Slant/Fin VGH-299-CH, Installation And Service Manual

Page: 77 / 128

E93.1601EN032.C VGH installation manual 77
Demand for Domestic Hot Water
12.9.1 N
O
D
OMESTIC
H
OT
W
ATER
; DHW
MODE
0
No domestic hot water is available. The T_DHW_Out sensor does not need to be connected.
12.9.2 DHW S
TORAGE WITH SENSOR
; DHW
MODE
1
Mode 1: DHW is prepared by warming up a store. Either a DHW circulator or 3-way valve can be used to switch
to DHW mode.
The DHW temperature in the tank is measured with sensor T_Store and set with parameter DHW_Store_Setpoint.
When this sensor drops below DHW_Store_Setpoint
minus DHW_Store_Hyst_Down the control detects a
demand for the store and starts the general and DHW circulator.
If the supply temperature T_Supply is below
DHW_Store_Setpoint
plus DHW_Store_Supply_Extra minus DHW_Supp_Hyst_Down the boiler is started as well.
When the boiler is ON, the power is PID-modulated so T_Supply is regulated towards
DHW_Setpoint
plus DHW_Store_Supply_Extra.
The boiler is stopped when the supply temperature rises above
DHW_Store_Setpoint
plus DHW_Store_Supply_Extra plus DHW_Supp_Hyst_Up.
The demand for the tank is ended when the tank-sensor rises above
DHW_Store_Setpoint
plus DHW_Store_Hyst_Up. The circulator continues DHW_Post_Pump_Period.
DHW Priority
Standard DHW demand has priority over CH demand but the priority period is limited up to
DHW_Max_Priority_Time. The priority timer starts when both CH and DHW demand are present. After the
DHW_Max_Priority_Time is achieved, the control will switch from DHW to CH operation. CH has priority now for
a maximum period of DHW_Max_Priority_Time.
Different DHW Priority types can be chosen:
DHW priority Description
0  Time DHW has priority to CH during DHW_Max_Priority_Time
1  OFF CH always has priority to DHW
2

ON DHW always has priority to CH
Default DHW_Priority is set to 2.
Store warm hold function
Because of the presence of the indirect tank sensor ( T_Store ) the control can detect demand for holding the indirect
tank hot.
If T_Store drops below DHW_Store_Setpoint
minus DHW_Store_Hold_Warm the boiler starts at minimum power.
The boiler stops if T_Store is higher than DHW_Store_Setpoint plus DHW_Store_Hyst_Up.
Relevant variables
Specific Parameters Level (Default) Value Range
DHW_Mode 2: Installer 5 ??? 0, 1, 2, 3, 5, 6, 7, 8
DHW_Store_Setpoint Sets the desired DHW temperature. 1: User 149 ºF ( 65 ºC) 104...160 ºF (40...71 ºC)
DHW_Store_Supply_Extra
Increases the supply temperature to the store until
DHW_Store_Setpoint + DHW_Store_Supply_Extra.
2: Installer 27 ºF (15 ºC) 0...54 ºF (0...30 ºC)
Status Variables Value
DHW control state
Central Heating controller state
0  Idle
1  Request
2

Demand
3

Post circulation
4  Off
Table 12. 18
Table 12. 19
Table 12. 20