I can’t believe it has been more than a year since I wrote my last column about the difficulties associated with commissioning systems with both on-board equipment controllers and central building automation DDC systems. That was February 2010, and only 16 months later did I find a contractor’s project manager who was actually changing “business as usual” to address those challenges.
To summarize the problem that plagues so many projects, the coordination between on-board equipment controllers and central DDC systems is typically abysmal, starting in the design phase and continuing through construction and start-up. My February 2010 column addressed what can be done during the design phase to improve the situation.
Clearly defined design requirements form the foundation upon which the equipment/controls integration can be painlessly executed throughout the remainder of the project. However, clearly specifying the interfaces between systems and detailed control sequences in the design phase does not ensure that the work will be executed properly during construction.
MAKING IT CLEARWe are still faced with a high probability of misunderstanding between equipment providers and the DDC system provider. Let’s use chillers as an example. The design should clearly define which controller (DDC or on-board chiller controller) has which control points wired to it (pump control, pump status, supply and return water temperatures, flow switch, compressor start/stop, compressor status, electrical demand, etc.). The design should also be clear regarding which controller is responsible for which control programming/logic (chiller enable, compressor staging, chilled water temperature setpoint, etc.). Finally, the design should clearly define exactly which on-board chiller controller points are to be mapped to the DDC system for central monitoring.
Regardless of all of these details in the design specification, equipment manufacturers do not typically consider it their responsibility to make sure the DDC contractor is doing his part. Alternately, most DDC contractors do not feel that it is their responsibility to confirm that the equipment manufacturers are doing their part. Everyone simply assumes that the other party is taking care of their business. Those seem like reasonably fair assumptions, but we have learned that this integration process is not always so simple and that two-way communication is required between manufacturers and DDC contractors. They both need to understand types of signals required, communication protocols, termination types, responsibility for wiring between controllers, etc.
In addition, the timing of when each party “takes care of their business” is critical. The equipment manufacturer needs the DDC system elements terminated, checked out, and communicating when the start-up technician arrives on site. Otherwise, the technician will be unable to set up and test the chiller side of the system integration.
This either means that the integration is not part of the manufacturer’s start-up process or it is rushed and piecemeal as the DDC contractor tries to catch-up under pressure. The manufacturer’s contract typically includes one start-up technician trip to the site. If integration coordination is not completed during that one visit, it may be attempted later without the benefit of the trained start-up technician (because another start-up trip would cost the contractor extra). This is invariably less efficient and effective than getting it done during the official equipment start-up.
As you can imagine, the fingerpointing can be rampant in these situations. “The equipment manufacturer didn’t tell us,” or “The DDC contractor wasn’t ready.” I believe it is the general contractor’s/construction manager’s responsibility to coordinate the work of these subcontractors. It may also be delegated to the mechanical subcontractor, as long as both the equipment manufacturer and the DDC contractor are under the mechanical subcontract. That means understanding the communication, installation, and start-up/check-out steps of the integration process and making sure they are all clearly identified on the construction schedule.
This will go a long ways towards successful start-up of the equipment and check-out of the integration elements during the manufacturer’s start-up visit. It should also minimize the amount of time spent finding, documenting, and troubleshooting system integration issues during subsequent commissioning functional performance testing.
A WORTHY PROPOSALThe best idea I’ve heard so far - the one I learned from a project manager last month - is to require the DDC contractor to be present and participate in the equipment manufacturer’s start-up process. All aspects of the integrated communications and controls can be addressed with knowledgeable technical representatives of both parties there in person. It should limit the opportunities for the start-up technician to give up because the DDC contractor “didn’t do something,” “did something wrong,” or “wasn’t available.” This start-up approach should maximize the efficient resolution of inevitable coordination issues before the commissioning professional enters the scene, finds the problems, and starts documenting them.
Although it sounds like extra work for the DDC contractor to participate in major equipment start-up procedures, I believe it is probably less time than the DDC contractor would otherwise need to spend dealing with coordination issues after the fact.ES