BAC HFL 36 Series Manual

HFL Hybrid Closed Circuit Cooling Tower
OPERATING AND MAINTENANCE INSTRUCTIONS
MHFLv14EN

Recommended maintenance and
monitoring programme
Baltimore Aircoil Company equipment needs to be properly installed, operated and maintained. Documentation of
the equipment used, including a drawing, technical data sheet and this manual should be kept on record. To
achieve long, trouble-free and safe operation, it is necessary to establish an operating plan including a programme
of regular inspection, monitoring and maintenance. All inspections, maintenance and monitoring actions should be
recorded in a cooling system logbook. The operating and maintenance instructions published here can be used as
a guide to achieve these goals.
In addition to establishing the operating plan and the cooling system logbook it is recommended to conduct a
cooling system risk analysis, preferably by an independent third party.
For the cooling system, scale, corrosion and biological control must be established and initiated when the system
is first filled with water and administered on a regular basis thereafter in accordance with recognized Codes of
Practice, (such as EUROVENT 9 - 5/6, ACOP HSC L8, Guide des bonnes pratiques, Legionella et tours
aéroréfrigérantes, etc.). Water sampling, test results and corrective actions should be recorded in the cooling
system logbook.
For more specific recommendations on keeping your cooling system efficient and safe, contact your local BAC
Balticare service provider or representative. Name, e-mail and phone number can be found on the website
www.BACService.eu.
Checks and adjustments Start-Up Weekly Monthly Quarterly Every 6
months
Annually Shutdown
Cold water basin & strainer X X
Operating level and make-up X X
Blow down X X
Sump heater package X X
Belt tension X X
Drive alignment X X
Locking collar X X
Rotation of fan(s) and pump(s) X
Motor voltage and current X X
Unusual noise and/or vibration X X
Inspections and monitoring Start-Up Weekly Monthly Quarterly Every 6
months
Annually Shutdown
General condition X X
Heat transfer section X X
Finned discharge coil (optional) X X
Drift eliminators X X
Water distribution X X
Fan shaft X X
Fan motor X X
Spray water pump X X
Electric water level control package X X
TAB test (dip slides) X X
Circulating water quality X X
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Inspections and monitoring Start-Up Weekly Monthly Quarterly Every 6
months
Annually Shutdown
System overview X X
Record keeping as per event
Lubrication Start-Up Weekly Monthly Quarterly Every 6
months
Annually Shutdown
Fan shaft bearings X X X
Motor bearings* X X
Adjustable motor base X X X
* only for motors with grease fittings with typical frame size > 200L (>30 KW)
Cleaning procedures Start-Up Weekly Monthly Quarterly Every 6
months
Annually Shutdown
Mechanical cleaning X X X
Disinfection** (X) (X) (X)
Drain basin and pump X
** depends on applied code of practice
Notes
1. Water treatment and auxiliary equipment integrated in the cooling system may require additions to the table
above. Contact suppliers for recommended actions and their required frequency.
2. Recommended service intervals are for typical installations. Different environmental conditions may dictate
more frequent servicing.
3. When operating in ambient temperatures below freezing, the unit should be inspected more frequently (see
Cold weather operations in the appropriate Operating and Maintenance Instructions).
4. For units with belt drive, tension on new belts must be readjusted after the first 24 hours of operation and
monthly thereafter.
