Global Warming opens before us a vast and uncertain expanse, as a crepuscular horizon on the plain at the dusk of our rapid industrialization looks increasingly threatening like never before. Unfortunately, the major pie of its cause is related to the energy that we can't live without. Looking at the inevitable our engineering design practices are bound to take a material shift. It no longer can restrict in merely doing the job, but need to do it in an energy efficient way.
Summary: This case study is a culmination of several hundred projects carried-out by us since decades covering a motley of intelligent-buildings across the length and breadth of India and world-wide, with its Total Power Management that involved Load and Parameter Optimization. The long experience brings out sustainable ways and means those helps in removing barriers to energy efficiency.
Green building revolution is spurting out across the globe but the crown tag itself is no Rosetta stone for a green energy norm. Those are in nascent stage. This case study propounds a direction towards possible development of one universal norm on a global scale. A pulse count that would broadly delineate the degree of greenness for an intelligent building. The Mean does not justify The End. For example, an inefficient building if powered by 100% green solar energy can't be tagged as efficient or for that matter a green building. It must be noted and understood, as like in any quality system, greenness can't be achieved at the delivery point or by trumpeting the purported altruism. The initial project design and equipment specifications are critical, and leaving out a much load end deficiency means those must come from the source, and that happens with substantial energy losses. In-addition those intrinsic barriers remain so long as that equipment remain in operation.
Do not limit your design rather challenge your limit. Unfortunately, most intelligent buildings world-wide are designed extraordinarily ordinary and operate below 40% Load Factor. The reason for this is to keep the Harmonic Distortion problem below the carpet within its latent stage. Load Factor in an electrical system is the actual-running-loads in mW/mVA divided by sum-total mW/mVA-ratings of all Transformers/ Diesel-generators. The primary harmonic problem in an electrical power system is the rise of Voltage Harmonic Distortion (THDv) which is proportional to the building's load factor. That explains why equipment de-rating helps in skirting out the problem albeit with a guzzling energy consumption. Succinctly, and compacting from several hundred projects, these 15-case-studies with ballpark descriptions constitute most problems and challenges that building engineers and technologists alike encounter during project design, start-up, and maintenance phases, root cause, and troubleshooting methods.
There is no wonder in the world that is not build through simple wonders. The simple fact is "smaller are the knots, better is the carpet". Modern world churns out sheaf of sophistication for modern buildings which are intertwined by yet more sophisticated chain of commands. The efficiency is a chain that is as strong as its weakest link. The long experience with the two-past contrasting economic phases, the recession period of 1996 -2002, and the economic surge period of 2003 -2008 brings forth a reflection. Riding high on economic prosperity our buildings have travelled far too a distance to be efficient again. Those barriers consistently and invariably came up primarily because of our incapability to think simple. This simple fact makes evident that the solution to global warming lies not with our money but with our energy.
Classifying intelligent building: Large buildings of yesteryears, the heritage buildings, were build at the opulence of nature that modern buildings with today's stakeholders believe to be effetely snob, and no-longer feasible. Economic prosperity coupled with technological advancement, mandate comfort conditions for the building occupants. Those bring in matching sophistication and thus create intelligent buildings, and increasingly more buildings are coming under this classification, and broadly the following business segments those employ enough sophistication could be tagged as Intelligent Building.
" Air Ports
" Sea Ports
" Shopping Malls
" District Coolers
" Corporate Houses
" Military Base Stations
" Tele-Communication facilities
" Newspaper and Printing Presses
" IT-facilities, Data centres, R&D Houses
" Refrigeration and large Cold Storage buildings
" Commercial Complexes, multi-tenanted buildings
Evolving a green building code: As every bird builds its nest; working with nature is the only sustainable way to embrace green energy. Green buildings are spurting out believing that it preserves our holistic ecology. That green Tag is no Rosetta-stone for achieving green energy norm. The fact is those norms are at nascent stage, evolving, and still miles to look forward to. The greenness is all about thrift that needs to be nourished at every sub-system, and those seamlessly intertwined, and scaled up, lead up to its final green delivery code. This proof of greenness must stop somewhere with a building's pulse count. And one way is to look at the building's Specific Energy Consumption (SEC). It's the kWh consumption per annum per square meter of total built-up space. A SEC line of below 200 for a 24/7-operation building is indeed an efficient building. It is very much achievable and that includes process loads like kitchen and laundry for hotels; biomedical equipment and labs for hospitals, data centres, workstations, and communication hubs for Information Technology, R&D centres, corporate houses, and other companies.
