As summer approaches, bringing elevat-ed ambient temperatures, producersare beginning their “chill” routines.

Even in northern climates, many produc-ers who had previously avoided chillingwater are finding that this practice resultsin profitable service for contractors.

Manufacturers of water-chilling equip-ment remind the producer to considerfive operational factors before purchasingchilling- and chilled-water storage equip-ment for the upcoming season.

1 Chilled-water volume needed.Calculating an accurate required daily rateof concrete is what matters, according toMichael Lee, owner of Coldcrete, a Colo-rado Springs, Colo.-based manufacturer ofconcrete cooling equipment. Lee recom-mends the producer size chilling equipmentbased on average maximum daily require-ments. But Lee also warns the producer tobe mindful of whether the schedule rou-tinely includes large-volume back-to-backproduction days. If 1000-cubic-yard daysare the exception rather than the rule, Leesays, calculate the maximum rate for mostdays and size the chiller and cold water

B Y D O N TA L E N D

� Considerthese 5 factorswhen settingup a water-chilling system

COLDWATER

How to Stay in

Proper s iz ing ofa water-ch i l l ingsystem requiresa thoroughknowledge ofmany facets o fthe producer’sent ire operat ion .

PH

OT

OS

CO

UR

TE

SY

PE

AR

SO

N H

EA

TIN

G S

YS

TE

MS

storage tank accordingly. “On the otherhand, if a guy’s doing a paving job and he’sdoing 1000 yards day after day, he’s goingto need to size his chiller and his tank forthat 1000 yards.” In that case, he advises,calculate the average concrete yardagerequired over a few days.

2 Material moisture content andtemperature. A plant’s daily chilled-waterrequirement depends on the physicalproperties of its cement, water, stone, andsand. A thorough knowledge of theseproperties can help the producer pinpointthe required chiller size.

Jack Womack, president of AmericanGeoThermal, Murfreesboro, Tenn., asksthe producer to document the averagemoisture content in an operation’s sandand rock, which limits the amount ofwater the producer can chill to achievethe target temperature. “The more batchwater you’ve got, the more you can movethe temperature of the final mix,” saysWomack.

Delivered concrete temperature isimportant, too. With many cement millspushed to the limits of their capacity,

cement storage time and thus cooling timeare often shorter than in the past. “A lot ofpeople are getting 150°, 160° F cement,which has added to the demand for chilledwater at locations that have not needed itin the past,” says Womack.

3Delivery time and distance. Thisfactor affects the level of fresh concretetemperature reduction chilled water canachieve. Keeping concrete cool is moredifficult than keeping it warm. For allpractical purposes, the delivery windowfor cooled concrete is less than that forconcrete delivered during the winter. Forplant operators, delivery distance has abearing on the make and model of chillerchosen. Available chillers normally pro-duce water with a temperature of 35° to40° F, although special measures such asrunning an ethylene glycol/water mixturethrough the heat exchanger can produce awater temperature as low as 33° F.

Say the producer has a 90° F concreteplacement specification, and the well orcity water supply is 80° F. The chilling sys-tem produces a typical water temperatureof 38° F for a 42° F water temperature

drop. The producer might get a 1° F con-crete temperature decrease for each 6° Fthe water temperature decreases, for a 7° Fdecrease in concrete temperature. Thatconcrete temperature decrease is usuallyenough to meet the placement spec for anormal haul time. A water temperature of35° F might allow the producer to makelonger hauls—and expand the company’sservice radius.

4 Water source and disposal. Theproducer’s water source affects the deci-sion of whether to buy an air- or water-cooled chiller, says Womack. Well-watertemperature is more consistent and lowerthroughout the year, allowing the produc-er to install a slightly less-expensive butlonger-lasting water-cooled unit.

However, the condenser water usedin a water-cooled chiller is often mixedwith coolant, so it must be disposed of andnot used in concrete. As a result, manyproducers are choosing models with air-cooled condensers.

5 Keeping supply constant. Aproperly sized insulated tank, designed formaximum concrete yardage under normalcircumstances or for average yardage whenbig back-to-back days are the norm, takespressure off the chiller. If the chiller breaksdown, chilled water will still be availablethroughout the day, Lee notes. Moreimportantly, a properly sized insulatedtank enables the chiller to produce chilledwater at a steady rate.

The key to steady production is anautomatic makeup system, Lee says.This system automatically monitorsboth the volume of water and its tem-perature. It also not only keeps the tankfull, but it also maintains stored-watertemperature.

When the chilled water in the tankis drawn down past a preset level, a floatswitch sends a signal to a makeup valve.Water is looped directly from the watersupply through the makeup valve andinto the chiller, keeping the water at aconsistent temperature. “At the end ofthe day, the tank won’t be full, but you

Ample water storage and p ip ing insu la t ion are two keys to ch i l l ing system ef f ic iency.

don’t have to do anything,” Lee says.“The system just continues to make upchilled water until the tank is full againduring the night, and then the floatswitch will shut off the chiller automat-ically. It only costs a couple of hundredbucks for all this stuff, and just the guy’stime paying attention to it is worthmore than that.”

To get their highest chilled-waterproduction rates, the producer should pipemakeup water into the chilling system,not directly into the tank, Lee adds. Thispractice better controls the stored-watertemperature so the plant makes full use ofequipment capacity.

Make sure you don’t overlook tankinsulation either, notes Marc Mariano, oper-ations manager at Pearson Heating Systems,Stevensville, Md., a manufacturer of bothwater-chilling and water-heating equip-ment. “Whether the customer is purchas-ing an insulated storage tank or insulatingan existing one, it should either be cov-ered with a vapor barrier or insulated withclosed cell insulation,” he says. “This pre-vents the tank from building up condensa-tion, or sweating, which lowers the insula-tion efficiency.”

Mariano also stresses the importanceof insulating with closed cell material thecirculation pipes and the pipes leadingfrom the tank to the plant.

Maintenance of an air-cooled chilleris perhaps the most important factor inkeeping water temperature constant,Mariano adds. “The condenser coils havea tendency to get covered with dirt anddust,” he says. “It’s very important to keepthese coils free of dust, because that lowersthe efficiency of the unit. When cleaningthese coils, use only compressed air.Spraying the coils with water can perma-nently clog them.”

For more information about custom sizing awater-chilling system to your operation, circle themanufacturers’ corresponding numbers on thereader service card.American GeoThermal 2Coldcrete 3Pearson Heating Systems 4

Publication #T01E043Copyright © 2001 Hanley-Wood, LLCAll rights reserved