# 4.24 DOAS

DOAS (Dedicated Outdoor Air System) provides centralized supply and/or exhuast ventilation air to IZXFER objects with the **izNVType** = AIRNETDOAS. The supply air may be preconditioned using heat recovery and/or tempering coils.

**oaName**

Name of DOAS.

## 4.24.1 DOAS Supply Fan Data Members

**oaSupFanVfDs= float**

Supply fan design or rated flow at rated pressure.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

cfm | x \(\ge\) 0 | Sum of referencing IZXFER supply flows | No | constant |

**oaSupFanPress= float**

Design or rated fan pressure.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

inches H_{2}O | x \(>\) 0 | 0.3 | No | constant |

Only one of oaSupFanElecPwr, oaSupFanEff, and oaSupFanShaftBhp may be given.

**oaSupFanElecPwr= float**

Fan input power per unit air flow (at design flow and pressure).

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

W/cfm | x \(>\) 0 | derived from oaSupFanEff and oaSupFanShaftBhp | If oaSupFanEff and oaSupFanShaftBhp not present | constant |

**oaSupFanEff= float**

Fan efficiency at design flow and pressure, as a fraction.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1 | derived from oaSupFanShaftBhp if given, else 0.08 | No | constant |

**oaSupFanShaftBhp= float**

Fan shaft brake horsepower at design flow and pressure.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

bhp | x \(>\) 0 | derived from oaSupFanEff. | No | constant |

**oaSupFanCurvePy=\(k_0\), \(k_1\), \(k_2\), \(k_3\), \(x_0\)**

\(k_0\) through \(k_3\) are the coefficients of a cubic polynomial for the curve relating fan relative energy consumption to relative air flow above the minimum flow \(x_0\). Up to five *floats* may be given, separated by commas. 0 is used for any omitted trailing values. The values are used as follows:

\[z = k_0 + k_1 \cdot (x - x_0)| + k_2 \cdot (x - x_0)|^2 + k_3 \cdot (x - x_0)|^3\]

where:

- \(x\) is the relative fan air flow (as fraction of oaSupFanVfDs; 0 \(\le\) \(x\) \(\le\) 1);
- \(x_0\) is the minimum relative air flow (default 0);
- \((x - x_0)|\) is the “positive difference”, i.e. \((x - x_0)\) if \(x > x_0\); else 0;
- \(z\) is the relative energy consumption.

If \(z\) is not 1.0 for \(x\) = 1.0, a warning message is displayed and the coefficients are normalized by dividing by the polynomial’s value for \(x\) = 1.0.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

x \(\ge\) 0 | 0, 1, 0, 0, 0 (linear) | No | constant |

**oaSupFanMtr= mtrName**

Name of meter, if any, to record energy used by supply fan. End use category used is specified by oaSupFanEndUse (next).

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

name of a METER | not recorded | No | constant |

**oaSupFanEndUse= choice**

End use to which fan energy is recorded (in METER specified by oaSupFanMtr). See METER for available end use choices.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

end use choice | Fan | No | constant |

**oaTEx= float**

Alternative supply fan source air dry bulb temperature. If given, oaTEx overrides the outdoor dry-bulb temperature read from the weather file or derived from design conditions.

Caution: oaTEx is not checked for reasonableness.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

^{o}F | Outdoor dry-bulb | No | subhourly |

**oaWEx= float**

Alternative supply fan source air air humidity ratio. If given, oaWEx overrides the outdoor humidity ratio derived from weather file data or design conditions.

Caution: oaWEx is not checked against saturation – there is no verification that the value provided is physically possible.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

\(\gt\) 0 | Outdoor humidity ratio | No | subhourly |

## 4.24.2 DOAS Exhaust Fan Data Members

**oaExhFanVfDs= float**

Exhaust fan design or rated flow at rated pressure.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

cfm | x \(\ge\) 0 | Sum of referencing IZXFER exhaust flows | No | constant |

**oaExhFanPress= float**

Design or rated fan pressure.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

inches H_{2}O | x \(>\) 0 | 0.3 | No | constant |

Only one of oaExhFanElecPwr, oaExhFanEff, and oaExhFanShaftBhp may be given.

**oaExhFanElecPwr= float**

Fan input power per unit air flow (at design flow and pressure).

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

W/cfm | x \(>\) 0 | derived from oaExhFanEff and oaExhFanShaftBhp | If oaExhFanEff and oaExhFanShaftBhp not present | constant |

**oaExhFanEff= float**

Fan efficiency at design flow and pressure, as a fraction.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1 | derived from oaExhFanShaftBhp if given, else 0.08 | No | constant |

**oaExhFanShaftBhp= float**

Fan shaft brake horsepower at design flow and pressure.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

bhp | x \(>\) 0 | derived from oaExhFanEff. | No | constant |

**oaExhFanCurvePy=\(k_0\), \(k_1\), \(k_2\), \(k_3\), \(x_0\)**

\(k_0\) through \(k_3\) are the coefficients of a cubic polynomial for the curve relating fan relative energy consumption to relative air flow above the minimum flow \(x_0\). Up to five *floats* may be given, separated by commas. 0 is used for any omitted trailing values. The values are used as follows:

\[z = k_0 + k_1 \cdot (x - x_0)| + k_2 \cdot (x - x_0)|^2 + k_3 \cdot (x - x_0)|^3\]

where:

- \(x\) is the relative fan air flow (as fraction of oaExhFanVfDs; 0 \(\le\) \(x\) \(\le\) 1);
- \(x_0\) is the minimum relative air flow (default 0);
- \((x - x_0)|\) is the “positive difference”, i.e. \((x - x_0)\) if \(x > x_0\); else 0;
- \(z\) is the relative energy consumption.

