Data sheet
NAT Actuator Submodule for Natural Ventilation
ACT / DIN / NAT / 3T / ... (Triac output) ACT / DIN / NAT / AOP / ... (0-10V)
Main Features Automatic Control of Atrium Windows, Roof Lights or Dampers in Naturally Ventilated buildings Night purge interlock with one or more AHU plants Control based on Cooling Demand, Wind Speed and Wind Direction and Outside Temperature Works in conjunction with a Sontay Weather Station and SeaChange Wind Interface Module

Summary Features

General

The SeaChange natural ventilation sub modules are used to provide automatic Control of  Atrium Windows, Roof Lights or Dampers in Naturally Ventilated applications.  They can be used to drive Raise/Lower type actuator motors or 0-10V DC actuator motors depending on the application and the design criteria.

The natural ventilation version of the Actuator sub module is generally similar to the standard version, however, the built-in control strategies have been extended to provide additional features and functionality for naturally ventilated buildings.

Control functions

The Window Controller controls the opening of automated windows and dampers in Naturally Ventilated buildings. The controller registers as an Actuator submodule and can be used with AHU, Secondary Cooling, Zone controllers as the parent module.

The window opening can be modified by Wind Speed and Direction as measured by a SeaChange Wind Interface module. Further settings allow the window opening to be limited by the Outside temperature.

When used on 3T hardware only one window actuator can be controlled per module with the raise/lower driver, whereas if Analogue output hardware is used then two diametrically opposed windows can be controlled from one Actuator submodule.

The module receives cooling demands and occupancy from it's parent module, while occupied the module will open the window as defined by the Minimum Fresh Air setting MNFA, unless the cooling demand is greater in which case the window will open an amount equal to the cooling demand. The maximum window opening can be overridden based on Wind Speed, Direction and Outside temperature as detailed below.

Depending on your application, the Actuators can be registered to either a  zone controller or a cooling secondary circuit module.

Where cooling demands in the building are generated multiple Zones and AHUsin the appropriate area of the building, a cooling secondary circuit controller is used to coordinate the cooling demands.  The Actuator submodule can be setup to modify the window opening based on demand, wind speed, wind direction and outside temperature.

Wind Speed Override

Two configuration parameters define the Wind speed operation.

MNWS Minimum Wind Speed defines the lower wind speed limit below which no wind override occurs
MXWS Maximum Wind Speed defines the upper wind speed limit at which the Window will be overriden closed

Between these limits the maximum window opening will be progressivly changed from 100% to 0%. The incoming demand signal will be rescaled to match the modified maximum opening, so if the demand was 50% and the Wind Speed was dictating a maximum opening of 60% then the window would be opened 30% (50% of 60%).

Setting both parameters to zero will disable this feature.

Wind Direction Override (NAT version only)

Three parameters define the Wind Direction override.

NOWS No Wind Speed, for wind speeds below this value the direction of the wind is ignored
WNWD Window Direction, this is the compass bearing measured from inside the building looking perpendicularly out of the window.

DDEV Direction Deviation. The window will be allowed to open to maximum when the wind is from the direction diametrically opposed to the Window Direction. Wind direction is always specified as the direction which the wind is coming from, so with a northerly wind, a south facing window is on the lee side of the bulding and can be opened. The Direction Deviation parameter specifies how much the wind direction needs to change from the downwind condition before the window needs to be shut. The diagram plots maximum window opening against wind direction deviation for a number of settings of DDEV Direction Deviation. It can be seen from this that if the DDEV is greater than 180 the window can be allowed to open a small amount even when the wind is blowing directly onto it.

Setting the DDEV Direction Deviation parameter to zero will disable the Wind Direction Override.

Outside Temperature Override (NAT version only)

This override prevents or limits window opening when the outside temperature is below or between preset temperature limits.

OUTT Outside Top limit, if the Outside temperature falls below this setting then the Maximum window opening will be progressivly reduced until
OUTS Outside Shut limit is reached where the Maximum window opening will be at 0%

If both these parameters are set to zero then this feature will be disabled.

Calculation Mode (NAT version only)

The factors calculated for each of the Window opening restrictions described above may be combined in one of two ways as defined by the CALC configuration variable.

CALC=0 Factors Multiplied

The indivudual factors from each calculation are multiplied together so for example if the Wind Speed factor is 80%, the Wind Direction Factor 50% and the Outside Temperature factor is 60% then the resulting re-scale applied to the window opening would be 0.8 *0.5 *0.6* 100 or 24%, in this case 100% cooling demand would open the window by just 24%

CALC=1 Minimum

In this case the lowest factor would be used to rescale the demand, with the same figures as above the Wind Direction factor of 50% is the lowest so 100% cooling demand would be re-scaled to 50%.

Each of the individual factors can be viewed on the sensor page, OSFR Outside Factor, WSFR Wind Speed Factor and WDFR Wind Direction Factor. The sensor FACT Resultant Factor displays the result of the combining calculation.

Options and Product Codes

ACT / DIN / NAT / 3T / [driver option]

Driver options

ACT / DIN / NAT / 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