5012886-YIM-B-0517
26
Johnson Controls Unitary Products
VFD
2-10 VDC (0-100%) output for the indoor blower
Variable Frequency Drive
Output is active with indoor blower operation. For CV units: this
output provides stepped IntelliSpeed control of the indoor
blower VFD based on fan-only, cooling stage and heating stage
outputs. For VAV units: this output provides control of the indoor
blower VFD based on supply duct static pressure input and
setpoint.
VFDFLT
24 VAC hot input from the normally open VFD
alarm contact
The VFD alarm contact switches from R within the unit wiring
harness. 24 VAC input results in unit shutdown and a “VFD
fault” alarm
Terminal at lower right corner of UCB
24V FOR OUTPUTS
24 VAC hot for H1, H2, CN-FAN, AUX HGR, FAN
C1 and
C2 output relay contact switching
Output relay circuitry is isolated from other UCB components
and the 24 VAC hot source may be from a second transformer
in the unit
Pin Heat section connections at right on lower edge of UCB
H1
24 VAC hot output for heat section stage 1
Not effective for cooling-only units. Output if demand is present
and permissions allow one stage or two stages of heat section
operation
H2
24 VAC hot output for heat section stage 2
Not effective for cooling-only units or units with single-stage
heat sections. Output if demand is present and permissions
allow two stages of heat section operation
MV
24 VAC hot input confirming heat section
operation
Sourced from gas valve in gas heat units or first stage heat
contactor in electric heat units. Input within 5 minutes from
initiation of H1 output initiates the “Heat On Fan Delay” timer,
loss of input following the termination of H1 output initiates the
“Heat On Fan Delay” timer, no input within 5 minutes from
initiation of H1 output initiates an “Ignition Failure” alarm, input
for longer than 5 minutes without H1 output initiates a “Gas
Valve Mis-wire” alarm
Pin Cooling and fan output connections at right on lower edge of UCB
CN-FAN
24 VAC hot output for the condenser fan contactor
coil
Output with either C1 or C2 output; interrupted during defrost
cycle for heat pump units
AUX HGR
24 VAC hot output for hot gas reheat components Effective only for reheat units, output with reheat operation
FAN
24 VAC hot output for indoor blower contactor coil/
indoor blower VFD enable relay coil
Output with heat/cool operation, G input or schedule demand
C1
24 VAC hot output for compressor 1
If demand is present and permissions allow compressor 1
operation; output with compressor cooling, comfort ventilation
cooling, reheat or heat pump heating demands
C2
24 VAC hot output for compressor 2
Not effective for one stage compressor UCBs. If demand is
present and permissions allow compressor 2 operation; output
with compressor cooling, comfort ventilation cooling or heat
pump heating demands
Pin Refrigerant circuit safety switch and indoor blower overload connections at center on lower edge of UCB
HPS1
(right pin)
24 VAC hot out for refrigerant circuit 1 High
Pressure Switch
Connects through circuit trace to the R terminal
HPS1
(left pin)
24 VAC hot return from refrigerant circuit 1 High
Pressure Switch
Input is only considered if C1 output is needed; input must be
present to allow C1 output. Three HPS1 trips in a two hour
period cause a “High Pressure Switch 1 Lockout” and C1 output
is then prevented until alarm reset. Connects through circuit
trace to the right LPS1 pin.
LPS1
(right pin)
24 VAC hot out for refrigerant circuit 1 Low
Pressure Switch
Connects through circuit trace to the left HSP1 pin
Table 9:
Smart Equipment™ UCB Details (Continued)
Description
Function & Comments