While going through a process for evolving solution with abstractly myriad subjects, constraints should not be guiding the solution, least it becomes a simplistic solution. Nevertheless, when constraints are built into the solution it could churn out to be truly one universal solution on a global scale. SEC line is a good way to look forward to the greenness of an Intelligent Building. It is unique of a building and simple. SEC line however needs adjustment and in particularly so when the process demand is much on the divergent scale, like a few as noted below.
" A non-24/7-operation building would have much lesser SEC and needs suitable adjustment.
" Buildings those use multiple forms of input energy like thermal etc., are to be converted into a common kWh equation.
" Large concentrated loads like exclusive Data centres, Telecommunication switching centres, POP internet centres etc. those use lesser space and pack higher intensity loads.
" District cooling facility that exports large BTU energy and conversely Buildings those import such BTU energy. Exports and/or imports are to be accounted for.
Barriers to Energy efficiency, and Why Total Power Management: The major pie of a building's energy are HVAC, lighting, business management and communications. Its primary objective is to achieve optimum comfort conditions for its occupants and guests. It necessitates employing matching control systems the degree of which varies from building to building. It could start from localized loop-in-control for individual space-zones and may reach up to the ultimate in today's technology, a centralized Building Automation, or Management System (BAS/ BMS). Control systems require equipment output to be variable in synchronism with its need for achieving the desired comfort levels.
That introduce Non-Linear-Loads, mostly in the form of Variable Frequency, or Speed Drive (VFD/ VSD) in HVAC equipment like in Chillers, Evaporator Pumps, Condenser Pumps, Cooling Towers and AHUs. In-addition, today's Lighting use nonlinear loads in the forms of Electronic chokes, CFL and Ballasts in discharge luminaire etc. Furthermore, business management and communications need large digital processing equipment for connectivity, which further brings in nonlinear loads in the forms of UPS, Computer, Internet POP and Exchanges. These nonlinear loads alter the very nature of sinusoidal waveform characteristic of the current and voltage waveforms and create bad Power Quality and harmonic distortions, the dirty powers, which are increasingly becoming apparent in the building's electrical power system. In its latent, or dormant stage it injects energy losses.
Fortunately, there exists an alternative that can effectively bring down the Power Quality Harmonic Distortions without resorting to equipment derating. This is the domain and usefulness of Tuned Harmonic Filter that when designed appropriately reap rewards that one can count on. It reconstructs the distorted voltage and current waveforms back into sine-waves thereby debottlenecks equipment capacity limitations and removes barriers to energy efficiency from the plant and machineries; and transforms them instantly into impossible is nothing like performance, on a sustainable basic.
Why Process Optimization: Many buildings subdivide its process into, high side and low side for air conditioning system; cold well and hot well for refrigeration system; and primary and secondary (or tertiary) for the associated pumping system depending upon the spread of the building's reach.
At Level-1, at equipment level, the design value determines individual equipment efficiency, and variations of its working parameters from the designed efficiency, could be verified easily.
At Level-2, at sub-system level, the working parameters are determined by a much larger force which are dynamic, and are controlled for the process needs, but deviate away from the equipment's best efficiency point. This brings in barriers to energy efficiency, and its extent varies, with the extent of the deviation.
At Level-3, at process level, the associated sub-systems are intertwined with appropriate chain of commands to ensure the final delivery. This process chain is as strong as the weakest link in the process. An un-optimised process has higher energy losses. Process optimisation removes those barriers to energy efficiency and improves SEC within the green building code. In-addition it brings out early maintenance signals for critical process equipment. A wake-up call if attended early could prevent future failures and costly break-down maintenances. Summarily, process optimization improves MTBF, equipment uptime, and helps in enhancing service quality and guest satisfaction levels.
