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By Paul Nalewajk

Why should a retailer perform post construction HVAC inspections?

Why should a retailer perform post construction HVAC inspections?

Post Construction Surveys are essential for the following reasons:

  1. Equipment, ductwork, piping, etc. are not always installed properly
    • Engineers and architects do not typically visit store sites prior to developing a design. If field conditions require that the installed system does not exactly follow the design drawings, the installing contractor makes design changes which may or may not be appropriate.
    • HVAC contractors and subcontractors can make honest mistakes.
    • Unscrupulous contractors and subcontractors will delete items from the work scope to increase their profits, or to reduce their losses, if there is no threat of a detailed inspection.
    • Sometimes, a general contractor will allow a subcontractor to make changes to the work scope in order to meet a budget price.
    • HVAC contractors may order or obtain equipment, which differs from the specified equipment.
    • HVAC contractors do not necessarily use skilled service technicians to perform the commissioning and start-up of new equipment.
  2. HVAC system deficiencies do not appear on the project manager’s punch list
    • Most HVAC system components are not visible.
    • It takes a great deal of specialized training to determine if the equipment was installed properly with the correct accessories.
    • Equipment operation can only be checked fully by a trained technician.
    • A system may be started up during the heating season and operate in a satisfactory manner, however it may not operate during the cooling season.
    • Many HVAC problems are only noticeable to laymen, and occupants when the system is operating under full load conditions.
    • Some deficiencies may not be noticeable to occupants, however they shorten equipment life, cause excessive energy usage, or affect indoor air quality.
    • Some deficiencies cause problems, which may not appear for years.
    • Project managers are not trained adequately to inspect HVAC systems.
  3. Examples of deficiencies found on post construction inspections of retail stores
    • Found that economizers were neither furnished or installed. Units would heat and cool, but no outdoor air was brought in for ventilation there was no ability to provide cooling using outdoor air. (A process which saves 25% of compressor run time.)
    • Found no toilet exhaust, but test and balance report shows toilet exhaust to be operating at 10% above the specified capacity. Found the duct to toilet exhaust fan blanked off below the fan. There is no way this fan ever moved any air from the bathrooms at this facility.
    • Found the contractor used unshielded cable between the thermostat and the remote temperature sensor. The thermostats would lock-up on an intermittent basis, not allowing a change of set point and causing continuous heating and cooling.
    • Found thermostats configured to use internal temperature sensors rather than remote temperature sensors. All thermostats at this location were responding to the temperature in the manager’s office rather than the temperatures within the conditioned zones. When the manager’s office got warm, the entire store got cooling. When the office got cool the entire store received heat.
    • Found two remote sensors wired to the wrong thermostats. When thermostat #1 called for cooling, the space served by unit #2 was over cooled, causing thermostat #2 to call for heat, overheating the space served by unit #1. This caused one unit to remain constantly in the cooling mode, one unit to remain constantly in the heating mode, the store to be severely uncomfortable, and extremely high utility costs.
    • Found contractor had energized compressors without opening discharge service valves, causing the head gaskets to be blown on 6 compressors. Start-up of equipment occurred in winter therefore store was heated adequately, and cooled adequately by the economizer.
    • Found a unit set flush to wrong side of the roof curb. Approximately 25% of the return opening in the bottom of the unit was open to the outdoors, causing the unit to bring in at least 50% outdoor air.
    • Found that the contractor had installed a 4 in waste vent below and within 3 feet of the outdoor air intake for a rooftop unit. The store staff couldn’t understand why the break room smelled like a sewer.
    • Found units circulating 50% of the specified air volume. The store was comfortable but the compressors were cycling off on low-pressure safety controls, and gas heat was cycling on and off on the high limit safety controls.
    • Found control transformers set up for 230 volts when actual line voltage was 208 volts. Units were operating fine, but during peak load days, drops in the utility line voltage would cause these units to drop out as the control voltage dropped below the minimum acceptable threshold.
    • Found no low ambient controls were installed. The unit was operating fine in mild weather, however the compressor would be destroyed if the unit were allowed to operate during winter.
    • Found that not all air outlets were connected to supply duct. One department of the store seemed too warm. The technician found that a 20-foot section of supply trunk duct was never installed, eight ceiling diffusers were not receiving any air, and the unit was discharging into the ceiling plenum space.
    • Found a roof curb was assembled wrong. One department appeared too warm and the roof membrane was billowing near one unit. The technician found that the wrong areas of the roof curb had been blanked off. The unit was discharging into the corrugations between the Q deck and the roof insulation instead of discharging entirely into the supply duct.

