EVAPCO AT Series Guida alla risoluzione dei problemi

Operation and

Maintenance Instructions

FOR EVAPCO INDUCED DRAFT AND FORCED

DRAFT COOLING TOWERS

Bulletin 113B

For EVAPCO Authorized Parts and Service, Contact Your Local EVAPCO

Representative or the Local Mr. GoodTower®Service Provider

AT USS UT LSTB LPT

Visit EVAPCOʼs Website at:

http://www.evapco.com

EVAPCO...

SPECIALISTS IN HEAT TRANSFER PRODUCTS AND SERVICES

EVAPCO, Inc. — World Headquarters & Research/Development Center

EVAPCO, Inc.

World Headquarters

P.O. Box 1300

Westminster, MD 21158 USA

Phone: 410-756-2600

Fax: 410-756-6450

E-mail: [email protected]

EVAPCO Asia/Pacific

EVAPCO Asia/Pacific Headquarters

1159 Luoning Rd. Baoshan Industrial Zone

Shanghai, P. R. China, Postal Code: 200949

Phone: (86) 21-6687-7786

Fax: (86) 21-6687-7008

E-mail:

[email protected]

EVAPCO Europe

EVAPCO Europe, N.V.

European Headquarters

Industrieterrein Oost 4010

3700 Tongeren, Belgium

Phone: (32) 12-395029

Fax: (32) 12-238527

E-mail:

[email protected]

EVAPCO East

5151 Allendale Lane

Taneytown, MD 21787 USA

Phone: 410-756-2600

Fax: 410-756-6450

E-mail: [email protected]

EVAPCO Midwest

1723 York Road

Greenup, IL 62428 USA

Phone: 217-923-3431

Fax: 217-923-3300

E-mail: evapcomw@evapcomw.com

EVAPCO West

1900 West Almond Avenue

Madera, CA 93637 USA

Phone: 559-673-2207

Fax: 559-673-2378

E-mail: [email protected]

EVAPCO Iowa

925 Quality Drive

Lake View, IA 51450 USA

Phone: 712-657-3223

Fax: 712-657-3226

EVAPCO Iowa

Sales & Engineering

1234 Brady Boulevard

Owatonna, MN 55060 USA

Phone: 507-446-8005

Fax: 507-446-8239

E-mail: [email protected]

Refrigeration Valves &

Systems Corporation

A wholly owned subsidiary of EVAPCO, Inc.

1520 Crosswind Dr.

Bryan, TX 77808 USA

Phone: 979-778-0095

Fax: 979-778-0030

E-mail: [email protected]

McCormack Coil Company, Inc.

A wholly owned subsidiary of EVAPCO, Inc.

P.O. Box 1727

6333 S.W. Lakeview Boulevard

Lake Oswego, OR 97035 USA

Phone: 503-639-2137

Fax: 503-639-1800

E-mail: [email protected]

EvapTech, Inc.

A wholly owned subsidiary of EVAPCO, Inc.

8331 Nieman Road

Lenexa, KS 66214 USA

Phone: 913-322-5165

Fax: 913-322-5166

E-mail: [email protected]

Tower Components, Inc.

A wholly owned subsidiary of EVAPCO, Inc.

5960 US HWY 64E

Ramseur, NC 27316

Phone: 336-824-2102

Fax: 336-824-2190

E-mail:

[email protected]

EVAPCO Newton

701 East Jourdan Street

Newton, IL 62448 USA

Phone: 618-783-3433

Fax: 618-783-3499

E-mail: evapcomw@evapcomw.com

EVAPCO Europe, S.r.l.

Via Ciro Menotti 10

I-20017 Passirana di Rho

Milan, Italy

Phone: (39) 02-939-9041

Fax: (39) 02-935-00840

E-mail: [email protected]

EVAPCO Europe, S.r.l.

