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HVAC System Start-Up Vs. Commissioning

System Start-Up HVAC system start-up takes place after all HVAC equipment has been installed, piped, and wired. The HVAC technician starts up each unit to ensure that they are fully operational and ready to provide energy-efficient heating and cooling. The startup process is more than just turning on each unit’s power: it’s a multi-step process that requires patience and fine-tuned attention. The startup checklist provided in the manufacturer’s documentation for each piece of HVAC equipment in the system should be followed carefully when starting the equipment for the first time. Our HVAC technicians look at the following elements during the startup process:

  • Check refrigerant piping for indications of leaks

  • Check gas piping for leaks

  • Check all electrical connections and terminals for tightness

  • Verify that all electrical wiring is not in contact with refrigerant lines

  • Are any relays failing?

  • Is the unit powered?

  • Is air flow consistent with the thermostat?


Commissioning HVAC commissioning has become more popular with the rise of LEED ratings because it confirms that a system has been installed according to the designer’s intent and specifications. Commercial HVAC systems are generally commissioned after a visual inspection of all components has been carried out to ensure everything has been installed properly and in the right place. Commissioning Types

  1. Initial Commissioning occurs during the production of a new building or on a new HVAC system within an existing building.

  2. Retro-commissioning occurs the first time commissioning has been implemented in an existing building on existing HVAC equipment.

  3. Re-commissioning occurs when HVAC systems have already been commissioned during the initial commissioning process, and the building owner wants to verify, improve, and document the performance of the existing HVAC systems for future needs.

After turning on all the equipment and verifying it all starts up according to the manufacturer’s specifications, a technician will begin the process of testing, adjusting, and balancing (TAB) the system. In testing the equipment, we use scenarios designed to ensure it will work as expected, reacting to changing conditions within the building – this includes testing motors, voltage, and amperage, taking flow measurements, adjusting fan motor speed, etc. When it comes to rooftop units, the outside air is balanced after supply and return air have been adjusted. Spot checks on supply diffusers per unit are recommended to ensure supply air was not displaced due to adjustments to outside air. Our technicians balance the unit(s) per industry standards, including the outside air and exhaust fans. Finally, measuring the building pressure is a very important factor for the comfort of the building occupants. A commissioning professional must know, or be aware of, all the new ASHRAE control strategies, federal and local standards, as well as the U.S. Green Building Council LEED requirements to name a few. In sum, startup is the process of ensuring that the equipment operates properly on a basic level. Commissioning is the process of ensuring that the equipment is operating at its design capacity and to its maximum potential. We offer both system start-up and commissioning for Daikin VRV, ABB, Evapco, as well as many other systems. We also include system start-ups in our maintenance agreements, so contact us today to learn how we can help you.

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