Hawaii Building Engineers Association

Chiller Efficency

Chiller Maintenance for Efficiency

Chiller plants represent up to 53% of the total energy used in a building and consume large amounts of electricity.  Chillers represent a substantial capital investment for our building and are a major contributor to operating costs in commercial buildings. For many buildings, chillers are the largest single energy users, and comprehensive maintenance is critical to ensure their reliability and efficient operation.

Building Facility Manager’s work with their contractors to operate at high standards of preventative, predictive and proactive maintenance in solving their chiller plant problems.  In addition to the daily, weekly, monthly and annual service requirements needed for their chillers, managers often include predictive maintenance in their maintenance plan to maintain the central plant. These predictive maintenance steps include vibration analysis, infrared thermography, rotor bar testing and eddy current testing. Each test helps to diagnose problems in advance. All preventive maintenance (PM) is geared to ensure the high performance and reliability of the chiller plant for everyday use.

Here are five simple things you can do to ensure a sustainable chiller plant.

Water Conservation

                                                    

Watergy by definition means “connecting water with energy.” In simple sense it takes a certain amount of electricity to deal with the water that we use. The connection can be seen when we turn on the faucet for hot water and the hot water tank must reproduce the hot water that was used. The water going down the drain must be purified and the cost to do so is billed back to us in the cost of the electricity and maintenance to perform that task. So what saves us more money turning off our lights or turning off our faucets? Given a scenario of five minutes of a faucet running would be equal to the cost of lighting a 60 watt light bulb, if not more. Water on Oahu needs to be conserved and we can do our part, by reducing our waste.  The Environmental Protection Agency (EPA) has come up with a program called Water Sense.  The U.S. General Accounting Office (GAO) has estimated that, even assuming non-drought conditions, at least 36 states will suffer some sort of water shortage by 2013. On Oahu the water shortage is expected to affect us by 2010. In an effort to promote water efficiency and help protect the future of our water supply, the EPA has launched the Water Sense Program that has been in effect since 2006. The program has found that the reduction in water is driven by the cost of building new wastewater plants and other projects to meet the demand for water. Taxpayers and users of water would be the revenue stream to provide new facilities and products to reduce consumption.  Demand side management is one means to reach their goal through the reduction of use and not utilize taxpayer’s money to increase the infrastructure. Regardless, the price of water is on the rise. With an estimated 7% - 12% increase annually.

AIR COMPRESSOR RUN TIME

Many building in Hawaii still have pneumatic controls systems or a hybrid system utilizing digital and air for controls. Many people do not know about compressor sizing and starts per hour. The compressor is normally sized to operate up to one half of the time to provide normal system air consumption. The air storage tank capacity is matched to the pump and is designed to give a reasonable number of cycles per hour. The storage tank provides sufficient storage capacity to carry peak air consumption loads. To determine the SCFM rating of compressors the load must be determined. The compressor should have a rated SCFM output of at least 33% or 50% of operation.

It may be necessary to determine the effects of sizing, pressure switch settings, and tank size on compressor starts per hour. Air compressors will specify maximum starts per hour. Some smaller sizes will specify no more than 12 while some larger models will enable 30 starts per hour. The minimum bleed off time should also be calculated. Then you can decide on other things like oil less, lubricated, single, or duplex compressors.

Run time testing should be accomplished because in many cases in some buildings the poor air compressors never shut off, due to leaks and improper air settings. A run test is an air compressor performance test that measures the percentage of time that a compressor runs to enable it to maintain a supply of compressed air to the control system. A run time test determines whether an air compressor is sized properly for the job. The run time test is performed under a normal compressed air load on the system. The length of time (in minutes and seconds) that the air compressor is on is measured with the length of time that the air compressor is off. The run time percentage is found by dividing the compressor on time by the compressor on time plus the compressor off time.  This number is multiplied by 100 to convert to a percentage. Use the following formula.

Future of CFC Chillers

The future of CFC chillers

Despite CFCs being banned in new equipment since 1995, many CFC chillers are still in use. The Montreal Protocol mandated that all chillers operating on outlawed CFC refrigerant be replaced or reengineered for refrigerant change outs by 2010. How ever the size and cost of a chiller puts replacement out of reach and will be every ones last thing to do. The time, money, planning, and possible building modifications required to replace a chiller is over whelming in some cases. When it comes to chiller replacement, the cost can be $200 per ton for equipment and another $100 per ton to install it. Often with a lengthy payback and not to mention the prospect of a helicopter lift or crane lift from a 30 story building.

            Building owners with aggressive preventive maintenance programs find that their chillers are working fine and can in some cases extend the life cycle for a chiller. Eventually the equipment must be overhauled and a decision must be made to repair or replace. Chillers today are lasting longer, leaking less, and keeping the building occupants comfortable. Run it into the ground or replace it is the question that owners face. Especially if a trouble free chiller would cost $120,000 to replace it, the economic argument run it till it quits. Chiller maintenance costs are low in comparison to purchased equipment costs and in many cases provide a better return on investment.

           Motivating factors to change out a chiller would be based on forward thinking to replace before a major breakdown or to provide a better level of service. Are the service frequencies going up? Are the efficiencies going down for the equipment and it costs more to operate? Are their still technicians available to work on the older equipment?

            Capacity reduction will occur with older chillers when the refrigerant is changed out. An old R-11 machine will be replaced with R-123 and capacity will be reduced because of the refrigerant characteristics. Before you know it a $50,000 conversion will be half the cost of a new chiller. New refrigerants will eat up the motor linings, and gaskets of the machine. If you wait to long the disposal of expired refrigerant will carry a hefty price tag. Today you may receive a credit tomorrow you may have to pay. R-410A and screw chillers are the rave and the other choices are still R-134A and R-22 chillers.

