A multizone unit uses a single fan to produce both cold and hot air. Cooling and heating coils are both used to produce either cold air, hot air, or a mixture of both when the space temperature has been satisfied. Actuators are used to move mixing dampers in the discharge of the unit to achieve the correct position to meet space temperature requirements. The unit can maintain a designed discharge air temperature on both the cooling and heating sides of the unit by modulating the chilled and hot water valves. The unit is made up of 2 or more zones serving various spaces. Each zone duct will have a manual balancing damper that MUST be installed to balance out the airflow on each zone duct. Design airflow should be set first by pitot tube traverse through the zones before any grille balancing is started. The following are steps that should be taken when balancing a multizone unit:
- Filters must be clean!
- Check fan rotation, belt tension, and motor amp draw.
- Check for installation of all zone dampers and to verify that they are in the full open position.
- Run all zones to full cooling.
- Verify that all ductwork has been sealed.
- Leaving air temperatures should be taken on each zone in full cooling to make sure that there is no leakage coming through the hot deck dampers. Same should be done in full heating.
- If unit has outside air set the damper to an estimated position. Recheck fresh air amount after unit airflow has been balanced.
- Condensate drain must be installed with vent in the correct location.
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