Pay Now or Pay Forever: The Design of Control System Software

摘要

The engineering community has typically done an excellent job advancing the capabilities of the HVAC system. However, it has been a common practice to specify control intent and then to allow the controls contractor to develop the final design documents. All too often, these documents are limited to a set of wiring diagrams and a book full of manufacturer's generic documentation for the devices installed on the job. A critical, yet often underspecified aspect of the design is the integration software. Design intent documents must specify, in detail, the sequence of operations at the integration level in order to ensure the building will operate to the desired level of occupant comfort, air quality, and operating cost. Commissioning agents engaged at the design phase must be able to recognize and resolve deficient integration software specifications, and then commission the resulting implementation. While this adds to the upfront costs for building owners, the alternative is higher utility and maintenance costs for the life of the building. This article uses case study data from a midwestern university to show the types of operational problems that exist because of improper or insufficient design intent specifications. It defines a set of deliverables ranging from control software logic specifications to the inclusion of an operator's instruction manual specific to the design of the project's HVAC systems. It concludes with examples showing re-specified control sequences and the operational commissioning process.