Removing Barriers - the possibilities:
Total Power Management (TPM): The Extent of Energy savings through TPM measures depend upon number of factors namely, extent of sophistication vis-à-vis nonlinear loads employed, operating load factor, Power System's transient impedance stability which has a bearing in determining the extent to which the voltage and current harmonic distortions could develop, and thus the ways the building's total power could be managed. Giving an example, Diesel Generators have higher fault levels, or for that matter higher transient impedance, and thus provide greater opportunity for both debottlenecking capacity limitations, from 5% up to 30%, and energy savings, from 3% up to 15%.
Process Optimization: It opens a vast expanse of opportunities for modern buildings which could yield large energy savings, from 3% up to 15% with centralized air-conditioning systems, and refrigeration process loads. Furthermore, it is achieved as a no-cost measure or for that matter through negligible investment cost. Process optimization substantially reduces building's operation cost and increases both profit and guest comforts.
Load Optimization: At final delivery points, the chilled waters or brine solutions are dispersed in a way that meet with the comfort conditions and process demands. By optimising it, we could readjust with the overall process demand along with its load end sub-systems and associated load end equipment like Air Handling Unit (AHU) and PAC. It must be noted and understood that initial project design and equipment specifications are very critical since any deficiency at load end equipment must come from the high-end source and that happens with great energy losses. Nevertheless, some barriers could be removed. Overall up to 3% energy saving is possible with a minimum to moderate investment cost.
Other measures: Technical and/or aesthetic considerations primarily determine design basis for measures like in lighting, UPS, thermal/boiler, water circulation system, laundry etc. Those can't be viewed from the prism of energy consumption alone. However there always exist scopes for energy savings as well as initiating corrective measures and those are best done on a case to case basis.
Objectives vis-à-vis problems faced and lessons learnt: The projects undertaken and presented here were carried-out through the two contrasting economic situations. During the recession periods of 1996- 2002, our greater attentions were on energy saving measures; and during the economic surge periods of 2003 -2008, we were primarily requisitioned for trouble-shooting measures. The job contradictions bring forth a reflection on the mindsets of our corporate citizens, wherein building efficiency or for that matter green energy is, inversely proportional to economic prosperity.
Nonetheless, looking from hind-side and summarizing the lessons learnt, followings should be the objectives of Total Power Management (TPM) and process optimization measures for a green building. Its end results may vary on quantitative terms, but the objectives should firmly be on those directions.
To achieve highest Profitability: The secret to highest profitability is simple, reduce cost and increase profit. By implementing TPM, and with a better Power Quality, buildings can operate at near 80 to 100% load factor. It considerably reduces CAPEX, the initial Project cost and continued financial holding cost, OPEX, the running energy bills and maintenance and AMC costs.
To achieve highest Energy Efficiency promoting Green Energy: Bad Power Quality and Harmonic Distortions are less efficient in utilizing electrical energy. Extent of losses depend upon the complexity of the harmonic distortions. Furthermore, equipment de-rating causes additional energy losses, increased footprint, and unutilized capital investment. Implementing Total Power Management saves up to 30% in initial capital investment cost and 3 to 15% in running energy bills as well as maintenance costs. An un-optimized system has higher energy losses. Process Optimization removes barriers to energy efficiency and saves 3% to 15% in air-conditioning and refrigeration energy consumptions. These energy saving data are based on actual achievement from over hundreds of intelligent building projects undertaken through the two contrasting economic phases.
