Johnson Controls SUNLINE 2000 BQ 060 - Manual (Page 34)

364985-XIM-B-0508
34 Johnson Controls Unitary Products
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.
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.
TABLE 30: ELECTRIC HEAT LIMIT CONTROL
SETTING
VOLTAGE kW TEMPERATURE LIMIT SWITCH Open Temp º F
5 1 140
7 1,3 140
10 1,2,3 140
15 2,4,6 140
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
15 2,4,6 140
20 1,2,3,4,5,6 150
1,3,5 160
2,4,6 150
7 2,4,6 140
10 2,4,6 140
15 2,4,6 140
20 3 160
30 3 150
10 2,4,6 140
15 2,4,6 140
20 5 160
30 5 150
20
30
230-3-60
460-3-60
575-3-60
230-1-60