Domestic Hot Water Recirculation Part 2: Where ASHRAE 90.1 Conflicts with OSHA

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When it comes to domestic hot water recirculation design, OSHA safety provisions and ASHRAE 90.1 energy efficiency requirements have put plumbing engineers between the proverbial rock and hard place. In an effort to minimize the energy penalty associated with mandatory domestic hot water recirculation, ASHRAE 90.1 has created operational parameters for these systems. The problem is that these parameters are in direct conflict with OSHA’s requirements for Legionella prevention.
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Domestic Hot Water Recirculation Part 1: What’s The Point?

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What could have led ASHRAE, and subsequently building codes all over the U.S., to require domestic hot water recirculation systems in non-residential buildings? This relatively bold stance on water conservation is quite simply a reaction to profound water shortages throughout the U.S. – shortages that will only get worse as the population continues to increase.
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How to Avoid Legionella Outbreaks in Domestic Hot Water Systems

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Domestic hot-water systems are frequently implicated as the source of legionellosis (Legionnaires’ disease) outbreaks. Very small quantities of Legionella, the bacteria that causes the disease, is commonly found in the ground, in water, and even in tap water. Legionella is not likely to become a health risk unless it begins to multiply and colonize. If not properly designed or maintained, a domestic hot water system (as well as other open water systems) can facilitate such growth....
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Understanding Primary Secondary Pumping Part 6: 5 Ways to Pump an HVAC System

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By Chris Edmondson

There’s more than one way to pump a chiller or boiler system.  In fact, there are five common approaches, and all but one includes some variation of our topic of late -- primary secondary pumping. 

Variable Primary Pumping

Contemporary systems that do not utilize primary secondary pumping are typically known as variable primary systems.  In this simple design, there is only one set of pumps (chiller or boiler pumps) creating flow for the entire system. 

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Understanding Primary Secondary Pumping Part 5: Best Practices for Piping

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By Chris Edmondson

Piping in a primary secondary pumping systems as a whole can be quite complex, but when it comes to the “primary” part of the system, there are really only two approaches:  Dedicated or Non-dedicated.

Figure 1 shows the chillers in a primary secondary system piped with one pump per chiller.  If the chillers

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