TECHNICAL FEATURE a system goes down will it noticeably impact TABLE 1 User Rights Matrix. the business and credibility of my client? If a USER/GROUP READ-ONLY SCHEDULE CHANGE OVERRIDE PROGRAMMING CREATE/ AUDIT chiller controller goes down and you are runROLE VALUE TOOLS MODIFY TRAIL USER ning the plant in manual for three days until you get a spare controller, is that impacting LEVEL 1 ü û û û û û û your business? What is the cost for your client, financially LEVEL 2 ü ü û û û û û and in terms of credibility, of the system LEVEL 3 ü ü ü ü û û û being impacted? When I worked with a certain data center company, they had a data LEVEL 4 ü ü ü ü ü ü û processing machine that cost $1 million dollars per minute if it was down. As you can LEVEL 5 ü ü ü ü ü ü ü imagine, the cost of triple redundancy (we used three supervisory controllers, field Putting it All Together controllers, and sensors) was negligible compared to Are all of these pillars required? How secure do you the downtime cost. want your building to be? The answer is easy when we Spec it Out use extreme examples like a federal reserve bank, but Table 2 shows the relationship between tier levels and what if the building is a medium-sized commercial the level of redundancy required. space? What would happen if someone hacked into the www.info.hotims.com/49808-49 68 ASHRAE JOURNAL ashrae.org SEPTEM BER 2014