Ductless or Mini-split systems continue to grow in popularity because they are a great choice when seeking comfort cooling or heating spaces such as offices, lobbies or windowless rooms. This type of unit is usually wall-mounted and paired with an outdoor condensing unit and avoiding duct work makes them more energy efficient as well. The Mini-split systems can be easier to install requiring just a small hole to be drilled during installation leading to reduced problems with security or leakage. When it comes to routine maintenance such as cleaning filters the ductless systems are much easier to access than many conventional AC systems that may be in a crawl space or other difficult to access area. Occupants enjoy the control of being able to enjoy different comfort zones such as producing cooling in one room and heating in a neighboring space. The United CoolAir “CoolSpot” model is another great alternative to accomplish the goals of the ductless system but installed as a packaged unit instead. At 1–3 tons of capacity, this ductless ceiling grid self-contained air conditioning system is offered as an air-cooled, water-cooled, chilled water or Magna cool precision cooling package. The CoolSpot fits easily above the drop ceiling, replacing a tile panel, and provides even air distribution through adjustable louvers and is well suited for laboratories. Additionally, there are considerable cost savings with the CoolSpot compared to conventional ductless split systems on the market.
IAQ is a major concern and can have a devastating impact on your life. Not providing the proper ventilation and fresh air in an occupied space can not only make people sick but can also have a major financial impact. Hundreds of schools annually are experiencing mold in their classrooms and as you can see in the article below (Mold Case Study) a state office building in Texas experienced just this situation. The cost to the state of Texas was over $15,000 dollars but it also sent staff home which has an impact on productivity as well as financial cost.
United CoolAir has an IAQ Product designed to provide fresh air to avoid mold growth. Alpha Aire is a packaged Dedicated Outside Air System, Air Source Heat Pump with both an Energy Recovery Wheel and Plate Heat Exchanger that brings in fresh air at very low dew points while exhausting the interior space air to the outside. Follow the link below for more information on this revolutionary product.
Please feel free to contact United CoolAir at (717) 843-4311 if you have any questions.
Variable-air-volume (VAV) systems with air terminal units have been used extensively in commercial and institutional buildings in the United States for decades. Unfortunately, the optimized design of a VAV system with terminal heat is difficult at best because of limitations inherent in VAV and complications posed by design standards and regulations. One new approach involves the pairing of a dedicated outdoor-air system (DOAS) with a variable-refrigerant-flow (VRF) system. By separating the goal of achieving ventilation rates from the goal of maximizing thermal comfort, we can avoid situations in which the two goals are in conflict and efforts suffer from the resulting compromises. What’s more, we can simplify the design process and find system efficiencies that go far beyond those commonly achieved with VAV systems with terminal heating.
In the simplest VAV system, incoming outside air and return air are mixed in a central air-handling unit (AHU) and then pre-heated or pre-cooled. The tempered air is sent by a supply-air fan to various occupiable zones at a temperature generally suitable for cooling. In each zone, a terminal unit adjusts airflow based on cooling demand. When a zone requires heating, supply-air flow usually is reduced to a minimum setting and heated, typically via a terminal-unit heating coil.
In its simplest form, a DOAS is an AHU dedicated to ventilation, not sized to provide cooling air. DOAS often are supply-only systems with relief to outdoors; however, they also can include exhaust heat recovery. Generally, they are not sized to provide 100 percent air economization (cooling using outside air in lieu of mechanical cooling).
VRF systems use individual high-efficiency fan coils in interior spaces in combination with high-efficiency condensing units that can serve multiple zones. VRF systems can be arranged to provide energy recovery, moving heat from zones requiring constant cooling to zones that sometimes require heating.
ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality, provides minimum outdoor-air-flow requirements for design conditions. ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except for Low-Rise Residential Buildings, meanwhile, requires some systems to be operated so ventilation capacity modulates to match ventilation load (i.e., demand). Designing systems to meet both of these requirements is complex.
To help match capacity to load, ANSI/ASHRAE Standard 62.1 allows “dynamic reset,” but leaves the details to the designer. A common approach combines system-level outside-air-damper reset with zone-level demand-control-ventilation (DCV) strategies. For VAV-system energy efficiency to be maximized, the system-level intake/exhaust/relief-damper-reset sequence for space-temperature control and building pressure must be coordinated with an air-economization-reset sequence. Such controls can be quite complex, particularly when pressurization between zones and interaction with exhaust systems also requiring variable-volume control are considered. Weather conditions also can have a major impact on building pressurization and space ventilation.