Via Dosso 2

23020 Piateda Sondrio, Italy

EVAPCO Europe, GmbH

Bovert 22

D-40670 Meerbusch, Germany

Phone: (49) 2159-69560

Fax: (49) 2159-695611

E-mail: [email protected]

Flex coil a/s

A subsidiary of

EVAPCO

,Inc.

Knøsgårdvej 115

DK-9440 Aabybro Denmark

Phone: (45) 9824 4999

Fax: (45) 9824 4990

E-mail: [email protected]

EVAPCO S.A. (Pty.) Ltd.

A licensed manufacturer of

EVAPCO

,Inc.

18 Quality Road

Isando 1600

Republic of South Africa

Phone: (27) 11 392-6630

Fax: (27) 11-392-6615

E-mail: [email protected]

Tiba Engineering Industries Co.

A licensed manufacturer of

EVAPCO

,Inc.

5 Al Nasr Road St.

Nasr City, Cairo, Egypt

Phone: (

20) 2-290-7483/(20) 2-291-3610

Fax: (

20) 2-404-4667/ (20) 2-290-0892

E-mail: [email protected]

Evapco (Shanghai) Refrigeration

Equipment Co., Ltd.

1159 Louning Rd., Baoshan Industrial Zone

Shanghai, P.R. China, Postal Code: 200949

Phone: (86) 21-6687-7786

Fax: (86) 21-6687-7008

E-mail:

marketing

@evapcochina.com

Beijing EVAPCO Refrigeration

Equipment Co., Ltd.

Yan Qi Industrial Development District

Huai Rou County

Beijing, P.R. China, Postal Code: 101407

Phone: (86) 10 6166-7238

Fax: (86) 10 6166-7395

E-mail: [email protected]

Evapco Australia (Pty.) Ltd.

A licensed manufacturer of

EVAPCO

,Inc.

34-42 Melbourne St.

P.O. Box 436

Riverstone, N.S.W. Australia 2765

Phone: (61) 29 627-3322

Fax: (61) 29 627-1715

E-mail: [email protected]

EvapTech Asia Pacific Sdn. Bhd

A wholly owned subsidiary of EvapTech, Inc.

IOI Business Park, 2/F Unit 21

Persiaran Puchong Jaya Selatan

Bandar Puchong Jaya,

47170 Puchong, Selangor, Malaysia

Phone: (60-3) 8070 7255

Fax: (60-3) 8070 5731

E-mail: [email protected]

EVAPCO North America

EVAPCO, Inc. • P.O. Box 1300 • Westminster, MD 21158 USA

PHONE:410-756-2600•FAX: 410-756-6450 • E-MAIL: [email protected]

Cert no. BV-COC-080211

Operation and Maintenance Instructions

Table of Contents

Introduction . . ...............................................................................3

Safety Precautions ...........................................................................3

Initial Storage and/or Idle Period Recommendations ...............................................3

InternationalBuildingCodeProvision ...........................................................3

Initial and Seasonal Start-Up Checklist ...........................................................4

General ................................................................................4

InitialandSeasonalStart-Up ...............................................................4

Maintenance Checklist ....................................................................5

Seasonal Shut-Down Checklist .............................................................7

FanSystem .................................................................................7

FanMotorBearings ......................................................................7

FanShaftBearings .......................................................................7

Recommended Bearing Lubricants ..........................................................7

Fan Belt Adjustment ......................................................................8

Fan and Motor Sheave Alignment ...........................................................8

Fan System Capacity Control ..............................................................10

Fan Motor Cycling .................................................................10

TwoSpeedMotors .................................................................10

VariableFrequencyDrives ...........................................................11

RecirculatedWaterSystemRoutineMaintenance .................................................12

ColdWaterBasin .......................................................................12

Suction Strainer Assembly ................................................................12

OperatingWaterLevels ..................................................................12

Water Make Up Valve . . . .................................................................13

Pressurized Water Distribution System ......................................................13

Drift Eliminator Orientation ...........................................................15

