Johnson Controls BQ 036, BQ 060 Electric Heat Limit Control Setting, Heat Anticipator Setpoints

364985-XIM-B-0508

DEFROST MODE

As mentioned earlier, the defrost control (DC) utilizes a time/temperature defrost scheme. The following two conditions must be met before the DC will enter a defrost mode:

The defrost thermostat (SD) must be closed. This nor- mally open thermostat is mounted on the liquid line and is set to close at 28 ± 4°F.

Once the defrost thermostat closes, the defrost control starts a run timer that must be satisfied before defrost can begin. This is accumulated compressor run time. The selection pin is factory set at 60 minutes, but is field adjustable to 30, 60 or 90 minutes.

When the DC enters the defrost mode, it’s on-board defrost relay is powered. This energizes the reversing valve, de-energizes the condenser fan motor and ener- gizes the unit’s optional electric heater. The DC remains in defrost mode until either of the following two conditions is met:

1.The liquid line thermostat is open. It is set to open at 55 ± 4°F.

2.The maximum defrost run time of 10 minutes is met.

FORCED DEFROST

The processor on the defrost board is only energized when the defrost sensor (DS) is closed.

To create a forced defrost:

1.The DS must either be closed or a jumper must be placed across the DFS terminals on the board.

2.Place a jumper across the test pin terminals on the board.

Depending on the selected defrost minimum run time of 30, 60 or 90 minutes, the board will go into defrost in 7.5, 15 or 22.5 seconds.

The DC will remain in defrost until the jumpers across the DS and the test pin terminals are removed.

Once the jumpers are removed, the board then ter- minates defrost when the DS opens or a maximum of 10 minutes after the test pin jumper is removed, whichever comes first.

SAFETY CONTROLS

The control circuit includes the following safety con- trols:

1.Temperature Limit Switch (TLS) - This control is located inside the heater compartment and is set to open at the temperature indicated in the Electric Heat Limit Control Setting Table 30. It resets auto- matically. The limit switch operates when a high temperature condition, caused by inadequate sup- ply air flow occurs, thus shutting down the heater and energizing the blower.

TABLE 30: ELECTRIC HEAT LIMIT CONTROL SETTING

VOLTAGE	kW	TEMPERATURE LIMIT SWITCH	Open Temp ºF
	5	1	140
	7	1,3	140
	10	1,2,3	140
230-1-60	15	2,4,6	140
	20	1,2,3,4,5	140
		6	150
	30	1,2,3,4,5,6	150
	5	1,2,3	140
	7	1,2,3	140
	10	1,2,3	150
230-3-60	15	2,4,6	140
	20	1,2,3,4,5,6	150
	30	1,3,5	160
		2,4,6	150
	7	2,4,6	140
	10	2,4,6	140
460-3-60	15	2,4,6	140
	20	3	160
	30	3	150
	10	2,4,6	140
575-3-60	15	2,4,6	140
	20	5	160
	30	5	150

HEAT ANTICIPATOR SETPOINTS

It is important that the anticipator setpoint be correct. Too high of a setting will result in longer heat cycles and a greater temperature swing in the conditioned space. Reducing the value below the correct setpoint will give shorter “ON” cycles and may result in the low- ering of the temperature within the conditioned space.

34 Johnson Controls Unitary Products