Troubleshooting HVAC Checklist
Sometimes to identify the problem, you need to work through a checklist. Here's an example of one:
ELEPHANT: When you're collecting data to diagnose the root of the problem, you are "looking for the elephant in the room." (Courtesy of Adobe Stock)
For years I've had the privilege to be asked to troubleshoot problematic heating, ventilating, and air-conditioning (HVAC) installations. You could say I have made a career of this, and I have always enjoyed the challenge of striving to find a solution to a building owner or facility manager's operational problem. Over time, I have created a master checklist of what to look for after you have met with your client (Step 1) and prior to heading out to walk the site.
While hindsight is 20/20, time-tested quality control tells individuals not to jump to the solution even if you think you have the answer. So often, by completing a survey of the problem issue, an optimum solution will take shape versus first impressions. Data collection is always Step 2, and it is the process I like to say is "Looking for the elephant(s) in the room."
Even on projects I have engineered in the past, I would reflect back and think of how that job provided the optimum solution at the time, but things change over time and I would change with the times too. Certainly, energy conservation measures have driven change, and equipment manufacturers have improved their products over the years. HVAC systems have also changed over the years, and an engineer today would probably not design the same system for certain applications now that they may have designed 15 years or more ago, e.g., constant volume reheat then and radiant heat with minimum outdoor air today.
Getting back to troubleshooting data collection, I have always been a proponent of the use of checklists, another quality control tool, and in this case, a sample of a troubleshooting checklist may look like the following:
On the Roof:
- Adequate distance between exhaust vents/louver(s) and plumbing vents from air intake louvers
- Safety concern relative to servicing equipment installed close to the edge of the building
- Safety concern relative to servicing equipment on a sloped roof
- Bee, wasp, and hornet hives/nests attached to equipment or near an outdoor piece of equipment (some individuals can be seriously affected by bee stings)
In the Equipment Room (boiler room, chiller room, and fan room):
- Adequate ventilation
- Safety hazard of excessive space temperature on occupants in a boiler room
- Boiler performance when room is under negative air pressure
- Safety hazard of chiller within a boiler room
- Safety hazard of refrigerant relief venting within the equipment room
- Safe service access to equipment
- Inadequate lighting in the area of equipment servicing
- Eye wash safety station
Around and Inside the Building:
- Experiencing building under negative pressure
- Experiencing building under negative pressure when central air systems are in minimum outdoor air ventilation mode sequence of operation
- Security and indoor air quality concern with outdoor air intake louver locations
- Indoor air quality from air intake location adjacent to exhaust louvers and/or loading dock vehicle engine exhaust
- Safety concern from lack of fire damper and smoke damper inspections per NFPA recommendation
Equipment:
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Pumps:
- Available adequate net positive suction head pressure (NPSH) at pump inlet
- Available water pressure gauges, across inlet strainer, to routinely monitor strainer pressure drop from dirty strainer screen
- Position of discharge pump balancing valve set point
- Location of differential head pressure control device location (within pump room or at furthest terminal device)
- Central Air-Handling Unit:
- Chronic outdoor air freeze-stat issue
- Water coil incorrectly piped (hot water and/or chilled water supply pipe connected at upstream airflow side of coil versus installed downstream of airflow through coil (water parallel flow versus counterflow to airflow))
- Excessive air resistance at fan discharge based on fan wheel rotation in relationship to discharge air duct connection, e.g., top horizontal fan discharge to discharge air duct outlet with upblast connection
The above observations are simple to note in a walk-around tour of the facility and are appropriate to consider when completing a facility assessment. But most troubleshooting tasks are more specific, such as inadequate water flow or airflow, indoor air quality, quest to reduce operating costs, etc.
Whatever the problem, Step 3 is to compile a list of potential solutions, with Step 4 being to make a recommendation for the optimum solution(s) including the estimate to complete the work. Step 5, after the solution implementation is completed, is to monitor and measure the results, and Step 6 is to submit the Final Report.
Sometimes the end results are not immediate, and one should always check back to make sure the solution is a continuous improvement considering outdoor air temperature through the heating, free-cooling, and air-conditioning seasons. This not only reinforces a positive feedback impression to your client, but it is also great feedback for you, the troubleshooting engineer. And don't stop there! Share your project story by writing a case study for others to learn from your experience, e.g., Engineered Systems magazine, April 2020, "Solving Another Mystery At The Watergate Office Building."
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