Bosch ZBR 21-3 A NG - Connecting the LWCO Device

Electrical connection
49
Greenstar – 6721822579 (2021/01)
7.4 Connecting the LWCO device
NOTICE
System damage or malfunction!
▶ Ensure the air box remains air-tight when routing the LWCO cable to
the outside.
▶ Do not route the LWCO cable through the ignition cable grommet as
appliance malfunction may occur.
▶ Push the existing cable grommet of the fan cable down through air
box sheet.
▶ Slip new cable grommet over the cable.
▶ Insert new cable grommet into the air box sheet.
▶ Push old cable grommet back up and into new cable grommet.
▶ Insert cable of the LWCO device into the second hole of the cable
grommet.
Fig. 60 Mounting the cable grommet (included in scope of delivery)
▶ Install a 24 VAC 20 VA transformer near the boiler.
▶ Follow LWCO manufacturer’s instructions.
▶ Connect the lead labeled BOILER GROUND (green) to pin 2 (center)
of the white plug in the junction box of the wall-mounted gas
condensing boiler.
▶ Connect the two leads labeled 24 V HOT (red) and 24 V COMMON
(white) to the external 24 VAC transformer.
▶ Connect the leads labeled SWITCH CONTACT (yellow) to the TB1
temperature switch ( Fig. 49, page 45) on the Heatronic.
Fig. 61 Wires of a LWCO device with LWCO adapter
[1] LWCO device (Hydrolevel Safgard 1100)
[2] BOILER GROUND (green)
[3] SWITCH CONTACT (yellow)
[4] SWITCH CONTACT (yellow)
[5] 24 V HOT (red)
[6] 24 V COMMON (white)
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