News | United CoolAir

August 13, 2020 by Kevin Stepp

Understanding DOAS and comfort cooling differences

While indoor air quality and ventilation have been major focuses of the HVAC industry for a long time, many misconceptions remain about what these applications require in terms of equipment and design. Today’s post will parse some of the most common questions about DOAS and comfort cooling equipment.

Purpose of DOAS

A dedicated outside air system (DOAS) or energy recovery unit (ERU) conditions air from the outdoors and delivers it to a space. It is essentially a dehumidifier in that its primary purpose is to remove moisture from the air, so when that air enters the space it is not adding additional load. This contrasts with comfort cooling equipment whose purpose is to maintain a consistent temperature in the space.

How

In order to achieve a cooling effect, a comfort cooling device must provide air to the space at a temperature much lower than the set point for that space. A DOAS or ERU, for its part, is not concerned with the temperature in the space. It monitors the temperature and humidity of the outdoor air and gauges how much capacity it needs to remove the moisture. The DOAS/ERU then discharges dry, room neutral air (roughly 70°-72°F and 30-40% RH).

When you need comfort cooling

A comfort cooling device operates only when the temperature in a space rises above set point. An outdoor air system, however, will typically operate during all occupied hours. ASHRAE 62.1 requires outdoor air be brought into in buildings at all times, so these machines rarely rest.

What is a DOAS unit?

Outdoor air equipment typically discharges air off of its cooling coil at 50-55°. The low leaving air temp effectively strips moisture from the air. However, constantly delivering low temperature air to a space will over cool it, so a modulating hot gas reheat coil is added to reheat the leaving air to a room neutral temperature around 70°.

DOAS and ERU equipment often feature some form of capacity control. Because outside air in cooling seasons can range from 65° to over 100°, these machines must be able to vary the amount of dehumidification they provide. Staged compressors, variable speed compressors, and modulating hot gas bypass are all options.

Space Temperature Control?

No, an outdoor air unit cannot replace a traditional air conditioner as the only device responsible for maintaining temperature in a space. The outside air unit operates constantly, meaning it cannot be turned off when the space is satisfied. Constant operation in a space temperature control design would lead to unacceptable temperature swings. More importantly, the mode of operation for a DOAS/ERU is determined by outside air temperature and humidity, not by space temperature. Space temperature control would become problematic when the space calls for heating, but it is 65° and raining outside. The unit must ignore the space and dehumidify instead, or the space humidity will rise out of control.

Not One or the Other

In order to properly apply a DOAS or ERU, it must be teamed with a comfort cooling device. This decoupling strategy allows designer to meet ventilation requirements while properly controlling space temperature and humidity. Thankfully, at United CoolAir we have solutions for both. Inquire today for more information on our comfort cooling equipment, DOAS, and ERUs.

June 29, 2020 by Kevin Stepp

What is DOAS?

With Independence Day weekend approaching Americans are making plans to celebrate with cookouts, swimming, and other outdoors activities. These simple pleasures become even sweeter knowing that, when outside, we are breathing clean, fresh air. What some don’t know is that when we return to work, we are often returning to buildings that have been consciously designed to bring in fresh outdoor air. This fresh air creates cleaner and safer indoor environments. You don’t need to be in the backyard in order to breathe fresh air!

We refer to HVAC equipment specifically designed to condition outside air as DOAS equipment, or a Dedicated Outdoor Air System. The goal is to flush recirculated air from a building and replace it with clean air from outdoors. Doing so reduces the quantity of unwanted particles in the air by diluting their concentration.

How does a DOAS unit work?

While technologies and applications differ, most DOAS equipment operates on the same basic principles. Outside air, which in the summer is hotter and more humid than indoor air, must be cooled and dehumidified before being discharged into the space. If it were not, temperature and humidity in the building would skyrocket. Air passes across a cooling coil that reduces its temperature to around 50°-55°F. This process removes much of the moisture from the air. Because 50°-55° is too low to comfortably blow into a room, DOAS units often offer hot gas reheat as an option to heat the now-dry air up to a more comfortable 68-72°. Now, fresh air is ready to enter the space.

