2 Replies Latest reply: May 21, 2012 11:37 AM by ikrull1 RSS

CDA Fault Detection for VAV's


Why should I manage VAV Box Faults with Panoptix?

  • Re: CDA Fault Detection for VAV's



    Thanks for the question about why using Panoptix with VAV boxes is so valuable.  As you know the management of VAV boxes (really all equipment) and the identification of abnormalities, or faults within pieces of equipment, is a very important part of running a highly energy and cost efficient facility.  Having a detailed view of the equipment's performance (not just limited to VAVs) allows a user to uncover opportunities for cost savings via minimizing energy waste, improving occupant comfort within a particular space, and even potentially detecting early mechanical failure.  Ultimately a solution such as the Continuous Diagnostics Advisor (CDA) helps buildings run more efficiently, which translates into energy and cost savings.  Additionally, CDA provides this data to the user automatically which saves the user time and resources furthering the cost savings.


    Marc Brandt

  • Re: CDA Fault Detection for VAV's

    Let me try to tackle this question with an example scenario we experienced at  BE headquarters. I worked with the on-site HVAC technician to try and troubleshoot why the Panoptix fault , "VAV Supply Flow Absolute Error", had been triggered on three VAV boxes.


    Analysis -


      There were no occupant complaints received regarding comfort yet all three boxes were in fault. Upon further investigation we learned that someone added custom control logic to override the Damper Position through a software point on the VMA controller. The control logic was correct in its application to the VAV strategy however, the default value for the damper position point was zero.  This resulted in overriding the damper position to zero upon a controller restart.  These circumstances had been in place for months and as mentioned earlier with no complaints from the occupants.

    You should be asking, "Why should service technicians and other HVAC professionals care about issues that are not reported by the occupants? I would answer that question with the following points


    1) By knowing all VAV faults that exist on site, a Facility Manager can defer fixing particular boxes when resources become available. The Facility Manager can also defer these fixes until an HVAC professional has a scheduled visit thus saving money on reducing the amount of service trips made.


    2) One or even a few faulty VAV boxes may have zero impact on a system as a whole. In fact, they may actually save money if the boxes are stuck closed. However, when there are numerous VAV boxes that start having issues this can lead to additional and costly energy consumption of an Air Handler Unit depending on the issue at the VAV level.  See examples below -

      a)  Multiple boxes that are hunting - These boxes put a burden on the AHU VFD to ramp up and down to meet their                needs.

      b) Multiple boxes starved - The VFD will stay at an abnormally high operating level to maintain Duct static pressure.  Very costly

      c)  Multiple boxes with low flow faults - give an owner false operating costs at the expense of the occupants.  A potential SBS (Sick Building Syndrome) issue.

      d) Multiple boxes with a combination of issues - very difficult to predict the operating costs of an AHU.

      Any box that hunts or cycles abnormal will contribute to higher than normal operating costs and a shorter equipment life cycle.


    3) Finally, lets not forget the occupants.  Do not assume because they are not complaining that they are comfortable, I myself had worked in an environment like this. For several months my work environment was extremely hot. I was told this was due to the amount of PCs and servers that were running in my work area, so I never called to complain about it. One day the on-site HVAC tech showed up and informed me the VAV damper, right above my head, had been stuck for months. Once he fixed the issue my work environment was so much more comfortable. To compensate for the hot environment I had to stop wearing sweaters in the winter time to work, which in Wisconsin is not always the best thing to do.