By Paul Nalewajk

Is there a rule of thumb that I can use that would tell me how many CFM’s an A/C would need per ton of cooling capacity?

Is there a rule of thumb that I can use that would tell me how many CFM’s an A/C would need per ton of cooling capacity?

Most packaged air conditioning equipment is designed for, and rated at, 400 CFM per ton. Typically, a 7.5 ton unit will be selected with a drive package that causes it to deliver 3,000 CFM against whatever resistance the ductwork and grilles offer. For example, the unit might be specified to deliver 3,000 CFM at 0.8 of an inch of static pressure.

While packaged equipment is designed at the 400 CFM per ton norm, most units are capable of operating at air volumes between 325 CFM per ton and 500 CFM per ton. As we increase the air quantity on a particular unit, three things happen:

  1. The total capacity the unit delivers increases.
  2. The sensible capacity of the unit increases.
  3. The latent capacity of the unit decreases.

For our purposes, latent capacity is the ability of the unit to lower the humidity or to remove moisture from the air and sensible capacity is the ability of a unit to lower the air temperature.

For a 10 ton packaged rooftop unit operating at standard conditions, consider the following:

Supply Air Quality Total Capacity Sensible Capacity Latent Capacity
3000 CFM 116 MBH 79 MBH 37 MBH
4000 CFM 123 MBH 90 MBH 33 MBH
5000 CFM 126 MBH 99 MBH 27 MBH

As you can see, the latent capacity varies more than 25%. This is extremely important today, when due to indoor quality issues we are forced to design for increased quantities of outdoor air. Typically, an engineer will specify the quantity of supply air and the capacity of the equipment based upon the entering conditions of the return and outdoor air, and the sensible and latent loads he is dealing with.

One exception to the 400 CFM per ton rule that you may encounter if your sites are restaurants is the treatment of make-up air. This is the air that is brought into your space to offset the air being exhausted through kitchen exhaust. Make-up air equipment is typically designed at 200 CFM per ton because the heat content of 100% outdoor air can be two times the heat content of a mixture of 80% return air and 20% outdoor air.

I find it curious that multiple contractors are claiming that your equipment has insufficient supply air at multiple locations. Unless there is a prototypical design flaw, insufficient supply air is usually due to dirty indoor coils, plugged filters, restricted duct work, or improper adjustment of the blower drive.

By Paul Nalewajk

What do we feel will be the biggest change in HVAC equipment in the next 3 to 5 years?

What do we feel will be the biggest change in HVAC equipment in the next 3 to 5 years?

Change of refrigerant type:

We are going to be forced to live with the phase out of Refrigerant 22. This is the refrigerant that has been used in almost all of the packaged air conditioning equipment manufactured over the last 40 years. It is also the refrigerant that is currently being used in most of the packaged equipment being manufactured today. Over the next 15 years, the production of R22 within the United States will be phased out completely.

Most manufacturers of packaged HVAC units are currently manufacturing equipment that uses Refrigerant 410-A. This is not simply a case of switching one refrigerant for another. Internal components such as compressors and metering devices must be redesigned to accommodate the new refrigerant, which operates at significantly higher pressures than R22.

Design of packaged equipment:

We We believe that the design of packaged equipment will change in response to concerns about mold growth and indoor air quality. More equipment will be built with plastic or stainless steel drain pans and these pans will have slopes built in. Manufacturers will give purchasers the option of having ultraviolet lights installed within the unit. These lights inhibit mold growth and allow coils to stay cleaner. We believe we will also begin to see more equipment manufactured with double-walled panels and that this trend will be partially driven by mall-required design criteria. If the interior surfaces of a unit are covered with sheet metal rather than with acoustic liner, it is less likely that mold growth will occur. New units will be purchased with factory installed variable frequency drives that modulate air flow based on load and save significant energy. New equipment will incorporate variable refrigerant flow strategies that allow the volume of refrigerant circulated to be modulated based on individual zone loads.