To Troubleshoot failures and tripping, debottleneck capacity limitations, and achieve Green Building Code:
a. A large data center of a MNC company's R&D facility was powered by 2nos 2500kva, 11kv/433v, Dyn11 transformers and 3nos 1500kva backup DG on a synchronous operation. The DGs were unable to power the facility's full load due to high Total Harmonic Distortions Voltage (THDv) arising out of the data center's UPS and blade server loads. The first option was to install a 4th DG that would have further reduced its load factor, and thus the harmonic distortions THDv, but its cost was high enough. The second option was decided and we installed 2nos 1000A tune variable harmonic filters for suppressing the data center generated harmonics and that solved all issues and in-addition saved 2.5% energy from the IT-company's monthly kWh consumption, which included building's all loads including data center, and in-addition air-conditioning, PAC, software development workstations, lighting, and utilities.
b. A renowned no.1/no.2, 5-star hotel group installed tuned harmonic filters at its incomer PCC and carried-out total power management and process optimization projects across several dozen hotels across India and abroad. We followed up with the results for a year's consumption before and after scenario, and could verify it for a few hotel locations. It saved 7.5% energy from the hotel's monthly kWh consumption.
c. We carried-out energy audits across dozens of renowned and no.1/no.2 Information Technology, Software Development and BPO companies, that including total power management and process optimizations for its loads. At several locations, those were done under performance contract, wherein we shared a part of the actual energy saving cost. We followed up with the results for a year's consumption before and after scenario, at each location, and verified in between 7% to 14% energy savings from respective facilities monthly total kWh consumption.
d. A Telephone Switching Exchange powered by a 725kva backup DG was facing cable lug burning and electronic card failure problems with its screw chiller control panel due to high harmonic distortions. It planned for new load addition and a second DG of capacity 725kva. We downsized the second DG capacity from 750kva to 500kva, installed one 500A tuned variable harmonic filter, and that resolved all failure issues. We followed up with the results for a year's consumption before and after scenario, and verified 4% energy savings from the facilities monthly total kWh consumption.
e. A no.1/no.2 soft drink MNC's cola bottling plant with major refrigeration load, was facing frequent tripping and electronic failure issues with its SIDEL blow molding bottling m/c and vfd drives in process loads. We installed 1no 700A tune harmonic filter, and carried-out total power management and process optimizations. Thereafter we followed up with the results for a year's consumption before and after scenario, and verified a whopping 11% energy savings from the plant's monthly total kWh consumptions, and in-addition it resolved all tripping and failure issues. With every tripping of the SIDEL blow molding m/c, the company used to lose all the in-process pet bottles/chips.
f. A large POP Internet data center with intercontinental fiber-optic cable landing station, and routing telephone and data exchanges, was powered by a sets of 2nos 2000kva and 1no 2500kva, 11/0.433kV transformers with equal numbers of matching DGs for backup power. It had 10nos each 400kva, 425v, 50hz UPS, and each was having an input active harmonic filter from the UPS OEM in believing that those resolves power quality harmonic problems. In-addition it has switching exchanges, air-conditioning, and other utility loads. Most active harmonic filters are installed in small sizes that in comparison to upstream transformer capacity that keeps its problem hidden. The real problem shows up when it is installed at full load capacity. It reported high incidence of nuisance tripping and electronic card failures with its POP internet equipment and switching exchange loads. Detailed power quality harmonic audit revealed very high voltage harmonic distortions and THDv was at 10% when all active filters were in ON, but reduced to below 5% once all those input active harmonic filters were switched off. The solution to this problem was simple; switch-off all the input active harmonic filters. In-addition, the switching-off measure saved considerable kWh energy cost saving. Active harmonic filters have an intrinsic kWh losses of in between 3% to 5% as per its OEM catalogue.
g. A renowned no.1/no.2 newspaper printing press was facing high incidence of electronic card failures across its presses located at three major metropolitan cities. Those were powered by a set of 2000kva, 11/0.433kV, Dyn11 transformers, depending upon the printing capacity of each location. The problem was diagnosed due to high harmonic distortions both current and voltages, and those were arising out from it automated process vfd/dc drives. We installed sets of 1nos 850A, and 5nos 1340A tuned harmonic filters at those three locations, and that resolved all problems across all three printing presses.