WaterTreatmentandWaterChemistryoftheRecirculatedWaterSystem .............................16

BleedOff ..............................................................................16

Biological Contamination .................................................................16

Air Contamination .......................................................................16

WaterChemistryParameters ..............................................................17

PassivationofGalvanizedSteel ............................................................18

WhiteRust .......................................................................18

UseofSoftWater .......................................................................19

UseofGrayWater .................................................................19

StainlessSteel ..............................................................................19

Maintaining the Appearance of Stainless Steel ................................................19

Cleaning Procedures for Stainless Steel .....................................................20

Cold Weather Operation ......................................................................20

ReplacementParts ..........................................................................23

Part Identification Drawings ...............................................................24

ICT 4ʼ Wide Towers ................................................................24

AT/USS 6ʼ, 8ʼ & 8.5ʼ Wide Towers . . . . . . ...............................................25

AT/USS 10ʼ, 12ʼ, & 14ʼ Wide Towers . . . . . . . . . . . . .......................................26

AT/USS 12ʼ, 15ʼ & 17ʼ Wide End Connection Towers . . ....................................27

AT/USS20ʼ&24ʼWideTowers .......................................................28

AT/USS 28ʼ Wide Towers . . . . . . . . . . . . ................................................29

UT 6ʼ, 7.5ʼ, 8ʼ & 8.5ʼ Wide Towers . . . . . . . ..............................................30

UT 10ʼ, 12ʼ, & 14ʼ Wide Towers . . . . . . . . . . . ............................................31

UT 12ʼ, 15ʼ & 17ʼ Wide End Connection Towers . . . . . . . . . . . ...............................32

UT20ʼ&24ʼWideTowers ...........................................................33

UT 28ʼ Wide Towers . . . . . . ..........................................................34

LPTUnits ........................................................................35

LSTA 4ʼ Wide Units . . ..............................................................36

LSTBUnits.......................................................................37

Notes............................................................................38

Operation and Maintenance Instructions

Introduction

Congratulations on the purchase of your EVAPCO evaporative cooling unit. EVAPCO equipment is constructed of the highest

quality materials and designed to provide years of reliable service when properly maintained.

Evaporative cooling equipment is often remotely located and periodic maintenance checks are often overlooked. It is important to

establish a regular maintenance program and be sure that the program is followed. This bulletin should be used as a guide to

establish a program. A clean and properly serviced unit will provide a long service life and operate at peak efficiency.

This bulletin includes recommended maintenance services for unit start up, unit operation and unit shutdown and the frequency of

each. Please note: the recommendations of frequency of service are minimums. Services should be performed more often when

operating conditions necessitate.

Become familiar with your evaporative cooling equipment. Refer to the isometric drawings located on pages 25-35 for information

on the arrangement of components in your equipment.

If you should require any additional information about the operation or maintenance of this equipment, contact your local EVAPCO

representative. You may also visit www.evapco.com or www.mrgoodtower.com for more information.

Safety Precautions

Qualified personnel should use proper care, procedures and tools when operating, maintaining or repairing this equipment in order

to prevent personal injury and/or property damage. The warnings listed below are to be used as guidelines only.

WARNING: This equipment should never be operated without fan screens and access doors properly secured and in place.

WARNING: A lockable disconnect switch should be located within sight of the unit for each fan motor associated with

this equipment. Before performing any type of service or inspection of the unit make certain that all power

has been disconnected and locked in the “OFF” position.

WARNING: The top horizontal surface of any unit is not intended to be used as a working platform. No routine service

work is required from this area.

WARNING: The recirculating water system may contain chemicals or biological contaminants including Legionella

Pneumophila, which could be harmful if inhaled or ingested. Direct exposure to the discharge airstream and

the associated drift generated during operation of the water distribution system and/or fans, or mists

generated while cleaning components of the water system require respiratory protection equipment

approved for such use by governmental occupational safety and health authorities.