More components / complete units from Mexico and China:

We believe that we are going to see more of the components within packaged air conditioning equipment being manufactured in Mexico and in China. We also believe that in the near future we will see complete units manufactured in China. These units may be built for American manufacturers with Chinese labor and components, or we may actually see Chinese air conditioning manufacturers competing against manufacturers who currently produce the majority of the equipment for the American market today. While most people within the United States prefer to buy American, a 30% reduction in cost can present a serious challenge to national loyalty.

New types of equipment as factory option:

We believe that we are going to see more equipment manufactured with high humidity removal capability and more equipment ordered with demand ventilation as a factory option. We are currently living with the effects of requiring increased quantities of ventilation air in our buildings. High interior humidity and the inability to remove this humidity are the result. Manufacturers cannot change the physical laws that dictate how much moisture current equipment will remove from the air, but they are now making equipment available that is capable of dealing with increased ventilation requirements. New equipment will be installed with carbon dioxide sensor that will function to modulate the quantity of outdoor air introduced into a building based on indoor carbon dioxide levels. This will serve to reduce energy consumption and decrease the need for humidity removal.

Manufacturers to increase their product and stock greater quantities:

We believe that manufacturers of packaged HVAC equipment are going to be forced to increase their inventory of completed product and to stock this equipment in greater quantities in most metropolitan areas. “Proactive replacement” is the current watch-word, but the bottom line is that a large percentage of the existing equipment serving our stores will not be replaced until it fails. Unless a unit exists, in stock, the retailer is looking at a 3 to 6 week lead time to produce the unit. This is obviously way too long to leave a unit inoperative. The end user may have a national account and brand loyalty, but when he has a hot store, the replacement unit is going to be whatever the local contractor can purchase and install within a week. If a manufacturer wants the lion’s share of the retail replacement market, he will have to take the risk of holding inventory.

By Paul Nalewajk

What is desiccant wheel technology? In what environments are they most efficient and in what environments are they least efficient? Do they really work well?

What is desiccant wheel technology? In what environments are they most efficient and in what environments are they least efficient? Do they really work well?

Desiccant wheels are also known as heat recovery wheels. The main purpose of a desiccant wheel is dehumidification without the use of refrigeration. A typical packaged air conditioning system removes humidity from the air by lowering the air temperature below the dew point and allowing moisture to condense onto the fins of the indoor coil. As shown by the latent heat removal capacities mentioned in the answer to question #6, only 20% to 30% of the cooling capacity of a packaged unit operating at full capacity is latent. Up until the late 1980’s, this limited latent capacity was sufficient to remove the required quantity of moisture from the air required to ventilate most buildings in most geographic areas of the United States.

Two events have occurred that changed this situation:

  1. The first event was the realization by our industry that if the quantity of ventilation air introduced into a building was insufficient to dilute the contaminants produced within the building, the quality of the indoor air became unacceptable. It didn’t matter if the contaminant was carbon dioxide, caused by human respiration, or formaldehyde, due to the out-gassing of pressed-board furniture. Indoor air quality issues were exacerbated by the fact that many buildings had tightened their envelopes and reduced their ventilation due to the energy shortage of the 1970’s and the ensuing energy saving initiatives. In most cases, the solution to poor indoor air quality is to introduce additional outdoor air into the building to dilute the contaminants. It was recognized that current codes did not require sufficient outdoor air for ventilation in many cases. Therefore, the codes were amended to require significantly greater outdoor air quantities to be introduced into new buildings. ASHRAE 62-1989 is the standard that forms the basis for most of the new ventilation codes. As we introduce additional outdoor air into a building, we increase the dehumidification load on our HVAC equipment. As the load exceeds the latent capacity of the equipment, the humidity level within the structure increases.
  2. The next issue working against our packaged HVAC unit is the current mold phobia we are experiencing. We all know that increased humidity levels within a structure lead to an environment that encourages mold growth. To make matters worse, some engineers were attempting to deal with the increased loads that increased ventilation put on the HVAC systems by increasing the total capacity of the systems they designed.

