Wednesday, March 31, 2010

Common Sense Saves Energy Dollars with Facility Air Conditioning

Seasonal Energy Efficiency Ratio (SEER)

As air conditioning equipment nears the end of its useful life, building owners and engineers are faced with the task of specifying and purchasing new, energy efficient equipment. An understanding of the United States Department of Energy’s (USDOE) Seasonal Energy Efficiency Ratio is necessary if the correct choices are to be made.

The Seasonal Energy Efficiency Ratio (SEER) rates each model of air conditioning equipment based on the amount of energy consumed while providing a specific amount of cooling. The SEER is an improvement of the EER (Energy Efficiency Ratio) used in the past, with the new method measuring the energy use over a wide range of operating conditions.

The SEER is calculated by using the old EER and including a part-load factor. The resulting number, ranging from a low below 9.0 to a high of over 13.0, advises the purchaser of the comparable cost of operation between competing models. The higher the number, the more efficient the unit.

USDOE regulations require an increase in the SEER rating of equipment manufactured after January 2006.

According to USDOE estimates, a 10-ton high-efficiency rooftop unit meeting the new standard of 13.0, compared to a currently installed standard unit with a SEER of 8.9, would save the owner $1,950 over the anticipated 15-year life of the unit. This calculation is based on relative purchase costs of the two units and energy consumption based on a national average of $0.08/kWh.

Wednesday, March 24, 2010

More HVAC Help from our Expert...Gary Xavier. Coil Cleaning Procedures to Keep Your Facility Air Conditioning in Form

Trained building maintenance personnel can easily create a preventive maintenance procedure for the coils on each unit in the facility. Every coil should be monitored on a regular basis, and a cleaning frequency determined and added to the scheduled preventive maintenance tasks.

Cleaning of evaporator coils must be performed while keeping in mind that anything on the coil can enter the building air stream. Care must be taken to use only products that are specifically labeled for evaporator and/or chilled water coil cleaning. The use of general, multi-purpose cleaners may result in residue on the coil that attracts dirt, as well as contamination of the building air stream with hazardous, or simply annoying, fumes. Air conditioning and refrigeration suppliers typically carry a complete selection of coil cleaning products, and should be consulted for recommendations. And, there is a lot of information here.

Evaporator coils can often be cleaned by shutting off the fan and simply spraying the coil with the selected cleaning solution. Most evaporator coil cleaning products are designed to be rinsed off by the condensate formed during the unit’s operation, thus requiring no rinsing by the technician. While the unit is shut down, the filter should be cleaned or changed, and the condensate drain pan and drain inspected and cleaned if necessary.

For condenser coils, the cleaning solution chosen should be matched to the contaminants on the coil. Cleaning compounds are available in both acid and base formulations, serving different purposes. Acidic (low pH) products are generally recommended only if corrosion deposits need to be removed; while basic (high pH) cleaners are used for removing grease and most types of fouling.

Regardless of the cleaner chosen, strict adherence to the labeled directions is critical, including following the recommended dilution guidelines. Maintenance personnel must also be aware of the hazards of handling and use of all chemical products, and follow the manufacturer’s guidelines for protective equipment. Consult the product Material Safety Data Sheet (MSDS) before use.

Condenser coils should be cool before the cleaning procedure is started. Using the proper cleaning compound, soak the coil with solution while making sure that the cleaner penetrates the entire depth of the coil. After allowing time for the solution to loosen the soil, rinse the coil with water, rinsing from the back to the front if possible.

High pressure water may be used as long as the water does not bend the fins on the coil or is aimed directly on motors and electrical connections. If necessary, the motor can be covered with plastic prior to cleaning.

Once the cleaning solution has been completely rinsed away, a fin comb should be used to straighten any bent fins on the coil, and the unit returned to operation.

Tuesday, March 16, 2010

Another in Our Spring Air Conditioning Series...Evaporator Coils & Indoor Air Quality

In addition to increased operating costs incurred as a result of dirty coils, evaporator coils (as well as chilled water coils) are placed in the building air stream. Thus, any contaminants on the coil or in the condensate pan beneath the coil may become airborne, affecting the quality of the air in the occupied spaces.

In addition to changing the filters and cleaning the evaporator coil, care should be taken to ensure there is no growth of bacteria, mold, or fungus in the condensate pan. Condensate pans, because of the incidence of standing water, are prone to this growth. Maintenance procedures should include routine cleaning of the condensate pan and drain, and treatment, if necessary, with an antimicrobial agent. Pan treatments are available in tablet form for ease of application.

Legionellosis, commonly known as Legionnaire’s Disease, has been found in evaporator and chilled water condensate pans. This disease, which can be fatal to those with impaired respiratory function, is a concern of all building owners and engineers. Further information on the source and prevention of this serious problem can be obtained from ASHRAE.

Next, we'll discuss coil cleaning procedures.

Wednesday, March 10, 2010

Another in Our Spring Air Conditioning Series...

