Home : Product Database : Warm Air Product Group : UDSBD Warm Air Centrif Blower Heaters : UDSBD Maintenance : UDSBD Servicing
UDSBD Servicing

UDSBD Servicing

The material contained in this Section of this manual is designed to aid a qualified service technician in maintaining and servicing this equipment. This heater will operate with a minimum of maintenance. To ensure long life and satisfactory performance, a heater that is operated under normal conditions should be inspected and cleaned at the start of each heating season (inspection and maintenance at least once a year). If the heater is operating in an area where an unusual amount of dust or other impurities are present in the air, more frequent maintenance is recommended. When any service is completed, be careful to reassemble correctly to ensure that no unsafe conditions are created.
When starting the heater, always follow the lighting instructions on the heater.

Warning : If you turn off the power supply, always turn off the gas.

Maintentance Schedule

NOTE: If replacement parts are required, use only factory-authorized parts.

Location of controls
Legend: 1) Burner 2) LC3 limit control (not shown) 3) Burner operating light (H6) 4) Reset switch (S3) 5) Spark igniter (ER) 6) Control panel assy located on a removable bracket (fig. 11b) 7) Gas valve (V1) 7a) Polarity check (S14) 8) Direct drive motor (M1) 9) Venter motor (model 008-020). illustrated. Venter motor is in the same location for all models, but appearance may differ (M3) 10) Time delay relay for blower (KFC) 11) Limit control LC1 12) Flame sensor (IS) 13) Reset LC3 (limit control) Sensor bulb is located in the air outlet of the heater. 14) Fuse (F3.1)

The following procedures should be carried out at least once each year (See figure below) :
• Clean all dirt, lint, and grease from the fan blade, fan guard, and motor.
• Check the heat exchanger both internally and externally for evidence of physical damage.
• Check the burner for scale, dust, or lint accumulation. Clean if required.
• Check the vent or vent/combustion air system for soundness. Replace any parts that do not appear sound.
• Check the wiring for any damage. Replace damaged wiring.

Control Panel assembly
Legend: 15) Control relay (ER) 16) Terminal blocks 17) Limit control LC3 18) Polarity check (S14) 19) Connector 20) Pressure switch (S3) 21) 2-stage burner relay (option) (K1..) 22) Electronic burner relay fuse (3.15F)

Heat exchanger Maintenance

This heater is equipped with a patented T-CORE2® heat exchanger. Remove any external dirt or dust accumulation. Visually check the heat exchange for cracks and holes. If a crack or hole is observed, replace the heat exchanger.

Burner Maintenance

his heater has a unique one-piece T-CORE2® burner assembly designed to provide controlled flame stability without lifting or flashback. The burner can be removed as a unit for inspection or service : see below for removal instructions. Inspect the burner/control compartment annually to determine if cleaning is necessary. If there is an accumulation of dirt, dust, and/or lint, clean the compartment and follow the instructions below to remove and clean the burner.

Caution : use of eye protection is recommended.

Instructions for burner removal

1. Outside the cabinet, shut the gas supply off at the manual valve ahead of the union
2. Turn off the electric supply.
3. Disconnect the gas supply at the union outside of the cabinet.
4. Open the access door.
5. Disconnect the manifold and move it out of the way. At the gas valve, mark and disconnect the connector. Carefully remove the burner orifice and orifice adapter locking nut. Slide the orifice adapter out through the bracket on the burner pushing the manifold to the right. This will move the manifold out of the way. Refer to the sketch below for component definitions.
6. Remove burner a) Locate the burner body front support. Remove the screws that attach it to the secondary air shield. Refer to the sketch below for component definitions. b) Holding the venturi tube, slide the entire burner slightly to the right to disengage the burner from the supports on the left. Then rotate the open end of the venturi tube outward away from the heater. Carefully pull the burner assembly out of the cabinet.




Burner removal steps

Inspect and clean the burner With the burner assembly removed, shine a flashlight on the burner ribbons. Look for carbon buildup, scale, dust, lint, and/or anything that might restrict flow through the spaces between the burner ribbons. Holding the burner assembly so that any foreign material will fall away from the burner, use a stiff bristle brush to loosen and remove any foreign material(s). If the burner is excessively dirty, remove one of the burner end caps. Remove the four screws that hold the end cap to the burner housing. Lightly tap the end cap to remove it. Clean all foreign material from the burner and venturi. After the burner is thoroughly clean, replace the end cap making certain that it is tight against the burner housing.

NOTE: If any of the burner components are damaged or deteriorated, replace the burner assembly.

Inspect the Internal Portion of the Heat Exchanger (with burner assembly removed)

At the burner flame entrance of each tube, shine a bright light into each heat exchanger section. With the light shining into the heat exchanger, observe the outside surface of the tube where discoloration is evident. Repeat this procedure with each heat exchanger tube. If any light is observed in these high temperature regions, replace the heat exchanger.

Reinstall the burner. Repeat ‘Burner removal’ steps above in the opposite order.

Burner orifice.

The burner orifice normally needs to be replaced only when a change in gas is made. When ordering a replacement orifice, provide (MJ/m3) heating value and specific gravity of gas, as well as the model and serial number of the unit. When removing or replacing the burner orifice be careful not to damage the venturi tube and/or the bracket.

