Developing a detailed test, balance plan
A detailed test and balance plan can help avoid timing issues and conflicts in the construction of a nonresidential building.
By Mike Wozniak, TBE, Air Systems Engineering Inc., Minnetonka, Minn.
The demand from building owners for contractors to maintain a construction schedule is growing every year. Building owners require a substantial construction completion date to be established and expect the construction team to meet this date to occupy the building on time.
Before a building can be occupied, there are many required processes throughout the course of construction that ensure the building is properly functioning and operating at the design intent. One of the most important is the process of total system balancing by means of testing and balancing the heating, ventilating, and air conditioning systems (HVAC). HVAC systems that lack a total system balance can result in inadequate indoor air quality, building/space pressurization issues, excessive energy consumption, and comfort issues for building occupants.
The testing and balancing process primarily consists of testing the HVAC equipment to ensure proper installation and design operation, adjusting/balancing the HVAC equipment to obtain the design intent and the most optimal level of system performance, and providing a report detailing the final HVAC system operation as compared to the system design. The testing and balancing report is typically reviewed by the mechanical design engineer and the building owner to verify that the HVAC systems are installed properly and operating as designed. The report will also document any deficiencies preventing a HVAC system from operating as designed if the design intent could not be achieved with the installed HVAC equipment. The HVAC system performance data documented within the report can be used to determine possible changes to the system design to achieve the design intent of the building. More and more often the report is also being reviewed by the city or state inspector to verify that proper indoor air quantity requirements are being met prior to occupancy.
Most construction schedules incorporate the testing and balancing process at the end of the project, usually to receive a certificate of occupancy. However, often there is not enough time for the testing and balancing contractor to complete the total system balancing prior to the completion date of the construction schedule. Failure to complete the balancing within the scheduled time can result in the general contractor, and, more importantly, the building owner being displeased with testing and balancing company regardless of the outcome of the final balanced systems.
Typically, project specifications for testing and balancing require a balancing plan; however, the specified requirements usually cover only the balancing techniques and/or testing procedures for individual systems and equipment. The typical balancing plan includes the following three components:
- A list of the test instruments that are planned to be used in the testing and balancing process. Each instrument manufacturer, model number, and test application should be included.
- A description of the testing procedure for each HVAC system to be tested. List all of the equipment to be tested for each system and the techniques to be used for the testing procedure.
- A list of the contractors that are required to assist with the testing and balancing process along with the expectations of each of the contractors to successfully complete a total system balance. Most importantly, the expectations of the temperature controls contractor should be listed. This may include automation software for balancing, automation system access, and the development of global overrides for system maximum performance testing.
This information is helpful for the design engineer, but does little to assist the construction manager and building owner to develop a realistic construction schedule. The addition of a few components to a standard balancing plan not typically listed in the project specifications can be important to the construction schedule. To help avoid conflicts with the construction schedule, a detailed balancing plan should also include the following key components:
- An outline of the required construction completeness prior to starting the testing and balancing process
- A realistic estimate of the time required to complete the testing and balancing process
- A listing of the necessary building accessibility to thoroughly test HVAC equipment and sub systems.
The balancing plan needs to describe in detail the required time to complete a total system balance. General contractors and building owners typically assume that the balancing process is something that happens all at one time, and if a schedule needs to be shortened, then the balancing company can simply put more technicians on the project to complete the process faster. This is rarely the case.
Many automation/control systems only allow communication with a few systems/pieces of equipment (sometimes only one) at a time. Buildings with direct digital control systems require a great deal of the testing and balancing process to be performed through adjustments to the HVAC systems via the automation/control system. Network access limitations and/or control software may prevent more than one operator from communicating with the automation/control system at a time. This makes it inefficient to have too many balancing technicians on a single project if the majority of the adjustments can only be made through one computer terminal.
It is also the balancing contactor’s responsibility to address any issues, whether that is design or installation, which prevents a system from operating at design performance. The resolution of these issues by the responsible party may take several days, possibly weeks. The general contractor and building owner need to be aware of these possibilities when outlining a detailed time estimate for the balancing process. If the estimated time to thoroughly test a building HVAC system is three weeks, the balancing contractor may incorporate an additional week or two into the balancing plan schedule to accommodate additional time required by the design engineer or mechanical contractor to correct any minor issues that are preventing design performance of the building.
Building accessibility during balancing
The building accessibility during the balancing process is another matter that is usually overlooked during the development of a construction schedule. Total system balancing requires access to all areas of the building, and large HVAC systems may require the balancing contractor to access these areas several times throughout the balancing process. General contractors and building owners will typically overlap some of the finishing processes of the building construction—such as laying carpet and tile flooring, waxing floors, construction cleaning, and fire alarm testing—that require the HVAC systems to be shut down. The balancing plan can inform the construction manager of possible conflicts so he or she can attempt to schedule the testing and balancing process around them. Building accessibility issues to address in the balancing plan include the following:
- Flooring work, such as carpet laying and tiling, must be performed either before or after the testing and balancing process for a particular system serving the area in which the flooring work is to be done. If the completed flooring will restrict the use of boom lifts, the testing and balancing of the system serving that area must be completed prior to the floor work if the HVAC system components are inaccessible by ladder.
- Final building cleaning that would prevent further access of contractors should be delayed until the testing and balancing is completed.
- If fire alarm testing will affect the HVAC system, the balancing contractor should be notified in advance when fire alarm testing is scheduled. For example, closing fire dampers or shutting down air handling units can disrupt total system balancing.
A detailed balancing plan should be submitted for most substantial-size projects, whether it is required or not. The best time to submit a balancing plan is at the same time as the required mechanical submittal data. A balancing contractor should also follow up with the general contractor and/or building owner to ensure that the balancing plan has been properly reviewed and incorporated within the construction schedule.
Most of the details in a balancing plan are common to almost all projects. A well-written balancing plan can be reused for future projects with few modifications. By submitting a detailed balancing plan, the general contractor and the building owner can develop a construction schedule that will incorporate a realistic balancing schedule, resulting in fewer scheduling conflicts and a better reputation for the balancing contractor.
Wozniak is vice president at Air Systems Engineering Inc. His expertise is in project coordination/management and HVAC system testing.
Required construction completeness prior to start of system balancing
Many of the construction completeness requirements prior to balancing are not considered by the general contractor or building owner when developing a construction schedule. The portion of the balancing plan outlining the required construction completeness prior balancing should include the following:
- All ductwork and associated grilles/registers/diffusers installed and complete
- Piping systems completed, flushed, and filled
- Equipment properly started by qualified personnel or start-up technicians
- Ceiling tiles installed
- Automation system (temperature controls) installed and completed for air and water systems
- All equipment controlled in automatic mode
- Access for balancing contractor to the automation/controls system provided.
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