Wireless Pneumatic Thermostat
Pneumatic thermostats: Wireless Retrofit vs. Conventional
Retrofit pneumatic thermostats with wireless pneumatic thermostats to allow DDC-type control with programmable setbacks, diagnostics, and communications capability
Item ID: 264
HVAC--Sensors & Controls
Technical Advisory Group: 2011 Energy Management TAG (#4)
Average TAG Rating: 2.07 out of 5
TAG Ranking Date: 09/29/2011
Invented in 1896, pneumatic thermostats were the most common HVAC control technology deployed for over 100 years. Consequently, many buildings still exist with pneumatic thermostats. Direct digital control (DDC) thermostats have been installed in most new commercial buildings since 1995. However, in some locations in the U.S., buildings constructed as late as 2008 have been found with pneumatic thermostats, even though many building codes now disallow their use in new buildings.
Pneumatic thermostats have the following limitations:
• The temperature on pneumatic thermostats must be changed manually. As a result, managing the temperature setpoint and establishing night setback policies is not practical.
• Without communications functions, pneumatic thermostats cannot participate in auto-demand response, be controlled remotely, or alert managers to issues.
• With pneumatic thermostats, tenant complaints are the only data points that maintenance crews can respond to. As a result, instead of finding and fixing issues quickly before tenants are aware of them, maintenance crews spend hours searching for the root cause of problems.
• In addition to the lack of functionality described above, pneumatic thermostats require manual calibration every six months. Calibration drives additional labor costs and, if not done routinely, results in even greater energy loss
By retrofitting a pneumatic thermostat system with wireless pneumatic thermostats, commercially available since 2009, the building can essentially be converted to DDC, giving scheduling, night setback, remote programming, fault diagnosis, and communications capability.
Baseline Description: College Building Dept of Psychology
Baseline Energy Use: 2561500 kWh per year per unit
McGill-Mandler Hall as UC San Diego is 112,500 square feet. They replaced 250 existing pneumatic thermostats with wireless pneumatic units at a cost of $295,700. They saved 538,900 kWh of electrical energy annually along with 57,000 therms of natural gas. (Energy Upgrade California Case Study).
Manufacturer's Energy Savings Claims:
"Typical" Savings: 25%
Savings Range: From 18% to 30%
Best Estimate of Energy Savings:
"Typical" Savings: 25%
Low and High Energy Savings: 18% to 30%
Energy Savings Reliability: 4 - Extensive Assessment
GSA estimates that transitioning from pneumatic to thermostats with DDC like control capabilities can reduce HVAC energy use by 18% to 30%(GSA, 2013). A retrofit of 250 pneumatic thermostats at a UCSD Department of Psychology building resulted in electrical energy use savings of 27% with a 51% annual savings in natural gas usage (Note: the full building project did include variable frequency drives on air handler fans and new outside air economizer dampers)(Energy Solutions, 2012). A building in Oakland replaced 264 pneumatic thermostats with WPTs and achieved a 15% reduction in energy use and a 35% decrease in gas use(Wilkinson, 2013).
Energy Use of Emerging Technology:
1,921,125 kWh per unit per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Currently no data available.
Installed first cost per: unit
Emerging Technology Unit Cost (Equipment Only): $295700.00
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.00
Baseline Technology Unit Cost (Equipment Only): $2957000.00
For a 50-thermostat system, including the repeater and green box, the cost would be about $600 per thermostat, installed. This is less expensive, less disruptive to install, and less invasive than a DDC system where the cost per thermostat is about $2500 installed. The County of Santa Clara, CA installed 350 WPTs for a total project cost of $175,000 (or $500 per thermostat)(edc Magazine, 2013). An equipment plus installation cost of $295,700 was incurred for the installation of 250 pneumatic thermostats at UCSD(Energy Solutions, 2012).