Unfortunately, these systems were designed for a full load day, which very rarely occurs, and so the amount of time at which the units operated continuously at full capacity was minimal. When a unit is oversized in this manner, it tends to run so little at full capacity that it has minimal ability to remove latent heat. This causes the humidity level within the building to increase, further increasing the possibility of mold growth.

But what has this to do with desiccant wheels?

The answer is that if you are operating a building that requires a great deal of ventilation air, chances are that packaged HVAC equipment will not meet the moisture removal requirements. There are several mechanisms being added to packaged equipment today as factory installed options to allow these units to remove significantly more moisture from the air than a typical packaged unit. One of these mechanisms is a desiccant wheel.

One manufacturer claims that its desiccant wheel has the ability to reclaim up to 83% of the energy lost due to ventilation. If one assumes that 20% of a building’s HVAC energy usage is used to heat and cool ventilation air, we are still looking at a 16.6% possible energy savings using a desiccant wheel. This is without the added advantage of possibly reducing the total installed tonnage in a building and reducing the relative humidity levels to an acceptable range.

What does a desiccant wheel look like?

A desiccant wheel is basically a circular plastic or styrene disk with an extended surface that is impregnated with silica gel. Silica gel is the stuff that’s inside the little white bag that comes packed with cameras and electronic equipment. It’s placed there to absorb any moisture that enters the box. Obviously, if it removes moisture from the air in the box your camera was packed in, it can remove moisture from the air passing through your air conditioner.

How are desiccant wheels positioned and why?

The desiccant impregnated wheel is normally positioned so that half of the wheel is in the stream of outdoor air being introduced into the building, and the other half of the wheel is in the stream of exhaust air being removed from the building. The wheel is slowly rotated so that any spot on the wheel rotates through the outdoor air, then through the exhaust air, and back into the outdoor air. As the outdoor air hits the silica gel, moisture is absorbed by the gel. As the heel rotates, the moisture laden gel is placed in the exhaust air stream. The air being exhausted is conditioned air, so it has relatively low moisture content. This air regenerates the silica gel by absorbing the moisture from the gel. The regenerated gel is now ready to absorb moisture again as it rotates into the outdoor air stream. In some cases, the gel is regenerated by raising its temperature with a heater.

What environment(s) are desiccant wheels most efficient and do they really work?

Desiccant wheels do work. They are best applied where one must treat large quantities of clean, extremely humid, outdoor air. A school in a humid climate would be a perfect application. Large quantities of ventilation air are required. The occupancy is consistent, and the outdoor air stream, as well as the exhaust air stream, is accessible. Big box, retail, warehouse type stores are also a good candidate for desiccant wheels when they are located in humid climates. In this situation, a typical strategy would be to have one or two 40-ton packaged rooftop units with heat recovery wheels handle the complete ventilation of the space. The additional rooftop units could be ordered without any outdoor air options, assuming that the climate was such that economizer operation was not realistic. The heat recovery wheels would probably reduce the overall installed tonnage and electrical service requirements as well as provide dehumidification of the ventilation air.

Like most innovations, there is a downside. There is an increased first cost and space requirement for equipment containing a desiccant wheel. There is energy expended by the motor that rotates the wheel and by the increased resistance that the wheel and filters add to the air passing through the wheel. There is also the cost of maintenance, which can be considerable. There is usually additional filtering required. The wheel must be kept extremely clean. The seals that separate the wheel into the exhaust and the outdoor air sections must be kept in good condition. Requiring monthly inspection and cleaning of a heat recovery wheel is a real possibility.

We believe that the best strategy for dealing with ventilation air is:

  • Start with a team comprised of your design people, your mechanical engineer and your service company.
  • Discuss – prototypically – how much outdoor air is being introduced.
  • How much is being heated and cooled.
  • How much is exhausted clean.
  • Then work on a strategy to reduce the amount of air that is heated and cooled.

