The last three articles outlined pump selection in domestic water recirculation systems. In general, these systems have low flow and low head pumps. What happens in a high rise with pressure reducing valves (PRV) in the hot water supply? The pressure reducing valve introduces a fixed pressure drop which must be added to the calculations.
The purpose of the domestic water recirculation system is to delivery hot water near a fixture during times when there is no draw. If someone is using hot water in the next room or apartment or process; the hot water is near enough to your fixture so the hot water is delivered in seconds, not minutes.
Let’s assume the domestic hot water supply is a total length of 1000 ft. That is the entire pipe on all of the floors. Let’s also assume an average of 15 BTU/hr/ft of loss through the supply pipe insulation. Now let’s assume the recirc piping is 300 ft total at an average of 10 BTU/hr/ft of loss. What flow rate is required for a 10 degree ΔT? What flow rate is required for a 5 ΔT?
Problem Identified CoCoWalk, a large multitenant lifestyle center in Florida, was faced with the following water quality challenges across their cooling tower and closed-loop …
Problem Identified The Indiana State Museum & IMAX Theatre was faced with the following water quality challenges across their closed loop and domestic water …
Problem Identified Henniges Automotive was faced with the following familiar water quality challenges in their closed loop chilled water system: Chronic corrosion Sludge buildup Frequent …
The R. L. Deppmann Monday Morning Minutes series will focus on the plumbing portion of the new construction and building facility business for the next few months. The topics will be domestic water recirculating systems, pressure booster systems, volume and instantaneous water heaters, and mixing valves. I’ve had 6 job site visits in the last 2 months to help engineers, service contractors, and facility managers solve problems with domestic water recirculating systems. It seems this is a good place to start.
Problem Identified Iowa State University (ISU) was faced with the following water quality challenges across their domestic hot water system: Chronic lime-scale buildup Hard, …
The last two weeks we used the Pump Affinity Laws and the Xylem Bell and Gossett System Syzer® to either trim the impeller or reduce …
Last week we used the Pump Affinity Laws to determine what size the impeller would be trimmed to in an oversized pump. Reducing the speed …