Bryant 551C - Manual (Page 59)

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Table 36—Perfect Humidity™ Adaptive Dehumidification System Subcooling Mode Service Analysis
PROBLEM CAUSE REMEDY
Subcooling Mode (Liquid Reheat)
Will Not Energize.
No power to control transformer from
evaporator-fan motor.
Check power source and evaporator-fan relay. Ensure all
wire connections are tight. Will Not Energize.
No power from control transformer to liquid line
solenoid valve.
1. Fuse open; check fuse. Ensure continuity of wiring.
2. Low-pressure switch open. Cycle unit off and allow
low-pressure switch to reset. Replace switch if it will
not close.
3. Transformer bad; check transformer.
Liquid line solenoid valve will not operate. 1. Solenoid coil defective; replace.
2. Solenoid valve stuck open; replace.
Liquid line solenoid valve will not open. Valve is stuck closed; replace valve.
Low System Capacity. Low refrigerant charge or frosted evaporator coil. 1. Check charge amount. Charge per Fig. 53---56.
2. Evaporator coil frosted; check and replace low-pres-
sure switch if necessary.
Loss of Compressor Superheat
Conditions with Subcooling/Reheat
Dehumidification Coil Energized.
Thermostatic expansion valve (TXV). 1. Check TXV bulb mounting, and secure tightly to suc-
tion line.
2. Replace TXV if stuck open or closed.
Table 37—Perfect Humidity™ Adaptive Dehumidification System Hot Gas Reheat Mode Service Analysis
PROBLEM CAUSE REMEDY
Reheat Mode Will Not Energize. No power to control transformer from
evaporator-fan motor.
Check power source and evaporator-fan relay. Ensure all
wire connections are tight.
No power from control transformer to hot gas
line solenoid valve
1. Fuse open; check fuse. Ensure continuity of wiring.
2. Low-pressure switch open. Cycle unit off and allow
low-pressure switch to reset. Replace switch if it will
not close.
3. Transformer bad; check transformer.
Hot gas line solenoid valve will not operate. 1. Solenoid coil defective; replace.
2. Solenoid valve stuck closed; replace.
Low refrigerant charge or frosted evaporator coil. 1. Check charge amount. Charge per Fig. 53---56.
2. Evaporator coil frosted; check and replace low-pres-
sure switch if necessary.
Loss of Compressor Superheat
Conditions with Subcooling/Reheat
Dehumidification Coil Energized.
Thermostatic expansion valve (TXV). 1. Check TXV bulb mounting, and secure tightly to suc-
tion line.
2. Replace TXV if stuck open or closed.
Excessive Superheat. Liquid line solenoid valve will not operate. Valve is stuck, replace valve. Excessive Superheat.
Hot gas line solenoid valve will not close. Valve is stuck; replace valve.
Table 38—EconoMi$er IV Input/Output Logic
INPUTS OUTPUTS
Demand Control
Enthalpy* Compressor N Terminal†
Demand Control
V til ti (DCV) Outdoor Return Y1 Y2
Stage Stage Occupied Unoccupied
Ventilation (DCV) Outdoor Return Y1 Y2
1 2 Damper
Below set
(DCV LED Off)
High
(F C li LED Off)
Low On On On On Minimum position Closed Below set
(DCV LED Off)
High
(Free Cooling LED Off)
Low
On Off On Off
Minimum position Closed
Off Off Off Off
Low
(F C li LED O )
High On On On Off Modulating** (between min.
i i d f ll )
Modulating** (between
l d d f ll )
Low
(Free Cooling LED On)
High
On Off Off Off
Modulating (between min.
position and full-open)
Modulating (between
closed and full-open)
Off Off Off Off Minimum position Closed
Above set
(DCV LED O )
High
(F C li LED Off)
Low On On On On Modulating†† (between min.
i i d DCV i )
Modulating†† (between
l d d DCV
Above set
(DCV LED On)
High
(Free Cooling LED Off)
Low
On Off On Off
Modulating†† (between min.
position and DCV maximum)
Modulating†† (between
closed and DCV
maximum)
Off Off Off Off
maximum)
Low
(F C li LED O )
High On On On Off Modulating*** Modulating††† Low
(Free Cooling LED On)
High
On Off Off Off
Modulating Modulating†††
Off Off Off Off
*For single enthalpy control, the module compares outdoor enthalpy to the ABCD set point.
†Power at N terminal determines Occupied/Unoccupied setting: 24 vac (Occupied), no power (Unoccupied).
**Modulation is based on the supply-air sensor signal.
††Modulation is based on the DCV signal.
***Modulation is based on the greater of DCV and supply-air sensor signals, between minimum position and either maximum position (DCV) or fully open (sup-
ply-air signal).
†††Modulation is based on the greater of DCV and supply-air sensor signals, between closed and either maximum position (DCV) or fully open (supply-air sig-
nal).
551B
,C