By Walt Rutherford Notes from the Facility Managers Survival Guide
Today’s Facility Managers have the ability to utilize cost saving measures only dreamt about a few short years ago. Digital control systems that provide extremely flexible equipment operating parameters, extensive zone monitoring & control and virtually unlimited scheduling points have become the norm. Coupled with the advanced mechanical equipment that condition & maintain the building environment, the control system provides for powerful management of the resources that affect the bottom line. However, as the old saying goes, ‘a building’s environment is only as good as its weakest link’.
And there is big potential for a facility to include multiple weak links, each less obvious and more impactful than another. For example; a fan running backward will still produce airflow in the proper direction, only at about half of its capacity and at 130% of the normal energy consumption (amp draw). A thermostat/sensor with an incorrect offset (or none at all) will still transmit zone temperature variances, but if it’s off even by 2⁰F it’s still not operating properly and needs 2⁰F of correction in order to do its part in efficiently controlling temperature . An outside air damper introducing fresh air into an AHU system that is allowing just 10% volume over the required amount puts an unnecessary strain on the cooling/heating operation. At 400 cfm and 12000 btu’s per ton, a 4000 cfm unit drawing 1200 cfm of osa as opposed to the required 800 cfm is wasting an obscene amount of energy each hour, like 60 tons of conditioning. Also, air & water conditioning can be accomplished, albeit far short of efficient if barely acceptable, with a pump moving less water than designed-especially if multiple pumps are available. These are just a few examples of very common issues found in a buildings HVAC mechanical, electrical & control systems. Issues that are not readily apparent, but have huge impact on energy-efficiency, indoor air quality and operating costs. That fan running backward will not only consume more energy but will also generate excessive heat which will cut its motor life at least in half. And a pump not carrying its full share requires others to pick up the slack. The reasons for system performance inadequacies range from design flaws, to devices installed improperly to component failure to years of maintenance personnel focusing on the product (an office is too cold, a hallway that becomes a wind tunnel every morning…) as opposed to the process. But these issues and many more like them can be identified and remedied with a thorough air & hydronic systems testing, adjusting & balancing (TAB) process.
The process is just as it sounds; the term ‘Test’ refers to the act of determining quantitative performance of the HVAC equipment. ‘Adjust’ refers to regulating the various fluid flows such as water thru a terminal coil or the amount of air a fan produces; and ‘Balance’ the proportioning of flows within a particular air or water distribution network to obtain specified or required quantities. But there’s a little more to the process that needs to be accomplished first in order to get the most from the TAB effort. The first step is to gather all related data. Engineered equipment schedules and system drawings, O & M manuals, equipment data sheets and sequence of operations need to be reviewed and relevancy to actual equipment and systems in place established. If this information is not available or no longer relevant a survey should be conducted to get actual equipment data and Google can be used to find equipment cut sheets, device operating parameters and fan & pump curves. From this document review a TAB plan can be formulated. Hint; break your plan down by system. This will allow for a coherent approach and once the work has begun tracking progress will be simpler and you won’t have an entire building in different stages of balancing with different systems working against each other wreaking havoc on the building environment. Next is the preliminary investigation of the system chosen to be addressed. This phase will uncover components that need repaired, replaced or calibrated, ductwork and piping that may not be installed per design and overall system integrity. This is also the time to ensure all manual volume dampers on the air side or circuit setters on the water side of a particular system are operational & set in the full open position. Once the initial investigation is complete the actual testing adjusting and balancing can proceed. Although the data gathering and preliminary investigation(s) would benefit greatly with in-house participation a certified balancing company should be called on to perform the TAB operations. They are equipped with the necessary tools & equipment to conduct the various tests and have the training needed to accomplish what may appear to be fairly simple procedures but are in fact rather complex and at times complicated. Another benefit to bringing a certified TAB company into the mix is that they provide a written guarantee that is backed by an alliance of companies that will step up to make things right if the original company fails to do so. The TAB technicians will test the various fan & pump systems to ensure the required total volumes are produced. They then proceed to adjust terminal devices, air outlets/inlets and water coils. They will bring these volumes into original design parameters or more realistic space demand requirements and when needed adjust to the occupants requests. The results of a good test & balance operation will be evident in that those doors that always seem to be held open by a breeze, that pesky bathroom that never regains a fresh clean smell once used, hot/cold spots and drafty areas will all be rectified. And more efficient, proper systems operation will show in the utility bill.
Walt Rutherford has been involved in all things MEP since 1986. He currently resides in Las Vegas, NV where he manages a branch office and regularly contributes to Nevada Industry Excellence. Walt manages a branch office in Las Vegas, NV for Precision Air Balance Co. If you have any questions or feedback, please feel free to comment on this article. You can also reach Walt by email.