Other common control sequences for large VAV systems include occupied-hours control, optimal start/stop, fan-pressure reset (“critical terminal unit” control), “ventilation optimization”1 (DCV), ventilation space-temperature setback, supply-air-temperature reset, dynamic space-pressure control, economizer, energy recovery, natural ventilation, and interfaces with building lighting controls, smoke detection, fire alarms, and even security systems. The interplay between these control schemes vastly complicates efforts to optimize building energy use.
Further complicating VAV-system design is the need to follow the ANSI/ASHRAE Standard 62.1 ventilation-rate procedure, which asks designers to use the multiple-space equation (MSE) to calculate the “critical” zone, the space driving the overall (system-level) outside-air fraction. Zone-level flows then are changed to meet zone-level requirements. Once the critical zone has been chosen, heating-turndown requirements push designers to over-ventilate some zones by increasing heating minimum settings. This typically changes the critical zone and reduces the overall outside-air fraction at the central-system level, substantially affecting AHU components.
To respond to changes in zone population, dynamic reset of VAV systems, combining zone-level DCV with system-level ventilation reset, often is applied. Ventilation reset is a control scheme by which the MSE is solved dynamically to change system outside-air setpoint. This often is applied with airflow-measuring stations, along with electronics and software to control dampers based on relative airflow, at the central system.
Central-system design usually is based on the static-condition (design) critical zone, while in the real world, zone population varies dynamically along with building HVAC load (internal and weather-related) over the course of a day. Maximizing energy efficiency under these conditions pushes the envelope in terms of building system design and building-operation hardware and software. Some commercial software packages can aid ventilation reset, calculating critical ventilation zone per ANSI/ASHRAE Standard 62.1. Calculating the minimum system outside air, however, usually requires the overriding of some terminal-unit turndowns, which changes the critical zone. This is allowed by ANSI/ASHRAE/IES Standard 90.1 because only a few zone overrides can change a system outside-air setting by many percentage points, saving considerable pre-treatment energy and reducing central-system size. Meanwhile, inputs to these calculations vary with system load, which also can change the critical zone. At the same time, other overrides, such as of supply airflow for makeup to areas with exhaust flows exceeding ASHRAE minimum rates, are necessary. These overrides and simultaneous variations result in the need for iterative calculations involving all environmental variables; such calculations currently are beyond the scope of commercially available software.
Zoning is another limitation. History shows building-construction economics can drive VAV-system designers to combine up to several rooms on a single ventilation and temperature-control zone. Because heating and cooling loads can vary widely between rooms on a single zone, this often leads to discomfort in certain rooms when other rooms on the same zone are not at the design load.
In summary, designing a VAV multi-zone HVAC system can be challenging to say the least. Overlaying the various requirements, exceptions, and system functions results in iterative design simulations that must be re-run whenever a room’s size changes. Complying with all codes while addressing the competing interests of ventilation and energy optimization is theoretically possible,2 and technical solutions partly exist and are being developed. But in practice, designing and redesigning systems with complex, iterative calculations is not very practical, and manual overrides generally do not fully optimize system designs. Meanwhile, designers often estimate “block” (net) load based on building-envelope heating and cooling, considering neither variations in internal and ventilation heating/cooling loads nor airflows needed for ventilation and space pressure control, significantly undersizing or oversizing systems as a result.
Fortunately, a design paradigm is emerging to compete with the old VAV model. This new model can reward us with simplified system design while letting us achieve the increased system efficiencies that energy costs are demanding.
The rapid increase of the cannabis industry within the United States creates a critical component needed in these facilities which is the proper HVAC equipment. Unlike most plants that are grown outdoors, marijuana is most often grown indoors which can be very tricky. It is critical that their HVAC needs are focused on cooling and dehumidification.