Simple payback, new construction (years): -46.2
Simple payback, retrofit (years): 5.1
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
Note: the simple payback calculated is based on electrical energy savings alone. The UCSD project also resulted in the savings of 57,000 therms of natural gas annually. The actual simple payback for the pneumatic thermostat upgrade project---absent any utility incentives, was 3.1 years.
Stand-alone pneumatic thermostats are not allowed under current building codes. The cost effectiveness for a retrofit project will depend on a number of factors, including the building, climate, how the building is currently controlled, the size of each zone being controlled, etc. Using the conservative 10% savings figure, a single thermostat could pay back in one to three years. Further, there is a significant maintenance savings that can sometimes exceed the energy savings (see case study in “Prior Work” below).
Buildings with pneumatic thermostats use significantly more energy and incur much higher labor costs than buildings with direct digital control (DDC) thermostats. Three characteristics of pneumatic thermostats make energy reduction and maintenance savings unachievable:
1. Not programmable i.e. cannot enter daily occupancy schedule with temperature setbacks for night and unoccupied periods
2. Lack communications functions i.e. building managers cannot change temperature setpoints or schedules remotely
3. Cannot produce diagnostic or temperature trending data. Cannot provide information on over-rides during evening hours.
The Wireless Pneumatic Thermostat (WPT) is a new retrofit technology that drastically reduces the cost and minimizes the disruption of retrofitting pneumatic thermostats. The WPT provides an option for the mass market to adopt programmable, communicating thermostats. Unlike DDC, the WPT is a hybrid pneumatic-digital technology that utilizes the existing pneumatic infrastructure. It eliminates the need to open walls, run wires and install new actuators. Instead of requiring hours to days for a retrofit, technicians can replace an existing pneumatic thermostat with a WPT in approximately 10 minutes. Due to the simpler installation, the total cost of the WPT retrofit is approximately 80% less expensive than alternative DDC solutions and pays back in approximately 18 months.
Existing pneumatic thermostats are designed to maintain a single setpoint temperature and have to be set back manually for unoccupied periods. This is seldom done. This WPT product can control the temperature, allow automatic setback, provide troubleshooting capabilities, and allow for diagnostics remotely.
Product has been commercially available since 2008. The original unit was designed by ex-Honeywell engineers.
This technology saves both electrical energy and natural gas. Due to the fuel-fired equipment savings, significant greenhouse gas emission reductions are often achieved.
End User Drawbacks:
There can be concern over the potential of communication interference with wireless technology. However, technology is available to determine if a site is vulnerable to interference.
Operations and Maintenance Costs:
No information available.
This is a newer technology so does not have a known operating lifetime, but it is an electrical system like any other control system and so there is no reason to think it would not also last about the same as other controls, or about 15 years.
DDC is what has replaced pneumatic. Now, however, DDC is expected to be replaced by wireless communications. DDC requires the building owner to open up walls and ceilings to run communication wire, which disrupts the tenants and costs about $2500 per thermostat.
Reference and Citations:
The HVAC Factor: Wireless Thermostat Conversion
Today's Facility Manager
Wireless Pneumatic Thermostats Help UCSD Reach Sustainability Goals by Reducing Greenhouse Gas Emissions by 538 Tons/Year
Energy Technology Assistance Program
Case Study: Wireless HVAC
Wireless Pneumatic Thermostat
GSA Green Proving Ground
County of Santa Clara Installs Cypress Envirosystems' Wireless Pneumatic Thermostat
Wireless Pneumatic Thermostat Ideal for Economic Stimulus Plan
Convert your old building to DDC with wireless pneumatic thermostats
WAPA Energy Services Bulletin
See page 5
Cypress Envirosystems ,
Retrofitting Existing Buildings for Demand Response & Energy Efficiency
Wireless Pneumatic Thermostats: Quality Commissioning is Essential
20th National Conference on Building Commissioning
SMART 2020: Enabling the low carbon economy in the information age
Boston Consulting Group