Bryant 551C installation instructions 551B,C, EconoMi$erIV Input/Output Logic

Table 36—Perfect Humidity™ Adaptive Dehumidification System Subcooling Mode Service Analysis

PROBLEM	CAUSE		REMEDY
Subcooling Mode (Liquid Reheat)	No power to control transformer from	Check power source and evaporator-fan relay. Ensure all
Will Not Energize.	evaporator-fan motor.	wire connections are tight.
	No power from control transformer to liquid line	1.	Fuse open; check fuse. Ensure continuity of wiring.
	solenoid valve.	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	Thermostatic expansion valve (TXV).	1.	Check TXV bulb mounting, and secure tightly to suc-
Conditions with Subcooling/Reheat		2.	tion line.
Dehumidification Coil Energized.			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	Check power source and evaporator-fan relay. Ensure all
	evaporator-fan motor.	wire connections are tight.
	No power from control transformer to hot gas	1.	Fuse open; check fuse. Ensure continuity of wiring.
	line solenoid valve	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	Thermostatic expansion valve (TXV).	1.	Check TXV bulb mounting, and secure tightly to suc-
Conditions with Subcooling/Reheat		2.	tion line.
Dehumidification Coil Energized.			Replace TXV if stuck open or closed.
Excessive Superheat.	Liquid line solenoid valve will not operate.	Valve is stuck, replace valve.
	Hot gas line solenoid valve will not close.	Valve is stuck; replace valve.

551B,C

Table 38—EconoMi$er IV Input/Output Logic

	INPUTS						OUTPUTS
Demand Control	Enthalpy*				Compressor		N Terminal†
	Outdoor	Return	Y1	Y2	Stage	Stage	Occupied	Unoccupied
Ventilation (DCV)
					1	2	Damper
Below set	High	Low	On	On	On	On	Minimum position	Closed
(DCV LED Off)	(Free Cooling LED Off)
			On	Off	On	Off
			Off	Off	Off	Off
	Low	High	On	On	On	Off	Modulating** (between min.	Modulating** (between
	(Free Cooling LED On)						position and full-open)	closed and full-open)
			On	Off	Off	Off
			Off	Off	Off	Off	Minimum position	Closed
Above set	High	Low	On	On	On	On	Modulating†† (between min.	Modulating†† (between
(DCV LED On)	(Free Cooling LED Off)						position and DCV maximum)	closed and DCV
			On	Off	On	Off
								maximum)
			Off	Off	Off	Off
	Low	High	On	On	On	Off	Modulating***	Modulating†††
	(Free Cooling LED On)
			On	Off	Off	Off
			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).

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