There are six main challenges that one will face when determining an HVAC system for a grow facility. Those six challenges are temperature, humidity, lighting, airflow, ventilation, and smart technology. Grow room facilities typically need to be between 70°F-75°F with humidity between 50-60%. Your HVAC system should be able to maintain the specific temperature need to ensure growth for the plants along with quickly removing any additional humidity that may arise during the watering process of the plants. The lights needed in these facilities also produce a large amount of heat, therefore, needing a strong HVAC unit to keep the rooms cool and prevent overheating. Airflow is critical and your HVAC system should provide enough to create a “natural like breeze” to ensure the plants have constant movement and vibration. Your HVAC system also needs to provide an extensive filtration system to ensure no smells are leaked to the outside along with the ability to capture all dust and sediment to prevent mold spores from occurring. And most importantly, your grow room cooling unit must have smart technology in order to control all of the above mentioned or alert you if something goes wrong.
When it comes to selecting your HVAC unit for a grow room facility, you need to think of United CoolAir. United CoolAir can manufacture exactly what you are looking for in order to create a successful grow room. We have both the expertise and experience to provide you the best operational equipment in the USA.
The late sixties, early seventies ushered a new era into many facets of our lives. The rising cost of oil along with the 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, causing 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 believed this would be sufficient ventilation to ensure adequate health and comfort, but they were quickly proven wrong.
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 was later known, caught the public’s attention with the sickening of 221 people and death of 34 others at an American Legion convention in Philadelphia through contamination in their air conditioning system.
Many studies have since proven beyond a doubt and established links between indoor air quality and human illness. When you consider the economic impact through lost productivity, lawsuits and increased insurance costs, building owners, HVAC design engineers, and operators all take this issue very seriously.
Outside Air is the Answer
ASHRAE Standard 62.1 – 2013–Ventilation for Acceptable Indoor Air Qualityforcommercialbuildings— quantifies the minimum ventilation rates and indoor air quality that will be acceptable to human occupants.
62.1 intends to minimize the potential for adverse health effects and has increased average ventilation rates from 5 CFM/person up to 20 CFM/person.
As a result, greater amounts of outside air must be introduced to the space, which also affects humidity levels. Humidity control becomes particularly important in the eastern half of the United States where mean dew point temperatures are 60°F e.g., 78°F/54% relative humidity, and higher during the summer.
These issues influence the need for an HVAC unit design capable of controlling ventilation, moisture levels and temperature in the space. To rectify the problem, traditional central station comfort cooling air conditioners must be “oversized” to handle peak latent load. To attempt to meet the new ASHRAE ventilation standards, a traditional air conditioning system generally requires 20%–70% more outside air than it was designed to cool, heat and dehumidify. Also, the traditional central HVAC must be set to provide the proper amount of outside air for the space with the greatest ventilation requirements. This ultimately causes over ventilating the rest of the building in the process and increasing the cost of conditioning that air.
Adapting DOAS Unit To Your HVAC System
There is a proven method that will meet the challenges of complying with the ASHRAE Standards, delivering precise amounts of ventilation to spaces regardless of load size, and do it cost-effectively.
Known specifically as a Dedicated Outside Air System, or DOAS HVAC unit, the outdoor air is conditioned separately from the air that controls the building’s space temperature (dry bulb). By having one system to provide and dehumidify all the ventilation air and a second system to control the space dry bulb temperature, both humidity control, and space temperature control are improved.
By conditioning the outdoor air and recirculated air independently, a DOAS unit effectively separates the sensible and latent loads. The outdoor-air DOAS unit removes the latent load to control humidity, and the main HVAC unit removes the sensible load to produce a comfortable temperature. This is important because the primary source of building humidity in most climate areas is fresh outdoor ventilation air that has not been properly dehumidified. Additionally, the DOAS unit can assist the main HVAC unit by controlling smaller internally generated amounts of latent load that naturally build from occupants and other sources. It does this by providing air that is slightly drier than the target humidity level. Generally speaking, a DOAS provides “neutral” air of 70ºF to 72ºF @ 50% RH.
If desired, a DOAS unit can also provide the dehumidified air directly to the space at 55°F where it will offset some of the sensible load of the local HVAC unit. By delivering the air “cold”, this operation strategy doesn’t waste the sensible cooling byproduct performed by dehumidification but allows the local heating/cooling units to be sized smaller and requires less valuable floor space. A smaller main heating/cooling system means less energy consumption through smaller fans and compressors. A DOAS delivering cold supply air requires less reheat, but some reheat may be needed during periods of low sensible loads so the space is not “over-cooled” by the DOAS unit.