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Table of contents
OPERATING AND MAINTENANCE INSTRUCTIONS
1 Construction Details 5
2 General information 7
Operating conditions 7
Connecting pipework 10
Safety precautions 10
Disposal requirements 11
Non-walking surfaces 11
Modifications by others 11
Warranty 12
3 Water Care 13
About water care 13
Biological control 16
Chemical treatment 16
Passivation 16
Overflow connection 17
4 Cold Weather Operations 18
About cold weather operation 18
Protection against sump water freezing 18
Capacity control 18
Protection against coil freezing 19
5 Maintenance Procedure 21
Checks and adjustments 21
Inspections and corrective actions 25
Lubrication 28
Cleaning procedures 29
6 Comprehensive Maintenance 31
About comprehensive maintenance 31
Prolonged outdoor stay 31
7 Further Assistance & Information 32
Assistance 32
More information 32
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1 Construction Details
1 Construction Details W W W . B A L T I M O R E A I R C O I L . E U
5
CONSTRUCTION DETAILS
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1. Casing
2. Water distribution system
3. Spray nozzles
4. Spray branches
5. Evaporative heat transfer coil
6. Finned discharge coil
7. Finned discharge coil inlet connection
8. Finned discharge coil outlet connection
9. Evaporative heat transfer coil inlet connection
10. Evaporative heat transfer coil outlet connection
11. Forward curved centrifugal fan
12. Fan screen
13. Fan shaft & Bearings
14. Fan motor
15. Fan motor adjustment screw
16. V-belt drive system
17. Strainer
18. Access door (rectangular)
19. Access door (circular)
20. Make-up
21. Electrical water level control
22. Water bleed line
23. Spray water pump
24. Heater package (optional)
25. Drift eliminators
26. Three-way flow control valve (optional)
27. By-pass connection (optional)
28. Orifice plate (optional)
29. Three-way valve actuator (optional)
30. Clean out port (optional)
31. Drain
32. Overflow
33. Water treatment connection
34. Operating level
35. Overflow level
36. Terminal box (optional)
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2 General information
2 General information W W W . B A L T I M O R E A I R C O I L . E U
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GENERAL INFORMATION
Operating conditions
BAC cooling equipment is designed for the operating conditions specified below, which must not be exceeded
during operation.
•Wind Load: For safe operation of unshielded equipment exposed to wind speeds above 120 km/h installed at a
height above 30 m from the ground, contact your local BAC-Balticare representative.
•Seismic Risk: For safe operation of equipment installed in moderate and high hazard area's contact your local
BAC-Balticare representative.
Standard electrical motors are suitable for an ambient temperature range from -25°C to +40°C.
• Design pressure: max. 10 bar
• Fluid inlet temperature: max. 82°C
• Fluid outlet temperature: min. 10°C
Fluids circulated through the inside of the coils must be compatible with the coil construction material, ie.
- black steel, for hot dip galvanized coils
- stainless steel AISI 304L or 316L (options)
- copper tubes when units are fitted with the optional finned discharge coil.
Maximum spray pressure: 14 kPa (If pump(s) are installed by others, it is recommended to install a pressure gauge
at the inlet of the water distribution system.)
Stand-by pump arrangements for evaporative fluid coolers require alternating operation of each pump at
least twice per week to avoid stagnant water conditions and bacteriological growth.
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PURGE REQUIREMENTS
The installer of BAC closed circuit cooling towers must ensure a proper air purging of the system prior to operation.
Entrained air can restrict the capacity of the cooler, resulting in higher process temperatures.
All connections (installed by others) must be leak free and tested accordingly.
CIRCULATING WATER QUALITY
The standard heat exchanger coils are made of black steel and are galvanized on the outside only. They are
intended for application on closed, pressurized systems which are not open to the atmosphere in order to prevent
internal corrosion of the coil and possible leaks.
The circulating water quality needs to remain within the following limits:
pH 7 - 10.5
Hardness (as CaCO3) 100 - 500 mg/l
Alkalinity (as CaCO3) 100 - 500 mg/l
Conductivity < 3000 µS/cm
Chlorides < 200 mg/l
Total suspended solids < 10 mg/l
COD < 50 ppm
Above values are general guidelines for pressurized closed systems closed systems with a leak rate lower than
15% of system volume per year.If the annual make-up of the closed system is greater than 15% yearly or if highly
corrosive water such as water with very low hardness or alkalinity is used, it is recommended to consider
alternative stainless steel material or implement a proper water treatment program to prevent steel corrosion.
