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I recently found myself sitting in a mechanical penthouse being told by the automated temperature controls (ATC) contractor, through the hum of rotating equipment and the incessant whine of variable frequency drives, that yet another sequence was not provided as specified. Instead, we got a canned routine. The ATC submittal reflects the specified custom sequences identified in the design documents word-for-word. The ATC as-built drawings mirror the submittal with crystal-clear clarity. So how did we wind up with yet another canned routine in the field?
A canned routine is a pre-programmed sequence with an established methodology intended to accomplish a specified task. It’s kind of like assembling a pre-fabricated structure; instead of framing each individual member, you use pre-assembled components. The allure of canned routines is obvious – less time spent programming means fewer hours on the job.
The problem is that, unlike pre-fabricated structures, building automation sequences can vary quite a bit in means and methodology on a building-by-building and even space-by-space basis. Design professionals are expected to customize their specified sequences to meet the client’s needs whether they’re designing an office building, BSL III laboratory, elementary school or operating room suite. The specified sequences are not just based on the intended operation; oftentimes, these sequences incorporate the capacity of the equipment, code requirements, and process-specific applications for the spaces served. Replacing a specified sequence with a canned routine can have significant ramifications on system performance, energy efficiency, and even life safety. The ATC contractor is obligated to submit on and provide the specified sequences in order to meet the design intent. Agreeing to one thing and providing another is simply not acceptable.
Now, having illustrated some of the evils of canned routines, I feel compelled to point out that they’re not all bad. But how do we know the difference? When a canned routine is used in place of a specified sequence, is it fair to place the blame solely on the ATC contractors if their intent was to provide a level of control or optimization in excess of what was specified? To what degree should the design professionals (engineers) be held responsible for researching control strategies and educating themselves on new products to provide the most economic and efficient building control system?
Several major temperature control companies have spent a considerable amount of effort on research and development to determine which sequences are the most efficient and which meet ASHRAE energy and ventilation control guidelines. These types of canned routines may exceed the performance requirements identified in the specified routines and can provide more efficient or more accurate control. Additionally, the capability of most operating systems has grown by leaps and bounds within the past few years and there are many features available of which design professionals may not be aware. Some systems even offer performance optimization packages for chilled water plants that, for example, include routines designed to maximize system efficiency through the use of established and tested routines.
Like so many other issues that exist in the sometime nebulous relationships between design professionals, consultants, and installing contractors, this issue also requires a diplomatic effort on all parts to achieve an acceptable solution. If the design engineer approached these canned routines with an open mind (as they often do), they may find that some of them are acceptable and may be an improvement over what they typically specify. If the ATC submittal reflected where and how they intended to deviate from the specified sequence (as they sometimes do), then the design engineer would have the opportunity to review and even approve it.
The commissioning provider can also help to identify these issues through focused collaborative sessions with the designer professionals and the ATC contractor. Typically, these sessions are held to clarify design intent and address specific concerns when developing functional testing documentation. However, these sessions have also proven to be a testing ground where a few simple questions can uncover the intended use of canned routines. The commissioning provider should have adequate experience and field knowledge to identify these discrepancies.
Waiting for the commissioning provider to find out in the field, weeks before occupancy, that a canned routine was used in lieu of the specified sequence without prior authorization is not the ideal approach. It results in everyone (design professionals and contractors alike) spending additional time to review the issues and could potentially cause delays to the project that could have otherwise been avoided.