Hitachi RAS-H(V)RNME-AF Service Manual page 146

5 Control system
Intelligent room thermostat (accessory ATW-RTU-02/03)
When an intelligent room thermostat is installed (as accessory), the unit and Room Thermostat communicate by means of
the receiver and Opentherm communication.
Room thermostat sends the actual room temperature and room temperature setting to the unit.
• Room set-point effect (Only heating operation)
The room temperature will modify the water set-point of the Outside Temperature Compensated (OTC) control (both OTC
Points and OTC Gradient) system.
At different times of the day, according to the time programme in the Room Unit, the room temperature set-point will cause
a shift of the heating curve down to reflect the change in desired room temperature. The change in supply set-point due to
the room set-point is dependent on the value of the outside temperature and the selected heating calculation.
Resulting Water Temperature Set-Point will be:
Where:
Ttwo: Resulting Water Set-Point
Ttwo OTCn: Water Set-Point as calculated by OTCn.
DTroom: Room Temperature Offset = RS – RD.
RS = Room set-point; RD = Room default temperature condition (20ºC)
Example:
Default OTC: Ttwo OTC = -1.3 x Ta + 43.2
Text (outside temperature) = 0ºC
Ttwo OTC = -1.3x 0 +43.2 = 43.2ºC
RS = 18ºC
RD: Better condition 20ºC.
Ttwo = function ( OTC + (Room temperature set-point offset) x2)
Ttwo = function ( OTC + (Room set-point - default room temperature condition (20ºC) x2)
Ttwo = function ( OTC + (( 18- 20 ) x2 )
Ttwo = 43.2 + (-4ºC)
136
SMGB0070 rev. 1 - 08/2011
Intelligent Thermostat
Thermostat Zone 1
Receiver
Wireless
Thermostat Zone 2
Wireless
Ttwo = Ttwo OTC + 2 x
à Ttwo = 39.2ºC
Unit
D
Troom