Commissioning: Don't Go Changing
As a design engineer, who has increasingly been involved with the commissioning side of projects, I often fight the urge to redesign a system as the commissioning process is underway. I know I am not the only one fighting this urge. It is, after all, easier to pick apart an existing design than it is to design the perfect system from scratch. Instead, focus needs to be shifted to asking questions of the design engineer when there are discrepancies. If the questions are phrased carefully, they will save the design engineer time researching the issue, the sequence of operation will be clarified, the control contractor will be able to program effectively, and the owner will receive the expected system operation. Just as importantly, the design engineer will remain responsible for the final system design.
The commissioning professional is usually easily accessible to the control contractor and to the owner during testing. Often during system testing, it is only the commissioning professional, the control contractor, sometimes the general contractor, and sometimes the owner's representative observing the testing. It is very easy for this group to make a decision while testing in the field, leaving the design engineer out of the loop.
Sometimes the implemented changes do not take into account the design engineer's original intent. The commissioning professional must make a conscious effort not to bypass the design engineer and implement changes. The commissioning professional needs to record field circumstances as a request for information (RFI) and allow the design engineer to review and respond to it. The design engineer usually has a valid reason for the sequences of operation that have been written and will provide that information if asked.
Several months to a year (or two) may have passed since the mechanical design was completed. The design engineer's intent a year ago is not always obvious while testing today. Sometimes, when something a little out of the ordinary crops up, the first reaction is that it must be a mistake or something was overlooked. However, careful planning by the designer may have resulted in an out-of-the-ordinary design. Only a question to the designer (or owner) would likely uncover the reasoning behind this out-of-the-ordinary design. Sure, making changes on the spot may save some time, but by not asking the question and assuming an answer, and the commissioning professional has now become responsible for part of the design, correct or not. The design engineer's intent may be compromised. For this reason, having the written design intent document (DID) available during testing, especially if the owner and design engineer are not present at testing, is a good idea.
The commissioning professional making design decisions without consent from the design engineer is not the ideal commissioning process. However, sometimes it may appear necessary to maintain project schedule or because of a lack of response from the design engineer. It should be avoided. The design engineer has to be given a chance to respond. Time should typically be budgeted in design engineering fees to answer RFIs (whether a building is commissioned or not). The engineer's choice not to respond to an RFI should be documented.
Working within the commissioning plan, the initial testing should include the following:
- Clearly document design decisions and/or assumptions made during testing.
- Ask questions of the owner if the differences observed were owner-requested.
- Ask questions of the design engineer in an RFI if the testing results were unexpected but not obviously incorrect. RFIs are often used during final test procedure development but should also be used when clarifications are needed during or after testing.
- Report the findings, highlighting the differences between the expected results and the actual results in the report.
- Use design expertise, but use it cautiously.
This must be done in order to maintain the intent of the engineer of record. The design engineer and the owner need to be aware of any changes made to the systems, and the design engineer needs to respond to questions. Then, the commissioning professional's role is to verify the design engineer's intent, with the owner's best interest always in mind. After all, it is the design engineer's signature on the construction drawings and reputation on the line. ES