Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Evaporative Coolers
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## The cabinet shall be of weather-resistant construction suitable for the installed exposure and shall not deflect or distort under operating and wind loads.
−## Water-contact surfaces shall be corrosion-resistant for the service water chemistry and the installed environment. {note}
+## Water-contact surfaces shall be corrosion-resistant for the service water chemistry and the installed environment.
## The sump, distribution headers, and wetted casing surfaces are continuously exposed to mineral-laden recirculating water and intermittent wet/dry cycling, which is far more aggressive than the dry air-side surfaces. Stainless steel or polymer water-contact construction is warranted in coastal, high-TDS, or corrosive-process environments; galvanized or aluminized steel is acceptable for benign inland water and air. {note}
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# Evaporative Media {toc}
−## Media shall be a rigid, self-supporting evaporative material that maintains its shape and saturation characteristics over the service life and resists sagging, channeling, and biological fouling. {note}
+## Media shall be a rigid, self-supporting evaporative material that maintains its shape and saturation characteristics over the service life and resists sagging, channeling, and biological fouling.
## Media is the heart of the cooler: its depth and surface geometry set both the saturation effectiveness and the air-side pressure drop. Rigid cellulose and corrugated PVC media hold their geometry and wet uniformly; loose aspen pads sag, channel, and degrade quickly. Thicker media raises effectiveness at the cost of pressure drop — 4 in. media yields roughly 80% effectiveness, 8 in. roughly 90%, and 12 in. media is reserved for high-effectiveness industrial duty. {note}
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# Water Distribution and Sump {toc}
−## The water distribution system shall wet the entire media face uniformly at the design recirculation rate. {note}
+## The water distribution system shall wet the entire media face uniformly at the design recirculation rate.
## Two arrangements are common: top-feed gravity distribution, where water is metered across the top of the media and trickles down, and recirculating pump-and-header systems, where a sump pump lifts water to a perforated header. Pump-and-header systems give more uniform wetting and are standard for larger commercial units; gravity systems are simpler and suit small units. {note}
## The sump shall provide a water reserve of at least three minutes at the full design evaporation rate to ride through makeup-supply interruptions without running the media dry.
−## A float-controlled automatic makeup water fill valve with an integral or upstream pressure regulator shall maintain sump level. {note}
+## A float-controlled automatic makeup water fill valve with an integral or upstream pressure regulator shall maintain sump level.
## Omitting the regulator or undersizing the makeup line is a frequent failure: the unit starves, media dries and degrades, and the recirculation pump runs dry and burns out. The regulator stabilizes fill against supply-pressure swings and protects the float valve. {note}
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## Direct evaporative coolers aerosolize recirculating water and therefore fall within the Legionella risk scope of ASHRAE 188. The Water Management Plan documents control measures, bleed-off and disinfection protocols, and monitoring, and is a non-negotiable deliverable for commercial installations. This obligation is independent of the cooling-tower water program in [[sync/hvac-water-treatment]] and [[sync/cooling-towers]], which serves a different purpose and risk profile. {note}
−## A continuous bleed-off (blowdown) system shall be provided to limit dissolved-solids accumulation in the recirculating water. {note}
+## A continuous bleed-off (blowdown) system shall be provided to limit dissolved-solids accumulation in the recirculating water.
## As water evaporates it leaves its minerals behind, concentrating dissolved solids in the sump. Without bleed-off, scale builds on media and headers, effectiveness falls, and biofilm proliferates. Bleed-off ratios commonly run between 1:3 and 1:6 of the evaporated water; a practical floor is about 1 gallon per hour per 1,000 CFM, adjusted to hold total dissolved solids below roughly 2,000 ppm. {note}
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## Fan power for commercial direct-drive units typically falls in the 1 to 3 hp range, with the full range from a fraction of a horsepower for small units to about 10 hp for large industrial coolers. Direct-drive fans eliminate belt maintenance; belt-drive fans allow speed adjustment by sheave change but introduce the most common maintenance failure mode. {note}
−## Where a belt-drive fan is provided, the Contractor shall commission belt tension at startup and furnish one spare belt set per unit. {note}
+## Where a belt-drive fan is provided, the Contractor shall commission belt tension at startup and furnish one spare belt set per unit.
## Belt slip is the leading cause of lost airflow in belt-driven coolers. Commissioning tension and stocking spares converts a recurring failure into a routine service item. {note}
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## Coordinate intake louvers with [[sync/louvers-and-dampers]]. {note}
−## A pre-filter shall be provided upstream of the media to protect it from airborne debris. {note}
+## A pre-filter shall be provided upstream of the media to protect it from airborne debris.