Initial Storage and/or Idle Period Recommendations

If the unit will sit idle for long periods of time it is recommended that the following be performed in addition to all component

manufacturers recommended maintenance instructions.

•The fan bearings and motor bearings need to be turned by hand at least once a month. This can be accomplished by

tagging and locking out the unitʼs disconnect, grasping the fan assembly, and rotating it several turns.

•If unit sits longer than a few weeks, run gear reducer for 5 minutes weekly.

•If unit sits longer than 3 weeks, completely fill gear reducer with oil. Drain to normal level prior to running.

•If unit sits longer than one month, insulation test motor windings semi-annually.

•If fan motor sits idle for at least 24 hours while the spray pumps are energized distributing water over the heat transfer media,

motor space heaters (if equipped) should be energized. Alternatively, fan motors may be energized for 10 minutes, twice

daily, to drive any moisture condensation out of the motor windings.

International Building Code Provisions

The International Building Code (IBC) is a comprehensive set of regulations addressing the structural design and installation

requirements for building systems – including HVAC and industrial refrigeration equipment. The code provisions require that

evaporative cooling equipment and all other components permanently installed on a structure must meet the same seismic design

criteria as the building.

All items attached to Evapco Cooling Towers must be independently reviewed and isolated to meet applicable wind and seismic

loads. This includes piping, ductwork, conduit, and electrical connections. These items must be flexibly attached to the Evapco

Operation and Maintenance Instructions

unit so as not to transmit additional loads to the equipment as a result of seismic or wind forces.

Initial and Seasonal Start-Up Checklist

General

1. Verify that the overall installation reflects the requirements of the installation guidelines found in EVAPCO Bulletin 311 –

Equipment Layout Manual.

2. For multi-speed fan motors, verify that 30 second or greater time delays are provided for speed changes when switching from

high to low speed. Also check to see if interlocks are provided to prevent simultaneously energizing high and low speed and

confirm both speeds operate in the same direction.

3. Verify all safety interlocks work properly.

4. For units operating with a variable frequency drive, make certain that minimum speed requirements have been set. Check with

VFD manufacturer for recommended minimum speeds and recommendations on locking out resonance frequencies. See “Fan

System Capacity Control” section for more information.

5. Verify that the sensor used for fan sequencing and by-pass valve control is located downstream of the point where the by-pass

water mixes with the condenser supply water, if applicable.

6. Verify that a water treatment plan has been implemented including passivation of galvanized steel units. See “Water

Treatment” section for more details.

7. For units subject to freezing climates, high humidity climates, or idle periods lasting 24 hours or more, motor space heaters (if

equipped) should be energized. Alternatively, fan motors may be energized for 10 minutes, twice daily, to drive any moisture

condensation out of the motor windings.

8. If the unit is going to sit idle for an extended period of time, follow all manufacturersʼ fan motor and pump instructions for long

term storage. Plastic sheets or tarps should never be used to protect a unit during storage. This practice can trap heat inside

the unit, and could potentially cause damage to plastic components. See your local EVAPCO representative for additional

information on unit storage.

BEFORE BEGINNING ANY MAINTENANCE, BE CERTAIN THAT THE POWER IS TURNED OFF

AND THE UNIT IS PROPERLY LOCKED AND TAGGED OUT!

Initial and Seasonal Start-Up

1. Clean and remove any debris, such as leaves and dirt from the air inlets.

2. Flush the cold water basin (with the strainer screens in place) to remove any sediment or dirt.

3. Remove the strainer screen, clean and reinstall.

4. Check mechanical float valve to verify it operates freely.

5. Inspect water distribution system nozzles and clean as required. Check for proper orientation. (This is not required at initial

start-up. The nozzles are clean and set at the factory).