I would sat that about 40% of chillers will replaced by 2010 and all the rest will be changed out as a last resort and come with a hefty price tag. Please respond to me if you have any comments on this topic. 

A SIMPLE WAY TO BALANCE AN AIR SYSTEM

When a building has been properly air balanced, the primary evidence to the occupants is that the rooms are all the same temperature. If you’re in the field without your air balancing hood, one way to test a building is to check temperature balance.The test procedure is quite simple. Test the temperatures in each of the rooms. If they’re all within two degrees of each other, the building is balanced. That’s it in the proverbial nutshell.

Of course, you must expect that The Doc is going to tell you there’s more to it than that. I will not disappoint you! So let’s take a closer look at a temperature balance and see how it really has to be done in the field.

Reverse Engineering

In the beginning heating ventilation and air conditioning system were designed the same. Mechanical systems that were ineffective were created. Complicated designs of the systems by engineers to meet the requirements of the architects were the norm. The architect and owners wanted less space and good looks.  This resulted in large systems crammed into small spaces.  In the early 1980’s the systems were energy robbers and as the years passed, the systems did not get any better. Big motors to overcome the resistance created by the small ducts consumed great power. What is the status today? The older system have been modified to adapt to modern ideas. The operating personnel are understaffed and under trained. The fact is the asset is a fat pig that needs to be constantly fed. To optimize our HVAC systems we need to understand the original design intent. Hard to do when people retire or pass away. Reverse engineering is usually the answer. Utilizing the rule of thumb for troubleshooting will help determine the current condition of the systems. New load calculations can help and CFM values can then be determined. Measurement and verification studies are essential to solve the problems associated with poor design. Whose fault is it anyway? We are stuck with it until the day that the plans are stamped with the statement of “design intent” explaining what the system was designed to do in the first place. Many engineers today have no field history and are thrust into the mechanical workplace based on their book learned knowledge. The reality is they can design anything but they would not know how to turn it on.

Maintenance

A driving lesson for operations and maintenance

An Article about Maintenance Planning & Scheduling Meetings

Picture this. Personnel from a plant are driving along a road in an automobile. The maintenance manager is driving blindfolded. Sitting beside the maintenance manager is the mill manager who is peering in the rear view mirror. In the back seat, the production manager is urging the maintenance manager to proceed at top speed while simultaneously warning him about a flat tire.

This situation is obviously out of control. In a plant setting, it is equally out of control. Plant management frequently focuses on past data analysis rather than future improvements. Maintenance is often “blindfolded” due to tight short-term cost control measures instead of long-term results. Meanwhile, the operations group is becoming desperate and therefore dictates what maintenance should do.

Standards, Assessments and Audits

The buildings in this country are aging much faster than they are being replaced. This means that these buildings and their components are expected to last longer, much longer, than their planned useful life. Consequently, many of these buildings are or will be pressed into services for which they were not designed. All of these factors and others as well, will increasingly stress our facilities and their infrastructure and place even greater demands on maintenance professionals to deliver more value for each repair and maintenance dollar. To meet this challenge, up to date condition status of the buildings, equipment, and systems must be continually assessed. In this evolving arena, the best weapons any facility manager can have are current condition knowledge of the processes by which buildings and their equipment and systems interact, skillful use of the repair/ replace model, knowledge of when and how to apply preventive and predictive maintenance, and most of all, avoidance of inappropriate measures taken because the problem was misunderstood.  It would be easy to predict a catastrophe if the foregoing processes were allowed to reach their conclusion. However, catastrophe is not an acceptable outcome, so ways must be found to counter trends happening in the facility management environment. Facility managers are stewards entrusted with maintaining and operating the organization’s physical assets. As such, they must ensure that the funds they are allocated are efficiently and wisely used. The bottom line is that they need to get the “biggest bang for the buck” while supporting the overall mission of the organization.

Article II

Article II

Troubleshooting air conditioning systems is a problem that happens each day. Following a standard procedure helps solve the problem quicker and satisfies your tenants’ problems. When troubleshooting an air handler we must look at many things; these include proper air flow in cubic feet per minute (CFM), proper water flow in gallons per minute (GPM), and the Delta T (difference in temperature) between water and air flows.

Many times a technician will take an infrared temperature reading of an air terminal to diagnose a problem with the temperature leaving a diffuser. In this article we would like to help you to determine the proper CFM of a unit and the proper water flow. In doing, so we hope to help you find other ways to diagnose an air conditioning air handler.

As a reminder to the novice engineer, the 2.4 and 3.0 gpm/ton figures are derived in the following manners:

Formula; BTUH = gpm x range in degrees F x 500

Where; 500 = 60 min/hr x 8.33 lb/gal of water

Q = 500 X GPM X DT, Therefore
Gpm = Q / (500 x DT)
DT = 10 degrees

In the cooling mode; Q = 12,000 Btuh/ton, therefore the chilled water flow = 12,000 / (500 x 10) = 2.4 gpm/ton

Today, many chillers are being manufactured to meet different requirements. Contact your chiller manufacturer to verify the recommended Delta T through your chiller.

A rule of thumb for determining Cubic Feet per Minute is (400-450 cfm per ton)

So a 9,300 CFM air handler could be said to be 23.25 tons or 20.66 tons.

Other things that may be used with these formulas are to find the correct valve sizing for a unit by finding the flow coefficient of the valve. www.deltacp.com can help you to size the correct valves during replacement.

Troubleshooting comes down tom is the system supplying the correct temperature water, is there an exchange of heat to the passing water, and is the air handler delivering the proper amount of air?

In the following article by Rob Falke, he talks about measuring duct loss in five minutes. I hope you enjoy the article.