h. An IT/BPO company reported that few servers randomly trip and reset by itself. By a walk-through audit we found the problem was non-generic, and happening with any server at any rack, across the data center. We first checked data center earthing and found them good. The problem persisted and remained elusive for some time. Meantime both the UPS and Server OEMs analyzed the problem from their sides, and found no-issue with their respective equipment. We undertook a detailed Power Quality and waveform signature analysis study for a long duration of several days. The signature analysis captured that occasionally and randomly, the UPS MALFUNCTION for about a millisecond and then readjust itself to its normal state. That was enough to randomly trip few servers across the data center. The OEM then replaced the defective UPS cards and the problem got resolved.
i. We attended one UNUSUAL PROBLEM from a large Data Center of a MNC R&D telecommunication company. It reported infrequent but out-of-the-blue black-out of its entire data center. The Problem was elusive at first and then its required to be studied for a longer time duration. And finally, the root-cause emerged, which was equally unusual, ATS MALFUNCTION. Its rating was 2000A, 415V, and the problem was captured in the waveform signature analysis. These types of equipment malfunctioning do not last beyond a few milliseconds, are difficult to diagnose using conventional methods which can't detect such faults. Please refer to the "RARE EVENTS" at the Home page of our website for full reporting with this case study.
j. An IT/BPO company reported repetitive server tripping and UPS component failures. We found that UPSs were installed without output transformers and were running in parallel mode. A detailed Power Quality harmonic analysis revealed, during the intervening period between the grid power failure and the backup DG taking over, harmonic distortions shoot up, and that was the root cause of the problem. Once the was root-cause identified, the UPS OEM solved the issue by developing a compatible paralleling firmware for the UPSs.
k. A large multi-tenanted IT-park that rents its space for IT/BPO-companies reported computer monitor flickering problem, across one vertical block affecting several companies, which was beyond the comfort level for human eye. We found it due to EMI interference problem, and resolved it by installing appropriate sized space EMI shields.
l. An IT- software development company was facing a peculiar problem, that while powered by back up DG, the air-conditioning chillers were not getting switched on. After carrying power quality and harmonic analysis, we diagnosed the problem, and its root cause was higher harmonic distortions. We installed a tuned harmonic filter and that resolved the problem.
m. We had carried out large numbers troubleshooting and energy audit projects, during the economic surge period of 2003 -2008 for renowned and no.1/ no.2 styled IT/BPO industries, Hotel, Hospitals, Telecommunications, and many other green-certified intelligent buildings. It revealed very high energy consumption, and the SEC was even higher by 25% to 50% than the propounded green building code here. Many discoveries were also with our design audit verification findings, which revealed too many energy efficiency barriers were brought in from the initial project design and equipment specification stage itself.
n. On the several dozens of exclusive troubleshooting projects, involving both electrical and HVAC systems, we found several issues were attributable to the OEM on equipment deficiency. Many were grounding related issues, and few were EMI related problems, in particular those with monitor fluctuations, and we resolved those by installing appropriate sized EMI shielding.
o. We attended several problems related to nuisance tripping and computer/server reset, from several IT/BPO companies, manufacturing companies and corporate buildings. Many such problems were also attributable to grounding related issues. We resolved most of those problems by strengthening the existing grounding system by interconnecting or by putting-up a few earth pits. However, at locations, and in particular for larges servers/loads, we had to design and install grid earthing.
p. A 5-star hotel reported frequent component failures mostly with computer monitor and SMPS power supply. We found loose connections in the UPS output neutral supply, and that was the root cause of the problem.
To achieve highest Productivity: By Implementing TPM, it solves PQ and harmonics related issues, and enhance equipment life. Process Optimization brings out early maintenance needs with critical process equipment those are at the heart of an intelligent building. Such measures considerably improve Mean Time between Failures (MTBF) and enhance productivity.
To achieve highest Quality: For the IT-industry, telecom, hospital, R&D house, and POP Internet Data Center; implementing TPM considerably enhance service quality, or for that matter the least possible down-time. For Hotels, malls, air-ports, and similar facilities, TPM helps to achieve greater customer satisfaction.