Cleaning Coils Doesn't Cost - It Pays!

Air conditioning and refrigeration coils must be clean in order to transfer heat as designed; dirty coils result in running a system longer and harder to accomplish the same amount of cooling.

Longer system running times obviously result in higher operating costs. In addition, as the system works harder the energy consumption increases, as does the wear on the compressor. This additional work appears as an increase in compressor discharge (head) pressure, which is detrimental to the unit’s operating efficiency. Keeping coils clean will result in overall energy savings, better performance, and longer equipment life.

The function of the coil, either evaporator or condenser, is to transfer heat. As the air moves across the coil, heat from the air inside the conditioned space is given up to the evaporator coil; and heat from the condenser coil is given up to the outside air around the condenser. Any material that insulates the coil surface, such as dirt, dust, lint, grease, leaves, and cottonwood seeds or other pollen reduces the rate of heat transfer and increases the operating cost of the unit.

Manufacturer’s studies suggest that dirty coils can increase energy consumption by as much as 35 – 40%.

Considering the cost of electricity at a nationwide average of approximately $0.08/kWh, and air conditioner operation based on average annual use, the increased energy cost for a 10 ton rooftop unit with dirty coils could exceed $ 350.00 per year.

System cooling capacity also decreases as coils become dirty. The coil is designed to allow a relatively high amount of heat transfer, which decreases as insulating dirt adheres itself to the coil. As this fouling occurs, system capacity may fall below what is required to cool the space.

For example, a dirty condenser coil on a rooftop unit may lower the system’s cooling capacity by as much as 30%, thus a 10 ton unit would have only 7 tons of cooling capacity. This capacity loss affects building occupants when they need the cooling most, that is, on the hottest days.

A cooling system’s life expectancy is shortened by increased pressure and temperature in the compressor, which is a direct result of a lack of coil maintenance. If the unit’s compressor has to work harder, as it does when pressures and temperatures get higher, the potential for chemical breakdown of the lubricating oil increases. As the oil degrades, loss of lubrication causes increased equipment wear, leading to premature compressor failure.

By comparison, cleaning of the unit’s condenser coil, a process taking no more than 1 - 2 hours and requiring very little cleaning material, may cost the building owner up to $50.00 per unit for labor and materials. The net savings thus amount to approximately $300.00, or $30.00 per ton of capacity. This savings will vary, of course, based on factors such as the unit size and type, coil condition, energy cost per kWh, and hours of operation per cooling season.

Tuesday, March 2, 2010

Air Conditioning: Common Sense Saves Energy Dollars

In keeping with our theme of saving money and managing in the economic re-set, our friend Gary Xavier weighs in with some timely advice on Air Conditioning. We'll have a few more of these topics over the next couple of weeks, just in time for cooling system seasonal maintenance.

Building owners and managers often hire a service contractor to perform repairs and maintenance on their air conditioning and refrigeration systems. While this is a viable option for buildings where the maintenance department is not equipped to fully service their cooling equipment, there are preventive maintenance items that can often be addressed in-house, which lead to better system performance, lower energy consumption, and more reliable service with fewer breakdowns – all resulting in cost savings to the building owner.

Filters, Filters, Filters

If a system has a filter, the filter needs routine attention. Air conditioning (comfort cooling) systems use filters to provide a modicum of cleaning to the air supply, and also to keep the evaporator coil form becoming loaded with contaminants carried in the air stream. Refrigeration systems most generally do not use filtered evaporator coils.

The filter’s job is to catch particulate matter and hold it, while still allowing air to pass through. As the filter holds more and more debris, however, the air flow is reduced, often to a point of virtual non-existence. Many air conditioning system problems can be traced to a dirty filter. As the filter plugs up, the lack of air flow reduces the amount of cooling occurring, resulting in a lowering of the efficiency of the unit. In addition, the unit must run longer to accomplish the task of cooling the conditioned space to the desired temperature, which it often cannot attain.

Dirty filters thus result in higher operating costs and more frequent system failures, both costing the building owner money.

Filter maintenance can often be performed by building maintenance staff even in situations where an outside contractor is used for system repair. Following the manufacturer’s specifications for filter type and replacement frequencies is important, as is establishing a reliable, consistent method of determining when each filter should be cleaned or replaced.

According to ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc.) standards, viscous impingement filters - the type commonly used in heating and cooling systems – should be changed when the operating resistance through the filter reaches 0.5 inches of water column.

Air-handlers are often equipped with magnehelic gauges to measure the drop in pressure through the filter, allowing the service person to simply read the gauge on a regular basis, and replace the filter when the pressure drop exceeds the recommended limit. Smaller systems, however, such as rooftop units and room air conditioners have no such mechanism, leaving the service person to decide if a filter change is necessary.

Small system filters are often changed on frequency alone, such as every 30 days; or on their appearance to the technician during routine maintenance. Most equipment manufacturers can offer specific guidelines for their systems, and filter distributors can often be of assistance in setting up a preventive maintenance schedule.