## A MERV-8 pre-filter is typical for commercial service: it captures the coarse dust that would otherwise foul and channel the media without imposing the pressure penalty of higher-efficiency filtration. Filtration efficiency selection should reflect the served occupancy and the air distribution devices downstream — see [[sync/hvac-air-distribution-devices]]. {note}
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# Controls and Integration {toc}
−## The cooler shall be controlled to maintain the space or supply setpoint while sequencing the recirculation pump and supply fan to avoid running the fan over dry media or the pump without airflow. {note}
+## The cooler shall be controlled to maintain the space or supply setpoint while sequencing the recirculation pump and supply fan to avoid running the fan over dry media or the pump without airflow.
## A proper sequence wets the media before or as the fan starts and continues a post-purge or drain cycle after shutdown. Running the fan over dry media wastes energy and delivers no cooling; running the pump with no airflow needlessly concentrates the sump. {note}
−## Where building automation integration is specified, the cooler controls shall expose monitoring and command points over a standard protocol and shall honor BAS occupancy schedules and demand-controlled ventilation; integrate with [[sync/building-automation-system]]. {note}
+## Where building automation integration is specified, the cooler controls shall expose monitoring and command points over a standard protocol and shall honor BAS occupancy schedules and demand-controlled ventilation; integrate with [[sync/building-automation-system]].
## Stand-alone thermostatic control is common and acceptable for simple installations, but it leaves the cooler disconnected from occupancy schedules and ventilation demand. Specifying the integration scope explicitly prevents the cooler from being stranded outside the BAS. {note}
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## Evaporative cooling is itself an efficiency strategy and can serve as the economizer or as evaporative pre-cooling of packaged-equipment condenser air for an EER credit. The design must still satisfy 90.1's ventilation and economizer provisions for the served system. {note}
−## Building relief and exhaust openings shall be sized to pass the full supply airflow at a slight positive building pressure. {note}
+## Building relief and exhaust openings shall be sized to pass the full supply airflow at a slight positive building pressure.
## Evaporative coolers move large outdoor-air volumes; if the building cannot relieve that air, pressure builds, airflow falls, and doors become hard to open. Relief area must be proportional to the high air-change supply rate — coordinate relief, exhaust, and TAB with [[sync/testing-adjusting-and-balancing]]. {note}
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# Winterization and Freeze Protection {toc}
−## In climates subject to freezing, the cooler shall include freeze protection appropriate to the exposure. {note}
+## In climates subject to freezing, the cooler shall include freeze protection appropriate to the exposure.
## Standing water left in the sump and distribution headers will freeze and crack the casing or sump pan. Two approaches are used: a drain-down sequence that empties the water system on shutdown for the season, which is sufficient for most applications, and electric heat trace on the sump and headers where the unit must remain wet through freezing periods. {note}
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# Structural Support and Mounting {toc}
−## Roof or structural support shall be designed for the cooler's full-sump operating weight, including the water charge. {note}
+## Roof or structural support shall be designed for the cooler's full-sump operating weight, including the water charge.
## Evaporative coolers are heavier than comparably sized packaged DX units once the sump is filled, and the water charge is a sustained dead load, not an incidental one. Verify the operating weight against the structural design with the structural engineer of record before setting the unit. {note}
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# Acoustics {toc}
−## The cooler shall not exceed the project's sound limit at the specified measurement location. {note}
+## The cooler shall not exceed the project's sound limit at the specified measurement location.
## Rooftop units commonly produce 65 to 80 dBA measured at 5 ft. Urban and noise-sensitive sites should specify a maximum NC level or a dBA limit at the property line rather than relying on the unit's free-field rating alone. {note}
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## The Contractor shall furnish the manufacturer's standard warranty against defects in materials and workmanship for the evaporative cooler.
−## The warranty shall separately address the casing and sump against corrosion perforation for the wetted-component service life. {note}
−
−## The water-wetted casing and sump corrode on a different timeline than the dry air-side cabinet, so the corrosion warranty is the meaningful coverage for this equipment. Calling it out separately prevents it from being absorbed into a shorter general parts warranty. {note}
−
```datasheet
−label: Cabinet and sump corrosion warranty period
+label: Fan and motor warranty period
type: range
unit: years
min: 1
−max: 10
+max: 5
step: 1
−default: 5
+default: 2
```
+## The warranty shall separately address the casing and sump against corrosion perforation for the wetted-component service life.
+
```datasheet
−label: Fan and motor warranty period
+label: Cabinet and sump corrosion warranty period
type: range
unit: years
min: 1
−max: 5
+max: 10
step: 1
−default: 2
+default: 5
```
+## The water-wetted casing and sump corrode on a different timeline than the dry air-side cabinet, so the corrosion warranty is the meaningful coverage for this equipment. Calling it out separately prevents it from being absorbed into a shorter general parts warranty. {note}
+
# Spare Parts {toc}
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- One spare float / fill valve per unit
```