In today's fast paced construction industry, critical deadlines can sometimes force a design team into STL mode (spread the lead). And we all know that mode's evil twin brother, CYA. When the design team slips into these modes, equipment tends to be oversized and the operational impact of oversized systems is often forgotten. Oversized equipment, combined with lack of consideration for part load operation, can result in serious operational headaches as well as unnecessary additional utility costs. In addition, the impact that a project has on other systems or buildings is often not seen through design deadline blinders. Let's take a look at the selection of chilled water coils for example.
I spent practically all of last year's brutally hot summer crawling through 120 degrees F steam tunnels (cue the violin), evaluating the performance of a chilled water distribution system for a client in Boston. The assignment was to identify measures that could potentially reduce chilled water flow (not necessarily load) and increase the overall campus chilled water Delta T. The client purchases chilled water from a remote plant and there were significant penalty charges resulting from returning water that is far below the minimum return temperature required by the contract. Reducing flow demand and increasing the Delta T would free up capacity in the overloaded piping system and reduce penalty charges at the same time.