chiller maintenance and control

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Centrifugal water chillers trane 2

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Centrifugal water chillers trane

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chiller maintenance and control

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chiller maintenance and control

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chiller maintenance and control

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12/19/2015

Water Chillers and Maintenance parti 4 Extended (long-term) maintenance checks


Water Chillers and Maintenance
 parti 4
Extended (long-term) maintenance checks


Extended (long-term) maintenance checks




Extended (long-term) maintenance checks:

1. Every 5 years (or more frequently as the chiller ages), perform eddy current
(electromagnetic) testing of heat exchanger tubes. [This testing will
typically detect tube pits, cracks, and tube wear (thinning).] If only 1–5
tubes are found defective, plug tubes. If more than 5 are found defective,
replace tubes. (Any tube that is replaced as a result of this testing should
be examined and cross-sections cut so the cause of the defects can be
evaluated.)
2. Other components must be serviced, inspected, and/or replaced at the
intervals recommended by the chiller manufacturer.
Recommended maintenance procedures for water-cooled electric-drive rotary
compressor water chillers are as follows:
Daily monitoring/visual inspection: The majority of chiller operating problems
and maintenance needs are discovered by visual inspection and
frequent monitoring of equipment operating parameters.

Monthly, quarterly, and annual preventative maintenance:
1. Clean the evaporator tubes every 2–4 years (annually for chillers serving
air washers or other “open” cooling loads).
2. Clean the condenser tubes every year.
3. Quarterly, calibrate pressure, temperature, and flow controls.
4. Annually, inspect starter wiring connections, contacts, and action. Tighten
and adjust as required. Perform thermographic survey every 5 years.
5. Annually, test the operation of safety interlocks devices, such as flow
switches, pump starter auxiliary contracts, phase-loss protection, and so
on. Repair or replace as required.
6. Annually, perform dielectric motor testing to identify failures in motor
winding insulation. For large chillers (100 tons or larger), additional
annual motor tests are required to test for the imbalance of electrical
resistance among windings, imbalance of total inductance with phase
inductances, power factor, capacitance imbalance, and running amperage
versus nameplate amperage.
7. Annually, check the tightness of the hot-gas valve (as applicable). If the
valve does not provide tight shutoff, replace it.
8. Annually, replace lubricant (oil) filter and drier.
9. Laboratory analysis of the lubricant should be performed annually during
the first 10 years of chiller life and every 6 months thereafter. Analysis
must address oil moisture content, acidity, and chiller wear as follows:
a. Maximum moisture content of 50 ppm. Higher levels may indicate
air leaks in low-pressure chillers or heat exchanger tube leaks.
b. Maximum acidity of 1 ppm is normal for a new or reclaimed refrigerant.
Higher levels may be caused by oxidation of oil during aging
and/or degradation of refrigerant. If higher levels are found, contact
the chiller manufacturer.
c.Trace amounts of metals could be metal oxides formed from moisture
in the oil or may indicate excess wear conditions. Due to variations
in metals used by different chiller manufacturers, there are no
standard limits. However, if metal content increases from year to
year, one or more of the following excess wear conditions may be
responsible:
Aluminum: impellor or bearing wear
Chromium: wear on rechromed shafts
Copper: corrosion
Iron: corrosion and/or gear wear
Tin: bearing wear
Silicon: leakage of silica gel from dehydrator cartridge or dirt
in system
Zinc: zinc left over from the manufacturing process or loss
of galvanizing from some parts
10. Valve and bearing inspection in accordance with manufacturer’s
recommendation.
11. Relief valves (both refrigerant and water) should be checked annually.
Disconnect the vent piping at the valve outlet and visually inspect the
valve body and mechanism for corrosion, dirt, or leakage. If there are
problems, replace the valve; do not attempt to clean or repair it.
12. Annually, inspect gearbox for wear and repair or replace it as needed.
13. Perform chemical testing of system water at least quarterly. Treat as
needed to ensure proper water chemistry.

