#hvac Archives | Page 3 of 4

July 3, 2019 by Matt Hanson

The Thermal Expansion Valve (TXV) Explained

What you need to know about refrigerant flow

The Thermal Expansion Valve (TXV) is an important piece of equipment in the HVAC industry. The valve is used to control the amount of refrigerant released to the evaporator section. In this way it controls the difference between superheat and the current refrigerant temperature at the evaporator outlet. Therefore, This in turn keeps its saturation temperature at the current evaporating pressure stable. The Thermal Expansion Valve function is the control the flow of refrigerant into the evaporator in response to the cooling load. Additionally, TXV’s measure the superheat at the outlet and react to this by increasing or decreasing the amount of refrigerant flowing into the evaporator to try and maintain a constant superheat.

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June 18, 2019 by Matt Hanson

Commercial vs Residential HVAC Units

Learn the similarities and differences between commercial and residential units

Commercial and Residential HVAC units share many similarities but contain many differences as well. While some HVAC manufacturing companies produce units for both markets, others specialize in one or the other. The biggest differences have to do with size, and also whether the unit is a packaged or split system. Commercial systems are typically modular in nature, which makes them more flexible and expandable. These units are for business applications and can serve very large office buildings to small shops.

Many times, HVAC units are installed while the building is under construction which presents a problem later on. Eventually the unit will be in need of replacement. Commercial units because of their size and complexity usually require more highly trained technicians to install and service the equipment. These types of HVAC units are designed to serve multiple zones and is capable of providing heating as well as cooling to the building. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) sets Minimum Ventilation Rates in Breathing Zone standards as to how much fresh air must be delivered for the number of occupants in a given room. HVAC units are based on tonnage or CFM (Cubic Feet per Minute). While ASHRAE advises 20 CFM per person in a health club, libraries only require 5 CFM per each individual.

The Common HVAC Installation

HVAC systems usually contain an outdoor condenser section along with an indoor evaporator section. In a residential installation, condenser sections are mostly located on the ground and duct connected. Alternatively, in commercial applications the condenser section is usually placed on rooftops while the evaporator section is placed indoors. Both commercial and residential outdoor units can be susceptible to weather damage and vandalism. Residential units are also usually much smaller than commercial units but cannot be expanded. If more cooling capacity is needed, the unit must be replaced with a new unit. Companies that install HVAC equipment usually include both commercial and residential installs. Installers have a product line card where they sell HVAC units from several different brands.

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April 9, 2019 by Matt Hanson

Business Owners Guide to Commercial HVAC

When business owners are in need of a new or replacement HVAC system, there may be many questions that arise. First and probably most importantly is the cost. However, cost not only pertains to the price of the equipment, but to the installation cost as well. Equipment cost will vary from one brand to another and between companies performing the install. Since most buyers are usually not HVAC experts, they often defer to the expertise of the engineer or contractor and may not search or understand that there are alternatives.

When it comes to Commercial HVAC systems many can be quite large. Furthermore, in many cases they were installed when the building was under construction. Typically, an HVAC system consists of condenser section placed on the rooftop or outside the perimeter on the ground. While outdoors these units are susceptible to weather damage and vandalism. Next, the installation of an evaporator section takes place, usually inside a mechanical room where it cannot be easily relocated.

How Replacements can be Made Easier

Generally, HVAC units need to be replacement after just a few decades. However, replacing an existing unit can be a very involved process. Installers routinely tell building owners that replacing the unit would be a daunting task. To complete the retrofit installation, it is often recommended to remove some of the walls or part of the roof. The reason is although the old unit can be chopped up and removed, it is very difficult to get a replacement unit in the space. Additionally, a crane is often needed to hoist the replacement unit into place, especially if the height of the building is several stories.

The total cost of an installation is broken down into separate categories; labor materials, and tasks. Installation companies will compute hourly wage times how many laborers it will take to complete the change out. Other expenditures could include permits, insurance, supervision, warehouse, crane rental, and delivery.

The selection of the proper HVAC system is yet another consideration. Owners, architects, engineers, and contractors have the choice of chilled water, refrigerant direct expansion, packaged, air-cooled, water-cooled, and VRF systems. Will the system be a central or floor-by-floor method? Each of these will have pro and cons and can be one of the more difficult decisions to be made. Sometimes decisions are based on building codes. Historic districts usually have restrictions on placing units outdoors or on the rooftop.

There is a better way!

For retrofit installations, the design of United CoolAir (UCA) products helps avoid all of the unnecessary costs that can occur. This is due to United CoolAir’s design that involves a complete indoor installation. This factor alone saves the unit from weather damage and potential vandalism. Additionally, UCA units are built as modular units that fit through doorways, meaning there is never a need for expensive rigging or demolition of the building. UCA units can also fit into historic buildings, thus avoiding the aggravation of code restrictions. Additional permits or non-allowance for outdoor equipment. United CoolAir HVAC units not only save in installation cost but their units last longer over the competition.

March 20, 2018 by Matt Hanson

Dedicated Outside Air Systems (DOAS)

The late sixties, early seventies ushered a new era into many facets of our lives. The rising cost of oil and uncertainty of supply made it necessary to evaluate what we had taken for granted for many years. The October of 1973 Arab oil embargo sent oil prices rocketing while shortening oil supplies. This caused building owners/operators to search for more reliable, less expensive ways to heat and cool large commercial spaces. The solution it seemed was to create a sealed building envelope thereby limiting the amount of infiltration and ventilation air to the minimum.

National energy conservation measures called for a reduction of outside air to 5 CFM per building occupant from 10 CFM. Most experts incorrectly believed this would be sufficient ventilation to ensure adequate health and comfort. The reduction in expensive OA resulted in a large increase in occupant complaints traced to their time at their workplace. Symptoms included nose or throat irritation, headache, dry cough, itchy skin, sensitivity to odors, nausea, and eye discomfort. Sick Building Syndrome (SBS), as it became known sickened 221 people and killed 34 others at an American Legion convention in Philadelphia. Later discoveries concluded the contamination occurred through their air conditioning system.

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March 5, 2018 by Matt Hanson

Hotel HVAC Solutions

Many hotels and other high-rise buildings can develop indoor humidity issues causing high moisture levels. As a result, these problems can lead to damage to the building or discomfort to their guests without having the proper DOAS system into place. It is critical for business designers to implement cost-effective strategies to ensure their buildings are operating efficiently.

A proper DOAS system combined with interior conditioning strategies such as chilled beams or VRF systems can help control high humidity levels within a building. Preventing high indoor moisture is extremely important not only for the building but for the health of their occupants. The initial upfront could be a costly endeavor, however, the long term benefits of investing in a DOAS will far outweigh the short term cost.

Moisture Level in Hotels is Key

Moisture removal is the key component to optimal IAQ (indoor air quality) and occupant comfort. This can maximize the life of the facilities equipment and furnishings. The recommended range of human comfort (defined by ASHRAE) and desirable humidity level for interiors is around 65% relative humidity. Anything above 65% will yield the likelihood of microbial growth. One way to minimize the reheat energy associated with dehumidification would be through an energy recovery wheel (ERV). If you had an extremely hot and muggy day at 88°F and 60% RH, an ERV could reduce the outside air temperature down to 77°F and 60% RH.

Dehumidification often tends to be ignored because of the high cost and high energy expenditure of operating today’s buildings. Consequently, the lack of dehumidification in hotels can not only cause occupant discomfort but building damage as well. The best way to address this concern is to properly design a dehumidification system. Using a system with an energy recovery wheel is a great solution. Contact United CoolAir today and ask about how our Alpha Aire unit can meet all the needs of your building.