6. Check to ensure drift eliminators are securely in place.

7. Adjust fan belt tension as required.

8. Lubricate fan shaft bearings prior to seasonal start-up.

9. Turn the fan(s) by hand to insure it turns freely without obstructions.

10. Visually inspect the fan blades. Blade clearance should be approximately 3/8” (1/4” minimum) from tip of blade to the fan cowl.

The fan blades should be securely tightened to the fan hub.

11. If any stagnant water remains in the system including “dead legs” in the piping, the unit must be disinfected prior to the fans

being energized. Please refer to Ashrae Guideline 12-2000 and CTI Guideline WTP-148 for more information.

12. Fill the cold water basin manually up to the overflow connection.

After the unit has been energized, check the following:

1. Adjust mechanical float valve as required to the proper water level.

2. Unit basin should be filled to the proper operating level. See “Recirculating Water System – Operating Levels” section for more

details.

3. Verify fan is rotating in proper direction.

4. Measure voltage and current on all three power leads. The current should not exceed the motor nameplate full load amp rating

taking the service factor into account.

5. Adjust bleed valve to proper flow rate. Maximum bleed off is 3 US GPM per 100 tons. Consult your qualified water treatment

person to fine tune the minimum bleed necessary.

6. Refer to the fan motor manufacturerʼs maintenance and long term storage instructions for more detailed information. Motors

should be serviced in accordance with manufacturerʼs instructions.

Operation and Maintenance Instructions

PROCEDURE

1. Clean pan strainer – monthly or as needed

2. Clean and flush pan** – quarterly or as needed

3. Check bleed-off valve to make sure it is

operative – monthly

4. Check operating level in pan and adjust float

valve if necessary – monthly

5. Check water distribution system and spray

pattern – monthly

6. Check drift eliminators – quarterly

7. Check the fan blades for cracks, missing

balancing weights, and vibrations – quarterly

8. Lubricate fan shaft bearings* – every 1000

hours of operation or every three months

9. Check belt tension and adjust – monthly

10. Sliding motor base – Inspect and grease –

annually or as needed

11. Check fan screens, inlet louvers and fans.

Remove any dirt or debris – monthly

12. Inspect and clean protective finish – annually

- Galvanized: scrape and coat with ZRC

- Stainless: clean and polish with a

stainless steel cleaner.

13. Check water quality for biological contamination.

Clean unit as needed and contact a water

treatment company for recommended water

treatment program** – regularly

1. Gear Reducer – Check oil level with unit

stopped – 24 hours after start-up & monthly

2. Gear Reducer/Piping – Do visual inspection

for oil leaks, auditory inspection for unusual

noises and vibrations – monthly

3. Gear Reducer - Replace oil – semi-annually

4. Oil Pump – Do visual inspection for leaks and

proper wiring – monthly

5. Gear Reducer/Coupling – Check alignment of

the system – 24 hours after start-up & monthly

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

OPTIONAL ACCESSORIES:

MAINTENANCE

CHECKLIST

* See maintenance manual for start-up instructions and lubrication recommendations.

** Cooling Towers must be cleaned on a regular basis to prevent the growth of bacteria including Legionella Pneumophila.

Operation and Maintenance Instructions

OPTIONAL ACCESSORIES:

6. Coupling/Shaft – Inspect flex elements and

hardware for tightness, proper torque &

crack/deterioration – monthly

7. Heater Controller – Inspect controller and

clean probe ends – quarterly

8. Heater – Inspect junction box for loose wiring

and moisture – one month after start-up and

semi-annually

9. Heater – Inspect elements for scale

build-up – quarterly

10. Electronic Water Level Controller – Inspect

junction box for loose wiring and moisture –

semi-annually

11. Electronic Water Level Controller – Clean

probe ends of scale build-up – quarterly

12. Electronic Water Level Controller –Clean

inside the standpipe – annually

13. Solenoid Make-up Valve – Inspect and clean

valve of debris – as needed

14. Vibration Switch (mechanical) – Inspect

enclosure for loose wiring and moisture –

one month after start-up and monthly

15. Vibration Switch – Adjust the sensitivity –

during start-up and annually

16. Sump Sweeper Piping – Inspect and clean

piping of debris – semi-annually

17. Water Level Indicator – Inspect and clean –

annually

1. Few Days: Energize motor space heaters

–when motor is idle

2. Few Weeks: Run gear reducer for 5 minutes

–weekly

3. Several Weeks: Completely fill gear reducer

with oil. Drain to normal level prior to running.

