DOAS CHECKLIST PDF

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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 Arab oil embargo sent oil prices rocketing while shortening oil supplies. 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.

It was later discovered the contamination occurred through their air conditioning system. Many studies have since proven beyond a doubt and established links between indoor air quality and human illness. Also, there is a negative economic impact through lost productivity, lawsuits and increased insurance costs.

Building owners, HVAC design engineers, and operators all take this issue very seriously. As a result, greater amounts of outside air must be introduced to the space, which also affects humidity levels.

These issues influence the need for an HVAC unit design capable of controlling ventilation, moisture levels and temperature in the space. 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. The goal is to deliver precise amounts of ventilation to spaces regardless of load size, and do it cost-effectively. With one system providing dehumidification and a second system controlling the ventilation.

We control the space dry bulb temperature and humidity 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. 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.

For many climates, an independent duct system is considered the best choice. This is 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. This is 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.

They 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 s. This provided 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. Simple installation, minimal maintenance and the ability to run multiple evaporator units from a single condensing unit are the result. 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.

According to a study by the U. Reports going as far back as indicated the U. More recent estimates of the U. S market indicate a compound annual growth rate of 5. The original HVAC system could have been installed in one of many configurations, requiring the design engineer and contractor to manage challenges as needed. 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.

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. 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. 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. Building modifications become a thing of the past saving time and cost and cranes are unnecessary.

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.

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After three days of conference committees to work out those gaps, budget negotiations have migrated to the budget chiefs and are expected to continue through the weekend. By Friday that number was whittled down to the tens of millions as they drew closer on spending plans for higher education, K, the environment, health care, criminal justice, transportation, agriculture and other government services. The bill was presented to the governor on Friday. Back story: Under pressure: House Speaker Oliva reverses course and agrees to hear firefighter cancer bill Assignment of Benefits — An important reform bill for the governor and insurance commissioner, this eliminates one-way attorney fees in insurance claims disputes. The biggest struggle all session with this bill was whether to carve out an exemption for auto glass repair shops. Back story: Up in smoke: Gov. DeSantis signs bill into law killing ban on smokable medical marijuana Dead on Arrival Fracking — Opponents to the oil and gas drilling technique known as hydraulic fracturing will have to wait until next year to get a ban in the Sunshine State.

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It covers tasks typically included in a contract. You can use this checklist when comparing vendors and prices. Replace filters on heating equipment Inspect ignition burner assembly Examine heat exchanger or heating elements Study flue system and ensure secure attachment to the furnace Inspect for gas leaks with gas furnaces Assess gas pressure Clear drain lines and pans Check electrical connections Lubricate motors, bearings and other moving parts Check thermostats and controls Check fan and blower operationa and adjust as needed Inspect heat pump Check out this Ultimate Commercial HVAC Preventative Maintenance Checklist for your business. Use this HVAC preventative maintenance checklist as a guide Now that you know some of the basics covered under preventative maintenance contracts, you can begin talking to different vendors. Look for a vendor that adjusts your HVAC preventative maintenance contract based on your needs, equipment and budget.

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