Explanation Of The Low Voltage Connections - Slant/Fin VGH-299-CH Installation And Service Manual

Explanation of the low voltage connections.

1-2 OUTDOOR SENSOR
If an outdoor temperature sensor is connected, the boiler will control the supply water temperature by using a
calculated setting based on outdoor reset curve, which is related to the outdoor temperature.
3-4 SYSTEM SENSOR
If a low loss header is used, this sensor measures the flow temperature at the system side. The sensor must
be mounted on the supply pipe or in a sensor well at the system side, close to the low loss header.
NOTICE: This sensor (See figure 7.9 or 7.10) must be used when boilers are cascaded with the internal
cascade manager.
PARAMETER: boiler parameter 122, see: 11.9 "programmable in- and outputs"
5-6 DHW SENSOR
When an indirect hot water tank is installed, the DHW mode must be set to 1 or 2. When the DHW mode is set
to 1, a sensor can be connected. This sensor must be mounted in a well in the tank. The boiler will now
modulate towards the hot water setpoint. When the DHW mode is set to 2, an aquastat can be connected.
When the set temperature is reached, the aquastat will switch off and the boiler will stop serving hot water.
7-8-9 MODBUS
Connections for a MODBUS communication signal.
7 = ground, 8 = A, 9 = B (A detailed Modbus bulletin is available at your supplier on request)
10-11 AL-BUS DEPENDING
Cascade connections for the dependent boilers, must be parallel linked together.
NOTICE: link all connections 10 to 10 and all connections 11 to 11, do not mix these.
Link connections 10 of the dependent boilers to 20 of the managing boiler, and connections 11 of the dependent
boilers to 21 of the managing boiler.
12-13 ON/OFF STAT OR
OPTION 1: An ON/OFF thermostat can be connected.
If these terminals are bridged, the set/ programmed flow temperature of the boiler will be used.
OPTION 2: An modulating controller can be connected to these terminals. The boiler software will detect and
use this modulating signal automatically.
PARAMETER: boiler parameter 124, see: 11.9 "programmable in- and outputs"
14-15 0-10 VDC CONTROL SIGNAL
These terminals are used for an external 0-10 VDC control input signal.
NOTICE: Terminal 14 [+] (positive) and terminal 15 [-] (negative).
16-17 DHW - FLOW SWITCH
For DHW_Mode 3 a flow switch can be connected. If a water flow is present, the switch closes, and the DHW
circulator is started. The temperature of the DHW is set with DHW_Setpoint.
PARAMETER: boiler parameter 117, see: 11.9 "programmable in- and outputs"
18-19 PWM – CIRCULATOR CONTROL
These connections are used to control the boiler circulator. The PWM signal determines the speed of the
circulator, when there is a heat demand. 18 = Signal, 19 = Ground
Parameter 136 has to be set to modulating (Factory set to on/off circulator) when using a modulating circulator.
20-21 AL-BUS MANAGING
Cascade connection for the managing boiler.
Link connection 20 of the managing boiler to connections 10 of the depending boilers, and connection 21 of the
managing boiler to connections 11 of the depending boilers.
22-23 LWCO EXTERN
To be used for an extra external Low Water Cut Off. The boiler goes into a lockout when this contact opens
24-25 GAS PRESSURE SWITCH
To be used for an extra external gas pressure switch. The boiler goes into a lockout when this contact opens
PARAMETER: boiler parameter 118, see: 11.9 "programmable in- and outputs"
26-27 SAFETY SWITCH 1
To be used for an extra external safety switch. The boiler goes into a lockout when this contact opens
28-29 SAFETY SWITCH 2
To be used for an extra external safety switch. The boiler goes into a lockout when this contact opens
Table 11. 1
MODULATING THERMOSTAT
E93.1601EN032.C VGH installation manual 57