Best of Engineer’s Notebook: What They Learned Along the Way
From ASHRAE Journal Newsletter, January 23, 2018
Written by ASHRAE Fellows who are senior consulting engineers with more than 100 years of collective practical experience, the recurring “Engineer’s Notebook” column shares what the authors have learned during their careers as well as design tips and tools. The column was established in 2013 with four authors contributing monthly articles on a rotating basis.
At the 2018 ASHRAE Winter Conference, the authors—Stephen W. Duda, P.E., BEAP, HBDP and HFDP, Fellow ASHRAE; Daniel H. Nall, P.E., BEMP, CPMP and HBDP, Fellow/Life Member; Kent W. Peterson, P.E., BEAP, Presidential/Fellow ASHRAE; and Steven T. Taylor, P.E., Fellow ASHRAE—are participating in “The Best of ‘Engineer’s Notebook’ 2nd Edition” seminar. In preparation for the seminar, each chose one of their favorite columns to discuss.
Prior to the conference, each of the authors discussed the significance of their chosen topics and why they chose the subject.
For those at the Palmer House Hilton in Chicago, “The Best of ‘Engineer’s Notebook’ 2nd Edition” begins at 11 a.m. today in the Empire room.
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Stephen W. Duda, P.E., BEAP, HBDP and HFDP, Fellow ASHRAE, shares a recent real-life investigation that highlights the complications that can arise when installing both chillers and boilers in a common equipment room.
This case study describes an incident that left boiler breechings acutely corroded and failed. This seminar highlights that investigation and reviews a number of problems uncovered, reviews applicable codes and ASHRAE Standard 15’s, Safety Standard for Refrigeration Systems and Designation and Classification of Refrigerants, provisions in this regard, and concludes with recommendations to avoid those problems on your projects.
1. Why did you choose to discuss this topic in this seminar?
Duda: “The ‘Chillers and Boilers in the Same Room: A Cautionary Tale’ column began with a real-world investigation in my recent work history. A client had called to say their boiler flues had acutely decayed after only a few years of service, and neither the flue manufacturer nor the Owner’s regular consulting engineer could determine why. After I was able to solve the mystery of why the boiler flues suffered such a dramatic failure, I felt other consulting engineers might be interested in the lessons learned – especially since the problems were quite avoidable. Since one of my deliverables to that client was a written report, it was rather easy to subsequently write a similar “report” in the form of an ASHRAE Journal column.
2. What is the significance of this topic?
Duda: “The topic is significant because it highlights a case where a chiller and boiler plant design met (on paper) applicable codes and standards, including ASHRAE Standard 15, and yet a very dangerous failure occurred. The integrity of fuel-fired boiler flues is critical to health and safety of building occupants, and the type of through-failure of these boiler flues that I witnessed could expose building occupants to carbon monoxide. In short, a serious but accidental leak of refrigerant from a chiller, combined with the building plant operator’s lack of understanding the hazard of operating a boiler with its service access open to the room, led to the boiler flue failure. Thankfully, there were no injuries reported in this case – but one of the actions I took after performing the investigation was submission of a Continuous Maintenance Change Proposal to Standard 15 suggesting a tightening of requirements for combined chiller and boiler plants, to help ensure this failure does not happen again. Even though it was user error and not a design error that most directly led to the hazard, there are very simple and inexpensive steps that building designers can take that would avoid a recurrence.”
3. What lessons, facts and/or guidance can an engineer working in the field take away from this topic?
Duda: “The column itself offers 13 recommendations aimed at a number of parties – the architect, the design engineer, the installing contractor, facilities operations staff, and even commissioning or test-and-balance technicians – all of whom could have taken simple steps to mitigate the failure experienced here. The most critical of those recommendations is to not operate boilers with their access panels open; to design two mechanical rooms to house chillers and boilers separately with no shared openings; and if separate rooms are not possible, to add an additional interlock to shut down boilers upon detection of refrigerant leak from a chiller. Standard 15 currently allows chillers and fuel-fired boilers to occupy a shared room if the boilers have sealed combustion via air ducted from outside the room OR if the combustion process is wired to shut down automatically upon refrigerant detection. I am suggesting that we change the “OR” to an “AND” thus requiring both sealed combustion AND automatic shutdown of combustion in rooms that house both chillers and boilers.”
4. Were there any surprises or unforeseen challenges for you when working with this topic?
Duda: “I did not experience any surprises or unforeseen challenges, and I attribute that to the 12 years I served on ASHRAE’s SSPC 15 (the committee that writes and maintains ASHRAE Standard 15) from 2002-2014. It was through service on that committee that I learned why chillers and boilers should be housed in separate rooms with no shared openings: an accidental leak of refrigerant from a chiller can expose refrigerant to the combustion flame of a boiler. Even though most HVAC refrigerants used in commercial buildings are non-flammable, the refrigerant can decompose into exceptionally corrosive gasses when put in contact with a flame. Without my time served on SSPC 15, I likely would not have known that fact and likely would have failed to solve the mystery of why the boiler flues corroded so quickly.”