While we will likely return to work still thinking about the fun we had outdoors over the holiday, we can do so knowing that some of the outdoors is still with us.

To learn more about United CoolAir’s DOAS offerings, click the following link to our Omega Air product or call us to discuss how we can modify our other products to fit your DOAS application.

June 2, 2020 by Matt Hanson

The Natural Disinfectant of UV-C Light

Due in part to recent pandemics, ultraviolet light is making a revival in the area of disinfecting air and surfaces in HVAC applications. Using UV-C light as a disinfectant is hardly a new concept. As early as 1878 Arthur Downes and Thomas P. Blunt, published a paper describing the sterilization of bacteria exposed to short-wavelength light. Later, the Westinghouse corporation followed with a commercialized germicidal lamp as early as the 1930’s. Since then, worldwide use of UV light to kill microorganisms has been implemented in: drinking and wastewater, indoor air quality, food safety, horticulture, healthcare and consumer products.

How UV-C light works

The sun emits different spectrums of UV light, but none is visible with the human eye. The wave lengths ranging from 10 to 400 nm, and include UV-A, UV-B, UV-C and UV-V. The earth’s ozone layer diminishes and prevents the shorter wavelengths of (UV-V, UV-C, and most of UV-B) from the sun to reach the earth’s surface. When pathogens like viruses, molds and bacteria absorb UV-C light it prevents the microorganisms from replicating their DNA and they quickly deteriorate. Once deactivated, these microorganisms are no longer able to reproduce and grow on surfaces. With this in mind, UV-C light emitters can now be added inside HVAC units or installed inside the duct. This enables HVAC units to be on the front lines of combating dangerous microbes that beget global illnesses.

For mold and bacteria, doses of UV-C energy may not cause immediate cell death but the microbe could be deactivated; while some biological activity may still exist, cell replication is impossible. The microbe is no longer able to spread. In order to maximize the effect of UV lights, it is best to pair them with an electrostatically charged filter. This allows them to capture and hold the microorganism for a long enough period of time for the UV light to deactivate its ability to reproduce. Finally, a DOAS (dedicated outdoor air system) can also be used to bring fresh air into the space. In this way, we create a system that greatly reduces harmful microbes.

Conclusion

Unfortunately, there is no guarantee that UV-C light will kill 100% of all microorganisms. Instead, recommendations are to take a multi-pronged approach to cleaning including filtration, air purifiers and disinfection of evaporator coils. With the proper filter, UV-C can kill and/or degrade what the filter has caught. Thus, for a given microbe, the filters effect can be an integral part of the resulting concentration in a space.

April 13, 2020 by Matt Hanson

BACnet Building Automation and Control Network

BACnet (Building Automation and Control Network), is the communications protocol that defines communication services used between building control systems and building automation end-devices. The protocol displays how data is represented and moved between BACnet nodes on the network and the services used to move it. For example, by sharing sensors and data, BACnet gives our applications similar abilities to sight, hearing, taste, smell and touch to help us make better decisions.

In June of 1987, a group of HVAC and Building Automation professionals met in Nashville to develop this standard, open protocol specifically for the building automation industry. Furthermore, in June of 1995, ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) also adopted this same standard. Therefore, BACnet became an alternative to the proprietary and closed protocols offered by large vendors that were in existence at that time.

How BACnet works

The BACnet protocol uses an Object-oriented approach (Object-oriented programming allows for simplified programming. Its benefits include reusability, refactoring, extensibility, maintenance and efficiency). As a result, this approach standardizes the representation of processes and data. Secondly, BACnet provides the ability to control and monitor any building automation process, to meet the needs of users, integrators, and equipment vendors. As a result, the BACnet protocol uses mobile and cloud-hosted devices, head-end computers, general-purpose direct digital controllers, and application-specific or unitary controllers with equal effect.

