Outdoor air flow rate is controlled primarily by the relief and coil path return dampers, and in the event that adequate outdoor air cannot be provided by manipulating these dampers (only in the event that that the relief air damper
is fully open and the coil path return damper is fully closed), then the bypass damper can be incrementally closed to force more air out through the relief damper, causing more air to enter through the outdoor air inlet.
The simulation results show that both controls can well prevent reverse relief airflow by fully closing the decoupled relief air damper
when the OAD faultily approaches the closed position.
Building designers requiring permanent access to air dampers
, plumbing, vents and electrical wiring behind drywall ceilings and walls now have a choice of round vs.
* The mixing-box model, with separate minimum and modulating outdoor air dampers
, was replaced with a model that has a single modulating outdoor air damper
We release the lockout once the outdoor air dampers
are effectively at 100% open and the supply air setpoint is not met, allowing the cooling coil to provide supplemental cooling.
The table lines up significant AHU parameters (OAT, outside air damper
, return air damper
, fan speed, setpoints, etc.) so I can quickly spot changes in any of the parameters.
Restore minimum outdoor air damper
setting during hot/ humid weather to minimum.
In the case of a fresh air damper
stuck, two cases are compared.
* Modulate the return air damper
off the supply air temperature loop in sequence with the mechanical cooling per standard economizer control logic.
2 Stuck exhaust 08/20, 08/22 Damper stuck fully air damper
closed and fully open.
In addition, the fan must create a low enough pressure at its inlet (B) to overcome pressure losses associated with drawing the return air out of the zone and through the return air path (which might include a return grille, ceiling plenum, and some ductwork), and then to draw the air through the return air damper
, filter, and coils inside the terminal unit.
When the heating coil is used during a winter season, the outdoor air damper
is maintained at a minimum position during the occupied period.
Starting with the return damper 100% open on the occupied cycle, open the outdoor air damper
to bring in the required minimum outdoor air.