To achieve Sustainability and maintain near UNITY PF: Intelligent Buildings employ variable loads, those also vary with ambient conditions, seasons, occupancy rates etc. In-addition, considerable loads are of nonlinear in nature due to which the conventional PF correcting capacitors degrade. In the post, tuned harmonic filter implementation scenario, wherein we implemented TPM, the PF steadily maintained at near UNITY level sustainably. Furthermore, the life expectancy of Encon tune harmonic filters are in the region of 40-years, and that ensures sustainability of all benefits those accrue with it.
Total Power Management and Building's Power distribution SLD, and typical Harmonic Distortion levels: Most intelligent buildings receive power from the grid/utility at 11kv/ 22kv/ 33kv/ 66kv levels and step it down to 415v at the main incomes PCC, using some sets of transformers as per its power demands, as shown in Fig.1. Few buildings set up their own electrical substations and employ grid transformer in between. Given here is a typical and broad Single Line Diagram that is representative for most buildings' electrical power systems. In-addition incoming transformers are backed up by appropriate numbers of DGs which runs either in island mode or synchronized mode.
This facility was facing high incidence of nuisance tripping and equipment failures with UPS cards, PC boards, hard disks, smps power supply cards, electronic cards involving vfd drives, PLC, control systems, and AC Motor failures, both vfd driven and fixed speed SQIMs. Harmonic distortions were high enough with THDv about 7% and THDi about 24% which resulted in bad Power Quality and high Harmonic Distortions. We installed 2nos each 1340A tuned variable harmonic filters across each of the 2000kva, 11kv/433v, Dyn11 transformers which catered for the full load of the facility.
The Problem with THDv is that it permeates through the entire electrical power system and thus affects all equipment connected within the same transformer supply. Furthermore, as waveforms get distorted, control and protection systems/relays mistake them as fault conditions and initiate tripping actions. For example, it could trip annunciating an over-current, under-voltage, or an earth-fault, though nothing like that seemed to have happened. THDv rises on four major factors, first the extent of total nonlinear loads in the transformer, second the transformer's load factor, third PF capacitors if used with nonlinear loads, and fourth the system impedance of the electrical power system at that load point, which is also the whole of 415v secondary PCC of the transformer.
THDi acts like a current source. Gets generated by the nonlinear loads at the downstream, and flows back to upstream, as it offers the least impedance path. Along the way it causes heating to cables, switchgears, capacitors, facility equipment, and the source transformer. Its effect causes energy losses and aging in the equipment. If THDi levels are high enough, it may overheat/ burn/ blast cable terminations, cable insulations, capacitors, switchgears, and the source transformer's winding insulation. Unlike THDv, it can't easily pervade to downstream equipment, unless through series resonance incident with the facilities electrical power system. In that event, it can cause good damage along its reverse flow path.
The current and voltage harmonic distortions, and waveforms at 415v transformer secondary PCC, are as shown in Fig.2, before installation of Tuned Harmonic Filter at one of the 2000kva transformers. Because of major nonlinear loads in the forms of UPS, computers, vfd drives etc., harmonic distortions were very high. The total current harmonic distortions (THDi) were at 24% with I5, I7, and I11 as major current harmonics. The total voltage harmonic distortions (THDv) were at 7% with I5, I11, and I7 as major voltage harmonics.
The current and voltage harmonic distortions, and waveforms at 415v transformer secondary PCC, are as shown in Fig.3, after installation of Tuned Harmonic Filter at one of the 2000kva transformers. The total current harmonic distortions (THDi) reduced to 3.5% with I5, I3, and I7 as major current harmonics. The total voltage harmonic distortions (THDv) reduced to 2% with I5, I7, and I7 as major voltage harmonics.
Process Optimisation: Every building has its own ways of installing its HVAC system, the air-conditioning and/or refrigeration installations. Those need adjustment for optimization, after installations, for the site-specific process parameters, and seasonal and ambient variations. The Pros and cons of those would merit for a separate case-study, but broadly, in this case study, our primary focus is on the approach towards removing the barriers to energy efficiency. Given below is a typical air-conditioning system that we optimized.