Extended (long-term) maintenance checks:
1. Every 5 years (or more frequently as the chiller ages), perform eddy current
(electromagnetic) testing of heat exchanger tubes. [This testing will
typically detect tube pits, cracks, and tube wear (thinning).] If only a
limited number of tubes are found defective, plug tubes. If more than few
are found defective, replace tubes. (Any tube that is replaced as a result
of this testing should be examined and cross-sections should be cut so
that the cause of the defects can be evaluated.)
2. Every 3–5 years, perform vibration test and analysis to evaluate motor
and rotor balance, bearing and gear alignment, and bearing and gear
wear. Use accelerometer-type sensors for gears and bearings (high frequency)
and piezoelectric velocity sensors for compressor motors, rotors,
and bearings (low velocity).
3. Every 5 years, perform an acoustic emission test to identify potential
stress cracks in pressure vessels, tubes, and tube sheets.
4. Other components must be serviced, inspected, and/or replaced at the
intervals recommended by the chiller manufacturer.

kandi younes

12/18/2015

Water Chillers and Maintenance part 3 Chiller data logging form


Water Chillers and Maintenance
 part 3
Chiller data logging form

annual preventative maintenance




Monthly, quarterly, and annual preventative maintenance:

1. Clean evaporator every 2–4 years (annually for chillers serving air
washers or other “open” cooling loads).
2. Quarterly, calibrate pressure, temperature, and flow controls.

FIGURE 7.1 Chiller data logging form.
3. Annually, inspect starter wiring connections, contacts, and action.
Tighten and adjust as required. Perform thermographic survey every 5
years.
4. Annually, test the operation of safety interlocks devices, such as flow
switches, pump starter auxiliary contracts, phase-loss protection, and so
on. Repair or replace as required.
5. Annually, perform dielectric motor testing to identify failures in motor
winding insulation. For large chillers (100 tons or larger), additional

annual motor tests are required to test for imbalance of electrical
resistance
among windings, imbalance of total inductance with phase
inductances, power factor, capacitance imbalance, and running amperage
versus nameplate amperage.
6. Annually, check the tightness of the hot gas valve (as applicable). If the
valve does not provide tight shutoff, replace it.
7. Annually, change the lubricant (oil) filter and the drier.
8. Laboratory analysis of the lubricant should be performed annually
during the first 10 years of chiller life and every 6 months thereafter.
[This oil analysis will define the moisture content (not to exceed
50 ppm), oil acidity (maximum 1 ppm) that may indicate oil oxidation
and/or refrigerant degradation due to high temperatures, and metals
or metal oxides that indicate chiller component wear and/or moisture
in the oil.]
9. Valve and bearing inspection in accordance with manufacturer’s
recommendation.
10. Relief valves (both refrigerant and water) should be checked annually.
Disconnect the vent piping at the valve outlet and visually
inspect the valve body and mechanism for corrosion, dirt, or leakage.
If there are problems, replace the valve; do not attempt to clean or
repair it.
11. Every 6 months, inspect and clean air-cooled condensers as follows:
a. Check unit casing and clear any leaf litter or organic matter in
contact
with the casing. Remove leaves, sticks, and so on, on or in
the unit casing. Check for condition of paint, metal, and so on and
repair as necessary.
b. Check outdoor fans for proper rotation and that the fans do not run
backward when off. Clean and, if needed, balance the fan blades.
c. Lubrication: Typically, fan motors have sealed bearings and require
no lubrication.
d. Inspect condenser coils and clean, if necessary.
12. Perform chemical testing of chilled water at least quarterly. Treat as
needed to ensure proper water chemistry.

kandi younes

Water Chillers and Maintenance part 2 Electric-Drive Chillers


Water Chillers and Maintenance
 part 2
Electric-Drive Chillers

Water Chillers and Maintenance



Electric-Drive Chillers:

1. Determine that the chiller full load amperes (FLA) is within 5% of design.
2. Test volts, phase-to-phase.
3. Compute voltage imbalance and determine that the maximum variation
between phases is less than 2%.

Absorption Chillers:
1. Determine that the high generator temperature is within the design range.
2. Test high/low generator solution level.
3. Determine that supply steam pressure is within 5% of design.
4. Test automatic overconcentration, dilution cycles, and dilution on
shutdown.

Water-Cooled Chillers:

1. Confirm that the cooling tower has been commissioned (see the section
“Tower Commissioning” in Chapter 15).
2. Determine the entering CDW temperature and confirm that it is within
1°F of setpoint.
3. Determine leaving CDW temperature and compare to design.
4. Determine CDW temperature range and compare to design.

