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5020803-UIM-M-0120
Electric Heat Limit Switch Operation
6HK single phase heat kits utilize a normally closed line voltage limit
switch and a normally closed fusible link. If the fusible link opens, it
must be replaced with the appropriate OEM part and the cause must be
investigated and corrected.
Table 20: Thermostat Signals
Signal
State
Board Function
ON
Indoor blower instant on
G
OFF
Indoor blower off after 60 s delay
Indoor blower instant on
ON
Electric heat stages on (if so equipped)
W
Electric heat stages off (if so equipped)
OFF
Indoor blower off after 60 s delay
Indoor blower instant on in heating speed
ON
Electric heat stages on (if so equipped)
G and W
Electric heat stages off (if so equipped)
W OFF
Indoor blower switches to continuous fan speed
Outdoor fan instant on
Indoor blower instant on in cooling speed
ON
Compressor on (after any anti-short cycle delay)
G and Y
System operates in heat pump heating mode
Compressor instant off
Y OFF
Outdoor fan instant off
Indoor blower switches to continuous fan speed
Outdoor fan instant on
Indoor blower instant on in cooling speed
ON
Compressor on (after any anti-short cycle delay)
Reversing valve energized
G, Y, and
System operates in cooling mode
O
Compressor instant off
Outdoor fan instant off
Y and O
OFF
Reversing valve de-energized
Indoor blower switches to continuous fan speed
* Motor program has 60 s blower off delay on all 5 speed taps.
FIGURE 10: Measuring External Static Pressure
18
STARTUP
1. Check the electrical supply voltage being supplied. Be sure that it is
within the specified range on the unit data plate.
2. Make sure all electrical connections are tight.
3. If unit is connected to 208 V supply power, the control transformer
must be wired accordingly.
4. Turn unit electrical power on.
5. Set the room thermostat to COOL mode and lower the desired tem-
perature setting lower than the room temperature to create a call for
cooling.
6. Measure the total system duct static and set the blower motor cool-
ing speed appropriately per airflow performance tables.
7. If an optional electric heat kit was installed make sure the minimum
blower speed required per Table 14 is set.
8. Make sure all units panels are in place and secured, and that an air
filter is installed.
EXTERNAL STATIC PRESSURE SETUP
To measure external static pressure:
1. Measure the supply air static pressure and record this positive num-
ber.
2. Measure the return air static pressure and record this negative
number.
3. Treat the negative number as a positive and add the two numbers
together. This is total system static.
Johnson Controls Ducted Systems
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