Cost-Effective Analog-to-Digital Thermostat Retrofits

According to David Roberts, director of marketing at Cypress Envirosystems, about 70% of existing commercial buildings have pneumatic thermostats. These thermostats contain a metal strip that bends one way when cold and another when hot, changing the air pressure in the system, which then opens and closes dampers in the mechanical system to let in conditioned air as needed. Though it is a reliable, proven technology that has been used for more than 100 years, pneumatic thermostats have a significant limitation: they are manual. “If you have an office or conference room that is not used after 4 p.m. but other people work until 8 p.m., you have to leave the entire building on,” said Roberts.

Direct digital controls (DDC) for HVAC are installed during construction in most new buildings, when access to walls and wiring is easier. Retrofitting digital controls into older buildings that contain pneumatic thermostats—which includes most buildings constructed prior to the mid-1990s—involves shutting down the building and tearing into the walls and ceilings to install the wiring and equipment. This can be impractical and expensive, particularly if asbestos is discovered during the process. With Cypress’s WPT system, facilities can simply take the old thermostat off the wall, remove the air pipes, reattach the pipes to the new thermostat, reinstall it, and calibrate the WPT. Then you set up the wireless network, which includes repeaters, controller, and hub (one wireless network can support up to 225 WPTs). Total installation time per WPT: 20–30 minutes.