Stainless steel coil are available to cool corrosive fluids or water and ethylene/propylene glycol solutions in
systems open to the atmosphere.In case of stainless steel heat exchanger coils the circulating water quality
needs to remain within the following limits:
SST304L SST316L
pH 6.5 - 10.5 6.5 - 10.5
Hardness (as CaCO3) 0 - 500 mg/l 0 - 500 mg/l
Alkalinity (as CaCO3) 0 - 500 mg/l 0 - 500 mg/l
Conductivity < 3300 µS/cm < 4000 µS/cm
Chlorides < 250 mg/l < 750 mg/l
Total suspended solids < 10 mg/l < 10 mg/l
COD < 50 ppm < 50 ppm
In all cases, regardless of the material of construction of the coil a competent water treatment company should be
consulted for the specific water treatment to be applied, suitable for all the materials of construction used in the
entire system.
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OPERATING MODES
The hybrid closed Circuit Fluid Cooler operates under three different operating modes:
1. Combined Dry-Wet Mode: During this mode, the process fluid flows through the finned coil bundle (sensible
heat transfer) and then through the wetted prime surface coil bundle (sensible and latent heat transfer). With
lower heat loads and/or ambient temperatures, the evaporative cooling portion (and hence the water usage) is
reduced by keeping the flow fed through the wetted prime surface coil bundle to a minimum. This is
accomplished by a modulating flow control valve, which controls the design outlet temperature.
2. Adiabatic Mode: During this mode, the process fluid flows through the finned coil bundle and by-passes the
wetted prime surface coil bundle completely. This entering ambient air is pre-humidified (cooled) by the spray
water before flowing over the high density finned coil bundle.
3. Dry Mode: The full process fluid flows through the finned coil bundle and the prime surface coil bundle. Since
the spray pump is turned off, only sensible heat transfer is used.
SEASONAL PERIODS
The optimal operation of the Hybrid Closed Circuit Cooling Tower is obtained by a combination of the above
mentioned operating modes, depending on the thermal load of the process fluid and the ambient conditions.
Typically two different seasonal periods are distinguished from each other:
1. Summer period: During this period all three operating modes are applied and as such the spray pump is
activated during the dry/wet and the adiabatic operating mode. Therefore the cold water basin is filled with
water at all time.
2. Winter period: during this period only the dry operating mode is applied and as such the cold water basin is
drained.
The following table summarises the use of the different operating modes during the seasonal periods.
Summer period Winter period
Dry mode Adiabatic
mode
Dry/Wet
mode
Dry mode
Fan motors Full / Half /
Variable speed
Full speed Full speed Full / Half /
Variable speed
Spray pump motor Off On On Off
Process fluid through finned foil
bundle
100% Design
flow
100% Design
flow
100% Design
flow
100% Design
flow
Process fluid through bare coil
bundle
100% Design
flow (2)
0% Variable flow
(1)
100% Design
flow (2)
Use of different operating modes during the seasonal periods
(1) Process fluid flow through bare coil bundle is controlled by the three way valve and is in function of the process fluid return temperature.
(2) The three way valve is locked and closes the bypass line completely.
When working dry during winter, the sump can be drained in which case power to the pump and heaters must be
switched off. If the sump is not drained during freezing conditions, heat tracing must be foreseen for pump/piping.
Frequent on/off cycling of the spray pump should be limited to a minimum operating period of 5 hours.
Rapid on/off cycling of the fan motors can cause the fan motors to overheat. This should be limited to a
maximum of six on/off cycles/h. If the limit is equipped with 2-speed fan motors, a 15 seconds delay should be
observed when switching from high to low speed.
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2 General information
2 General information

Connecting pipework
All piping external to BAC cooling equipment must be supported separately.
In case the equipment is installed on vibration rails or springs, the piping must contain compensators to eliminate
vibrations carried through the external pipework.
The equipment outlet piping must be installed under the operating level of the equipment to prevent air suction and
pump cavitation.
Suction pipe sizing should be done according to good practice, which may for larger flows require larger pipe
diameters than the outlet connection. In such cases adapter pieces need to be installed.