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Daniel H. Nall, P.E., BEMP, CPMP and HBDP, Fellow/Life Member, chose to discuss energy efficient ventilation systems for labs.
For laboratories, the greatest energy challenge is meeting ventilation air flow requirements while maintaining a comfortable and functional interior environment. Reheat is often the only alternative when exhaust driven ventilation requirements exceed the airflow required for sensible cooling, and supply temperature reset for the air supply is limited by humidity control or the presence of load-driven labs on the same air system. Nall demonstrates strategies for reducing reheat and the energy required for make-up air conditioning.
1. Why did you choose to discuss “Energy Efficient Ventilation Systems for Labs” in this seminar?
Nall: “I’m very interested in strategies for maintaining humidity control while avoiding reheat. Laboratories are among the worst offenders for reheat, because, frequently, in order to maintain the supply air dew point necessary for humidity control, the supply dry bulb temperature is so low that providing the required make-up airflow for lab exhaust results in significant space over-cooling. The typical approach is to reheat as necessary to ensure comfort conditions. My strategy significantly reduced the need for reheat.”
2. What is the significance of this topic?
Nall: “Laboratories are among the most energy intensive of building types, typically because of the mismatch between required exhaust make-up and comfort maintenance. Potential energy savings for each building could very very significant, with no reduction in functionality, safety or comfort.”
3. What lessons, facts and/or guidance can an engineer working in the field take away from this topic?
Nall: “Think about the thermodynamics of the systems you are designing. Understand what are your goals and what are your strategies from a first principles perspective.”
4. Were there any surprises or unforeseen challenges for you when working with this topic?
Nall: “The added benefit for a high outdoor air fraction for the non-exhausted spaces also proved to be a major energy saver.”
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Kent W. Peterson, P.E., BEAP, Presidential/Fellow ASHRAE, chose underground piping distribution systems.
One of the main components of heating and cooling systems serving multiple buildings is the distribution or piping network that conveys the energy. The piping is often the most expensive portion of these types of systems. The piping usually consists of a combination of pre-insulated and field-insulated pipe with isolation valves in both direct burial and concrete tunnel applications. It is important to understand available pipe materials and means of isolation when designing these systems
1. Why did you choose to discuss this topic in this seminar?
Peterson: “It is one of the main components of heating and cooling systems serving multiple buildings such as at a university campus that conveys the energy. The piping is often the most expensive portion of these types of systems. The piping usually consists of a combination of pre-insulated and field-insulated pipe in both direct burial and concrete tunnel applications.”
2. What is the significance of this topic?
Peterson: “With aging infrastructure all over the world, many engineers are tasked with replacing end-of-life underground piping systems and it is important to understand the available material and installation options available today to provide robust systems for the future.”
3. What lessons, facts and/or guidance can an engineer working in the field take away from this topic?
Peterson: “A fundamental understanding of material characteristics is an inherent part of the design process for any underground piping system. With such an understanding, an engineer can use the properties of the material to design for optimum performance for the intended service. Based on decades of experience with campus direct-buried chilled water and heating hot water systems, it is best to use piping systems that do not corrode and do not allow joint leakage. If ferrous metals must be used in underground applications, they should be installed in utilidors or designed with corrosion protection.”
4. Were there any surprises or unforeseen challenges for you when working with this topic?
Peterson: “I continue to be surprised by the sheer number of underground piping system failures I have encountered through the years. It is extremely important to pay attention to all the details of construction in these systems to accomplish a long life for the system.”
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Steven T. Taylor, P.E., Fellow ASHRAE, chose to discuss Building Automation System (BAS) control of variable air volume (VAV) laboratories.
Traditionally, controls for VAV laboratory supply and exhaust systems have been separate from the primary BAS, resulting in two separate control systems. Taylor shows how to use the BAS to do all lab controls, allowing dedicated lab controls to be eliminated.
1. Why did you choose to discuss BAS Control of VAV Labs in this seminar?
Taylor: “I enjoy solutions that both cost less and improve performance. This is an example.”
2. What is the significance of this topic?
Taylor: “Again, it is a design concept that both saves money and improves performance.”
3. What lessons, facts and/or guidance can an engineer working in the field take away from this topic?
Taylor: “Many designers may be reluctant to use this approach to lab control since it is new and different from current practice. So I provided a lot of detail in my article, including control schematics and proven sequences of operation, which should allow engineers to use this design with confidence.”
4. Were there any surprises or unforeseen challenges for you when working with this topic?
Taylor: “We had a few problems the first time we implemented this design primarily due to the lack of experience typical controls contractors have with lab control systems and sequences. But we worked them out and we expect these problems to disappear over time if this concept is widely adopted.”