Carrier Understand the Key Features of 48HC Heating Systems

Table 9 – RTU Open Controller Inputs and Outputs

		POINT NAME	BACnet OBJECT	TYPE OF I/O	CONNECTION PIN
			NAME		NUMBER(S)
			DEDICATED INPUTS
Space Temp / Zone Temp			zone_temp	AI (10K Thermistor)	J20--- 1, 2
Supply Air Temperature			sa_temp	AI (10K Thermistor)	J2--- 1, 2
Outdoor Air Temperature			oa_temp	AI (10K Thermistor)	J2--- 3, 4
Space Temperature Offset Pot			stpt_adj_offset	AI (100K Potentiometer)	J20--- 3
Safety Chain Feedback			safety_status	DI (24 VAC)	J1--- 9
Compressor Safety Status			comp_status	DI (24 VAC)	J1--- 2
Fire Shutdown Status			firedown_status	DI (24 VAC)	J1--- 10
Enthalpy Status			enthalpy_status	DI (24 VAC)	J2--- 6
Humidistat Input Status			humstat_status	DI (24 VAC)	J5--- 7
			CONFIGURABLE INPUTS
Indoor Air CO2			iaq	AI (4--- 20 ma)
Outdoor Air CO2			oaq	AI (4--- 20 ma)	J4--- 2 or J4--- 5
Space Relative Humidity			space_rh	AI (4--- 20 ma)
Supply Fan Status*			sfan_status	DI (24 VAC)
Filter Status*			filter_status	DI (24 VAC)	J5--- 1 or J5--- 3 or
Door Contact Input*			door_contact_status	DI (24 VAC)	J5 5 or J5--- 7
Occupancy Contact*			occ_contact_status	DI (24 VAC)
			OUTPUTS
Economizer Output			econ_output	AO (4--- 20ma)	J2--- 5
Supply Fan Relay State			sfan	DO Relay (24VAC , 1A)	J1--- 4
Compressor 1 Relay State			comp_1	DO Relay (24VAC , 1A)	J1--- 8
Compressor 2 Relay State			comp_2	DO Relay (24VAC , 1A)	J1--- 7
Heat Stage 1 Relay State			heat_1	DO Relay (24VAC , 1A)	J1--- 6
Heat Stage 2 Relay State			heat_2	DO Relay (24VAC , 1A)	J1--- 5
Power Exhaust Relay State			pexh	DO Relay (24VAC , 1A)	J11--- 3
Dehumidification Relay State			dehum	DO Relay (24VAC, 1A)	J11--- 7, 8
LEGEND
AI	---	Analog Input
AO	---	Analog Output
DI	---	Discrete Input
DO	---	Discrete Output

*These inputs (if installed) take the place of the default input on the specific channel according to schematic. Parallel pins J5---1 = J2---6, J5---3 = J1---10, J5---5 = J1---2 are used for field---installation.

48HC

The RTU Open controller requires the use of a Carrier space sensor. A standard thermostat cannot be used with the RTU Open system.

Supply Air Temperature (SAT) Sensor —

On FIOP-equipped 48HC unit, the unit is supplied with a supply-air temperature (SAT) sensor (33ZCSENSAT). This sensor is a tubular probe type, approx 6-inches (12.7 mm) in length. It is a nominal 10-k ohm thermistor.

The SAT is factory-wired. The SAT probe is wire-tied to the supply-air opening (on the horizontal opening end) in its shipping position. Remove the sensor for installation. Re-position the sensor in the flange of the supply-air opening or in the supply air duct (as required by local codes). Drill or punch a 1/2-in. hole in the flange or duct. Use two field-supplied, self-drilling screws to secure the sensor probe in a horizontal orientation. See Fig. 40.

Outdoor Air Temperature (OAT) Sensor —

The OAT is factory-mounted in the EconoMi$er2 (FIOP or accessory). It is a nominal 10k ohm thermistor attached to an eyelet mounting ring.

EconoMi$er2 —

The RTU Open control is used with EconoMi$er2 (option or accessory) for outdoor air management. The damper position is controlled directly by the RTU Open control; EconoMi$er2 has no internal logic device.

Outdoor air management functions can be enhanced with field-installation of these accessory control devices:

Enthalpy control (outdoor air or differential sensors) Space CO2 sensor

Outdoor air CO2 sensor

Field Connections

Field connections for accessory sensors and input devices are made the RTU Open, at plugs J1, J2, J4, J5, J11 and J20. All field control wiring that connects to the RTU Open must be routed through the raceway built into the corner post as shown in Fig. 31. The raceway provides the UL required clearance between high- and low-voltage wiring. Pass the control wires through the hole provided in the corner post, then feed the wires thorough the raceway

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