Safety precautions
All electrical, mechanical and rotating machinery constitutes a potential hazard, particularly for those not familiar
with its design, construction and operation. Accordingly, adequate safeguards (including use of protective
enclosures where necessary) should be taken with this equipment both to safeguard the public (including minors)
from injury and to prevent damage to the equipment, its associated system and the premises.
If there is doubt about safe and proper rigging, installation, operation or maintenance procedures, contact the
equipment manufacturer or his representative for advice.
When working on operating equipment, be aware that some parts may have an elevated temperature. Any
operations on elevated level have to be executed with extra care to prevent accidents.
CAUTION
Do not cover units with PVC eliminators with a plastic tarpaulin. Temperature increase due to sun
radiation could deform the eliminators.
AUTHORIZED PERSONNEL
The operation, maintenance and repair of this equipment should be undertaken only by personnel authorized and
qualified to do so. All such personnel should be thoroughly familiar with the equipment, the associated systems
and controls and the procedures set forth in this and other relevant manuals. Proper care, personal protective
equipment, procedures and tools must be used in handling, lifting, installing, operating, maintaining and repairing
this equipment to prevent personal injury and/or property damage. Personnel must use personal protective
equipment where necessary (gloves, ear plugs, etc...)
MECHANICAL SAFETY
Mechanical safety of the equipment is in accordance with the requirements of the EU machinery directive.
Depending upon site conditions it also may be necessary to install items such as bottom screens, ladders, safety
cages, stairways, access platforms, handrails and toe boards for the safety and convenience of the authorized
service and maintenance personnel.
At no time this equipment should be operated without all fan screens, access panels and access doors in place.
When the equipment is operated with a variable fan speed control device, steps must be taken to avoid operating
at or near to the fan's «critical speed».
For more information consult your local BAC Balticare representative.
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ELECTRICAL SAFETY
All electrical components associated with this equipment should be installed with a lockable disconnect switch
located within sight of the equipment.
In the event of multiple components, these can be installed after a single disconnect switch but multiple switches
or a combination thereof are also allowed.
No service work should be performed on or near electrical components unless adequate safety measures are
taken. These include, but are not limited to the following:
• Isolate the component electrically
• Lock the isolation switch in order to prevent unintentional restart
• Measure that no electrical voltage is present anymore
• If parts of the installation remain energized, make sure to properly demarcate these in order to avoid confusion
Fan motor terminals and connections may have residual voltage after unit shut-down. Wait five minutes after
disconnecting the voltage at all poles before opening the fan motor terminal box.
LOCATION
All cooling equipment should be located as far away as possible from occupied areas, open windows or air intakes
to buildings.
LOCAL REGULATIONS
Installation and operation of cooling equipment may be subject to local regulations, such as establishment of risk
analysis. Ensure regulatory requirements are consistently met.
Disposal requirements
Dismantling of the unit and treatment of refrigerants (if applicable), oil and other parts must be done with respect to
the environment whilst protecting workers from potential risks related to exposure to harmful substances.
National and regional legislation for material disposal and protection of workers should be taken into account with
regard to:
• Appropriate handling of construction and maintenance materials when dismantling the unit. In particular when
dealing with materials that contain harmful substances, such as asbestos or carcinogenic substances.
• Appropriate disposal of the construction and maintenance materials and components such as steel, plastics,
refrigerants and waste water according to local and national requirements for waste management, recycling
and disposal.
Non-walking surfaces
Access to and maintenance of any component needs to be performed in accordance with all local applicable laws
and regulations. If the proper and required access means are not present, temporary structures need to be
foreseen. Under no circumstance can one use parts of the unit, that are not designed as an access mean, unless
measures can be taken to mitigate any risks that might occur from doing so.
Modifications by others
Whenever modifications or changes are made by others to the BAC equipment without written permission of BAC,
the party who has done the modification becomes responsible for all consequences of this change and BAC
declines all liability for the product.
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2 General information
2 General information

Warranty
BAC will guarantee all products to be free from manufactured defects in materials and workmanship for a period of
24 months from the date of shipment. In the event of any such defect, BAC will repair or provide a replacement.