One example of reducing the required quantity of conditioned ventilation air is the use of kitchen hoods that use unconditioned make-up air ducted to the perimeter of the hood rather than conditioned air dumped into the kitchen, in front of the hood. Another possibility is demand ventilation where the quantity of outdoor air introduced into a space close to zero and is varied based on the carbon dioxide levels in the space or the number of people present. Then, after minimizing the quantity of conditioned outdoor air you are handling, speak with manufacturers about heat recovery wheels and other hardware, and the projected ROI.

By Paul Nalewajk

How Do You Evaluate a National HVAC/R Service and Maintenance Plan?

How Do You Evaluate a National HVAC/R Service and Maintenance Plan?

  1. Does the management company provide technical troubleshooting assistance for the contractor making repairs or diagnosing a problem?
  2. Does the management company assist both the Owner and the Contractor in the decision making process when considering alternate solutions for an existing problem?
  3. Does the management company police the contractors to make certain that the owner gets exactly what he or she pays for?
  4. Does the management company carefully review each invoice to make certain that the owner pays only for the minimum amount of work required to repair a system, or maintain a system at reasonable levels of efficiency and reliability?
    • What qualifications do the people reviewing invoices possess? Does an experienced technician review all invoices to determine the integrity of the work performed?
    • What qualifications do the people reviewing proposals possess? Does an experienced technician review all proposals for recommended or required repairs to determine if quoted amounts are real or inflated and if work is truly required?
  5. Does the service management company review the history of each location prior to authorizing a service call to make certain that the call is not a call back, and to make certain that the work should not be performed under warranty?
  6. Does the service management company allow the subcontractors to charge surcharges to make up for labor rates, which appear low?
  7. Does the service management company check the model and serial number of each unit where a compressor change is required to determine if the compressor can be obtained under the five year extended warranty?
  8. Does the management company check the cost of replacement parts with the equipment manufacturer to make certain that the cost of parts does not exceed the manufacturer’s suggested list price?
  9. Does the management company have the respect of the subcontractors and manufacturers within the HVAC industry?
  10. Does the management company claim expertise in multiple fields? Or only in the HVAC field?

The correct answers to these questions define quality service management and has provided the basis for the development of our national HVAC service company. With 45 years of experience designing, building, and servicing HVAC systems for large retail chains we have all of the skills, ability, and history required to solve any HVAC related problem.

Prior to our entering the national service arena, we operated and still operate a local HVAC service and contracting company. We developed a level of technical expertise which allowed us to operate then and now, as national troubleshooters for several retail chains. We also acted and continue to act as consultants developing prototype mechanical plans and lease exhibits as well as performing post and pre construction inspections.

This experience makes us unique in the national service market. We have the experience of actually performing the work we supervise, superior technical knowledge, personal relationships with every major equipment manufacturer, and for the cost of a plane ticket, we have the ability to send out one of our own technicians to inspect and or make repairs.

By Paul Nalewajk

What Are The Benefits of Instituting a National HVAC/R Service and Maintenance Plan?

What Are The Benefits of Instituting a National HVAC/R Service and Maintenance Plan?

  1. Greater Buying Power
    A quality national HVAC maintenance company has greater buying power and gets first priority service from its subcontractors than an individual retailer would, due to the volume of work the national contractor gives the subcontractor in any geographical area. Therefore the retailer receives faster response times, at the minimum rates possible, for a competent contractor in a specific area.
  2. Consolidation of Work
    A national HVAC maintenance agreement allows for consolidated invoicing of service and maintenance work, and transfers the functions of quality assurance, technical assistance, and follow-up to the national contractor. This reduces the overall costs of HVAC maintenance.
  3. Specialized Expertise
    In today’s world of specialization, allowing people with specialized training and experience to deal with complex technical issues obtains maximum efficiency and lowest cost. Specialization, volume, and experience allow the properly run national HVAC company to provide savings to the owner which amounts to substantially more than the mark-up of the service company.
  4. Increased Efficiency
    Increased comfort in a retail store leads to increased sales. No one stays in an uncomfortable environment out of choice. Less down time translates into maintaining a comfortable environment during a greater percentage of time over the life of a location. This translates into more sales over the life of the location, as well as better employee relations.
  5. Consolidated Reporting
    A quality national HVAC maintenance company can provide the facilities manager with the tools and free time required to perform his or her job. Consolidated, concise information, furnished to the facilities manager is a necessity. The facilities manager must distribute information to the stores and corporate management, as well as make decisions based upon the information he or she receives. The more easily this information is obtained, the easier the dissemination of information becomes. This information, including performance reports (used to determine how well the contractor is doing his job) can be downloaded from a third party web site at will. If the retailer prefers, all required information can be E-mailed in Excel format on an agreed schedule. The information transfer options available today can greatly reduce the time a facility manager spends doing rote work like data entry. This allows the facilities manager more time to “manage” his contractors, visit sites, and respond to requests from site managers.

