Bryant Understanding Two-Stage Air Conditioners and Their Key Specifications

TWO-STAGE 286B/289B/180B/187B

Application Guidelines

Bryant designed and tested the two-stage air conditioner and heat pump products with Puron refrigerant to operate at a minimum outdoor operating ambient in cooling mode at 55_F without low ambient cooling enabled and the maximum outdoor operating

ambient in cooling is 125_F/51.6_C. On Evolution communicating systems, only low ambient cooling is available to 0_F/-17.8_C.

The maximum outdoor operating ambient in heating mode is 66_F/18.8_C on all heat pumps. Continuous operation in heating mode is approved to -30_F/-34.4_C. Thermostat options for the two stage units are as follows:

SA,B,C,D four-wire connections for Evolution User Interface.

SR,C,W,Y1,Y2, and O wire connections for standard, non-communicating thermostat.

286BNA, 289B, 187B, and 180B units can run, and are matched with, User Interface (UI) communicating and non-communicating indoor fan coils and furnaces. Only unit combinations listed in the two-stage Product Data are recommended.

Line sets for two stage units are similar to the single stage units. However, some restrictions may apply to specific combinations in long line applications. Refer to the Long Line Guideline for further information.

The Tennessee Valley Authority (TVA) requires that electric strip heat have a lockout feature. This is achieved through Bryant thermostats required per above and must be used on all TVA approved units.

The new control board in the two stage units with Puron refrigerant has dip switches for defrost timing. The Evolution controls provide these two stage units with high stage latching and Hybrid Heatt (dual fuel) capabilities. The standard Hybrid Heatt (duel fuel) thermostat can be used on two stage units with Bristol reciprocating compressors only.

Model Plug

Each control board contains a model plug. The correct model plug must be installed in order for the system to operate properly. (See Table 18.)

The model plug is used to identify the type and size of unit to the control. On 286BNA models, the model plug is also used to determine the start sequence timing for each individual model.

On new units, the model and serial numbers are inputted into the board’s memory at the factory. If a model plug is lost or missing at initial installation, the unit will operate according to the information input at the factory and the appropriate error code will flash temporarily. An RCD replacement board contains no model and serial information. If the factory control board fails, the model plug must be transferred from the original board to the replacement board for the unit to operate.

NOTE: The model plug takes priority over factory model information input at the factory. If the model plug is removed after initial power up, the unit will operate according to the last valid model plug installed, and flash the appropriate fault code temporarily.

Table 18—Model Plug Information

	MODEL	PIN RESISTANCE
MODEL		(K---ohms)
	PLUG
NUMBER
	NUMBER
		Pins 1---4	Pins 2---3
286BNA024	HK70EZ041	18	91
286BNA036	HK70EZ043	18	150
286BNA048	HK70EZ045	18	220
286BNA060	HK70EZ047	18	360
289BNA036	HK70EZ012	5.1	180
289BNA048	HK70EZ014	5.1	270
289BNA060	HK70EZ016	11	5.1
180BNA024	HK70EZ009	5.1	91
180BNA036	HK70EZ011	5.1	150
180BNA048	HK70EZ013	5.1	220
180BNA060	HK70EZ015	5.1	360
187BNA024	HK70EZ040	18	75
187BNA036	HK70EZ042	18	120
187BNA048	HK70EZ044	18	180
187BNA060	HK70EZ046	18	270

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