Ignition system


Disconnect the wire; remove the screw and the ignitor.
Clean the ignitor assembly with an emery cloth.
Spark gap must be maintained to 3 mm. See sketches below.

Important: When reassembling, the wire must remain attached to the ignitor.

Igniter showing required spark gap measurement

Flame sensor

Caution : Due to high voltage on the spark wire and electrode, do not touch when energized.

Flame sensor -Locate the flame sensor. Disconnect the wire, remove the screw and the flame sensor. Clean with an emery cloth.

Control relay - See photo below.

The electronic burner relay monitors the operation of the heater including ignition. Do not open the control relay. Each heating season check the lead wires for insulation deterioration and good connections.
Proper operation of the direct spark ignition system requires a minimum flame signal of 1.0 microamps (DC) as measured by a microammeter.
For further information and check out procedure on the direct spark ignition system, refer to section 12 and the Troubleshooting Flow Chart.

Control relay

Blower motors

The blower motor is wquipped with thermal overload protection of the automatic reset type. Should the motor fail to run, it may be because of improper voltage characteristics. Make certain that the correct voltage is available at the motor.

Centrifugal fan

Remove dirt and grease from the motor and the blower wheel. Use care when cleaning the fan blades to prevent causing misalignment or imbalance. Follow these instructions for replacement of the fan guard, fan motor and/or fan blades.

1. If the heater is installed, turn off the gas and disconnect the electric power.
2. Open the connection box on the blower and disconnect the fan motor wires.
3. Remove the blower.
4. Reposition the new blower on the heater.
5. Reconnect the fan motor wires according to the wiring diagram and close the connection box on the blower.
6. Restore power to the heater and turn on the gas. Light, following the instructions on the lighting instruction plate. Check for proper operation.

Venter motor & wheel

Remove dirt and grease from the motor casing, the venter housing, and the venter wheel. Venter motor bearings are permanently lubricated.
Follow these instructions for replacement of the venter motor and wheel assembly. Keep all hardware removed to be used in reassembling and installing the replacement parts.

1. Turn off the gas and disconnect the electric power.
2. Open the control compartment access door.
3. Disconnect the three venter motor wires at the control relay and ground screw (located on the control panel).
4. Holding the motor, remove the screws that attach the motor plate to the venter housing. Remove the motor and wheel assembly from the heater.
5. Reassemble with the replacement venter motor and wheel assembly.
6. Follow the wiring diagram to properly connect the wires.
7. Restore power to the heater and turn on the gas. Light, following the instructions on the lighting instruction plate. Check for proper operation. Replace the access door.

For wiring details of replacement venter motors, please see related articles below.

Venter wheel position on shaft

UDSA models 008 - 020 (Rotation clockwise from motor shaft end)

UDSA models 025 - 030 (Rotation clockwise from motor shaft end)

UDSA models 035 - 100 (Rotation counter clockwise from motor shaft end)

Operating gas valve

The main operating quick opening gas valve is powered through the thermostat and safety controls. The main control valve is of the diaphragm type providing regulated gas flow and is preset at the factory. The gas valve requires no field maintenance except careful removal of external dirt accumulation and checking of wiring connections.

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 correct sealing.

Gas valve (UDSA models 008 - 030) (PN 03_25250)

Gas valve (UDSA models 035 - 100) (PN 03_25136)

Combustion air pressure switch

DANGER : Safe operation of this unit requires proper venting flow. Never bypass the combustion air pressure swtich or attempt to operate the unit without the venter operating.

The combustion air pressure switch ensures that proper combustion airflow is available. The switch senses the differential pressure between the negative pressure in the flue gas collector box and the pressure in the control section.
On startup when the heater is cold, the sensing pressure is at the most negative level, and as the heater and flue system warm up, the sensing pressure becomes less negative.
If a restriction or excessive flue pipe length causes the sensing pressure to be below the allowable level, the pressure switch will shut off the main burner.
If it is determined that the pressure switch needs replacing, use only the factory authorised replacement part that is designed for the model and size of the heater being serviced.

Pressure Switch (PN 03 24959)

If it is determined that the pressure switch needs replacing, use only the factory-authorized replacement part that is designed for the model and size of heater being serviced.

Limit controls.

If a limit control needs replacing, use only the factory authorized replacement part for the size of heater. Warning : Never bypass the limit controls, hazardous conditions could result. All units are equipped with temperature activated limit controls. The controls are factory set and non-adjustable. If either setpoint is reached, the corresponding limit control will interrupt the electric power to the gas valve. These safety devices provide protection in the case of motor failure or lack of airflow due to restrictions.

LC1 (PN 03 24969 01)

LC3 (PN 03 24959)

Fan control (KFC) (PN 03 25167)

Flue and Combustion air piping

Check the complete system at least once a year. Inspection should include all joints, seams, concentric adapters and the flue terminal cap. Replace any defective or heavily corroded parts.

Related Articles
Q10698 - INFO: Warm Air Replacement AACO Venter Motors

Article Attachments
No Attachments Available.

Related External Links
No Related Links Available.
Help us improve this article...
What did you think of this article?


Tell us why you rated the content this way. (optional)
Approved Comments...
No user comments available for this article.
Last Modified on 21/03/2006.
Print Article
Email Article