Perimeter Control

The perimeter is an additional heating source, independent from the ventilation system, for example, an underfloor heating. The perimeter control is based on the heating demand from the space temperature heating control loop – in full range of the loop – or as the first (or second) heating stage (in half range of the loop) with DualHeat active (for works with reheater).

Additionally, if used simultaneously with a reheater, it can be specified whether both heaters should work together simultaneously or which should be the first and second stage of the primary/secondary heating level (in half range of the space temperature heating loop).

Perimeter Control According to HVAC Modes

Depending on the HVAC Mode settings (HeatLoop folder):

• Auto: working according to the heating demand,

• Heat: working according to the heating demand,

• Cool: switched off,

• MorningWarmUp: if the WarmUpHeater variable is set to true, the perimeter works according to the heating demand,

• PreCool: switched off,

• NightPurge: switched off,

• Off: switched off,

• Fire: switched off,

The perimeter can work in three modes defined in the ReheaterCommand variable:

• Auto: perimeter works based on the heating demand,

• Full Open: perimeter is set to the maximum control output, 100%,

• Full Close: perimeter is set to the minimum control output, 0%.

DualHeat

The DualHeat function for perimeter allows to meet energy efficiency requirements by allowing to select between two modes of heating. The DualHeat function is activated according to the setting of the HeaterPriority variable.

The heaters priority is set in the HeaterPriority variable (ReheaterControl folder):

• HeaterPriority set to reheater:

  • primary mode: reheater in the range of 0-50% (directly from the space temperature heating loop),

  • secondary mode: perimeter in the range of 50-100% (directly from the space temperature heating loop);

• HeaterPriority set to perimeter:

  • primary mode: perimeter in the range of 0-50% (directly from the space temperature heating loop),

  • secondary mode: reheater in the range of 50-100% (directly from the space temperature heating loop);

• HeaterPriority set to simultaneous:

  • reheater and perimeter work in full range of the heating loop.

Perimeter Types

Depending on the configuration (see: Methods of Configuration), the perimeter can be controlled by the triac output (TO3, TO4) as follows:

• time-proportional (PWM) water perimeter with a valve and actuator with a period set in the TimePropPerimeterPeriod variable, controlled by the TO3 output,

• water reheater with a valve and actuator controlled as floating type with a full-position switch time set in the FloatPerimeterValveDriveTime variable, controlled by the TO3 output for closing and TO4 output for opening

• water perimeter with a valve and actuator, on/off type, controlled by the TO3 output.

Regardless of the configuration of the control type, the perimeter is simultaneously controlled in analog mode by the AO2 output.

If the outside temperature signal is connected (from the BACnet/Modbus network), the perimeter is blocked over the setpoint in the MaxOatPerimeter variable (by default, 18°C/65°F).