A DOAS doesn’t rely on totally new technology, but rather uses HVAC equipment configured to condition outdoor ventilation air separately from return air. The outside air conditioning system design consists of a cooling/dehumidification-reheat coil and supplemental heating system. The deep evaporator coil’s consist of 10 fins per inch/6 rows deep design, positioned in the draw-through air flow arrangement that provides the most effective moisture removal efficiency. It is this technique that differentiates it from conventional HVAC systems. This configuration will cool and dehumidify air in the summer and heat or cool it in the winter.
The operation is simple in design with the outdoor air first passing through an optional preheat coil (if used), which is sometimes used for winter operation. When a heat exchanger is used, it brings the outdoor air closer to the temperature and humidity of the conditioned exhaust air.
A DOAS unit provides design engineers with installation flexibility to meet the requirements of the application. Variables facing the engineer include, but are not limited to, if it’s new construction, retrofit or an installation having an existing system in place. Other considerations include the type of new or existing HVAC system installed such as constant volume, VAV, and even the newer variable refrigeration flow (VRF) terminal units.
Delivering the conditioned Outside Air from the DOAS unit to where it’s needed usually includes a separate ducting system running parallel to the HVAC supply air. For many climates, an independent duct system is considered the best choice because the ventilation air volume better meets the volume requirements of the project, and the DOAS ducting can be smaller than the conventional HVAC saving on the installation cost. Smaller ducting is also easier to manage in retrofit and existing HVAC installations.
A popular alternative ducting choice is a single duct system where the conditioned Outside Air is blended with return air from the main HVAC system in a mixing box, or in a terminal unit that serves just one zone. If using a multi-zoned HVAC control system, individual zones are controlled separately and the DOAS will deliver the proper amount of outdoor air directly to each zone. In all cases, the DOAS system can vary the fraction of ventilation to supply air, which can reduce the outdoor airflow rate by 40 percent by conditioning only the amount of air necessary for each zone.
DOAS and VRF
The choice of installing a DOAS, especially if the existing HVAC system already includes provisions for Outside Air, is for operating efficiencies and the need to meet ventilation code requirements or occupant comfort. But we are now seeing new cooling technology being specified that has no provisions for Outside Air and requires a dedicated outside air system for this purpose. One of these systems is the variable refrigerant flow (VRF) system.
Japan introduced the variable refrigerant flow technology in the 1980s as a flexible way to condition spaces without the complexity of large HVAC systems that require bulky mechanical rooms and expensive ducting. As technology improved, the American market embraced VFR systems but to a lesser degree.
Today’s VRF units offer the building owner/manager many benefits including low first cost, simple installation, minimal maintenance and the ability to run multiple evaporator units from a single condensing unit. But with all its benefits, VRF systems have limited to no ability to satisfy ASHRAE ventilation requirements or remove excess latent loads typical of certain geographical regions.
With rising energy costs and expanding energy consumption awareness, it’s no wonder variable refrigerant flow technology continues to gain ground in the U.S. marketplace. VRF has the potential to achieve significant energy savings compared to older HVAC systems, according to a study by the U.S. General Services Administration.
Reports going as far back as 2012 indicated the U.S. market was estimated to be worth over $7 billion for VRF systems. More recent estimates of the U.S market indicate a compound annual growth rate of 5.2 percent is expected through 2019. You can expect the sales of DOAS systems will grow as much if not better to match the upcoming surge in OA units.
Not All DOAS Systems Are Built Alike
DOAS systems are an ideal choice for new construction, retrofit installations or adding to your existing HVAC system to improve performance. Traditional HVAC rooftop systems require adequate space for the air handler location and ducting large enough to handle both the ventilation/supply and return air. A DOAS is an ideal unit to handle the latent load requirements for OA requirements and dehumidification while the existing HVAC system manages the sensible load.
A DOAS system is ideally suited for retrofit applications where the new HVAC system (air handler and DOAS) must work within the confines of the existing space. The original HVAC system could have been installed in one of many configurations, requiring the design engineer and contractor to manage challenges as needed. Some manufacturers of DOAS units like United CoolAir Corporation have taken this serious problem into account and designed their units with special features to overcome even the most perplexing installation challenges.
