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US/CA
3.2
Making the electrical
connections
3.2.1 Electrical connection in boiler
B Installation of the controls automatically
produces BUS connection via the three
contacts (
Fig. 8 on page 14).
AF
ST 19
A F
1
2
Fig. 16
Controls installed in boiler via BUS
contacts in BUS-enabled Heatronic 3.
The controls recognize that the
boiler is installed via the third
contact.
3.2.2 Electrical connection to wall
B For BUS connection use AWG 18 (0.75 mm
cable and do not exceed 492 ft. (150 m) total
length.
B For the outdoor sensor AF use AWG 18
2
(0.75 mm
) cable and do not exceed 66 ft
(20 m) total length.
B Route all low-voltage cables separately from
cables carrying line voltage to avoid inductive
interference (minimum separation 4"
(100 mm)).
B In case of inductive external influences, use
shielded cables.
This way, the cables are shielded against
external influences (e.g. high-voltage cables,
contact wires, transformer stations, radio and
Heatronic 3
FW 200
4 B B
6 720 612 481-04.1R
Installation (for installers only) | 19
TV devices, amateur radio stations, microwave
devices, etc.).
AF
FW 200
B
B
Fig. 17
Controls connected to BUS-enabled
Heatronic 3.
If the BUS cables feature different
cross-sections:
B Connect BUS link via a junction
box.
2
B
B
B
2
)
(≥ 100 mm)
Fig. 18
Connection of BUS links via junction box
A
Junction box
B
BUS devices
Heatronic 3
ST 19
A F
1
2
4 B B
A
2
B
B
B
≥ 4"
≥ 4"
(≥ 100 mm)
6 720 643 256 (2010/05)
6 720 612 481-05.1R
2
B
B
B
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