For more details, please refer to the Limitation of Warranties applicable to and in effect at the time of the
sale/purchase of these products. You can find these terms and conditions on the reverse side of your order
acknowledgement form and your invoice.
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3 Water Care
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WATER CARE
About water care
In all cooling equipment, operating in evaporative mode, the cooling is accomplished by evaporating a small portion
of the re-circulating water as it flows through the equipment. When this water evaporates, the impurities originally
present in the water remain. Unless a small amount of water is drained from the system, known as blow down, the
concentration of dissolved solids will increase rapidly and lead to scale formation or corrosion or both. Also, since
water is being lost from the system through evaporation and blow down, this water needs to be replenished.
The total amount of replenishment, known as make-up, is defined as:
Make-up = evaporation loss + blow down
In addition to the impurities present in the make-up water, any airborne impurities or biological matter are carried
into the equipment and drawn into the re-circulating water. Over and above the necessity to blow down a small
quantity of water, a water treatment programme specifically designed to address scale, corrosion and biological
control should be initiated when the system is first installed and maintained on a continuous base thereafter.
Moreover there must be an ongoing programme of monitoring in place to ensure the water treatment system is
maintaining the water quality within the control guidelines.
Check and adjustments of blow down depends on the blow down device actual in use.
To prevent excessive build-up of impurities in the circulating water, a small amount of water must be «bled » from
the system at a rate to be determined by the water treatment regime. The amount of blow down is determined by
the design cycles of concentration for the system. These cycles of concentration depend on the quality of the
make-up water and the design guidelines for the quality of the recirculating water given below.
Make-up water to the evaporative unit should have minimum 30 ppm hardness as CaCO3.
Where use of a softener is necessary to achieve this, the supply to the evaporative unit should not be totally
softened, but blended with the incoming unsoftened water to achieve the minimum hardness between 30 and
70ppm as CaCO3.
Maintaining a minimum hardness in the make-up water offsets the corrosive properties of totally softened water
and reduces the reliance on corrosion inhibitors to protect the system.
To control corrosion and scale, the water chemistry of the circulated water has to be kept within the water quality
guidelines of the specific materials of construction used, as listed in the following table(s).
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Baltibond®Hybrid Coating and SST304L
pH 6.5 to 9.2
pH during initial passivation Below 8.2
(for units with HDG coil only)
Total hardness (as CaCO3) 50 to 750 mg/l
Total alkalinity (as CaCO3) 600 mg/l max.
Total dissolved solids 2050 mg/l max.
Conductivity 3300 µS/cm
Chlorides 300 mg/l max.
Sulfates* 350 mg/l max.*
Total suspended solids 25 mg/l max.
Chlorination (as free chlorine / halogen): continuous 1.5 mg/l max.
Chlorination (as free chlorine / halogen): batch dosing for cleaning &
disinfection
5-15 mg/l max. for 6 hours max.
25 mg/l max. for 2 hours max.
50 mg/l max. for 1 hour max.
Circulated water quality guidelines for Baltibond®Hybrid Coating
*Note: Higher concentration of sulfates is allowed, provided the sum of chlorides + sulfates parameters does not exceed 650 mg/l for
Baltibond/SST304L.
Baltiplus protection
pH 6.5 to 9.0
pH during initial passivation Below 8.2
Total hardness (as CaCO3) 50 to 600 mg/l
Total alkalinity (as CaCO3) 500 mg/l max.
Total dissolved solids 1500 mg/l max.
Conductivity 2400 µS/cm
Chlorides 250 mg/l max.
Sulfates* 250 mg/l max.*
Total suspended solids 25 mg/l max.
Chlorination (as free chlorine / halogen): continuous 1 mg/l max.
Chlorination (as free chlorine / halogan): batch dosing for cleaning &
disinfection
5-15 mg/l max. for 6 hours max.
25 mg/l max. for 2 hours max.
50 mg/l max. for 1 hour max.
Circulated water quality guidelines for Baltiplus protection
*Note: Higher concentration of sulfates is allowed provided the sum of chlorides + sulfates parameters does not exceed 500 mg/l for Baltiplus
protection.
