By / Norm Grusnick
The demand from building owners to have contractors maintain a construction schedule is ever increasing. Building owners require a substantial construction completion date and expect the team to meet this date.
Before a building can be occupied, there are many processes throughout the course of construction that ensure the building is operating at the design intent. One of the most important is the process of total system balancing by means of testing and balancing the HVAC system.
The testing and balancing process primarily consists of testing the HVAC equipment to verify proper installation and operation, adjusting/balancing the HVAC equipment to obtain optimal system performance, and providing a detailed report of system operation compared to design. The testing and balancing report is typically reviewed by the design team and the owner. The report will document any deficiencies preventing a system from operating as designed. The HVAC system performance data documented in the report can be used to make changes to achieve the design intent of the building.
Most construction schedules incorporate all the testing and balancing in the final stages of construction. However, often there is not enough time left to do a complete system balance. Failure to complete the balancing in the scheduled time can result in the general contractor and owner being displeased. Typically, project specifications for testing and balancing require a balancing plan; however, specifications usually only cover the balancing techniques and/or testing procedures.
Specifications should call for performance of a total system balance in accordance with Testing, Adjusting, and Balancing Bureau (TABB) tabbcertified.org and/or other certified programs. The typical balancing plan includes the following three components:
1. A list of test instruments and with that the model and application use.
2. A description of each system test procedure and list of equipment to be tested.
3. A list of subcontractors required to assist with the testing and balancing process along with expectations of each contractor. Most importantly, the expectations of the controls contractor should be listed.
All this information is helpful to the design engineer but still does little to assist the construction manager and owner. The addition of a few extra components to the balancing plan will be of great advantage to the construction schedule. These extra components include:
4. An outline of construction completeness prior to testing and balancing.
5. A realistic estimate of time required to complete the testing and balancing process.
6. A listing of the building accessibility required to thoroughly test all HVAC systems.
The balancing plan needs to describe in detail the required time to complete a total system balance. General contractors and owners typically assume that the balancing process is something that happens all at one time, and if the schedule is shortened, then the balancing company can simply put more technicians on the job. This is unrealistic and leads to problems near the conclusion of the project.
Many control systems only allow communication with a few systems at a time. Buildings with DDC systems require a great deal of the testing and balancing process to be performed through adjustments to the HVAC systems via the automation system. Network access limitations may prevent more than one operator from communicating with the control system at a time. This hinders having too many balancing technicians on site at the same time as many adjustments can only be made through a single terminal.
It is also the balancing contractor’s responsibility to address any issues that prevent the system from operating at design performance. Some of these resolutions may take days or weeks and the general contractor and designer need to be aware of these possibilities and their effects on the schedule.
As well as the balancing time requirements, building accessibility during the balancing process is another extremely important matter. Total system balancing requires access to all areas of the building, and large HVAC systems may require repeated access throughout the balancing process. ▪