Solar System Design Guide
21
6020 457 - 01
Solar Control Unit SCU 345
Construction
The control unit comprises:
– PCB
– LCD
– Selector keys
– Connection terminals:
– 5x Sensor inputs
– 3x Variable speed outputs for controlling the solar
circuit pumps
– 1x Mechanical relay for actuating the pumps and
valves
– Pulse counter input for connection of flow meters
– VBus connectivity
– Power supply (on-site ON/OFF switch)
– SD card slot for data logging
For systems with Viessmann DHW tanks, the tank
temperature sensor is installed in the solar brass elbow
located in the heating water return (see page 35).
Functions
■
Switching the solar circuit pumps for DHW and/or
swimming pool heating or other consumers
■
Electronic limiter for the temperature in the DHW tank
(safety shutdown at 194°F (90°C)
■
Collector safety shutdown and collector cooling
■
9 basic system layouts
■
Up to 3 storage tanks (thermal loads)
■
Operating hour counter for relays
■
Energy metering
■
Heat dump function
■
Time controlled thermostat function
For further functions, see page 22.
The standard delivery includes 2x collector temperature
sensor 2x tank temperature sensor (swimming pool water/
heating water buffer tank).
– SCU 345
– 2x collector temperature sensors (FKP6)
– 2x tank temperature sensors (FRP6)
Delivered Condition
Specification
Rated voltage
100
−
240 VAC
Rated frequency
50
−
60 Hz
Rated current
4A
Power consumption
2W (in standby mode 0.9 W)
Safety category
II
Permissible ambient temperature:
– During operation
32 to 104°F
(0 to +40°C)
use in the living space or
boiler
room
– During storage and transport
−
4 to +150°F
(
−
20 to +65°C)
Rated relay output breaking capacity
– Semi-conductor relay 1 to 3 1A, 100
−
240 VAC
– Mechanical relay 4
2A, 100
−
240 VAC
– Total
max. 4 A
Collector temperature sensor (FKP6)
For connection inside the control.
On-site extension of the connecting lead:
– 2-core copper lead, cable length up to 197 ft. (60 m)
AWG 15-16 [cross-section of 0.00233 in
2
(1.5 mm
2
)]
– Never route this lead immediately next to 120/240V cables
Cable length
5 ft. (1.5 m)
Sensor type
PT1000
Permissible ambient temperature
– during operation
−
58 to 356°F
(
−
50 to +180°C)
– during storage and transport
−
4 to +158°F
(
−
20 to +70°C)
Tank temperature sensor (FRP6)
For connection inside the control.
On-site extension of the connecting lead:
– 2-core lead, cable length up to 197 ft. (60 m)
AWG 15-16 [cross-section of 0.00233 in
2
(1.5 mm
2
)]
– Never route this lead immediately next to 120/240V cables
Cable length
8.2 ft. (2.5 m)
Sensor type
PT1000
Permissible ambient temperature:
– during operation
23 to +176°F
(
−
5 to +80°C)
– during storage and transport
−
4 to +158°F
(
−
20 to +70°C)
Solar Control