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SST304L
SST316L with HDG coil
SST316L
(with SST316L coil)
pH 6.5 to 9.2 6.5to 9.5
pH during initial passivation Below 8.2
(for units with HDG coil only)
Not applicable
Total hardness (as CaCO3) 50 to 750 mg/l 50 to 750 mg/l
Total alkalinity (as CaCO3) 600 mg/l max. 600 mg/l max.
Total dissolved solids 2050 mg/l max. 2500 mg/l max.
Conductivity 3300 µS/cm 4000 µS/cm
Chlorides 300 mg/l max. 750 mg/l max.
Sulfates* 350 mg/l max.* 750 mg/l max.*
Total suspended solids 25 mg/l max. 25 mg/l max.
Chlorination (as free
chlorine/halogen): continuous
1,5 mg/l max. 2 mg/l max.
Chlorination (as free
chlorine/halogen): batch dosing for
cleaning & disinfection
5-15 mg/l max. for 6 hours max.
25 mg/l max. for 2 hours max.
50 mg/l max. for 1 hour max.
5-15 mg/l max. for 6 hours max.
25 mg/l max. for 2 hours max.
50 mg/l max. for 1 hour max.
Circulated water quality guidelines for Stainless Steel
*Note: Higher concentration of sulphates is allowed provided the sum of chlorides + sulphates parameters does not exceed 650 mg/l for
SST304L and 1500 mg/l for SST316L.
For Ozone water treatment application:
• Stainless steel 316L execution is required.
• Ozone levels are to be maintained to 0.2 ppm ± 0.1 ppm for at least 90% of the time, with absolute maximum
peaks of 0.5 ppm
Cycles of concentration are the ratio of the dissolved solids concentration in the circulating water compared to the
dissolved solids concentration in the make-up water. The blow down rate can be calculated as follows:
Blow down = Evaporation loss / (Cycles of concentration – 1)
The evaporation loss is not only function of the heat load but also depends on climatic conditions, the type of
equipment used and the method of capacity control, which is applied. The evaporation loss at summer conditions
is approximately 0.431 l/ 1000 kJ heat rejection. This number should be used for blow down valve sizing only and
not for the calculation of annual water consumption.
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3 Water Care
3 Water Care

Biological control
The growth of algae, slimes and other micro-organisms, if uncontrolled, will reduce system efficiency and may
contribute to the growth of potentially harmful micro-organisms, such as Legionella, in the recirculating water
system.
Accordingly a treatment programme specifically designed to address biological control should be initiated when the
system is first filled with water and administered on a regular base thereafter in accordance with any regulations
(national, regional) that may exist or in accordance with accepted codes of good practice, such as EUROVENT
9-5/6, VDMA Detailsheet 24649 etc.
Also during shutdown periods it is recommended to continue the water treatment programme.Alternatively, the
basin and pump should be drained.
It is strongly recommended to monitor the bacteriological contamination of the recirculating water on a regular base
(for example, TAB test with dip slides on a weekly base) and record all results.
Certain products used for water treatment, particular some dispersant and bio-dispersant additives, might change
the properties of the water (such as the surface tension), which can cause excessive drift loss (water passing
through the eliminators). In such case we recommend to review the water treatment (product type, dosage) with
your water treatment expert.
In case of doubt, a short test can be performed, after cleaning & disinfection, using fresh water without addition of
the concerned chemical (within the limits of the local legislation).
Chemical treatment
1. Water treatment chemicals or non-chemical systems need to be compatible with the materials of construction
used in the cooling system including the evaporative cooling equipment itself.
2. In case of chemical water treatment, chemicals should be added to the recirculating water by an automatic
feed system. This will prevent localised high concentrations of chemicals, which may cause corrosion.
Preferably the water treatment chemicals should be fed into the cooling system at the discharge of the
recirculation pump. The chemicals should not be fed in concentrated form, nor batch fed directly into the cold
water sump of the evaporative cooling equipment.