United CoolAir’s DOAS, like their entire line of air conditioning equipment, is designed specifically for indoor installation. This feature is extremely important for multi-story buildings that have limited or no access to the roof or ground pad. Units are sized to accommodate floor-by-floor installations, and multiple units are easily installed if more cooling capacity is needed. Air-cooled condensers are easily mounted indoors near an outside wall for waste heat removal, or a water-cooled condenser option is offered if tower water is available.
Unlike the “one size fits all” approach by some manufacturers, the United CoolAir outside air system is made specifically for each project. Vertical configurations are ideal for small mechanical rooms, including closets while horizontal styles offer in-ceiling mounting, saving valuable floor space.
Having the ability to customize your DOAS unit to fit your installation requirements can save thousands of dollars in contractor charges and shorten installation time. United CoolAir’s OmegaAir II allows modification in air paths, component configuration, and utility placement before leaving the factory. They also offer a comprehensive list of factory-installed options to meet even the most complex cooling requirements.
Unlike new installations, retrofit applications generally have limited access to the job site. United CoolAir’s indoor, customizable DOAS units can be broken down into sections that fit through standard doorways, halls and into elevators. Lifting units by crane and modifying the building structure to accommodate equipment becomes a thing of the past, saving time and thousands of dollars in building modifications.
United CoolAir charges and tests each of their units before leaving the factory. DOAS units include resealable refrigerant couplings between separable sections to preserve the factory refrigerant charge. Refrigerant couplings are reattached during job site assembly, and ready for immediate operation. Brazing, recharging, and testing is eliminated saving additional time and money.
Dedicated outside air systems are as necessary to the safe and efficient cooling and dehumidification operation in commercial buildings as their HVAC cooling counterparts. It is important to investigate the many systems available to find a DOAS unit that best fits your unique retrofit installation requirements.
Millions of HVAC systems are reaching replacement age. The life cycle for most will elapse several times over the life of commercial, industrial and institutional structures. It is estimated that there are over 5 million buildings available for HVAC retrofit upgrades. While 70% of commercial buildings built prior to 1980 have not had any HVAC improvements. With changes in building codes, government regulations, technology, IAQ and environmental standards many building owners face a plethora of challenges. One of the issues that building owners have little control over is the cost of energy. Current rates range from 6.5 cents to over 12 cents dependent on region. All projections show tremendous increases over the next few decades. Considering that 40% of building power cost consumption is HVAC related, gaining efficiency and cost savings will be paramount for owners.
When these original HVAC systems were installed during initial new construction size, weight, ease of installation and refrigerant were of no concern. Large chillers were lowered into basements and rooftop units could be installed using apparatus onsite already before construction was finished. Now twenty to thirty years later things are more complicated. No longer is there open access or a crane onsite to simplify upgrading an HVAC system.
With emphasis on green building, what is the best solution? Buy a replacement rooftop unit and spend thousands of dollars on installation. Installation could cost half of the cost of the replacement unit. How do you remove and retrofit large tonnage chillers from a basement in a dense metropolitan area.
Keeping this in mind, there are products to solve these retrofit dilemmas. Selecting an off the shelf or stock unit will not be a perfect fit like the initial installations. United CoolAir adapts units to make retrofit projects simple and easy to install. Choosing a splittable system that can maneuver through a standard 32 inch doorway into a standard elevator resolves getting the units inside an existing structure. This will also mitigate the total cost of installation by using less manpower; overcome other technical issues that would be necessary for the installation of standard commercial units. What can make these EZfit units even more attractive is they can fit above the ceiling or in a mechanical room.
By bringing your units indoors you can gain valuable roof space for green projects such as solar panels or a living roof. Additionally, repairs can be made anytime indoors, promote longer unit life; eliminate damages from storms, vandalism or even theft of valuable copper destroying your units.
Owners can expect a shorter ROI, lower energy costs and an overall lower lifecycle cost. Objections from building owners vary from too costly, tenant interruption, no funding and others. In today’s climate, the governments along with others are providing programs to lessen the financial burden. PACE bonds, leasing and energy programs like Potomac Edison provide tremendous incentives to become more energy efficient. Potomac ED’s program provides up to 50% rebate of the purchase price, excluding taxes for each VFD installed capped at a total of $250,000. These programs give building owners every reason to retrofit their outdated HVAC systems.
Repair or retrofit is going to become more prevalent then new construction in the upcoming years. Retrofitting your old high energy consuming system with a unique characteristics split unit can make a retrofit project as simple as screwing in a light bulb.