Johnson Controls 100 Series User Manual

JOHNSON CONTROLS
90
FORM 100.50-NOM12
ISSUE DATE: 04/02/2019
SECTION 5 – SEQUENCE OF OPERATION
• Sends 24 VAC to the digital multiplexor con-
trol, which sends a 0–5 VDC signal back to
the IPU board. This 0–5 VDC signal proves
furnace 1A status is good.
• Once the IPU board receives the appropriate VDC
signal from the digital multiplexer control, the IPU
board removes 24 VAC from the 6R relay, which
causes:
1. The induced draft motor to switch to low speed
2. The modulating gas valve to switch to mini-
mum low fire
• Furnace 1A is now in Modulation mode.
• When ame rectication is not established, the ig-
nition control removes the high voltage spark and
24 VAC from the gas valve, waits 30 seconds, and
then tries again.
• The ignition sequence is tried three times. When a
ame is not established by the third try, the igni-
tion control locks out for 1 hour.
• Furnace sections 2, 3, and 1B follow the same se-
quence as staged gas heat.
LD21613
FIGURE 47 - DIGITAL MULTIPLEXOR
CONNECTIONS FOR MODULATING GAS HEAT
Modulating Operation
• Once Furnace 1A has successfully ignited, the
IPU board enters the normal modulating heat se-
quence.
• On a modulating gas heat unit. furnace 1A is al-
ways the rst ON and last OFF.
• Furnace 1A has a 2 stage gas valve and a modu-
lating gas valve controlled by a Maxitrol
®
Signal
Conditioner.
• The signal conditioner receives a 0–10 VDC sig-
nal from the IPU board depending on the required
heating demand.
1. Furnace 1A Low Fire
• Furnace 1A starts with the low fire solenoid of
the 2 stage gas valve being energized.
• Modulating gas valve at minimum position
at approximately 0.5–2 VDC from the IPU
board.
• The inducer motor is on low speed.
• When the heating demand increases, the
0–10 VDC signal increases, which further
opens the modulating valve.
• When the heating demand decreases, the
0–10 VDC signal decreases, which closes the
modulating gas valve.
• Modulating gas valve is at maximum posi-
tion at approximately 6.5 VDC from the IPU.
• When more heat is needed, furnace 1A
switches to high fire.
2. Furnace 1A High Fire
• The IPU energizes the high fire solenoid of
the 2 stage gas valve.
• Modulating gas valve at minimum position,
approximately 4–4.5 VDC from the IPU
board.
• The inducer motor switches to high speed.
• When the heating demand increases, the
0–10 VDC signal increases, which further
opens the modulating valve.
• When the heating demand decreases, the
0–10 VDC signal decreases, which closes the
modulating gas valve.

Johnson Controls 100 Series Specifications

General

Brand	Johnson Controls
Model	100 Series
Category	Air Conditioner
Language	English