JOHNSON CONTROLS
94
FORM 100.50-NOM12
ISSUE DATE: 04/02/2019
SECTION 5 – SEQUENCE OF OPERATION
MIN VOLTS
DC
MAX
VOLTS DC
MODULATING
FURNACE 1A STATUS
FURNACE 1A
STATUS
FURNACE 2
STATUS
FURNACE 3
STATUS
FURNACE 1B
STATUS
3.115
3.411
OFF
ON
ON
OFF
ON
3.252
3.559
ON
ON
ON
OFF
ON
3.390
3.706
OFF
OFF
OFF
ON
ON
3.528
3.854
ON
OFF
OFF
ON
ON
3.665
4.001
OFF
ON
OFF
ON
ON
3.803
4.149
ON
ON
OFF
ON
ON
3.941
4.296
OFF
OFF
ON
ON
ON
4.078
4.444
ON
OFF
ON
ON
ON
4.216
4.592
OFF
ON
ON
ON
ON
4.354
4.739
ON
ON
ON
ON
ON
• When a particular furnace section is lighting and
one of the above warnings is present, check for
the proper 24 VAC input at TB1 of the digital mul-
tiplexer control board. When the 24 VAC input is
not present, check for loose or broken wires or
loose connections.
• When the proper 24 VAC input is present at TB1,
check for the proper 0–5 VDC output from TB2.
When the proper 0–5 VDC output is present at TB2,
check for the 0–5 VDC signal at the IPU board.
• See
and
for staged
and modulating gas output signals.
Electric Heat
• The Series 100 unit can be ordered with optional
electric heat.
• There are numerous electric heat capacities avail-
able:
1. 40 kW
4. 120 kW
6. 200 kW
2. 80 kW
5. 160 kW
7. 240 kW
3. 100 kW
• The electric heat capacity determines the number
of electric heaters installed.
Electric Heat Setup
• Set the heating system type to electric under the
OPTIONS-HEATING menu.
• Set the Electric Heat Capacity to the appropriate
selection under the OPTIONS-HEATING menu.
• Ensure that Heating System is User Enabled un-
der the PROGRAM-HEATING menu.
TABLE 37 -
MODULATING GAS HEAT 0–5 VDC OUTPUTS TO IPU BOARD (CONT'D)
Troubleshooting the Multiplexer Control Board
• Ensure the digital multiplexer control board has both
5 VDC power and 24 VAC power at the appropriate
terminals.
• The board does not function properly if both 24
VAC and 5 VDC are not present.
• A quick check of this can be made by looking at
the DS1 and DS7 LEDs. When both LEDs are lit,
both power sources are present.
• When 5 VDC is not present, neither DS1 nor DS7 is
lit. When 5 VDC is present but 24 VAC is not, only
DS7 is lit.
• Digital multiplexer warnings:
• WRN-FURNACE MULTIPLEXER FAULT
(used when the unit has modulating gas heat)
• WRN-GAS FURNACE (used when the unit
has staged gas heat)
• Ensure the unit’s heating capacity matches what is
set under the HEATING menu:
• On modulating gas heat, furnace 1 is divided
into two halves: 1A and 1B. This correlates to
one heating section and the heating capacity is
375 MBH. A 750 MBH capacity is used with
furnace sections 1A, 1B, and 2. A 1125 MBH
capacity is used with furnace sections 1A, 1B,
2, and 3.
• On staged gas heat, 375 MBH is used with fur-
nace section 1. A 750 MBH capacity is used
with furnace sections 1 and 2. A 1125 MBH ca-
pacity is used with furnace sections 1, 2, and 3.
