York DM120 Installation Manual download pdf (Page 65)

264973-YIM-A-0806

Unitary Products Group 65

The ICB monitors the Pressure and Rollout switches of gas

heat units.

The control circuit includes the following safety controls:

PRESSURE SWITCH (PS)

Once the draft motor has reached full speed and closes the

pressure switch during a normal ignition sequence, if the

pressure sw opens for 2 seconds, the GV will be de-ener-

gized, the ignition cycle is aborted, and the ICB flashes the

appropriate code. See Table 81 Ignition Control Flash Codes.

The draft motor is energized until the pressure switch closes

or “W1” is lost.

ROLLOUT SWITCH (ROS)

The rollout switch is wired in series with the pressure switch.

As such, the ICB cannot distinguish the rollout switch opera-

tion from that of the pressure switch.

Consequently, the control will only respond in the same man-

ner as outlined above under “Pressure Switch”. An open roll-

out will inhibit the gas valve from actuating.

INTERNAL MICROPROCESSOR FAILURE

If the ICB detects an internal failure, it will cease all outputs,

ignore inputs, and display the proper flash code for control

replacement. The ICB remains in this condition until replaced.

FLASH CODES

The UCB will initiate a flash code associated with errors

within the system. Refer to UNIT CONTROL BOARD FLASH

CODES Table 80.

RESETS

Remove the call for heating by lowering the thermostat set-

ting lower than the conditioned space temperature. This

resets any flash codes.

GAS 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 lowering of the temperature within the

conditioned space. Refer to Table 68 for the required gas

heat anticipator setting.

START-UP (COOLING)

PRESTART CHECK LIST

After installation has been completed:

1. Check the electrical supply voltage being supplied. Be

sure that it is the same as listed on the unit nameplate.

2. Set the room thermostat to the off position.

3. Turn unit electrical power on.

4. Set the room thermostat fan switch to on.

5. Check indoor blower rotation.

• If blower rotation is in the wrong direction. Refer to

Phasing Section in general information section.

• Check blower drive belt tension.

6. Check the unit supply air (CFM).

7. Measure evaporator fan motor's amp draw.

8. Set the room thermostat fan switch to off.

9. Turn unit electrical power off.

OPERATING INSTRUCTIONS

1. Turn unit electrical power on.

NOTE: Prior to each cooling season, the crankcase heaters

must be energized at least 10 hours before the sys-

tem is put into operation.

2. Set the room thermostat setting to lower than the room

temperature.

3. First stage compressors will energize after the built-in

time delay (five minutes).

4. The second stage of the thermostat will energize second

stage compressor if needed.

TABLE 68: GAS HEAT ANTICIPATOR SETPOINTS

SETTING, AMPS

W1 W2

0.65 0.1

FIGURE 28 : TYPICAL FLAME

H E A T E X C H A N G E R T U B E

G A S

S U P P L Y

P I P E

B U R N E R

B U R N E R B R A C K E T

I G N I T O R

B U R N E R F L A M E

( B L U E O N L Y )

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York DM120 Installation Manual Page 65

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