The Viega SmartLoop system can provide major benefits to domestic hot water (DHW) temperature maintenance systems, as evidenced by a project in Washington, when compared to both a traditional recirculation system and a heat trace system.
Ecotope, Inc., a company focused on energy efficiency and Mechanical Design in Seattle, Washington, conducted a study comparing different types of temperature maintenance systems for central DHW loops. The study was supported by Bonneville Power Administration and developer Asani, LLC, and was installed in the second phase Grow Community Development on Bainbridge Island in Washington. The program contained three similar 12-unit, three- story buildings.
One of the primary goals of the project was to develop net-zero energy housing – homes that can provide as much renewable energy as they use, leaving occupants with a net energy use of zero. This goal required the water heating systems to use high-efficiency air-to-water heat pumps in order for the DHW systems to meet targets. Each of the three buildings has a central heat pump hot water plant, but each was designed and installed with a different variation on temperature maintenance. These three systems were a traditional circulation loop, the Viega SmartLoop recirculation system and electric heat trace on the supply piping only. All of the heat plants included a data collection system.
“We wanted to run an experiment and see if we could tell what was the best way to deal with temperature maintenance loads in projects seeking high efficiency water heating systems,” explained Shawn Oram, P.E., Director of Engineering and Design with Ecotope, Inc.
“We wanted to answer this question and sort of a bigger question for the Pacific Northwest region: what are the energy impacts between different methods for maintaining hot water loops? We went through the designs and kept a good research basis so we could compare the results of the three different systems and how much energy they use. There aren’t any studies like this and designers don’t really understand how large these loads can be and what steps can be taken to reduce these loads.”
One building uses a traditional recirculation system. The second building incorporates heat trace and the third was constructed with Viega SmartLoop technology. Oram said he expected significant savings between SmartLoop and the traditional system, and he wasn’t disappointed in results.
“These represent a pretty typical case of construction, and the basic findings were that SmartLoop is about a 40-percent savings over the traditional recirculation,” Oram said. “You reduce the heat loss area and that’s really the whole game here. It’s the function of the insulation when you put the return pipe inside the supply.”
After crunching data on all the apartment buildings, Oram had interesting findings on SmartLoop as compared to the heat trace building, too.
“Even though heat trace results in less heat loss for a building, as only the supply pipe surface area needs to be maintained, the well-insulated SmartLoop allows us to apply heat pump efficiency to the temperature maintenance load. This further reduces the energy associated with temperature maintenance beyond what an electric heat trace system provides,” he said.
The buildings were constructed and acquired tenants over the course of the past three years. Oram said in the spring of 2017 there were enough tenants in each building to begin collecting measurable data.
Originally, SmartLoop was pitched by Viega Technical Manager Ralph Baumann as a system to prevent legionella, a type of bacteria that can be found in stagnant water. The Viega Smart Loop is a proprietary internal recirculation system that keeps water moving and keeps it hotter longer, which reduces waste, increases energy savings and – the target for this project – helps maintain temperature.
“SmartLoop seemed to be marketed not so much as an energy piece, but more with the Legionella prevention – but when we looked at it, our minds were focused on energy and we thought it could cut costs,” Oram said. “We sort of stumbled upon SmartLoop, and we saw the savings potential based on what we knew about heat losses.”
Oram noted that SmartLoop has a smaller profile, with only one pipe to mount and insulate versus a traditional system. However, in some markets, including Washington, he noted that copper has a lot of competition with plastics, particularly with copper costs on the rise. Still, the energy savings with the pipe-in-pipe are large and most utilities are set up to provide an incentive for the first year of savings.