In a typical HVAC application BACnet would handle lighting, heating/cooling with a programmable thermostat, smoke detection and some form of security/safety applications. In these applications, motion detectors can be used to more efficiently measure human presence and activity and with a timer to make sure lights are off after hours. To further simplify things, with BACnet, devices from various manufacturers work in conjunction with each other with little or no additional integration. This leads to cost savings over proprietary systems, but also tremendous savings in resources, installation costs, maintenance costs, and energy savings.

Today, the majority of users prefer to use Ethernet. For example, the Control and Information Protocol (CIP) used in industrial application, BACnet uses objects to represent data on a network. These objects are defined by the BACnet specification and have both required and optional data. BACnet is an unconnected, peer network where any device can send service requests to any other device. Unlike connected protocols where devices have ongoing data transfers, communication in BACnet is unscheduled without any time critical operations. With ease of use in mind, BACnet is a certifiable standard, though certification is not required.

What are the 2 Protocols?

There are two distinct BACnet protocols being BACnet IP and BACnet MSTP.

BACnet IP:

The BACnet/IP allows users to transfer data to and from devices over Ethernet using BACnet/IP Protocol. BACnet/IP communication is implemented by defining a new protocol layer called the “BACnet Virtual Link Layer” or BVLL. There are many advantages to this approach. First it is extensible to other, future transport mechanisms such as IPv6, ATM, Sonet among others. Secondly, the concept of defining an extensible mechanism for peer-to-peer management of BACnet messages means that other manipulations. This includes such things as encryption/decryption and compression/decompression that can be performed outside of the process of generating BACnet APDU/NPDUs, i.e., without altering the existing standard. Routing between BACnet/IP and non-BACnet/IP networks is specified, including the case where IP and non-IP BACnet devices reside on the same LAN.

BACNet MSTP:

The MS stands for Master – Slave although in practice there are not many slaves out there and the TP stands for Token Passing. This method of BACnet the most common use to connect field devices to controllers and routers, to control applications. Up to 128 devices can be installed on a single network in the physical layer using RS485 with a max physical length of 4000 feet, and speeds up to 115k baud. Nevertheless, if more length is needed, it can be increased by the use of repeaters. You can compare to Ethernet, where the spec allows a max of 100 meters (330ft) on a single, unrepeated segment. Common baud rates are 19200, 38400 and 76800 and all devices must operate at the same baud rate. More and more devices can auto sense the baud rate and configure themselves correctly.

However, a disadvantage of the token system is that any one device gets a limited use of the bandwidth. Thus, a device may need to keep an internal queue of application layer messages it wants to send waiting to use the token. There are some vendor systems which fill their queue and then drop subsequent messages without notifying the user of the problem. Finally, limited access, combined with the overhead, makes it easy to use up all the bandwidth on the network. This happens if there are many devices with many objects and many properties of interest.

Key Points

Developed by: ASHRAE
Use: Communication across devices
Markets: Industrial, Transportation, Energy Management, Building Automation, Regulatory and health and safety
Examples: Boiler Control, Tank Level Measurements
Proprietary: no
Transmission Modes: Ethernet, IP, MS/TP, Zigbee
Standards: ANSI/ASHRAE Standard 185 ;ISO-16484-5; ISO-16484-6
Costs: Low; No charge for usage or licensing fees
Network Interfaces: Existing LANs and LANs infrastructure
Testing: BACnet Testing Labs
Advantages:
- Scalability between cost, performance and system size
- Endorsement and adoption by nearly every major vendor in North America and many other countries
- Robust internet working including multiple LAN types and dial-up
- Unrestricted growth and the ability to add new innovations and new features anytime •
Disadvantages:
- Limited the number of field devices that can connect to a master station except Ethernet TCP/IP
- MT/TP-Wire Length
- Ethernet-Infrastructure
- New standard has security standard but not implemented in all devices

