York YPAL 051 User Manual

JOHNSON CONTROLS

FORM 100.50-NOM6 (1207)

The Unit Controller monitors the operation of the 
Staged and Modulating Gas Heat sections and displays 
the status through the STATUS screen of the User 
Interface.  The operation of each of the gas heat sections 
is monitored by a multiplexer installed in the gas heat 
section.  When a gas heat section is energized, it sends a 
24-volt signal to the multiplexer.  The multiplexer takes 
the fi ve “ON”/”OFF” inputs and converts them into a 
0 to 5 volt DC signal that is sent to the Unit Controller.  
The Unit Controller then decodes this analog input and 
displays the furnace section status.  Tables 8-9 and 8-10 
show the relationship between the DC voltage and the 
furnace operation status.

80

0.20

1120

2.80

160

0.40

1200

3.00

240

0.60

1280

3.20

320

0.80

1360

3.40

400

1.00

1440

3.60

480

1.20

1520

3.80

560

1.40

1600

4.00

640

1.60

1680

4.20

720

1.80

1760

4.40

800

2.00

1840

4.60

880

2.20

1920

4.80

960

2.40

2000

5.00

1040

2.60

Two CO

2

 sensors are used in conjunction with the 

“DEMAND VENTILATION” option.  In “DEMAND 
VENTILATION” the Unit Control monitors the CO

2

 level 

of the outdoor air and the CO

2

 level in the conditioned 

space and varies the amount of ventilation air based on 
the relationship between these two values.  Table 8-7 
gives the volts DC output for a given CO

2

 level.