By Paul Nalewajk

Why is Preventative Maintenance Necessary?

Why is Preventative Maintenance necessary?

Preventive Maintenance is essential to the proper functioning of HVAC equipment. If preventive maintenance is not performed regularly or if it is done haphazardly, the equipment will require extensive and costly repairs at a later date. This is not just a case of “pay me now or pay me later.” It is a case of “pay me now or pay me considerably more, later,” and lose reliability in the process. The following will explain the specific cause and effect between neglected maintenance tasks, the failures that result, and why preventive maintenance is necessary.

Preventive maintenance of HVAC equipment, of the types typically installed in retail stores, consists of several regular inspections each year. During these inspections, proper operation of the equipment is checked and verified, air filters are replaced, drive belts are inspected and replaced as required, bearings are lubricated, and heat transfer surfaces are cleaned. In addition, if the unit utilizes combustion of fossil fuels for heating, the burners will be serviced and cleaned during at least one inspection. All mechanical equipment is designed to operate within certain limits. A passenger car, for example, is designed to carry the weight of four occupants plus luggage, perhaps 1200 pounds. If you were to load that vehicle with 5000 pounds of weight, catastrophic damage would result. Similarly, if you operated a personal computer in a closed box for a length of time, it would burn up. The damage in both cases is a direct result of the equipment being required to operate under conditions that are far beyond the operating limits set by its designer and builder. Similarly, HVAC equipment also has certain design limits, and if not properly maintained, the equipment will exceed its design limitations with the result being catastrophic failure.

Why must we replace air filters?

Air conditioning equipment is designed to operate with a specific quantity of air passing over its indoor coil surface, typically between 300 and 400 cubic feet of air/per minute/ per ton of air conditioning. When air filters are not replaced at regular intervals, they clog and become coated with dirt. Similarly, the indoor coils get coated with dirt. This dirt blocks a portion of the air flow, which means that the amount of air passing through the unit drops below the 300 cubic feet of air/ per ton design limit, leading to catastrophic failures.

In the cooling mode, if there is not enough air over the indoor coil, the coil temperature drops. When the coil temperature drops below the freezing point, ice forms on the coil, which further reduces the airflow, which further reduces the coil temperature. The compressor within the unit is a pump, which is designed to pump a vapor. As the airflow through the indoor coil drops, there isn’t enough heat being removed from the air passing over the coil to vaporize the liquid refrigerant inside the tubes, which make up the coil. Therefore, instead of receiving a vapor, the compressor receives liquid refrigerant. This is commonly known as “liquid slugging”. The effect of “liquid slugging” is similar to the effect of pouring a liquid into the cylinders of an operating automobile engine. Because liquids are not compressible, the pressure within the cylinders exceeds the design limit of the cylinder, and the valves, connecting rods, pistons, or other internal components are destroyed. The units start out requiring that its filters be replaced. Now it needs a new compressor.

In the heating mode, low airflow leads to overheating of the heat exchanger. This tubular steel assembly separates the air being circulated from the flame and the products of combustion. The heat exchanger is designed to operate at a temperature between 120fF and 200fF. If the operating temperature exceeds theses temperatures, the heat exchanger oxidizes quickly and its useful life is reduced below the anticipated normal life-span, or the heat exchanger cracks and breaks. In either case, it makes far more sense to replace air filters regularly than to replace a heat exchanger costing thousands of dollars.

