Controls Specification Development
In past columns, we have talked about the elements of a good controls specification. As a recap, a good controls specification includes the following parts:
• Specification: Typically appears in section 230900 or 230923. This includes three sections: General, which describes the system, interaction with other specification sections, and submittal requirements; Product, which describes the required hardware and software; and Execution, which talks about workmanship and installation requirements.
• Sequence of Operations: The sequence is probably the most important part of the controls design. Sequences describe, in a text-based format, how each system should be operated.
• Points (or object) list: The points list shows the required hardware and software points that are to be provided. Often the point list also describes which points are scheduled, alarmed, and trended as well. Note that the sequence of operations and points list can be shown on project drawings, in the execution section of the specification, or in section 230933.
It is not at all unusual to see projects that include significantly less-detailed controls designs. One reason given for this is that controls are viewed as “design build” and the designer has left the design details of the controls system up to the contractor. For simple systems, this may be a valid option, but it is not recommended for larger, more complex systems.
We are also seeing projects where the designer has decided to include significantly more detail. Examples of this include control logic diagrams (shown as flow charts) on project drawings. On the more extreme end, some projects include full controls engineering, including drawings showing point-to-point wiring and panel layouts (the type of detail that would normally be found only in the controls submittals). This typically occurs when the owner is adding to an existing control system and in fact may be doing some of the programming with his own in-house staff.
What is the right approach? It really depends on the project and the owner’s needs. We tend to favor a fairly detailed design with careful attention to specifying and open systems that works with what the owner may already have installed (without going to the extreme of showing submittal level wiring/panel details). Our designs typically have detailed sequences and points lists to help owners get the most out of their systems. You can make a good argument that for a simple, largely unitary solution, less detail may adequate. After all, unitary systems typically come with factory-installed controllers that have fairly limited flexibility. Providing more details can also be valuable in special cases, but that does not necessarily replace the detail that is provided in a controls submittal and as-built diagrams (including portable documents which include schematics, sequences, valve and damper schedules, and wiring details). ES