February 19, 2020 by Matt Hanson

Replacing a self-contained water-cooled air conditioner

A business owner in Vero Beach, Florida had just bought a building to produce his radio and TV shows. He thought the purchase of the building and the renovation to follow would be the end of his cost. This turned out to be only the beginning of his ordeal. As it turns out, this was an older building and the AC units were about to fail. He made calls to several HVAC companies but each company gave him the same awful news. Although the price of each self-contained unit was affordable, he was looking at several thousands of dollars in additional fees. The extra cost involved tearing down walls and rebuilding them afterwards in order to bring in the new AC units.

The owner seemed shocked to find that this was a usual practice in the industry. In fact, several decades ago self-contained water-cooled unitary devices were installed in mechanical rooms while the building was under construction. Most of these units are enclosed behind walls and replacing them is a major challenge. Surprisingly, although the outdated units could be disassembled and removed, bringing in new units was a nearly impossible. Thankfully, the owner found United CoolAir. We offered him a water-cooled self-contained unit that breaks down into small sections. This enabled them to move units into the space without making modifications to the building. The reassembly went smooth and easy and left this owner without the headaches typical to these types of installations.

Replacing Unitary Systems

Thousands of similar installations exist across the country. United CoolAir has been replacing these units for years with our modular EZ-Fit product. Now, we offer the Renovator, another modular, water cooled, self-contained unit. The Renovator is designed specifically to replace Trane^® SWUD units, the most common self-contained system in existing buildings. Our unit matches the exact footprint and features list of the Trane^® SWUD using smaller modules than a Trane^® equivalent. Additionally, the Renovator features a modular design that allows swift installations of a fully charged and tested unit, all without making costly alterations to the building. Call United CoolAir today or click on the General Inquiry form in the Contact tab above, to see how United CoolAir can save you money on your next replacement project.

January 6, 2020 by Kevin Stepp

Recovering Energy from Class 2 Exhaust Air

The Problem

Providing a healthy environment must be the top priority for any air conditioning design. This can be difficult though, especially in spaces that generate less-than-ideal breathing conditions. Nail salons, health clubs, and bathrooms are just a few examples of spaces where processes or people taint the air with undesirable chemicals or odors. In these spaces, building designers are missing an opportunity to save valuable energy while providing healthy buildings.

ASHRAE 62.1 – 2019 designates air in these spaces as Class 2 air and stipulates that it must be exhausted. Fresh, but expensive to treat, outside air must be brought into the building to replace the exhaust. Here, designers are dropping the ball if they simply throw away the exhaust air. It contains valuable heat energy that should be recovered and used to reduce the energy needed to condition outside air.

The Solution

United CoolAir’s Alpha Aire utilizes two energy recovery devices to extract heat energy from the exhaust and pre-cool (in summer) and pre-heat (in winter) outside air before it reaches a coil. The unit design reduces the load on the cooling and heating coils to as little as 1/3rd that of a standard outside air unit. At a fraction of the operating cost, Alpha Aire delivers room-neutral (roughly 73° and 50% RH), fresh air to a building.

One common concern with Class 2 applications is whether the exhaust air will be transferred back into the building by way of the energy recovery wheel. United CoolAir utilizes a molecular sieve enthalpy wheel with a rated EATR of 0.5% or less. This means that less than one half of one percent of air leaving the building will be trapped in the wheel and recirculated into the space, a rate undetectable to humans and one far lower than the 10% allowed by ASHRAE 62.1 – 2019.
Designers should not hesitate to use all of the energy at their disposal. Alpha Aire gives them the opportunity to do just that. Call or click the link above to find out more.

Applications

Toilet rooms	Nail salons	Museums
Locker rooms	Pet shops	Hotels
Shower rooms	Barber shops	Health clubs
Science labs	Restaurants	Laundry rooms
Libraries	Bars	Pharmacies
Art classrooms	Bowling alleys	Churches