Capacity 2nos each 200TR, R -123, water-cooled
Type Centrifugal with 110kW motor with VFD
Operation Condition 2Runs in Summer/peak load durations and 1Runs otherwise
Chilled Water Pump 3nos. CHWP, 18.5kW, one each runs per chiller
Condenser Water Pump 3nos. CDWP, 15.0kW one each runs per chiller
Cooling Tower 2sets. 200TR CT, 7.5kW, one each runs per chiller.
How to remove, barriers to energy efficiency: After carrying out an Energy Audit that including total power management and process optimization, we had found following barriers and remedied them and realized 20% energy savings with the air-conditioning system. Air-conditioning energy consumption constitutes 60% energy PIE for an average intelligent building. Thus, net energy savings on the building's total kWh consumption was 12%.
I. Air-Conditioning, High Side, the Centrifugal Chillers
a. 200TR Chiller-1: Designed for 200TR at an efficiency of 0.55 IkW/TR. Measured load was 194TR at an efficiency of 0.67 IkW/TR. Efficiency loss found was at 22%.
b. 200TR Chiller-2: Designed for 200TR at an efficiency of 0.55 IkW/TR. Measured load was 167TR at an efficiency of 0.69 IkW/TR. Efficiency loss found was at 25%.
II. Air-Conditioning, Low Side, the Chiller Auxiliaries
a. Chilled Water Pump: Designed for 109m3/hr. flow capacity at 77% efficiency at its BEP head. Measured head was much away from its BEP point, and the flow was at 193m3/hr., with an efficiency loss of 28%. We trimmed the pump impeller, aligned its head and flow in line with its BEP specification, and that improved the pumping circuit efficiency, and also, the chiller's evaporator circuit efficiency.
b. Condenser Water Pump: Designed for 136m3/hr. flow capacity at 78% efficiency at its BEP head. Measured head was much away from its BEP point, and the flow was at 218m3/hr., with an efficiency loss of 21%. We trimmed the pump impeller, aligned its head and flow in line with its BEP specification, and that improved the pumping circuit efficiency, and also, the chiller's condenser circuit efficiency.
Detecting early maintenance needs, and enhancing equipment MTBF: Every equipment gives out early maintenance signals, those if attended early prevent future failures and costly break-down maintenance. Process Optimization helps detecting signals those act as a wakeup call. The ways and means of the diagnosing would merit for a separate case-study, which is beyond the scope in this case study. Broadly, those enhance MTBF; UPTIME for critical equipment, quality of service, and guest satisfaction levels. Listed below are summary of few early maintenance signals.
a. Occasional chiller hunting.
b. Higher pressure drops at the evaporator and/or the condenser circuits.
c. Purge pumps not effective.
d. Oil pump runs at boundary conditions.
e. If running at lower efficiency, the Chiller would deliver lesser TR output, not enough cooling, but could run at a higher current stressing its motor and switchgear.
f. If running at lower efficiency, auxiliary pumps would draw a higher current beyond its rated value stressing its motor and switchgear.
g. Pumps running near cavitation, which stresses its mechanical components, and that being a higher current operation, stresses its motor and switchgear.
Kanai Banerjee graduated in Electrical Engineering from Indian Institute of Engineering Science and Technology, Shibpur, India in the year 1983. Worked at Bharat Heavy Electricals Limited from 1983 to 1995, and thereafter until date, as a promoter at Encon Engineers (www.enconengineers.in/) in Bangalore.
His special fields of interest include power quality engineering, harmonic solutions, and manufacturing passive tuned harmonic filter and triplen harmonic filter, of all sizes, LV and HV, troubleshooting failures, energy conservation, electrical consultancy and HVAC engineering for setting up truly the green building and retrofitting large centralized HVAC projects.
A member and chartered professional engineer with the institute of engineers, India, a member at the Indian society of heating, refrigerating and air-conditioning engineers, ISHRAE and a member at the Canadian and American EMTP-ATP user group.
Date: 10th January 1997