#hvactechnician 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.

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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