3. BAC specifically discourages acid dosing as mean of scale control (unless under certain strict circumstances
for open circuit cooling towers with very large system volume and remote sump, or constructed from stainless
steel).
4. A competent water treatment company should be consulted for the specific water treatment programme to be
applied. Next to the supply of dosing and control equipment and chemicals, the programme should include
regular monthly monitoring of the circulating and make up water quality.
5. If it is proposed to operate a treatment programme outside the BAC Water Quality Control Guidelines, the BAC
factory warranty may be invalidated if the water quality is persistently outside the Control Guidelines, unless
specific prior written BAC approval. (Some parameters may be exceeded under certain strict circumstances.)
It is strongly recommended to check the key parameters of the circulating water quality on a monthly base. See
table: "Circulated water quality guidelines". All test results need to be recorded.
Passivation
When new systems are first commissioned, special measures should be taken to ensure that galvanized steel
surfaces are properly passivated to provide maximum protection from corrosion. Passivation is the formation of a
protective, passive, oxide layer on galvanized steel surfaces.
To ensure that galvanized steel surfaces are passivated, the pH of circulating water should be kept between 7.0
and 8.2 and calcium hardness between 100 and 300 ppm (as CaCO3) for four to eight weeks after start-up, or until
new zinc surfaces turn dull grey in colour. If white deposits form on galvanized steel surfaces after the pH is
returned to normal service levels, it may be necessary to repeat the passivation process.
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Full stainless steel units and units protected by the Baltibond®hybrid coating do not require passivation.
An exception to this are units with a galvanized steel coil bundle which do still require the proper
passivation procedure as described here in this section.
In case you can't keep the pH below 8.2, a secondary approach is to conduct a chemical passivation using
inorganic phosphate or film-forming passivation agents. Consult your water treatment specialist for specific
recommendation.
Overflow connection
A slight loss of water through the overflow on forced draft units is normal when the fans are in operation, since the
unit is in overpressure and some saturated air will be blown out to the unit, carrying several droplets of water.
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3 Water Care
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COLD WEATHER OPERATIONS
About cold weather operation
BAC cooling equipment can be operated in sub freezing ambient conditions provided the proper measures are
taken. Listed below are general guidelines which should be followed to minimize the possibility of coil freeze-up.
As these guidelines may not include all aspects of the anticipated operation scheme, system designer and
operator must thoroughly review the system, location of the equipment, controls and accessories to ensure reliable
operation at all times.
Protection against sump water freezing
Units exposed to below freezing ambient temperatures, require protection to prevent freezing of the water in the
wet sump. During dry operation all water will drain into the wet sump, that is shielded from the air stream. Heaters
in the wet sump are sufficiently sized to prevent freezing at temperatures as low as -18°C at full speed of the fan
system.
CAUTION
Switch off heaters when the sump is drained.
Capacity control
In addition to protecting the sump water, all exposed water piping, in particular make-up water lines should be heat
traced and insulated.
Spray pumps also need to be heat traced and insulated from pump suction to the overflow level, if they can be
exposed to sub-freezing ambient conditions.
It is necessary to prevent the recirculating water from approaching freezing conditions when the system is
operating under load. The most «critical » situation occurs, if operation at subfreezing conditions coincides with
light load conditions. The key to protecting the recirculating water is capacity control by adjustment of air flow to
maintain the temperature of the recirculating water minimal above freezing point. As a rule of thumb this minimum
temperature is 5°C, but there are applications, where even lower temperatures can be accepted. (Contact your
local BAC Balticare representative for advice.)
The desired method to match the cooling capacity to load and weather conditions is to adjust the air flow by the
use of modulating controls (variable speed drives).
Alternatively, multi speed fan motors or fan cycling can be applied, but fans operating on a common heat exchange
section should always be operated simultaneously.
It is not recommended to cycle the spray pump as a means of controlling the unit capacity.
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Whenever two speed motors are used for capacity control, a time delay of at least 15 seconds is required when
switching form high to low speed. Sudden switch over might damage the drive system or the motor.
