Feature Notes
Air Handing Unit Damper Submodule with 3 x Triac Outputs (3T version) with 2 x 0-10V DC Outputs (with Air Quality control option)
DAM / DIN / 3T / ... DAM / DIN / AOP / ...
Main Features Controls Mixing Dampers in AHU Plants Works with SeaChange AHU Controller to ensure correct interlocks Optional Mixed Air Temperature sensor Can also be used with CO2 sensor or Humidity Sensor for Swimming Pool Applications (/AOP version) Optional Air Quality Sensor (/AOP version) for Minimum Fresh air control Control can be based on Enthalpy of Outside and Inside air streams Can be controlled as first stage of AHU heating or cooling

Description of Features

General

This Damper Controller is an AHU Submodule, and must be used in conjunction with a SeaChange AHU Controller; it can be used to control Mixing Dampers with Raise/Lower type Actuators or 0-10V DC Actuators. The sense of the dampers is such that 100% output from the controller represents 100% fresh air.

The Damper Controller will provide heat recovery when Outside Temperature, Return Temperature and Supply Control conditions allow. It will also vary the Minimum Fresh Air Position of the dampers according to the Air Quality of the Return Air; this is measured by an Air Quality Sensor connected to the Damper Controller. In order for the Damper Controller to function, the AHU Controller must be fitted with a Return Air Sensor; the Damper Controller will then automatically acquire this temperature (and the Outside Temperature) over the network.

Temperature Control- with no Mixed Air Sensor fitted:

If no sensor is wired to the Controller, it will control in an On/Off manner. If free cooling is available (i.e. the Outside Temperature is lower than the Return Temperature) and the AHU is currently calling for cooling, the Dampers will be positioned in a full fresh air position. Similarly, if free heating is available and the AHU is calling for heating, the dampers will be positioned at full fresh air. At all other times, the dampers will be positioned at either minimum fresh air position (during occupancy) or fully closed to fresh air (during non-occupancy) .

Demand Percent- with no Mixed Air Sensor fitted:

The damperscan be made to modulate dependant upon the heating and cooling demands calculated by the AHU controller. To activate this mode set the configuration parameter DeMand PerCent (DMPC) to the percentage of the AHU output over which the heat recovery should modulate. The dampers can be considered to be the first stage of heating or cooling (dependant on return air and Outside air conditions). For example if DMPC is set to 20, if the outside temperature is lower than the return air temperature then as the AHU cooling output modulates from 0 to 20% the damper output will modulate from the zero to 100%. If this option is enabled then the AHU driver should be re-scaled to match, eg set C154 HRMN to 20 and C156 CRMN to 20 this will delay the operation of the heating and cooling batteries until the heat recovery has been utilised to the full extent.

Temperature Control - with Mixed Air Sensor fitted:

If a sensor is wired to the Controller, it will control the dampers to maintain the mixed air temperature at the same setpoint being used by the Supply Air Control loop in the AHU Controller. .

Enthalpy selection

If the AHU has an Outside Temperature and Relative Humidity (TRH) sensor and a Return TRH sensor registered to it then the controller will calculate the enthalpy of the Outside and Return air streams and use these values to determine the viability of energy recovery. The enthalpy values can be monitored on sensors EOUT (outside) and ERTN (return). If either of the TRH sensors fails then the control will revert to using the temperature of the air streams.

Air Quality Control

During periods of heat recovery (i.e. when the Controller is not calling for free cooling or free heating) the damper position is determined by 2 factors; one is the Minimum Fresh Air Position (see “Setting Minimum Fresh Air Position”). The Dampers will never close beyond this setting (Configuration Parameter MNFA ) during Occupation.

The Second Factor is Air Quality; as Air Quality deteriorates, the Fresh Air requirement will increase, and the dampers will open until they reach the full fresh air position. This means that Air Quality Control will override Temperature Control, which is the requirement for spaces which have variable numbers of occupants and heavy contamination of the air (e.g. cigarette smoke). Conversely, as Air Quality improves, the dampers will close until they reach the Minimum Fresh Air Position.

The points at which the Air Quality signal starts to override the Temperature Control may be set on 2 parameters MNAQ and MXAQ. If the Air Quality feature is not required set MNAQ and MXAQ to zero.

CO2 Control

CO2 is an accurate measure of the Occupancy rate of a building; it is particularly useful in spaces with variable occupancy e.g. auditoria, meeting rooms. A CO2 sensor may be substituted for the Air Quality sensor, and the controller will now increase the Fresh air quantity as CO2 levels rise.

Humidity Control

This Controller can provide a simple but effective means of controlling humidity in Swimming Pool Halls where the plant has no mechanical cooling capability. The Air Quality sensor is replaced by a Humidity sensor in the pool hall or return air stream; as humidity levels rise, increasing amounts of outside air (presumed to be at a lower humidity) are introduced to the space.

Manual Override

Allows the outputs to be exercised during commissioning and maintenance activities. Holding the override button pressed until the Status Lamp flashes green will cause the controller to be switched from automatic control to Override Mode. Subsequent pressings of the manual override button will cycle through the available Override modes.

1. Hold down Override until Status lamp flashes
   Controller changes to Override Mode and becomes Occupied, controlling to current Occupied Setpoint.

2. Press Override again
   Controller changes to Manual Mode and output is set to 100% heating.
   Temperature lamp shows red.

3. Press Override again
   Controller changes to Manual Mode and output is set to 100% cooling.
   Temperature lamp shows amber.

4. Press Override again
   Controller cancels Manual Override and reverts to automatic control.

As this feature does not time out, care should be exercised to ensure the module is returned to the automatic mode on completion of the commissioning or maintenance activities.

Occupancy Override can also be achieved via Doorway and InSite; using AUTO and OVRD monitoring parameters. The status lamp indication shows a different sequence.

Override from Off to ON : Status lamp flashes long ON, short Off
Override from ON to Off : Status lamp flashes long Off, short ON
See our ‘Design Guide’ publication for details of the Override features.

Registration

Registration is the simple process by which logical connections are made between Controllers in a SeaChange system; it is done at time of commissioning and involves pressing buttons on the Controllers in a specific sequence (for further details of the registration process, see our publication “Commissioning Guide”).

The Damper Controller must be registered to an AHU Controller; this is done by putting the AHU Controller into Configuration Mode, and registering the Damper Controller to it. This automatically enables all necessary demand signals, interlocks, temperatures etc. to be exchanged between the Controllers across the network. Note only 1 Damper Controller or 1 Heat Recovery Controller may be registered to an AHU Controller.

The module is registered to it's AHU controller by putting the AHU controller into config mode and then pressing the registration button on the Mixing Damper Controller. Registration is confirmed by the status LED on the module flashing once. Only one Mixing Damper controller is supported per AHU. Note also that a particular AHU can only have EITHER one Mixing Damper controller OR one Heat Recovery controller.

The AHU controller must be AHU3b or later to support a Mixing Damper controller.

Options and Product Codes

Air Handling Unit Damper Submodule

DAM / DIN / 3T / [driver option]

Driver options

DAM / DIN / AOP / [driver option]

Driver options

SC Controls Ltd

PO Box313
Wadhurst
East Sussex
TN5 6JL

phone 08707 606040
fax 08707 606041
e-mail seachange@sccontrols.co.uk
http:// www.seachange.co.uk