Affordable Thermostat Retrofits: Analog to Digital in 30 Minutes
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This Cypress Envirosystems' Wireless Pneumatic Thermostat replaced the old thermostat (lower left) allowing remote control and monitoring of building temperatures at a fraction of the cost of direct digital controls. Photo: Cypress Envi... Installing a digital retrofit is not so easy Unfortunately, retrofitting old buildings with new wiring and ceiling-mounted equipment is disruptive, often requiring the work area be closed down (which can also be expensive!). Workers need to access walls and ceilings, and the labor required is significant, particularly in old buildings that might still contain asbestos. Cypress Envirosystems' WPT system, on the other hand, requires almost no invasive work. Installers, certified by the company, take the old thermostat off the wall and remove the air pipes, reattach the pipes to the new thermostat, and attach it to the wall. Next, they set up the wireless network, and the system is up and running. It takes about half an hour. Demand-response capable WPTs communicate back to a central box that can be hooked into any building automation control (BAC)--a Web interface is used if the building has no BAC--and provides a platform that can monitor zones and control chillers, making it possible to systematically manage building temperatures. This is a valuable tool that keeps occupants comfortable and allows commercial buildings to participate in demand-response programs (where utilities are linked to a building's HVAC controls to lower energy use during periods of peak demand when electricity is expensive and often created with more polluting equipment). Commercial buildings account for 50% of peak-demand power consumption, but only about 4% of commercial buildings participate in demand response, said Roberts. Old pneumatic thermostats like the one shown here have to be adjusted manually yet are still used in the majority of commercial buildings. Photo: Cypress Envirosystems Does it work? WPTs have been installed in a number of high-profile buildings, including the Capitol Hill Government Offices in Washington. The somewhat less powerful county of Santa Clara installed the WPT in 300,000-square feet of its government buildings and showed a 7% reduction (227,327 kilowatt hours) in electrical consumption over seven months and an estimated annual savings of $42,000 in equipment and electricity. Walt Dubois, P.E., facilities manager at the 550-bed St. Joseph Hospital in Phoenix, has installed more than 60 of the thermostats in patient rooms and is impressed by the technology. He said he has diagnosed stuck dampers and other problems from home, and has been able to schedule repairs when the patient was out of the room. "We cannot just lift ceiling tiles in patient rooms," he said. "There are issues with infection controls and risk assessment." In over a year's worth of use, he notes, not a single WPT has failed. The best part: cost Dubois installed pure direct digital controls in the hospital prior to 2008 at around $2000¬–$3000 per thermostat, but after 2008 he no longer had the budget. At around $400 each (Cypress Envirosystems says the current price is in the $500–$600 range, including labor and wireless set up) WPTs were inexpensive enough that he was able to pay for them as a standard operating expense. What are the tradeoffs? You won't get quite as much data and performance from WPTs. "Pure digital systems with digital motors at the damper will give you better granular data," Roberts admits. And you will have to change the batteries every few years (the dashboard will give you a warning). Direct digital controls "are the Cadillac and we are the Chevy, but we think we are getting 90% of the benefit at 20% of the cost," he said. Cypress Envirosystems estimates a payback of less than two years on the WPT and all of its other products, which include wireless steam-trap monitors, gauge readers, and transducer readers. Brent Ehrlich is the products editor at BuildingGreen, Inc.