When operating with VFD drives above nominal frequency be aware of the potential risk for motor overload
or mechanical damages.
It is recommended to provide sinus filters on the VFD to prevent bearing damage on fan motors.
CAUTION
Refer to fan motor nameplate data when programming a VFD.
Spray pumps should be switched off when the fan(s) are idle. Operation with pump but without fan(s) does not
provide cooling capacity of any significance but could lead to occasional water splash out at the air intake. For this
reason this operation mode should be avoided. Spray pump should be switched off with a time delay of maximum
30 seconds after switching off the fan(s) and should be activated maximum 30 seconds prior to the anticipated
start of the fan(s).
The purpose of a low level cut out switch for pump protection is to protect the pump from running dry in case of
make-up failure or extreme water loss. The status of the alarm can be checked prior to pump start-up, but should
not be considered during the first minute after start-up, since activation of the pump can cause a water level drop,
that might trigger the alarm. Normal make-up will stabilize the water level after a short period of time.
In case the low level alarm signals, that there is no longer enough water in the cold water sump to guarantee a
proper operation, the pump should be stopped (after a time delay of 60 seconds) and only manually restarted after it
has been verified that the water in the sump is at or near the overflow level.
In case the low level pump alarm is used to stop the pump, appropriate control logic should be incorporated
to prevent hunting of the pump motor. Once the spray pump is stopped, the water in suspension will drain
back to the tank and raise the water-level above the alarm level, which will reset the alarm immediately. A manual
reset of the alarm after solving the root cause of the low level alarm is recommended. Frequent start/stop or
hunting will damage the motor.
Protection against coil freezing
The best protection is the use of glycol or other anti freeze solutions in appropriate concentrations. The use of such
solutions influences the thermal performance of the closed circuit cooling tower and this should be taken into
account, when selecting the model(s). The table below indicates the freeze protection range for various ethylene
glycol concentrations (% by volume).
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% Ethylene Freeze protection
20% -10°C
30% -16°C
40% -25°C
50% -39°C
Freeze protection of ethylene glycol solutions
Glycol systems require specific inhibitors compatible with the materials of construction they come into
contact with. These inhibitors generally come pre-mixed with the glycol additive for the cooling circuit.
If the system must be operated with water, the following conditions must be met simultaneously:
1. Maintain a minimum flow through the unit at all times. (see table below)
2. Maintain a minimum heat load, so that the temperature of the water leaving the coil(s) will not fall below 10°C
based on -14°C ambient temperature and 20 m/s wind velocity.
3. In order to prevent coil freezing, the 3-way valve must be positioned to let the full flow circulating through the
prime surface coil.
If the process load is extremely light or shut off, it may be necessary to apply an auxiliary heat load during freezing
conditions. Consult your local BAC Balticare representative for advice, if these conditions cannot be met.
Draining of the coil(s) is not recommended as a normal method of freeze protection unless the coil(s) are
constructed from stainless steel or are of the cleanable type. For standard hot dip galvanized coils draining is
ONLY acceptable as an emergency method of freeze protection, since draining will lead to internal corrosion of the
coil. For this purpose an automatic drain valve and air vent needs to be installed to drain the coil(s) if flow stops or
the fluid temperature drops below 10°C when the ambient temperature is below freezing.
Ensure that all coils and/or coil sections (split coils/multi-circuiting) can drain individually.
Model Minimum flow (l/s)
HFL 36X - 48X 4,1
HFL 72X – 96X 7,9
HFL 108X – 144X 12
HFL 150X – 192X 15,8
HFL 180X – 240X 19,9
HFL 216X – 288X 24
Minimum requirements for water flow
Draining of the coil is not recommended as a normal method of freeze protection. Frequent draining promotes
oxidation inside the coil tubes. Full draining of the heat exchanger coil is not guaranteed because of rising coil
circuiting on the finned discharge coil (optional) and the risk for coil freeze-up remains. The local BAC Balticare
representative should be consulted for guidelines on the installation of an emergency coil drain system.
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