Table 19: How economizer enable/disable tests are selected
Table 18: Economizer enable/disable tests defined
Temperature Comparison with Enthalpy Comparison requires both an optional OA humidity sensor and an optional IA humidity sensor.
Note –
Temperature Comparison with Enthalpy Comparison Economizer (optional)
If the optional Leading Edge economizer function is selected, the unit ventilator is provided from the factory with both the IA humidity and OA humidity sensors, which are used along with the IA temperature and OA temperature sensors to calculate IA enthalpy and OA enthalpy. In this case, the UVC is factory set for Economizer Strategy 2 and uses the Temperature Comparison with Enthalpy Comparison Economizer function.
Note –
Temperature Comparison with OA Enthalpy Setpoint Economizer requires an optional OA humidity sensor.
Description of Operation
• Expanded (optional)—Temperature Comparison with OA Enthalpy Setpoint Economizer (Strategy 1)
• Leading Edge (optional)—Temperature Comparison with Enthalpy Comparison Economizer (Strategy 2)
Temperature Comparison Economizer (default)
If the default Basic economizer function is selected, the unit ventilator is provided from the factory without the optional IA and OA humidity sensors. In this case, the UVC is factory set for Economizer Strategy 1—the UVC automatically detects that no OA humidity sensor is present and adjusts to use the Temperature Comparison Economizer function.
Temperature Comparison with OA Enthalpy Setpoint Economizer (optional)
If the optional Expanded economizer function is selected, the unit ventilator is provided from the factory with the optional OA humidity sensor, which is used along with the OA temperature sensor to calculate OA enthalpy. In this case, the UVC is factory set for Economizer Strategy 1 and uses the Temperature Comparison with OA Enthalpy Setpoint Economizer function.
| Tests | Economizer | Enable test | Disable test |
| enable/disable tests |
| A | OA temp set point | EffectiveOATemp < (EconOATempSetpt – EconTempDiff) | EffectiveOATemp >= EconOATempSetpt |
| B | IA/OA differential temp | EffectiveOATemp < (EffectiveSpaceTemp – 3.6°F – EconTempDiff) | EffectiveOATemp >= (EffectiveSpaceTemp – 3.6°F) |
| C | OA enthalpy set point | EffectiveOAEnthalpy < (EconOAEnthalpySetpt – | EffectiveOAEnthalpy >= EconOAEnthalpySetpt |
| EconEnthalpyDiff) |
| | | |
| D | IA/OA differential | EffectiveOAEnthalpy < (EffectiveSpaceEnthalpy – | EffectiveOAEnthalpy >= EffectiveSpaceEnthalpy |
| enthalpy | EconEnthalpyDiff) |
| | |
| Economizer | Space temp sensor | OA temp sensor | Space humidity | OA humidity sensor | Economizer enable/ |
| strategy | sensor | disable tests |
| | | |
| All | Unreliable | Don’t care | Don’t care | Don’t care | OA damper closed |
| Don’t care | Unreliable | Don’t care | Don’t care | OA damper closed |
| |
| Basic | Reliable | Reliable | Don’t care | Unreliable | Test B |
| Reliable | Reliable | Don’t care | Reliable | Test C |
| |
| Expanded | Reliable | Reliable | Don’t care | Reliable | Test C and Either |
| Test B or Test A |
| | | | | |
| | Reliable | Reliable | Reliable | Reliable | Test D and Test B |
| Leading Edge | Reliable | Reliable | Unreliable | Reliable | Test B |
| Reliable | Reliable | Reliable | Unreliable | Test B |
| |
| | Reliable | Reliable | Unreliable | Unreliable | Test B |
| | Note: | The hard-wired sensor and the equivalent input must both be unreliable for the value to be considered |
| | | unreliable. | | | |
