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Ten Steps to Preparing HVAC Systems for Testing, Adjusting, and Balancing

To avoid problems, delays, cost overruns and conflicts due to issues identified during TAB (testing, adjusting and balancing, also known as air and water balancing), mechanical contractors and/or construction managers must put procedures in place that ensure systems are fully ready to undergo the TAB process.


On almost all new construction and renovation projects, similarly experienced AABC- or NEBB-certified TAB contractors bid against one another, and the contract is generally awarded to the lowest bidder. This means the balancer’s margins are tight, so when problems are identified – and they always are – the TAB contractor has very limited time for troubleshooting and making the necessary adjustments to balance systems to within +/- 10% of design specification. Therefore, multiple problems are usually kicked back to the mechanical contractor or construction manager, usually on an ongoing list. This results in change orders, increased project costs, and unnecessary back-charges to the mechanical contractor. The schedule may be extended, missing critical Certificate of Occupancy dates. Rampant finger-pointing ensues, and there are hard feelings all around.


Here is a list of ten things mechanical contractors and construction managers can do to prevent costly, schedule-busting issues during testing, adjusting and balancing.

  1. Verify that all air systems are running properly and continuously without tripping or going into alarm. Verify BMS system is communicating and controlling.

  2. All manual dampers, fire smoke dampers, and control dampers should be open to allow full flow.

  3. Check to ensure that all flex duct is taut, kept to minimum lengths, and not kinked or crushed.

  4. Make sure all diffusers are installed properly, with no restrictions.

  5. Verify that AHU static pressure and flow match design intent.

  6. Check to make sure all filters have been installed.

  7. VFDs should be operating at the proper frequency with spare capacity for filter loading.

  8. All supply, return and exhaust should have proof of airflow with no major pressure drops or restrictions.

  9. Verify basic HVAC sequence of operation with the BMS system along with temperature and humidity control.

  10. Walk the HVAC systems down with the balancer to ensure everything is ready for TAB.


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