#hvaclife Archives | United CoolAir

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

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

October 18, 2019 by Matt Hanson

Retrofitting Commercial HVAC Units

Retrofitting Major Commercial HVAC Brands

Millions of HVAC systems are reaching replacement age. The life cycle for most will pass several times over the life of commercial, industrial and institutional structures. Estimates show that there are over 5 million buildings available for retrofit HVAC 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 forecasts show great increases over the next few decades. Considering that 40% of building power cost use is HVAC related, gaining efficiency and cost savings are vital for owners.

Why The Difficulty in Replacing Outdated Units

When initially installing HVAC systems, size, weight, ease of installation and refrigerant there were of no concern. During construction, large chillers were lowered into basements, and rooftop units were installed using machinery already onsite. Now twenty to thirty years later things are more difficult. No longer is there open access or a crane onsite to simplify improvising an HVAC system. Brands of HVAC units reaching the end of life include Trane^® SWUD units, Bohn HVAC Systems, Blazer units, McQuay^® HVAC, Mammoth^® v cube and Carrier^® AC units.

Going Green is the Future

In order to make energy cleaner, greener and more efficient, governments are constantly developing new refrigerant liquids. Many of today’s HVAC units are using the less efficient R22 refrigerant and are therefore in need of replacement. Newer units are using R410a refrigerant but even this will soon be outdated as well. With an emphasis on green buildings, 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 urban area?

There is a Solution

Keeping this in mind, there are products to solve these retrofit problems. Selecting an off the shelf or stock unit will not be a perfect fit like the initial installations. United CoolAir modifies units to make retrofit projects simple and easy to install. Choosing a splittable system that can move through a standard 32-inch doorway into a standard elevator, resolves to get the units inside an existing structure. This will also lessen 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 EZ Fit units even more appealing 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.

In Conclusion

Additionally, repairs can be made anytime indoors, support longer unit life; eliminate damages from storms, vandalism or even theft of valuable copper destroying your units. Owners can expect a shorter return on investment, lower energy costs, and an overall lower lifecycle cost. Complaints from building owners vary from too costly, tenant interruption, no funding, and others. In today’s climate, governments along with others are providing programs to lessen the financial burden.

PACE bonds, leasing, and energy programs like Potomac Edison provide fantastic 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 obsolete HVAC systems. Besides repair or retrofit is going to become more widespread than new construction in the upcoming years. Lastly, retrofitting your old high energy-consuming system with a unique feature split unit can make a retrofit project as simple as screwing in a light bulb.

September 13, 2019 by Matt Hanson

All about packaged units in air conditioning

Since the invention of the air conditioner in 1902, engineers have developed various ways of handling the HVAC process. The evaporator and condenser sections are the two major components of Heating, Ventilation and Air Conditioning (HVAC). This is the case as it applies to Direct Expansion (DX) type systems. At the same time, the indoor air absorbs heat inside the evaporator section. The condenser converts the vapor to a liquid by cooling it down. This section is usually located outside on the roof or on the ground. Because the two sections are located in different areas we call this a split system.

A packaged unit is when the heating and cooling components are contained in the same unit. This type of system can be beneficial when space is minimal. Many times, the placement of this type of HVAC is located outdoors but can also be installed completely indoors. Connected to both the supply and return air ducts; these operate similar to a central air system. The delivery of these packaged units can occur as both air-cooled or water-cooled systems.

The Refrigeration Cycle

In the refrigerant cycle, air-cooled or water-cooled liquid travels through an expansion valve where it converts to a vapor. The vapor then absorbs heat inside the evaporator before moving on to the compressor. After the compressor, the vapor then goes to the condenser where the refrigerant is air or water-cooled. The application of a heat exchanger component is installed with shell and tube; plate and frame, or coil.

The cooling effect is achievable by means of a continuous supply of water added to the system. Sometimes building codes do not permit an HVAC system to be installed outside. In this case, packaged units are installed as a solution. United CoolAir produces these all-indoor packaged systems. By the way, the self-contained HVAC units and are available with multiple air path configurations.

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 installed to control the flow of refrigerant into the evaporator in response to the cooling load. 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.