Hitachi YUTAKI Series - Room Setpoint Parallel Shift

83
Heating control functions
SMGB0066 rev.0 - 12/2009
Controller pack
Service Manual
4
Theheatingcurveshouldbeselectedaccordingtothelocalclimaticconditions,buildingstructureandtypeofheating
distribution system. The gradient of the heating curve describes the relation between the change in the supply
temperature and the change in outside temperature. In the case of large heating surfaces (and therefore low supply
temperatures)likeoorheatingsystemstheheatingcharacteristiccurveislesssteepcomparedtosmallerheating
surfaces(egradiators).Typicallyawell-insulated,modernbuildingwithunderoorheatingwoulduseaheatingcurve
value of 0.4-0.6 and one with radiator heating a value of around 1.6.

P4 OTC Heating Curve Gradient (default value 1.1)
Thegraphshowsthesupplywatertemperaturesetpoint,whentheroomsetpoint=20°Candnoroomcompensationis
applied.
Outside Temperature (ºC)
Supply water temperature (ºC)

P4=1.1,
TEXT(outsidetemperature)=0°C,
SR1 (room setpoint) = 20°C
=>Fromgraph,S1(supplysetpoint)=49°C
 

Atdifferenttimesoftheday,accordingtothetimeprogrammeintheRoomUnit,theroomtemperaturesetpointwill
cause a parallel shift of the heating curve. The change in supply setpoint due to the room setpoint is dependant on the
actual value of the outside temperature and the selected heating curve.

P4 = 1.1
TEXT (outside temperature) = 0°C
SR1 (room setpoint) = 18°C
=> S1 (supply setpoint) = 45°C
Inthiscase,fora2Kchangeinroomsetpoint,thesupplysetpointischangedby4K

note
The room setpoint value is sent from the Room Unit to the System Controller by a wireless signal. There can -
be a short delay in response between a room setpoint change and the system controller changing the supply
setpoint.