Feature Notes
Air Handing Unit Heat Recovery Submodule with 3 x Triac Outputs (3T version) with 2 x 0-10V DC Outputs (AOP version)
HRC / DIN / 3T / ... HRC / DIN / AOP / ...
Main Features Controls Heat Recovery via Heat Wheel, Run-Around Coil or Face/Bypass Dampers Works in Conjunction with a SeaChange AHU Controller to ensure correct interlocks Works with or without Post-Recovery Air Temperature sensor Control can be based on Enthalpy of Outside and Inside air streams On coil sensor can be used instead of AHU Outside temperature Can be controlled as the first stage of AHU heating or cooling

Description of Features

General

This Heat Recovery Controller is an AHU Submodule,and must be used in conjunction with a SeaChange AHU Controller; it can be used to control Run-Around Coils or Face/Bypass Dampers with On/Off or Raise/Lower type Actuators, or 0-10V DC devices (e.g. Heat Wheel speed).

The Heat Recovery Controller will provide heat recovery when Outside Temperature, Return Temperature and Supply Control conditions allow. In order for the Heat Recovery Controller to function, the AHU Controller must be fitted with a Return Air Sensor; the Heat Recovery Controller will then automatically acquire this temperature (and the Outside Temperature) over the network.

Control - with no Post-Recovery Sensor fitted:

If the Heat Recovery device is not capable of modulating its heat output, but is essentially an On/Off device (e.g. a Run-Around Coil with single-speed pump) then it may be controlled without a Post-Recovery Temperature sensor. 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 Controller will drive its outputs to call for full heat recovery. Similarly, if free heating is available and the AHU is calling for heating, the Controller will again call for full heat recovery. At all other times, the Heat Recovery Controller will drive its outputs to the “off” i.e. No Heat Recovery state. If the Heat Recovery device is only capable of providing free heating, or free cooling, but not both, a special version of the Controller is available; contact SeaChange for details.

Demand Percent - with no Post-Recovery Sensor fitted:

The on/off control described above can give problems where the energy recovered over corrects the demand requirements. For example with the pump on a run arround coil running continuously the heat gain may provide too high a supply air temperature from the Air Handler and it will then switch to cooling mode at which point the pump will be stopped but the Air Handler output may swing widely. Pumps and other on/off devices can be 'modulated' by running them for short periods in proportion to the demand. This method, using a Time Proprtioning driver setting, can smooth out the heat recovery and improve the Air Handler performance.

The heat recovery device can 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 heat recovery 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 heat recovery 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 Post-Recovery Sensor fitted:

If the Heat Recovery device is capable of Modulating control of its heat output (e.g. a Run-Around Coil with modulating valve, heatwheel speed, or Face/Bypass dampers) then a Post-Recovery sensor should be used. If a sensor is wired to the Controller, it will control the device to maintain the Post-Recovery temperature at the same setpoint being used by the Supply Air Control loop in the AHU Controller. As before, if the Heat Recovery device is only capable of providing free heating, or free cooling, but not both, a special version of the Controller is available; contact SeaChange for details.

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.

Additional Inlet Air sensing

Sometime the inlet to the Air Handler is from a plenum chamber or Atrium and the system outside temperature does not represent the incoming air temperature. An additional sensor can be fitted on the inlet side of the energy recovery unit and wired to input channel a on the controller. This sensor will then be used instead of the system Outside air temperature, its value mat be monitored on the sensor INLT Inlet Temperature..

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 Heat Recovery Controller must be registered to an AHU Controller; this is done by putting the AHU Controller into Configuration Mode, and registering the Heat Recovery 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 Heat Recovery controller. Registration is confirmed by the status LED on the module flashing once. Only one Heat Recovery 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 Heat Recovery controller.

Options and Product Codes

Air Handling Unit Heat Recovery Submodule

HRC / DIN / 3T / [driver option]

Driver options

HRC / 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