33
0
6/16 - Subject to change. © Belimo Air
controls
(USA
), Inc
.
ZIP Economizer
Method of Operation
High Limit Changeover
(Four possibilities depending on installed sensors)
Note: Economizing is enabled based on one of the following and becomes
active in Free Cooling and Integrated Cooling.
Single Dry Bulb Changeover
• If only an OAT sensor is connected, it will be analyzed against the reference
Outdoor Air changeover temperature value (based on entered ZIP code).
• IF OAT is 2°F below the reference value
THEN
economizing will be enabled.
• IF OAT is above the reference value
THEN economizing will be disabled.
Differential Dry Bulb Changeover
• Must have OAT and RAT sensors connected. OAT and RAT will be analyzed
against each other and the OAT will be analyzed against the reference
differential temperature high limit (based on entered ZIP code).
• IF OAT is 2-8°F below the RAT (Value Climate Zone Dependent)
AND OAT is 2°F below the reference differential temp high limit DTHL
THEN economizing will be enabled.
• IF OAT is greater than or equal to 0-6°F below the RAT (Value Climate
Zone Dependent)
OR the OAT is greater than the reference differential temp high limit DTHL
THEN economizing will be disabled.
Single Enthalpy Changeover
• Must have OAH (RH) and OAT sensors connected. Outdoor air enthalpy
(Outdoor Enth) will be calculated. They will be analyzed against the
reference values as follows:
• IF Outdoor Enth is 2 btu/lb less than the reference enthalpy high limit
(default is 28 btu/lb – 2 btu/lb = 26 btu/lb)
AND OAT is 2°F below the reference temperature high limit ETHL (based
on entered ZIP code)
THEN
economizing will be enabled.
• IF Outdoor Enth is greater than reference enthalpy high limit (default is 28
btu/lb)
OR OAT is greater than the reference temperature high limit ETHL (based
on entered ZIP code)
THEN
economizing will be disabled.
Differential Enthalpy Changeover
• Must have OAH, OAT, RAH and RAT sensors connected. Outdoor Air
Enthalpy and Return Air Enthalpy will be calculated.
• IF Outdoor Enth is 2.5 btu/lb less than Return Air Enth
AND Outdoor Enth is 2 btu/lb less than the reference differential enthalpy
high limit DEHL (30 btu/lb)
AND OAT is 2°F below the reference differential temperature high limit
DTHL (based on entered ZIP code)
THEN economizing will be enabled.
• If Outdoor Air Enthalpy is 1 btu/lb less than Return Air Enthalpy
OR Outdoor Air Enthalpy is greater than reference enthalpy high limit
DEHL (30 btu/lb)
OR OAT is greater than reference differential temperature high limit
(based on entered ZIP code)
THEN economizing will be disabled.
Operational Modes
Free Cooling
• Outdoor air ambient conditions are analyzed by one of the 4 changeover
strategies above (Single or Differential Dry Bulb; Single or Differential
Enthalpy) and has been deemed suitable for “free” cooling.
• Y1 is energized indicating a call for stage 1 cooling.
• Y2 is de-energized.
• W1 is de-energized.
• G input could be energized or de-energized (occupied or unoccupied state).
• Compressor 1 is off
2
.
• Compressor 2 is off
2
.
• Fan Speed could be energized (low speed, when OAT is below 50°F) or
de-energized (high speed) for indoor fan
1
.
• Exhaust Fan could be running or not based on % damper open position
1
.
• Damper Pos output is modulated between the respective current minimum
damper position setpoint and 100% open to attempt to maintain SAT
setpoint (55°F). When OAT is at 55°F the damper will be fully open to
outside air. As outdoor air continues to rise above 55°F, SAT will rise with it.
Integrated Cooling
• Outdoor air ambient conditions are analyzed by one of the four changeover
strategies above (Single or Differential Dry Bulb; Single or Differential
Enthalpy) and has been deemed suitable for “free” cooling.
• Y1 is energized indicating a call for stage 1 cooling.
• Y2 is energized indicating a call for stage 2 cooling.
• W1 is de-energized.
• G input could be energized or de-energized (occupied or unoccupied state).
• Compressor 1 is on
2
.
• Compressor 2 is off
2
.
• Fan Speed is de-energized (indoor fan is operating on high speed)
1
.
• Exhaust Fan is on
1
.
• Damper Pos output is fi xed at 100% (fully open to outdoor air).
Note:
Outdoor Damper must be fully open for 60 seconds before mechanical
cooling will be enabled.
