Thomas & Betts UDAP Operating Gas Valve, Combustion Air Pressure Switch, Limit Control, UDAS only

FIGURE 22 - Venter Wheel Position on Shaft

5.Holding the venter motor, remove the three or four screws that attach the venter motor mounting plate to the venter housing. Remove the motor and wheel as- sembly from the heater.

6.Re-assemble with the replacement venter motor and wheel assembly. See FIG- URE 22.

7.Follow the wiring diagram to connect the venter wires.

8.Sizes 30 and 45 - Reconnect the gas supply at the union outside of the cabinet. Leak test the connection with leak detecting solution.

9.Replace the access panel. Restore power to the heater and turn on the gas. Light, following the instructions on the lighting instruction plate. Check for proper operation.

Venter Wheel,	Venter Motor Plate
Sizes 30-75	Fan

Motor Mounting

Bracket

Motor Sizes 30-75

Venter Wheel, Sizes 100-175*

Venter Motor Plate

Fan

Motor Mounting Bracket

Motor Sizes 100-400

*Venter wheel has different appearance on Sizes 200-400. Motor spacing is the same.

5/16” (8mm) inside

5/16” (8mm) inside

32.Operating Gas Valve

The gas valve requires no field maintenance except careful removal of external dirt accumulation and checking of wiring connections. Instructions for testing pressure settings re in Paragraph 12.

WARNING: The operating valve is the prime safety shutoff. All gas supply lines must be free of dirt or scale before connecting to the unit to ensure positive closure. See Hazard Levels, page 2.

Single	Optional
Stage	Two
Gas	Stage
Valve	Gas
	Valve

33.Combustion Air Pressure Switch

See FIGURE 18, page 31, for location. If it is determined that the pressure switch needs replacing, use only the factory-autho- rized replacement part that is designed for the model and size of heater being serviced.

NOTE: A unit operating above 6000 ft elevation requires a high altitude pressure switch. See Paragraph 7.

34. Limit Control

If it is determined that the limit control needs replacing, use only a factory-authorized replacement part that is designed for the size of heater.

For approximate limit location, see FIGURE 18, page 31.

35. Door Switch	If it is determined that the door switch needs replacing, use only
	a factory-authorized replacement part that is designed for the
- UDAS only	heater.
	For approximate switch location, see FIGURE 18, page 31.
36. Transformer	See FIGURE 18, page 31, for location. Use a voltmeter to verify
	that there are 24 volts output from the transformer. If the trans-
	former is not functioning, it must be replaced. Use a replacement
	transformer identical to the factory-installed model.

Form RZ-NA I-UDA, Mfg #195673 Rev 5, Page 33