Auxiliary Limit Switch (Als); Pressure Switch (Ps); Rollout Switch (Ros); Internal Microprocessor Failure - York Predator MagnaDRY DR090 Series Installation Manual

264276-XIM-B-1208
equate supply air flow occurs, thus shutting down the heater
and energizing the blower.

AUXILIARY LIMIT SWITCH (ALS)

This control is located inside the supply air compartment and
is set to open at the temperature indicated in the Gas Heat
Limit Control Settings Table 30. It resets manually. The limit
switch operates when a high temperature condition, caused
by inadequate supply air flow occurs, thus shutting down the
heater and energizing the blower.
The auxiliary limit switch is wired in series with the limit
switch. As such, the UCB cannot distinguish the auxiliary limit
and the gas heat limit switch operation except the auxiliary is
manual reset. Consequently, the control will respond in the
same manner as outlined above under "Limit Switch".
TABLE 30: GAS HEAT LIMIT SETTINGS
# of HX Tubes
4
6
*.
Rollout = 300°F (148.9°C), Auxiliary Limit = 200°F
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 35 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 34.
44
*
Natural Gas LPG
Main Limit Setting
185°F (85°C) 200°F (93.3°C)
195°F (90.5°C) 195°F (90.5°C)
(93.3°C)

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 31 for the required gas
heat anticipator setting.
TABLE 31: GAS HEAT ANTICIPATOR SETPOINTS
SETTING, AMPS
W1
0.65
G A S
S U P P L Y
B U R N E R
P I P E
B U R N E R B R A C K E T
I G N I T O R
FIGURE 28 -TYPICAL FLAME

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.
W2
0.1
H E A T E X C H A N G E R T U B E
B U R N E R F L A M E
( B L U E O N L Y )
Johnson Controls Unitary Products