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Installation Instructions
Bosch 96% AFUE Condensing Gas Furnace - BTC 770503101 J (06.2023)
10 Electrical Connections
WARNING: ELECTRICAL SHOCK HAZARD
f Blower access panel door switch opens 115V power to
control. No component operation can occur. Do not bypass
or close the blower access panel door switch with panel
removed.
See Fig. 37, (page 42) for field wiring diagram showing typical field 115V wiring.
Check all factory and field electrical connections for tightness. Field-supplied
wiring shall conform with the limitations of 63°F (35°C) rise.
WARNING: ELECTRICAL SHOCK AND FIRE HAZARD
f The cabinet MUST have an uninterrupted or unbroken
ground according to NEC ANSI/NFPA 70-latest edition or
local codes to minimize personal injury if an electrical fault
should occur.
This may consist of electrical wire, conduit approved for
electrical ground or a listed, grounded power cord (where
permitted by local code) when installed in accordance
with existing electrical codes. Refer to the power cord
manufacturer's ratings for proper wire gauge. Do not use gas
piping as an electrical ground.
NOTICE: FURNACE MAY NOT OPERATE
f Furnace control must be grounded for proper operation or
else control will lock out. Control must remain grounded
through green/yellow wire routed to gas valve and manifold
bracket screw.
10.1 115V Wiring
Verify that the voltage, frequency, and phase correspond to that specified on unit
rating plate. Also, check to be sure that service provided by utility is sufficient to
handle load imposed by this equipment. Refer to rating plate or Table 18 (page 41)
for equipment electrical specifications.
Make all electrical connections in accordance with National Electrical Code (NEC)
ANSI/NFPA 70-latest edition and any local codes or ordinances that might apply.
WARNING: FIRE HAZARD
f Do not connect aluminum wire between disconnect switch
and furnace. Use only copper wire.
Use a separate, fused branch electrical circuit with a properly sized fuse or circuit
breaker for this furnace. See Table 18 for wire size and fuse specifications. A
readily accessible means of electrical disconnect must be located within sight of
the furnace.
Proper polarity must be maintained for 115V wiring. If polarity is
incorrect, control LED status indicator light will flash rapidly and furnace
will NOT operate.
Junction box relocation
If factory location of J-Box is acceptable, go to next section
Electrical Connection to J-box.
On 14" wide cabinet models, the J-Box shall not be relocated to other
side of furnace cabinet when the vent pipe is routed within the cabinet.
1. Remove and save two screws holding J-Box (See Figure 35).
The J-Box cover need not be removed from the J-Box in order to move
the J-Box. Do NOT remove green ground screw inside J-Box. The ground
screw is not threaded into the cabinet flange and can be lifted out of
the clearance hole in cabinet while swinging the front edge of the J-Box
cover away from the cabinet.
2. Move J-Box to desired location.
3. Fasten J-Box to cabinet with two screws removed in Step 1.
4. Route J-Box wires within furnace away from sharp edges, rotating parts and
hot surfaces.
Figure 35
J-box
J-box cover
GND screw
Door switch
J-Box
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