Failures in facilities will not stop occurring in our industry, but we must learn from them so as not to repeat them.
by Camilo Botero*
Seeking topics that might be of interest to the appreciable readers of ACR, the editor of the journal suggested to me, which I now present for your consideration hoping that it will contribute to the improvement of our projects.
Since 2010 I have studied with great interest everything that has to do with quality assurance in air conditioning projects (commissioning, and I will use this anglicism because there is still no word in Spanish that means what this methodology implies), and I have recently heard the term "Commissioning by Results" that has seemed very appropriate, which in the end of purposes what it means is that the systems operate as they were designed, for a specific purpose throughout the life cycle of said project, and that will be used as the basis for this article.
In 2013, ASHRAE issued its Standard 202: Commissioning Process for Buildings and Systems, which began with Guide 0 - 2005: Commissioning Process, evolved into Guide 1.1 - 2007: HVAC&R Technical Requirements for the Commissioning Process, until reaching the aforementioned Standard 202 which is even more generic because it includes buildings and other systems.
Both the two guidelines mentioned, and Standard 202, which is the current document to ensure that the air conditioning systems (for the case of this article), are successful, throughout their life cycle, if they were followed with discipline and regulation.
But in reality, even in developed countries and very commonly in Latin America and of course in Colombia, projects result in multiple failures and errors, which could have been avoided if the quality assurance process of the systems were used rigorously. This process has four perfectly defined stages that are obvious and that perhaps because they are, are often not followed. These stages are:
- Pre-design.
- Design.
- Construction.
- Operation & Maintenance.
The assumption is that the system works according to how it was designed for a perfectly defined application and for its entire useful life, say 20 years or more, but the reality is that either from the beginning there are failures and errors or soon after due to poor operation and / or maintenance the systems lose much of their RDP (Owner Requirements for the Project) and stop meeting temperature parameters, relative humidity, indoor air quality; also consuming excess energy.
When it is defined to make a project, the commissioning agent must be present from the very conception of the project, which in our country does not happen or happens very eventually with air conditioning, despite being one of the most important and expensive items both in initial investment and in the cost of operation, of a modern building. Nor is it taken into account in a quantified way that impacts the architectural and structural design of the building from the beginning. In-depth training in thermofluid topics is required for some architects offering bioclimatic comfort solutions in tropical climates, which do not meet the ASHRAE 55 standard for thermal comfort. It is also very common for construction companies to offer air conditioning solutions that represent less initial investment and low efficiency, but without taking into account the cost of energy that end users will pay; nor do they care about indoor air quality or equipment maintainability.
In the design phase there are multiple shortcomings. The RITE, which is the Regulation for Thermal Installations in Buildings, says:
Article 14. Technical documentation of design and sizing of thermal installations.
1. Thermal installations falling within the scope of the RITE shall be implemented on the basis of technical documentation which, depending on their importance, should adopt one of the following modalities:
a) when the nominal thermal input to be installed in heat or cold generation is greater than 70 kW (20 TR), the realization of a Design Project will be required (see Article 15); ........
Most of the time this is not fulfilled, or is not executed through a duly accredited consultant with professional registration that empowers you to do so and instead is done as part of "turnkey" offers that favor the final economic result for a contractor or an equipment supplier, but that generally does not meet all commissioning requirements, as described in the ASHRAE 202 Standard.
Any well-crafted HVAC design must carry its particular psychromometries, thermal load calculation, elaborated with the specific local climate of the project, the indigenous materials and the level of radiation in the project area.
Calculation programs are used with foreign data whose results are not properly analyzed, leading to serious errors. The calculation of thermal loads rather than science and technology, is an art and requires great experience and knowledge of the local climate, the real coefficients of thermal conductivity, the equivalent temperature delta also real, the thermal radiation and its effective attenuation, and the behavior of such thermal calculations at partial loads. I clarify that I am not against thermal load calculation programs, but the way they are used.
Errors in the construction phase
During the construction phase, multiple errors are also made, the most common being due to a lack of design and/or poor designs. In addition, the designs must be accompanied by quantities of work with reasonable precision, so that there are no shortages or excesses during the work, and details of assembly and connection to the equipment must be made to facilitate its installation, operation and maintenance. There must be very strict coordination between contractors from other disciplines and the HVAC contractor.
Throughout the work there must be a log and especially during the construction phase, which serves to obviate the difficulties that undoubtedly arise in the work.
The commissioning agent must facilitate the following: communication, documentation and verification of the entire project; but this usually does not occur, leading to conflicts during installation.
At the end of the assembly, the equipment must be put into operation, by specialized personnel and the protocols of said starts must remain; At the same time, the Manual of the System and Subsystems involved must be elaborated, with all the technical information and the plans of the system, as it was built, for its correct operation and maintenance. Designers, contractors and manufacturers' personnel must give clear and precise instructions to the personnel who will perform the operation and maintenance.
In the last phase and perhaps the most important in terms of costs and compliance with specifications (a very relevant fact is that the typical initial investment of an air conditioning installation is only 3% of the value of energy costs, maintenance and shutdown costs throughout its useful life); but in reality, most of the time the log and/ or the boot protocols have not been taken or are not delivered, much less a system manual, which is scattered in multiple documents that are very difficult to consult; to top off this cloudy panorama, no training is given to expert personnel in the operation of the equipment and its maintenance and it is left to "Doña María" the lady of the coffee, to "operate there while he is making the coffee" or to "Don José" the guard on duty, "while he makes his round".
To finish I must say that our air conditioning guild requires an urgent change in its regulations, professionalization and certification, to position it as a business to which we are all proud to belong and that is lucrative for all participants, including of course, end customers, and also careful of the environment and with a rational use of energy.
* Camilo Botero is the current Secretary of the Federation of Ibero-American Associations of Air Conditioning and Refrigeration - FAIAR; he was president of ACAIRE and is president of Camilo Botero Ingenieros Consultores Ltda. He has worked as a teacher in several Colombian universities, guilds and currently in ACAIRE in diploma courses of air conditioning projects, energy efficiency in air conditioning and refrigeration, cogeneration and trigeneration, applied psychometrics, thermodynamics, fluid mechanics, heat transfer and turbomachinery. ([email protected]).