Air-Cooled Chillers:

1. Determine ambient air temperature.
2. Determine chiller head pressure and compare to rated value.

Operations and Control:

1. Confirm that the chiller appears to meet load.
2. Confirm that the chiller operates without alarm conditions or safety
shutdowns.
3. Confirm that the chiller start sequence operates properly.
4. Confirm that multichiller staging sequence operates properly.

CHILLER MAINTENANCE:
When establishing a maintenance program for chillers, maintenance managers
have three options:

1. Implement the program fully in-house.
2. Outsource the entire program.
3. Use a combination of in-house and outsourced functions.

One of the most important benefits of a program that uses in-house personnel
is the institutional knowledge of those systems. Maintenance personnel who have
been working with those chiller systems for years are most likely to know what
many of the existing maintenance problems are.
Another benefit of using in-house personnel is long-term quality. Maintenance
managers and in-house personnel are better able to focus their attention and
efforts on both short- and long-term requirements, up to the expected life of the
equipment. Outsourced programs tend to have a much shorter focus, that is, the
period of the maintenance contract.
However, the cost of establishing a complete in-house program can be very
high. Managers have to arrange for the training of maintenance personnel on the
specifics of maintaining the chiller(s) installed in the facility, provide specialized
training for infrequent testing and servicing, and purchase specialized test
equipment
for many of the inspection and maintenance activities that must be
performed.
Combination of in-house and outsourced programs typically assign the routine
and preventive maintenance tasks to in-house personnel, while contracting is utilized
for specialized activities that require a higher level of expertise than is available
in-house. This approach maintains in-house personnel being actively involved
in the maintenance, while outside experts assist them by performing the more
complex and infrequent tasks. This arrangement helps preserve the institutional
knowledge and typically is the most cost-effective approach.
No matter which maintenance scheme is utilized, a preventative maintenance
program to ensure that the chiller operates reliably over its design life is required.
The majority of chiller operating problems and maintenance needs are discovered
by visual inspection and the monitoring of equipment operating parameters.
Figure 7.1 is a form that can be used to guide chiller visual inspection and to collect
operating data every 2 h during the day. These data will give a complete
“snapshot” of the running conditions of the chiller, and variations in data between
observations can be a prime indicator of operating problems.
Over the long term, these data can be used to predict maintenance requirements.
These data, along with the data collected during periodic checks and routine
maintenance
procedures, can be plotted against time so that a trend or change
in conditions can be identified. A decision on maintenance can then be made from
the trend.
Recommended preventative maintenance procedures for air-cooled electricdrive
water chillers are as follows:

Daily monitoring/visual inspection: The majority of chiller operating problems
and maintenance needs are discovered by visual inspection and
frequent monitoring of equipment operating parameters.

kandi younes

Water Chillers and Maintenance part 1 Installation Checklist for Absorption Chillers

Water Chillers
and Maintenance
part 1
Installation Checklist for Absorption Chillers

Installation Checklist for Absorption Chillers



CHILLER COMMISSIONING:

Every chilled water system can be operated on the basis of meeting two goals:
Goal 1: Satisfy imposed cooling loads

• Maintain proper chilled water supply temperature to offset imposed sensible
and latent cooling loads.

• Maintain proper supply water flow in variable flow systems to minimize
pumping energy consumption.
Goal 2: Minimize the cost of cooling

• Maintain chilled water temperature as high as possible, but still low
enough to satisfy both sensible and latent cooling loads.

• Maintain condenser water supply temperature as low as feasible. Most
chillers operate satisfactorily with entering condenser water temperature
as low as 70°F. And, at least one chiller manufacturer rates its machines
for operation with an entering condenser water temperature of 55°F.

• Operate each chiller, to the maximum possible extent, in the 40–80%
load range.
To ensure that this type of operation is attainable, the chilled water system
must be properly installed and placed into service and its operation verified by
test, a process called commissioning.
The first step in this process is to verify that the chiller installation is correct
and in accordance with both the design and the manufacturer’s recommendations.
The design engineer should be retained to review the installation process and
perform a final inspection to ensure compliance with the design requirements.
Before the chiller can be started for the first time, the chilled water pump(s)
must be placed in operation and the chilled water flow “balanced” to within ±5%
of design rates. The basic steps required to place the chilled water pump in service
include the following:

1. Check pump installation, including mountings, vibration isolators, and
connectors,
and piping specialties (valves, strainer, pressure gauges,
thermometers, etc.).
2. Check pump shaft and coupling alignment.
3. Lubricate pump shaft bearings as required by the manufacturer.
4. Lubricate motor shaft bearings as required by the manufacturer.
5. Turn shaft by hand to make sure the pump and motor turn freely.
6. “Bump” the motor on and check for proper rotation direction.

