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12.8.3 CH
WITH CONSTANT CIRCULATION SYSTEM OUTDOOR RESET
When CH_Mode is set to 2, full weather compensator is chosen. For this mode an outdoor sensor has to be
connected. The CH_Setpoint is calculated on the same way as described in § 12.7.2.
However, the demand does not depend on the Room Thermostat input but on the outdoor temperature and the
outdoor reset setpoint. When the outdoor temperature is below Warm_Weather_Shutdown (settable) CH demand
is created.
During the night an input signal from an external clock can lower the CH_Setpoint. When the RT input opens
CH_Setpoint will be decreased with Night_Setback_Temp. The RT input does not influence the CH demand
directly!
This can be done by connecting a relay contact or clock thermostat to terminal 12 and 13 on the low voltage
connectors of the boiler. The room thermostat is only being used in this function to switch between a night
setback temperature and a daytime temperature, there is always a constant demand for heat in CH mode 2.
The Night Setback temperature can be set by using the installer password and changing parameter 28 in the boiler
parameters, default value is setpoint - 50 °F.
Boiler Parameters
(25) Warm Weather Shutdn
(26) Boost Temp increment
(27) Boost Time Delay
(28) Night Setback
Temp.
Adjustable constant Circulation Parameters
Parameters
CH_Mode
Warm_Weather_Shutdown
Set max. outdoor temp.
Above this temperature heat demand is blocked.
CH_Setpoint_Diff
Adjusts the calculated CH setpoint.
Table 12. 14
12.8.4 CH
WITH CONSTANT CIRCULATION AND PERMANENT HEAT DEMAND
For this mode the CH_ Mode must be set to 3, no outdoor sensor is needed. The supply temperature is kept
constantly at the setpoint temperature. The boiler is controlled in a similar way as described in paragraph 12.7.1.
When the room thermostat contact opens CH_Setpoint will be decreased with Night_Setback_Temp. In this
condition the circulator is always ON.
Please note that the circulator starts every 24 hours function is not performed during this mode. In this mode the
circulator will be running continuously.
Parameters
CH_Mode
CH_Setpoint
Table 12. 15
74
72 °F
▲
0
°F
20 min
7 °F
▼
Picture 12.15
Level
(Default) Value
2: Installer
2: installer
1: User
Level
(Default) Value
2: Installer
0
2: Installer
176 ºF (80 ºC)
E93.1601EN032.C VGH installation manual
; CH
2
MODE
Settable
0
Mode 0 - 5
72 ºF (22 ºC)
32...95 ºF (0...35 ºC)
0 ºF (0 ºC)
-18...+18 ºF (-10...+10 ºC)
; CH
3
MODE
Settable
Mode 0 - 5
68.....194 ºF (20.....90 ºC)
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