York ZF150 Installation Manual

Also see for Predator ZF078: Technical guide

518674-YIM-C-061054 Johnson Controls Unitary ProductsFlash CodesThe UCB will initiate a flash code associated with errors withinthe system. Refer to UNIT CONTROL BOARD FLASH CODESTable 29.ResetRemove the call for heating by lowering the thermostat settinglower than the conditioned space temperature.This resets anyflash codes.Electric Heat Anticipator SetpointsIt is important that the anticipator setpoint be correct. Too highof a setting will result in longer heat cycles and a greatertemperature swing in the conditioned space. Reducing thevalue below the correct setpoint will give shorter “ON” cyclesand may result in the lowering of the temperature within theconditioned space. Refer to Table 24 for the required electricheat anticipator setting.Gas Heating Sequence Of OperationsWhen the thermostat calls for the first stage of heating, the low-voltage control circuit from “R” to “W1” is completed. A call forheat passes through the UCB to the Ignition Control Board(ICB). The UCB monitors the “W1” call and acts upon any callfor heat by monitoring the Gas Valve (GV). Once voltage hasbeen sensed at the GV, the UCB will initiate the fan on delay forheating, energizing the indoor blower the specified delay haselapsed.When the thermostat has been satisfied, heating calls areceased. The GV is immediately closed. The blower is de-energized after the fan off delay for heating has elapsed. Thedraft motor performs a 30-second post purge.Ignition Control BoardFirst Stage Of HeatingWhen the ICB receives a call for first stage of heating, “W1,” thedraft motor is energized. Once the draft motor has been proven,a 30-second purge is initiated. At the end of the purge, the GVis opened, and the spark ignitor is energized for 10 seconds.The ICB then checks for the presence of flame. If flame isdetected, the ICB enters a flame stabilization period. If flamewas not detected, the GV closes, and a retry operation begins.During the flame stabilization period, a loss of the flame for 2seconds will cause the GV to close and the retry operation tobegin. After the flame stabilization period, a loss of flame for 3/4second will cause the GV to close and the retry operation tobegin.At the conclusion of the flame stabilization period, the ICB willoperate the gas heat in high fire for an additional 60 seconds(for a total for 120 seconds of high fire operation). After this 60seconds, the ICB will then use the call for the second stage ofheat to control second stage operation of the GV.When “W1” is satisfied, both valves are closed.Second Stage Of HeatingWhen the ICB receives a call for the second stage of heating,“W2,” the ICB conducts a complete first stage ignitionsequence. If this sequence is satisfied, the second main valveof the GV is opened.When “W2” is satisfied, the second main valve is closed.Retry OperationWhen a flame is lost or is not detected during an attempt toachieve ignition, a retry operation occurs. A 30-second purge isperformed between ignition attempts.If the unit fails after three ignition attempts, the furnace islocked-out for one hour. The furnace is monitored during thisone-hour period for unsafe conditions.Table 23: Electric Heat Limit Setting 42” CabinetUNIT (TONS) VOLTAGE HEATERkWLIMITSWITCHOPENS °FZF078, 090 (6.5, 7.5) 208/2309 13518 15024 16534 190ZF078, 090 (6.5, 7.5) 4809 13518 15024 16534 185ZF078, 090 (6.5, 7.5) 6009 13518 15024 15034 185Table 24: Electric Heat Anticipator SetpointsSETTING, AMPSW1 W20.13 0.1For units with VFD and gas heat, the speed of the indoorblower motor continues to be controlled by duct staticpressure via the VAV control board.If there are VAV boxes present in the duct system, theboxes must be driven to the full-open position using acustomer-supplied power source to assure adequateairflow across the heat exchanger tubes.