Economizer controls

Economizer controls

HVAC system controls that operate mixed air dampers to mix return and outdoor air to obtain air of a temperature appropriate for free cooling. Economizer controls are used during periods when outdoor air requires less cooling energy input than return air.
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For reasons related to construction economy and simplification of the waterside economizer controls, the chillers were ultimately selected with a condenser water flow of approximately 1.
You might also consider a fixed or differential dry bulb rather than enthalpy sensors: "Dry bulb-based economizer controls are more reliable due to the error potential of enthalpy sensors.
In addition, in order to find an alternative solution for optimal economizer controls, it is necessary to understand how the optimal high-limit curves are created.
Differential enthalpy controls are theoretically considered as the most energy-efficient economizer controls (CEC 2003; ASHRAE 2009a).
Oversizing the return damper has no operational value; the damper will simply throttle to deliver the required return air/outdoor air ratio required by the economizer controls or the minimum outdoor air controls.
There may also be missing equipment, such as economizer controls with modulating air dampers that were specified but never installed.
The following is the schematic/ physical layout of the proposed HERV system--Most of the heat recovery systems available on market are either HRV or ERV or ERV without economizer controls.
Desirable economizer controls use a dry bulb high limit to enable economizer use only when the OAT is appropriate.
The outside air inlet at the roof was equipped with a minimum outside air damper that was operable for demand-controlled ventilation and an economizer damper that was operable by standard airside economizer controls.
DCV systems can be incorporated into existing HVAC equipment and often times operate in conjunction with existing economizer controls, sharing the same outdoor air damper (OAD).
Items like optimum start thermostats, economizer controls, and demand controlled ventilation can be independently prescribed, but a package of measures provides the synergy of addressing common problems together and building installer expertise and efficiency.
However, over-reliance on the added factory quality control and assumptions that all economizer control sequences are alike, can lead to failure conditions as explained later in this paper.