172988-YUM-A-0106

1.The inducer is energized and ramps up its speed until airflow is proven by the pressure switch and by the pressure sensor on the control board.

2.The hot surface ignitor is energized.

3.After a 17-20 second igniter heatup, the gas valve opens and the burners light.

4.When the control senses that flame is present, the circulating blower starts at low speed.

5.The furnace fires at 70% of full rate for 30-45 seconds, then drops to the minimum (35%) firing rate.

6.The firing rate is automatically adjusted to meet demand, increas- ing gradually to maximum (100%) firing rate if the thermostat is not satisfied within a defined time.

7.When the thermostat R and W contacts open (thermostat is satis- fied) the furnace control recalculates the demand and a new firing rate.

a.If demand exceeds the minimum firing rate, the burners will continue to fire at a recalculated reduced firing rate, decreas- ing if the thermostat remains off for a defined time.

b.If demand does not exceed the minimum firing rate, the burn- ers will shut off immediately.

8.After the burners shut off, the circulating blower will continue to run until the temperature sensor detects that the supply air tempera- ture has dropped to the desired level, which should take from 30 to 90 seconds.

ADJUSTMENT OF FAN CONTROL SETTINGS

Cooling - The airflow delivered by the furnace during cooling operation can be adjusted to match the cooling capacity of the A/C condensing unit. This is done by moving the COOL and ADJ jumper on the control board to give the desired airflow.

The COOL jumper has four positions, which will deliver sufficient airflow in cooling mode for the cooling capacities shown in the Table 2.

TABLE 2: Cooling Airflow - A/C Capacity in Tons

Models

 

Cool Jumper Position

 

 

 

 

 

 

 

 

D

 

C

B

 

A

60/1200

1-1/2

 

2

2-1/2

 

3

80/1200

1-1/2

 

2

2-1/2

 

3

80/1600

2-1/2

 

3

3-1/2

 

4

100/1600

2-1/2

 

3

3-1/2

 

4

100/2000

3

 

3-1/2

4

 

5

120/2000

3

 

3-1/2

4

 

5

Continuous Fan Operation - The airflow delivered by the furnace dur- ing continuous fan operation can be adjusted as desired. This is done my moving the RECIRC jumper on the control board to give the desired airflow.

The jumper has three positions. The "A" position delivers maximum air- flow, 100% of the blower capacity. Position "B" delivers approximately 70% of the blower capacity. And Position "C" delivers minimum airflow, approximately 35% of the blower capacity.

CFM

INDICATORHUMIDIFIER TERMINALS

CFM

DIAGNOSTIC

 

 

 

 

LIGHT

 

 

 

EAC

 

 

 

 

 

DELAY COOL ADJUST

 

 

 

 

 

 

TERMINALS

 

 

 

 

R

 

 

LOW VOLTAGE

 

W

 

ADJUST

 

Y/Y2

TERMINALS

 

Y1

 

JUMPER

 

HUM

ERROR

 

G HUMIDISTAT

 

 

C

CONNECTED

 

BUTTON

 

 

YES NO

 

 

 

AIR RECIRC

 

TEST

ERROR

 

 

BUTTON

 

 

TEST

 

 

 

 

 

 

 

 

 

 

 

 

 

CONTINUOUS FAN

 

DELAY

COOLING

SPEED JUMPER

 

 

JUMPER

SPEED JUMPER

FIGURE 8: Furnace Control Board

Delay Taps Selection

The set of jumper pins on the control board labeled "DELAY" are used to set the delay profiles for the furnace. These can be chosen so as to maximize the comfort and sound levels for various regions of the coun- try.

Tap A is the default profile. It provides a 30-second ramp-up from zero airflow to full capacity and a 30-second ramp-down from full capacity back to zero airflow. Whenever there is a change in airflow mode, such as from low heat to high heat, the motor will take 30 seconds to ramp from one speed to the other.

Tap B is the humid profile. This profile is best-suited for installations where the humidity is frequently very high during cooling season, such as in the southern part of the country. On a call for cooling, the blower will ramp up to 50% of full capacity and will stay there for two minutes, then will ramp up to 82% of full capacity and will stay there for five min- utes, and then will ramp up to full capacity, where it will stay until the wall thermostat is satisfied. In every case, it will take the motor 30 sec- onds to ramp from one speed to another.

Tap C is the dry profile. This profile is best suited to parts of the country where excessive humidity is not generally a problem, where the sum- mer months are usually dry. On a call for cooling the motor will ramp up to full capacity and will stay there until the thermostat is satisfied. At the end of the cooling cycle, the blower will ramp down to 50% of full capac- ity where it will stay for 60 seconds. Then it will ramp down to zero. In every case, it will take the motor 30 seconds to ramp from one speed to another.

Tap D is the normal profile, best suited for most of the country, where neither excessive humidity nor extremely dry conditions are the norm. On a call for cooling, the motor will ramp up to 63% of full capacity and will stay there for 90 seconds, then will ramp up to full capacity. At the end of the cooling cycle, the motor will ramp down to 63% of full capac- ity and will stay there for 30 seconds, then will ramp down to zero. In every case, it will take the motor 30 seconds to ramp from one speed to another.

Humidistat

When a humidistat is installed in the system, the “Humidistat con- nected?” jumper on the control board should be moved to the “YES” position. The cooling airflow will then be reduced by 15% whenever the humidistat indicates high humidity.

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Unitary Products Group

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York PC9 service manual Adjustment of FAN Control Settings, Delay Taps Selection, Humidistat, Models Cool Jumper Position

PC9 specifications

The York PC9 is an advanced air conditioning system that has gained recognition for its efficiency and versatility in various applications. Specifically designed for both residential and commercial settings, it showcases a blend of innovative technologies, exceptional performance, and user-friendly features.

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