4. One Month or longer: Rotate motor shaft/fan

10 turns – bi-weekly

5. One Month or longer: Megger test motor

windings – semi-annually

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

DURING IDLE PERIODS:

MAINTENANCE

CHECKLIST

Operation and Maintenance Instructions

Seasonal Shut-Down Checklist

When the system is to be shut down for an extended period of time, the following services should be performed.

1. The evaporative cooling unit should be drained.

2. The cold water basin should be flushed and cleaned with the suction strainer screens in place.

3. The suction strainer screens should be cleaned and re-installed.

4. The cold water basin drain should be left open.

5. The fan shaft bearings and motor base adjusting screws should be lubricated.

6. The water make up valve needs to be closed. All water make-up piping needs to be drained, if not heat traced and

insulated.

7. The finish of the unit should be inspected. Clean and refinish as required.

8. The fan bearings and motor bearings need to be turned at least once a month by hand. This can be accomplished by

making sure the unitʼs disconnect is locked and tagged out, and grasping the fan assembly, rotating it several turns.

9. Energize motor space heaters.

Fan System

The fan systems of both centrifugal and axial driven units are rugged, however, the fan system must be checked regularly and

lubricated at the proper intervals. The following maintenance schedule is recommended.

Fan Motor Bearings

EVAPCO evaporative cooling units use either a T.E.A.O. (Totally Enclosed Air Over) or a T.E.F.C. (Totally Enclosed Fan Cooled) fan

motor. These motors are built to “Cooling Tower Duty” specifications. They are supplied with permanently lubricated bearings and

special moisture protection on the bearings, shaft and windings. After extended shut-downs, the motor should be checked with an

insulation tester prior to restarting the motor.

Fan Shaft Ball Bearings

Lubricate the fan shaft bearings every 1,000 hours of operation or every three months for induced draft units. Lubricate the fan

shaft bearings every 2,000 hours of operation or every six months for forced draft units. Use any of the following synthetic

waterproof, polyurea inhibited greases which are suitable for operation between -20°F and 350°F. (For colder operating

temperatures, contact the factory).

Mobil – Polyrex EM Chevron - SRI

Feed grease slowly into the bearings or the seals may be damaged. A hand grease gun is recommended for this process.

When introducing a new grease, all grease should be purged from the bearings.

All EVAPCO units are supplied with extended grease lines to allow easy lubrication of the fan shaft bearings.

Operation and Maintenance Instructions

Fan Shaft Sleeve Bearings – (4ʼ wide LSTA units only)

Lubricate the intermediate sleeve bearing(s) before unit start up. The reservoir should be checked several times during the first

week to ensure that the oil reserve is brought to full capacity. After the first week of operation, lubricate the bearing(s) every 1,000

hours of operation or every three months (whichever occurs first). High temperatures or poor environmental conditions may

necessitate more frequent lubrication. The oil reservoir consists of a large felt packed cavity within the bearing housing. It is not

necessary to maintain the oil level within the filler cup.

Use one of the following industrial grade, non-detergent mineral oils. Do not use a detergent based oil or those designated

heavy duty or compounded. Different oils may be required when operating at temperatures below 30°F continuously. Table 2

provides a short list of approved lubricants for each temperature range. Most automotive oils are detergent based and may not be

used. Detergent oils will remove the graphite in the bearing sleeve and cause bearing failure.

All bearings used on EVAPCO equipment are factory adjusted and self aligning. Do not disturb bearing alignment by tightening the

sleeve bearing caps.