The air-cooled condenser or condenser water system must be placed into operation
(see the section “Tower Commissioning” in Chapter 15). System controls
must be tested and their proper operation must be confirmed. Chillers should be
initially placed into service only by the manufacturer’s service technicians, a process
often called factory start-up.
The following checklist may be used for verifying both chiller installation and
functional performance upon start-up:

General Installation Checklist

1. Test and balance completed (chilled water (CHW) and condenser water
(CDW) flows with –5% to +10% of design).
2. Observe no visible water or oil leaks.
3. Observe no unusual noise or vibration.
4. Chilled water piping insulation in good condition.
5. Pressure gauges, thermometers installed and operable.
6. Confirm that O & M manuals are onsite.
7. Confirm that training was provided for operating staff.

Additional Installation Checklist for Absorption Chillers

1. Confirm that the steam control valve is installed and operating for an
indirect-fired chiller.
2. Confirm that the chiller has been leak tested according to manufacturer’s
instruction.
3. Confirm that unit was evacuated properly before charging with refrigerant
and solution.
4. Confirm that distilled water was used for refrigerant charge and proper
amount of inhibitor added.
5. Confirm that the proper amount of lithium bromide was installed.
6. Confirm that the proper amount of octyl alcohol was installed.
7. Test electrical service to each pump for
8. Test operating amps for each pump.


Functional Performance Checklist

1. Confirm that the factory start-up and tests were completed and the chiller
is ready to be placed into service.
2. Determine entering CHW temperature and compare to design.
3. Determine leaving CHW temperature is within 1°F of setpoint.
4. Compute CHW range and compare to design.

kandi younes

12/13/2015

HVAC Water Chillers Chiller Configurations Pump Parallel Configuration parti 1

HVAC Water Chillers
Chiller Configurations Pump Parallel Configuration
parti 1

Multiple-Pump chiller 



One-Pump Parallel Configuration:

The one-pump parallel chiller configuration is shown in Figure 2.3 and the overall system performance and temperature conditions are summarized in Table 2.2.
With this configuration, there is an inherent problem. If both machines were operated for the full-load range (15–100% of peak capacity), by the time the total system load drops to 30% of full load, each individual chiller would be operating very inefficiently. Thus, most designers utilize controls to shut off one chiller
when the total system load, as evidenced by the return chilled water temperature, falls below 40% of full load.

One-pump parallel chiller configuration.


One-pump parallel chiller configuration.



One-pump parallel chiller configuration with isolation valves.

However, with this piping arrangement, if one chiller is not in operation, chilled water from the operating chiller will mix (blend) with the return water passing through the nonoperating chiller, effectively raising the system’s chilled water supply temperature. In many cases, this may not be a problem. But, generally the interior spaces of large buildings still require more or less full cooling even when the perimeter spaces require no cooling at all and an elevated chilled water supply temperature may not satisfy these interior load conditions. In hot, humid climates, an elevated chilled water supply temperature may result in loss of humidity control. To attempt to eliminate the blended supply water problem with the one-pump
configuration, some designers have used chiller flow isolation valves, as shown in Figure 2.4. With this configuration, flow through the nonoperating chiller is  closed off when the chiller is not in operation. This arrangement results in increased flow through the operating chiller, but does reduce the blending problem, as illustrated in Table 2.3.

Multiple-Pump Parallel Configuration:

To ensure that the blended water condition does not occur, the multiple-pump parallel chiller configuration shown in Figure 2.5 is widely used.

One-Pump Parallel Configuration


Multiple-pump parallel chiller configuration.
With this configuration, each chiller has an individual chilled water pump. Thus, when one chiller is not operating, one pump is off, flow through the nonoperating chiller is zero, and no blending results.
Table 2.4 summarizes the performance and temperature conditions for this configuration at various load conditions.