If \(z\) is not 1.0 for \(x\) = 1.0, a warning message is displayed and the coefficients are normalized by dividing by the polynomial’s value for \(x\) = 1.0.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

x \(\ge\) 0 | 0, 1, 0, 0, 0 (linear) | No | constant |

**oaExhFanMtr= mtrName**

Name of meter, if any, to record energy used by exhaust fan. End use category used is specified by oaExhFanEndUse (next).

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

name of a METER | not recorded | No | constant |

**oaExhFanEndUse= choice**

End use to which fan energy is recorded (in METER specified by oaExhFanMtr). See METER for available end use choices.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

end use choice | Fan | No | constant |

## 4.24.3 DOAS Tempering Coils Data Members

**oaSupTH= float**

Heating setpoint for tempering and/or heat exchanger bypass.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

^{o}F | – | 68 | No | subhourly |

**oaEIRH= float**

Energy Input Ratio of the heating coil. This is the inverse of the coil efficiency or COP. A value of zero indicates that the coil does not use energy (e.g., hot water coils). Specifying input triggers the modeling of a heating coil.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

x \(\ge\) 0 | 0 | when modeling heating coil | subhourly |

**oaCoilHMtr= mtrName**

Name of meter, if any, to record energy used by the heating coil.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

name of a METER | not recorded | No | constant |

**oaSupTC= float**

Cooling setpoint for tempering and/or heat exchanger bypass.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

^{o}F | – | 68 | No | subhourly |

**oaEIRC= float**

Energy Input Ratio of the cooling coil. This is the inverse of the coil efficiency or COP. A value of zero indicates that the coil does not use energy (e.g., chilled water coils). Specifying input triggers the modeling of a cooling coil.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

x \(\ge\) 0 | 0 | when modeling cooling coil | subhourly |

**oaSHRtarget= float**

Sensible Heat Ratio of the cooling coil. If the required sensible capacity of the coil and the entered SHR do not produce a valid psychrometric state, the SHR is adjusted and reported through the SHR probe.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

x \(\gt\) 0 | 1.0 | No | subhourly |

**oaCoilCMtr= mtrName**

Name of meter, if any, to record energy used by the cooling coil.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

name of a METER | not recorded | No | constant |

**oaLoadMtr= ldMtrName**

Name of load meter, if any, to record load met by the heating coil or cooling coil.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

name of a LOADMETER | not recorded | No | constant |

## 4.24.4 DOAS Heat Recovery Data Members

**oaHXVfDs= float**

Heat exchanger design or rated flow.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

cfm | x \(\gt\) 0 | Average of supply and exhaust fan design flows | No | constant |

**oaHXf2= float**

Heat exchanger flow fraction (of design flow) used for second set of effectivenesses.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\lt\) x \(\lt\) 1.0 | 0.75 | No | constant |

**oaHXSenEffHDs= float**

Heat exchanger sensible effectiveness in heating mode at the design flow rate. Specifying input triggers modeling of heat recovery.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1.0 | – | when modeling heat recovery | constant |

**oaHXSenEffHf2= float**

Heat exchanger sensible effectiveness in heating mode at the second flow rate (**oaHXf2**).

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1.0 | 0 | No | constant |

**oaHXLatEffHDs= float**

Heat exchanger latent effectiveness in heating mode at the design flow rate.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1.0 | 0 | No | constant |

**oaHXLatEffHf2= float**

Heat exchanger latent effectiveness in heating mode at the second flow rate (**oaHXf2**).

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1.0 | 0 | No | constant |

**oaHXSenEffCDs= float**

Heat exchanger sensible effectiveness in cooling mode at the design flow rate.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1.0 | 0 | No | constant |

**oaHXSenEffCf2= float**

Heat exchanger sensible effectiveness in cooling mode at the second flow rate (**oaHXf2**).

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1.0 | 0 | No | constant |

**oaHXLatEffCDs= float**

Heat exchanger latent effectiveness in cooling mode at the design flow rate.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1.0 | 0 | No | constant |

**oaHXLatEffCf2= float**

Heat exchanger latent effectiveness in cooling mode at the second flow rate (**oaHXf2**).

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

0 \(\le\) x \(\le\) 1.0 | 0 | No | constant |

**oaHXBypass= choice**

Yes/No choice for enabling heat exchanger bypass. If selected, the outdoor air will bypass the heat exchanger when otherwise the heat exchanger would require more heating or cooling energy to meet the respective setpoints.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

NO, YES | NO | No | constant |

**oaHXAuxPwr= float**

Auxiliary power required to operate the heat recovery device (e.g., wheel motor, contorls).

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

W | x \(\ge\) 0 | 0 | No | subhourly |

**oaHXAuxMtr= mtrName**

Name of meter, if any, to record energy used by auxiliary components of the heat recovery system.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

name of a METER | not recorded | No | constant |

**endDOAS**

Indicates the end of the DOAS definition. Alternatively, the end of the DOAS definition can be indicated by the declaration of another object or by “END”.

Units | Legal Range | Default | Required | Variability |
---|---|---|---|---|

– | – | N/A | No | constant |

**Related Probes:**

- @doas