Fan Belt Adjustment

The fan belt tension should be checked at start up and again after the first 24 hours of operation to correct for any initial stretch. To

properly adjust the belt tension, position the fan motor so that the fan belt will deflect approximately 1/2” when moderate pressure

is applied midway between the sheaves. Figure 1 and Figure 2 show two ways to measure this deflection. Belt tension should be

checked on a monthly basin. A properly tensioned belt will not “chirp” or “squeal” when the fan motor is started.

Table 1 - Location of Grease Lube Line Fittings for Belt Driven Units.

Please note, the removal of the fan screens is not necessary on forced draft units to access the extended lube line fittings.

Unit Description Location of Lube Line Fittings

Induced Draft Units: Located just beside the fan casing

6', 8', 8.5', 12', 15' and 17' wide access door

Induced Draft Units: Located inside the fan casing

All Others access door

LSTB Forced Draft Units Located on the front of the unit

LPT Forced Draft Units Located on the front of the unit

LSTA 4' Wide Forced Draft Units See Below

Ambient Temp Texaco Drydene Exxon

30°F to 100°F Regal R&O 220 Paradene 220 Terrestic 220

-25°F to 30°F Capella WF 32 Refrig. Oil 3G ------------------

Table 2 - Sleeve Bearing Lubricants

Figure 1 – Method 1 Figure 2 – Method 2

Operation and Maintenance Instructions

On induced draft belt driven units provided with externally mounted motors (6, 8, 8.5, 12, 15 and 17 foot wide units), Figure 3, and

LSTB forced draft units, Figure 4, both J-type adjustment bolts on the adjustable motor base should have an equal amount of

exposed thread for proper sheave and belt alignment.

Figure 3 – Externally Mounted Motors Figure 4 – LSTB Externally Mounted Motor

Figure 5 – Internally Mounted Motors

On induced draft belt driven units with internally mounted motors (10, 12, 14, 20, 24 and 28 foot wide units), Figure 5, and LPT units,

Figure 6, a motor adjustment tool is provided. The tool will be found on the adjustment nut. To use, place the hex end over the

adjustment nut. Tension the belt by turning the nut counterclockwise. When the belts are properly tensioned, tighten the lock nut.

Operation and Maintenance Instructions

Direct drive fan units do not require any adjustment (4' Wide Induced Draft ICT Models Only).

Fan System — Capacity Control

There are several methods for capacity control of the evaporative cooling unit. Methods include: Fan motor cycling, the use of two

speed motors and the use of variable frequency drives (VFDʼs). In all cases, if motors are idle for extended periods of time with

water still being directed over heat transfer media, motor space heaters are suggested.

Fan Motor Cycling

Fan Motor Cycling requires the use of a single stage thermostat which senses the water temperature. The contacts of the

thermostat are wired in series with the fan motorʼs starter holding coil.

Fan Motor Cycling is often found to be inadequate where the load has a wide fluctuation. In this method, there are only two stable

levels of performance: 100% of capacity when the fan is on and approximately 10% of capacity when the fan is off. Please note,

rapid cycling of the fan motors can cause the fan motor to overheat. Controls should be set to only allow a maximum of six (6)

start/stop cycles per hour.

Two Speed Motors

The use of a two speed motor provides an additional step of capacity control when used with the fan cycling method. The low

speed of the motor will provide 60% of full speed capacity.

Two speed capacity control systems require not only a two speed motor, but a two stage thermostat and the proper two speed

motor starter. The most common two speed motor is a single winding type. This is also known as a consequent pole design. Two

speed two winding motors are also available. All multi-speed motors used in evaporative cooling units should be variable torque

design.

It is important to note that when two speed motors are to be used, the motor starter controls must be equipped with a decelerating

time delay relay. The time delay should be a minimum of a 30 second delay when switching from high speed to low speed.

Figure 6 – LPT Motor Adjustment

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