Paving the Path to DDC from Pneumatics
How much money are your pneumatics blowing?
Pneumatics have been successfully utilized for decades in many mechanical control environments with some installs dating back to 1950’s. Many engineers and technicians found the beauty of pneumatics to be in its flexibility, ease of repair, and availability of parts. Pneumatics utilized some of the main components of modern control applications including PID loops, advanced sequencing, and local zone controls. So why are commercial upgrades to a DDC (Direct Digital Control) system so prevalent? What are some pitfalls to maintaining your current pneumatic system? HVAC controls have greatly evolved from the introduction of pneumatics presenting the possibility of annual cost reductions in a commercial environment.
Although some pneumatic controls have been around for more than fifty years, air powered systems contain many limitations that are often overlooked by building owners.
- When was the last time you tuned your pneumatics for the right control pressure?
- How often do you re-balance your local VAV pneumatic controllers?
- How often do you check for air leaks in your control lines?
Preventative Maintenance on Pneumatic Systems
Preventative maintenance is crucial for a pneumatic control system as a controller can fall out of calibration within a 6-12 month period of commissioning (Reference this Predictive Maintenance article for cost associated with using preventative maintenance techniques). A 25% percent deviation from command to actual output could cost a building owner thousands of dollars in over consumption; Multiplied over the course of two hundred or more controllers out of calibration and the energy bill could be 30-50% higher than expected.
When considering annual maintenance on your pneumatic system, who can you hire? How many resumes are presented in the market with 3-5 years pneumatic experience? Many college graduates and entry level engineers are educated on more modern HVAC controls and strategies, making in-house repairs typically impossible and contractor reliance more prevalent. The above table presents a typical pneumatic maintenance schedule. Notice how often preventative system maintenance is required that would be irrelevant in a DDC system that doesn’t require compressed air as a control medium.
DDC Systems – From Luxury to Cost Savings
In their infancy, DDC systems were seen as a luxury to facility engineers. When a malfunction occurred engineers typically had to go inspect the pneumatic controls locally as remote monitoring was unavailable. So what are the benefits of DDC in a monitoring application? If you could predict local failures through your control system would it increase tenant satisfaction? As DDC technology has evolved so have the features it presents to the end user. If a valve suddenly becomes inoperable, the facility engineer is notified and can react accordingly to prevent any negative tenant feedback.
Although not always easy to quantify, upgrading from a pneumatics control system can logistically save hundreds of annual maintenance hours. Rebate programs offered by utility providers often overlook the energy savings associated with pneumatic upgrades; Typically because energy models present the pneumatics in an perfectly maintained state. Even with limited utility rebates for direct replacement of pneumatics, the energy reductions strategies electronic DDC systems offer can greatly increase ROI (Return of Investment) for installations.
What has been your experience when maintaining or retrofitting pneumatic systems and devices?