation valve on a CRAH row, the ASCO 8210 series, the Bona ZCQ-20B brass pattern and the ATO 2-way pneumatic-class bodies all occupy the same functional slot — the right pick is the one your controls contractor stocks locally, because a failed valve at 02:00 is fixed by a truck-roll, not a datasheet [S1][S3][S5]. Second, always size on Kv at the worst-case pressure drop, not on pipe size — an oversized solenoid chatters, an undersized one starves the coil.
For a control-loop companion, the solenoid coil selection note in our encyclopedia walks through the 24 VDC class-F vs 110 VAC class-B trade-off in more detail.
What the new 2026 product pages actually show
Reviewing the vendor catalogs refreshed in the past six months, the pattern is consistent. Bona's July 2026 product list is dominated by 2/2-way brass and 2/2-way N.C. aluminum bodies (ZCQ-20B-2, ZCQ-06B) for welding and air service, plus 2/2 and 2/3-way Nylon magnetic valves (ZCS-06PM, ZCS-04P-3T, ZCS-08P, ZCS-100P) for irrigation and drain duty [S1]. Chelic's pneumatic-solenoid catalog stays in the 2/2 and 3/2 pilot-assisted pattern for air, with manual, pneumatic and electric actuation options called out as distinct control modes [S4]. ATO's pneumatic-solenoid page lists the 2-way 12V/24V/110V/220V part at USD 42.07 list (USD 48.85 OEM-style) — a reference price point for the entry-level 1/4"-3/8" NC brass body [S5].
For control valves in liquid service, the adjacent decision is sizing, and the control valve sizing and selection process-engineer field guide walks the same Kv-and-pressure-drop logic for the proportional side of the loop. The ASCO-led Valvate distributor page, refreshed January 2026, confirms that the 2/3/4-way ASCO and Numatics lines remain the workhorses for air, water, natural gas, steam, vacuum and cryogenic, in sizes 1/8" through 3" [S3].
Two trackable signals from the current cycle. First, watch whether your incumbent vendor moves their default coil from class F to class H — that is the leading indicator that they are qualifying for hotter CDU return loops. Second, watch for revised minimum-operating-differential figures on pilot-operated 1" bodies; any drop below 0.3 bar means dead-head-pump compatibility, which in turn means the valve can replace a direct-acting part on more of the CRAC drain circuits.