54/Plumbing Engineer May 2021

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revolution is happening in today's commercial plumbing marketplace, specifically when it involves domestic hot water system designs. Manufacturers now supply better-performing digital mixing valves stacked with features and enhancements that carry the capabilities of remote temperature adjustment, high-temperature saniti- zation, building management system integration, multiple temperature and pressure measurement points, flow mea- surement, self-cleaning, self-monitoring and self-balancing. These features and the parallel capabilities and advances in digital smart circulator pumps for these applications, allow building designers and specifying engineers to think about the domestic hot water system in ways never previ- ously imagined. In the past, conventional mixing valve technologies such as bellows, wax or bi-metal would sim- ply allow the end-user to set the temperature at initial flow condition. Active monitoring of upstream (inlet) or down- stream (outlet) temperatures or pressures was not an option. The balancing of the recirculation system was accom- plished by an iterative process of manually throttling a return ball valve or circuit balancing valve on the return line, based on a fixed temperature loss in the system. Typically, it would take multiple iterations over days to stabilize system temperatures under pure circulation. If system conditions experienced even slight variations in temperatures or pressures, facility managers were faced with reactionary tactics in the face of no active feedback loops or data that could be served up from the device. Today, due to the stacked features within DMV offerings, there is an active shift from reactive to proactive manage- ment of the domestic hot water system. This is now allow- ing facility managers a complete thought process transfor- mation. Previously, the master mixing valve was thought of as a high-maintenance device - "the enemy." Now, the thinking is that DMVs combined with energy-efficient smart pumps can "change the game." Simply put, feature-packed DMVs provide the vehicle for an ultra-safe and efficient domestic hot water system design. Several frameworks are available to operate when choos- ing the applicable path to domestic hot water system design, depending on the specific application. This discussion is not, by any means, comprehensive but rather hopes to illustrate how today's DMVs can help a system designer or specifying engineer achieve mutual outcomes of enhanced domestic hot water safety while satisfying an established standards directive. VHA Directive 1061 The Department of Veterans Affairs issued a Transmittal Sheet (Feb. 16, 2021) with updates to the Veterans Health Administration directive addressing the prevention of health-care-associated Legionella infection and scald injury from water systems in VHA buildings. Specifically, these buildings were those where patients, residents or visitors stayed overnight; where employees are required to sleep overnight; and for the management of select outdoor non- potable water systems. Engineering control strategies exist for the ongoing prevention of Legionella growth within those situations, the deadly bacteria responsible for Legionnaire's Disease. Specifically, for incoming potable water, the pressure and temperature must be monitored in addition to measurement at water storage tanks, discharge from hot water source equipment, water at the return of circulation loops and water supplied to representative areas of the building (i.e., risers). The directive also stipulates the data must be reviewed, at a minimum, weekly. Q: If the digital mixing valve monitors temperatures and pressures at the mixing valve inlets, how could one also measure incoming potable water temperature and pressure and measure all the additional points previously stipulated? A: With a DMV such as the Leonard Nucleus, the pri- mary valve offering allows four temperature measurement points and two pressure measurement points. With the addition of a simple plug-in expansion card, one can now

Product Application

By Rick Cota

Raising the Bar for Safer DHW System Design and Distribution

Feature-packed DMVs provide the vehicle for an ultra-safe and efficient domestic hot water system design.

Leonard Valve's Nucleus electronic mixing valve, Megatron NV-150-LF.