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HVAC Water Chillers Chiller Configurations Pump Parallel Configuration parti 2


HVAC Water Chillers
Chiller Configurations Pump Parallel Configuration
parti 2


Multiple-Pump Parallel 




Primary–Secondary Parallel Configuration:

Each of the configurations discussed above is essentially a constant flow system that utilizes three-way control valves at the cooling coils. Constant flow systems circulate the same amount of chilled water, no matter what the imposed cooling load, and, consequently, impose high pumping energy requirements.
To reduce these costs, the primary–secondary variable flow piping arrangement illustrated in Figure 2.6 is very commonly applied. Here, the production loop through the two chillers is hydraulically isolated from the distribution loop by a piping bridge. The bridge is a short section of piping shared by both loops
and designed to have little or no pressure drop. Thus, the flow in one loop is not affected by flow in the other.On the primary or production loop side, the system acts as multiple-pump parallel chiller installation, as described in the section “Multiple-Pump Parallel

Multiple-Pump Parallel Configuration
Primary–secondary parallel chiller configuration.

Configuration.” Flow in this loop varies in “steps” as the chillers are staged on or off and their respective pumps are started and stopped. However, in the secondary or distribution loop, the cooling coils utilize two-way control valves and the distribution pump(s) utilize a variable frequency drive(s) so that the
chilled water flow rate is modulated from 0% to 100% of peak design flow as a function of the imposed cooling load. Thus, this loop has fully variable flow, but maintains a constant temperature range. At any load condition, the supply water temperature is the same as the water temperature leaving the chiller(s),as long as the production loop flow rate equals or exceeds the distribution loop flow rate.  Table 2.5 summarizes the performance and temperature conditions for this configuration at various load conditions. 



Primary–Secondary Configuration Flows and Temperatures

Variable flow primary parallel chiller configuration


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HVAC Water Chillers Chiller Configurations CHILLER SYSTEM

HVAC Water Chillers
Chiller Configurations CHILLER SYSTEM


MULTI CHILLER SYSTEMS




THE SINGLE-CHILLER SYSTEM:

The basic chilled water piping configuration for a single chiller is shown in Figure 2.1. Here, a single chiller provides chilled water to the cooling coils utilizing a single chilled water pump.
For small systems, this configuration has the advantage of lower initial cost, but does have some basic disadvantages:

1. With the single-compressor system, failure of any component (compressor, pump, or condenser) will result in no cooling being available. For most facilities, this is unacceptable and the use of multiple chillers allows at least some cooling (50% or more) be provided even if one chiller fails. In cases where cooling is critical to the facility (computer centers, hospital, laboratories, pharmaceutical or textile manufacturing, etc.), multiple chillers with at least one redundant chiller are often used. In this case, even if one chiller fails, 100% of the design cooling load can still be met.

2. As discussed in Chapter 1, once the cooling load imposed on a rotary compressor chiller falls to below about 30% of the chiller capacity, theefficiency of the chiller begins to decline. Thus, the use of multiple chillers allows a better overall capacity-to-load ratio and improved operating efficiency.

MULTI CHILLER SYSTEMS:

For multiple chiller systems, there are two basic configurations that can be utilized,series or parallel flow. 
In a series configuration with two chillers, as shown in Figure 2.2, each chiller is selected to produce half of the required cooling at the full system flow rate.Thus, half of the total design range is produced by each chiller. Load ratios other than 50/50 are possible, but this is by far the most common condition because of 
control problems with chillers at very small temperature differences.
Table 2.1 summarizes the temperatures at various load conditions for the configuration shown in Figure 2.2.
Series chiller systems are rarely utilized in present times because this configuration requires a constant chilled water flow rate at all times, resulting in high pumping costs. But, if a relatively large temperature difference is required or if there is a very steady base cooling load, the series configuration may offer some advantages.

Constant flow, single chiller configuration.

The parallel chiller configuration is far more common. In a two-chiller configuration, each chiller is typically selected to operate with the same design range, but with only a half of the total system flow requirement. This again results in a 50/50 load split, but other load ratios may be selected if dictated by operational requirements. And, there is no real limitation on the number of parallel chillers that can be utilized in one system.

Series chiller configuration.

Series Configuration Temperatures

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