Why must we replace drive belts?

Loose or broken drive belts cause the same problems that dirty filters cause. This is due to the fact that they also cause the airflow through the equipment to be reduced below design limits. In addition, loose drive belts slip on the pulleys they are meant to drive. This wears the groove in the pulley so that when the belt is finally replaced, the new belt is ruined in a short period of time by the worn pulleys. Once again replace the $15.00 belt on a regular basis or spend $300.00 replacing pulleys.

Why must we clean condenser coils?

Equipment is designed to operate between certain outdoor temperature limits. Cooling and condensing of the refrigerant vapor is designed to occur with a particular volume of air flowing through the condenser at a maximum outdoor ambient temperature. (Usually 115°F) If the finned surfaces of the outdoor coils are fouled with dirt, the ability of these coils to transfer heat is reduced and the airflow through the condenser coil is reduced. When the ability to transfer heat is reduced, the operating temperatures and pressures of the unit increase. If the unit’s ability to dissipate heat is reduced, a unit, which may have been designed to operate at ambient temperatures of 115fF or more, may stop operating at an outdoor temperature of 90fF. Due to the reduced heat transfer capability, the operating temperatures and pressures within the unit exceed the manufacturer’s safe limit and the unit shuts down. If the unit does not exceed the manufacturer’s limits by enough to require a shut down, it will continue to run at reduced capacity and efficiency, and at an increased rate of wear due to the increased work load.

Why Inspect Relays and Contactors?

Electrical relays are designed to open and close a predetermined number of times with a particular current load, before the contact points are damaged to the degree that the relay requires replacement. If more than the design current is passed through this relay due to a motor working too hard, or low voltage conditions, the contact points overheat and become damaged. If the electrical contacts in a contactor (large relay) begin to get pitted, and the contactor is not replaced, eventually the compressor motor or the fan motor controlled by the contactor will burn up and require replacement. Once again, if we exceed the design limitations of the device, or its anticipated life span, additional damage is caused.

Why Must We Lubricate Bearings and Rotating Components?

Bearings and other rotating parts are designed to have a useful life span of hundreds of thousands of hours. However, this projected useful life is based upon the assumption that the bearings will be lubricated at appropriate intervals and that the bearing surfaces will not be overloaded due to vibration from defective drive belts or dirty blower wheels. If bearings are not lubricated regularly, they will overheat and seize. When this occurs, the bearings fall apart, and the blower wheel, shaft, and housing are destroyed. This is a prime example of a situation where inexpensive maintenance was neglected with catastrophic results.

Why Must We Check the Refrigerant Charge on a Regular Basis?

Sufficiency of refrigerant charge must be checked on a regular basis. A unit operating with an insufficient refrigerant charge can ruin its compressor via two scenarios. The unit icing up due to a low-pressure condition causes the first type of failure, causing the compressor to fail due to liquid slugging, as described before. The second type of failure is due to the fact that the compressor requires a certain quantity of cool refrigerant vapor to cool its motor windings. If the refrigerant charge is not sufficient, the motor within the compressor will overheat and burn up.

The scenarios described all cause damage to occur slowly, over a period of time, usually without being noticed by the occupants of the conditioned space until catastrophic failure has occurred. Compressors and indoor blower motors should last for 10 years if their design limitations are not exceeded due to poor maintenance or failure of another component. Without proper maintenance, a typical rooftop unit can ruin its compressor within 1.5 years.

Regularly scheduled preventive maintenance properly performed, in addition to lowering overall annual HVAC service costs, and reducing the number of emergency calls due to catastrophic failures, will also result in lower utility costs. Properly maintained equipment operates more efficiently.

Brinco Mechanical offers customized preventive maintenance programs designed to suit each client’s specific needs. Geographic location, type of retail facility, usage, and budget are all factors in setting up a customized program. Brinco Mechanical has developed individualized preventive maintenance programs for book chains, clothing stores, restaurants, schools, nursing homes, religious facilities, paper goods stores and hotels. Let us customize an agreement, which meets your individual requirements.