Thomas & Betts UDAS, UDAP dimensions Ignition System cont’d, SW1 SW2 Time

Page 20

20.Ignition System (cont’d)

Normal Heat

Cycle Operating

Sequence (cont’d)

Abnormal Heat Cycle Functions

When the pressure switch is proven closed, the control begins the prepurge time. If flame is present any time while in prepurge, the prepurge time is restarted. If flame is present long enough to cause lockout, the control responds as defined in “Fault Modes, Undesired Flame”.

The control runs the venter motor for a 20 second prepurge time, then proceeds to the ignition trial period.

3)Ignition Trial Period - The control energizes the spark and main gas valve. The venter remains energized. If flame is sensed during the first 16 seconds, the spark is de-energized and the control proceeds to heat fan/blower on delay. If flame has not been sensed during the first 16 seconds, the control de-energizes the spark output and keeps the gas valve energized for an additional one second flame proving period. If flame is not present after the flame proving period, the control de-energizes the gas valve and proceeds with ignition re-tries as specified in “Ab- normal Heat Cycle, Ignition Re-try”. If flame is present, the control proceeds to the fan/blower on delay.

4)Fan/Blower On Delay - The control waits for 30 seconds from the time the gas valve opened and then energizes the fan/blower motor. The gas valve and venter motor remain energized. The control proceeds to steady heat mode.

5)Steady Heat - Control inputs are continuously monitored to ensure limit and pressure switches are closed, flame is established, and the thermostat call for heat remains. When the thermostat call for heat is removed, the control de-energizes the gas valve and begins post-purge and fan/blower off delay timing.

6)Post Purge - The venter motor output remains on for a 45 second post-purge period after the thermostat is satisfied.

7)Fan/Blower Off Delay - The fan/blower motor is de-energized after a blower off delay as selected by the dip switches. Timing begins when the thermostat is satisfied. Delay times are as follows:

SW1 SW2 Time

OFF

OFF

120 seconds (default when shipped)

OFF

ON

90 seconds

 

ON

OFF

160 seconds

 

ON

ON

180 seconds

 

Interrupted Thermostat Call for Heat - If the thermostat demand for heat is removed before the flame is recognized, the control will run the venter motor for the post purge period and de-energize all outputs.

If the thermostat demand for heat is removed after successful ignition, the control will de-energize the gas valve, run the venter motor through post purge, and run the fan/blower motor on heat speed for the selected delay off time.

Ignition Retry - If flame is not established on the first trial for ignition period, the control de-energizes the gas valve and the venter motor remains energized for an inter-purge period of 10 seconds. The spark and gas valve are then re-energized, and the control initiates another trial for ignition.

If flame is not established on the second trial for ignition, the control de-energizes the gas valve, energizes the fan/blower motor on heat speed, and venter motor remains energized. The fan/blower motor is shut off after the longest selectable fan delay time (180 seconds). When the fan/blower motor de-energizes, the spark and gas valve are re-energized and the control initiates another trial for ignition. (This fan delay is self-healing feature for an open auxiliary limit switch).

If flame is not established on the third trial for ignition period, the control de- energizes the gas valve, and the venter motor remains energized for an inter-purge period of 10 seconds. The control then re-energizes the gas valve and spark and initiates another trial for ignition.

Form RZ-NA I-UDA, P/N 195673 Rev 5, Page 20

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Contents Table of Contents Series Fan-Type Unit HeatersInstallation Codes GeneralHazard Levels of Warnings in this Manual Venting Manual by ModelWarranty Uncrating and Preparation Massachusetts RequirementDimensions SizeModel Udas Separated Combustion Fan Technical Data Size 100 125Instructions for Changing Pressure Switch Pressure SwitchHigh Altitude Operation ClearancesCombustion Air applies to Model Udap and Model Model Udap and Model UDAP-CVLocation Recommendations Unit Heater LocationHeater Throw Unit Heater Location cont’d Hanging the HeaterModel Udap Size 100 125 150 175 225 250 300 350 400 Model Udas Size 100 125 150 175 225 250 300 350 400Connectors are Recommended maximum hanger rod length is 6 feet 1.8MBe sure Threaded swivel Locked toGas Connection Size Gas Piping and PressuresSizing Gas Supply Line Instructions Manifold Pressure Settings by Altitude for Canada Gas Piping and Pressures cont’dInstructions for High Altitude Derate Two -Stage ValveHigh Altitude Capacity Changes Feet MetersBurner Electrical Supply and Connections Thermostat and ConnectionsCombustion Air Proving Switch Pressure Switch Limit Control Pressure Switch SettingsCombustion Air Proving Door Switch Model Udas only Ignition System Dip SwitchNormal Heat Cycle Operating Sequence StatusLED LightsIgnition System cont’d SW1 SW2 TimeContinuous Fan Operation Fault Modes Fault Modes cont’d Lockout Gas Valve Fan MotorWiring Diagrams Operating SequenceWiring Diagrams cont’d SW1 Operating Instructions Operating Sequence Check Installation and StartupCheck the installation prior to startup Heater Startup Check installation after startup Vent System Testing Procedure Model UdapUse only factory-authorized parts Maintenance ScheduleStartup cont’d Heat Exchanger Maintenance Burner Maintenance Burner Removal Instructions Refer to FigureBurner Maintenance cont’d Inspect and Clean the Burner Re-Install the BurnerInstructions to Re-Install the Burner Refer to Figure Burner OrificeDSI Ignition SystemCont’d Fan BladesCombustion Air Pressure Switch Door SwitchOperating Gas Valve Udas onlyFlame Rollout Switch Sizes 30-125 only SwitchAir System Troubleshooting DisconnectGeneral Troubleshooting Venter motorWill not start Burner willTroubleshooting cont’d Cont’d

UDAP, UDAS specifications

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