Temperature control features - EasyIO - LIT-12014127 - EASYIO-FW-VAV - FV-VAV - 1.0

EasyIO FW-VAV Application Note

Brand
EasyIO
Product name
FV-VAV
Document type
Application Note
Document number
LIT-12014127
Version
1.0
Revision date
2024-04-09
Product status
Active
Language
English

The application uses a proportional–integral–derivative (PID) algorithm for all modulating control.

Cooling only

In an occupied room, if there are no cooling or CO2 ventilation demands, the application sets the VAV primary air flow cubic feet per minute (CFM) set point at the minimum. When the room temperature rises above the cooling set point, the primary air flow set point switches from the minimum air flow set point to the maximum air flow set point in response to the increasing cooling demand. The opposite occurs when the cooling demand decreases. The central VAV AHU or RTU morning warm up mode is subject to the global outside air heating lockout.

If the room temperature rises to either the cooling unoccupied or standby temperature set points, the system operates in the cooling mode until the cooling demand is met. The cooling mode is subject to conditioned primary air availability from the central VAV AHU or RTU.

Cooling with 2-stage electric heating

In an occupied room, if there are no cooling or CO2 ventilation demands, the application sets the VAV primary air flow CFM set point at the minimum. When the room temperature drops below the heating set point, and when not locked out by a global heating outside air lockout command, the primary air flow set point switches to the reheat air flow set point and the room reheats in response to the increasing heating demand, subject to the adjustable VAV box leaving air temperature high limit set point. The opposite occurs when the heating demand decreases. A factory provided, wired, and installed air flow safety switch does not permit electric heat operations without the central AHU VAV primary air flow.

When the room temperature rises above the cooling set point, the primary air flow set point switches from the minimum air flow set point to the maximum air flow set point in response to the increasing cooling demand. The opposite occurs when the cooling demand decreases. The heating mode is subject to the global outside air heating lockout.

If the room temperature drops or rises to the heating or cooling unoccupied or standby temperature set points, the system operates in the heating or cooling mode accordingly until the heating or cooling demands are met. The cooling mode is subject to conditioned primary air availability from the central VAV AHU or RTU and the heating mode is subject to the global outside heating lockout set point and the VAV AHU or RTU primary air flow.

Cooling with modulating heating valve

The VAV primary air flow CFM set point automatically sets to the minimum air flow set point when the room is in occupied mode and there is no cooling, heating, or CO2 ventilation demand. When the temperature in the room drops below the heating set point, and the central plant hot water is available, the primary air flow set point switches to the reheat air flow set point and the hot water reheat valve adjusts in response to the increasing heating demand. The opposite occurs when the heating demand decreases. The heating mode is subject to the central plant outdoor air heating lockout.

When the room temperature rises above the cooling set point, the primary air flow set point switches from the minimum air flow set point to the maximum air flow set point in response to the increasing cooling demand. The opposite occurs when the cooling demand decreases.

If the room temperature reaches either the heating or cooling unoccupied or standby temperature set points, the system starts to operate in the heating or cooling mode until the heating or cooling demand is met. The cooling mode is subject to conditioned primary air availability from the central VAV AHU or RTU and the heating mode is subject to the central plant hot water availability.

Cooling and heating with series fan

The VAV primary air flow CFM set point automatically sets to the minimum air flow set point when the room is occupied and there is no cooling, heating, or CO2 ventilation demand. During the occupied mode the VAV series fan starts and runs continuously and automatically starts and stops with unoccupied or standby heating and cooling demands.

When the temperature in the room drops below the heating set point, and the central plant hot water is available, the primary air flow set point switches to the reheat air flow set point and the hot water reheat valve adjusts in response to the increasing heating demand. The opposite occurs when the heating demand decreases. The heating mode is subject to the central plant outdoor air heating lockout.

When the room temperature rises above the cooling set point, the primary air flow set point switches from the minimum air flow set point to the maximum air flow set point in response to the increasing cooling demand. The opposite occurs when the cooling demand decreases.

If the room temperature reaches the heating or cooling unoccupied or standby temperature set points, the system starts to operate in the heating or cooling mode until the heating or cooling demands are met. The cooling mode is subject to conditioned primary air availability from the central VAV AHU or RTU and the heating mode is subject to the central plant hot water availability.

Cooling with parallel fan powered heating

The VAV primary air flow CFM set point automatically sets to the minimum air flow set point when the room is in occupied mode and there is no cooling, heating, or CO2 ventilation demand.

When the room temperature drops below the heating set point and when the central plant hot water is available, the VAV parallel fan runs and the hot water reheat valve adjusts in response to the increasing heating demand. The opposite occurs when the heating demand decreases. The heating mode is subject to the central plant outside air heating lockout.

When the room temperature rises above the cooling set point, the primary air flow set point switches from the minimum air flow set point to the maximum air flow set point in response to the increasing cooling demand. The opposite occurs when the cooling demand decreases.

If the room temperature reaches the heating or cooling unoccupied or standby temperature set points, the system starts to operate in the heating or cooling mode until the heating or cooling demands are met. The cooling mode is subject to conditioned primary air availability from the central VAV AHU or RTU and the heating mode is subject to central plant hot water availability.