The thermoelectrically cooled condensation trap, better known as "Peltier Drier" is an optional accessory device for the Model 500 combustion-emissions analyzer. Its purpose is to replace the standard condensation trap of the Model 500 for those critical applications that demand higher accuracy for the measurement of nitrogen dioxide (NO₂) and sulfur dioxide (SO₂).

NO₂ and SO₂ are gases that are highly soluble in water. The exhaust sample contains typically between 5% and 20% of water vapor, most of which will condense in the probe and sample line.

To prevent significant loss of NO₂ and SO₂ during transport of the sample from the probe to the analyzer, the following conditions must be satisfied:

• Rapid sample transport. This is accomplished by maintaining a high flow rate using a relatively small diameter sampling line.
• Use of a sample line made from a highly hydrophobic material. A Teflon sample line limited to 15 ft. long is used.
• Minimum contact of the gas sample with the water collection mechanism and also no additional condensation occurring following the Peltier drier. This is accomplished by using a specially designed Peltier cooled manifold to separate the gas from the water.

The Peltier drier requires electrical power for operation. This is available from the analyzer through the drier's electrical connector. When operating the Peltier drier, the analyzer's battery life is limited to 2 hours, approximately. It is therefore recommended, but not necessary, to use the battery charger for longer operation.

The Peltier drier will maintain the sample at a certain temperature below ambient temperature to ensure no further condensation inside the analyzer. You can control this temperature differential by adjusting the "COOLER DUTY CYCLE", if necessary. The following table shows the approximate relation between duty cycle and temperature differential:

*At 75 degrees F. ambient.

Battery life for the analyzer with the Drier in operation is approximately 2.5 hours for 50% duty cycle to 1.5 hours for 100% duty cycle, assuming freshly charged batteries or new alkaline batteries. This temperature differential between sample temperature and ambient temperature is set at the factory to 75%, but can be adjusted as follows:

1. Press the SHIFT key. SETUP MENU will be displayed.
2. Press the ENTER key. To select SYSTEM SETUP.
3. Press the UP/DOWN keys until the cursor points to COOLER DUTY.
4. Press the ENTER key
5. Use the UP/DOWN keys to set the Peltier duty cycle. A minimum of 50% is recommended.
6. Press the ENTER key.

The condensation trap will fill with water after 2 to 4 hours depending on the fuel used. To empty the condensation trap simply unscrew it from the manifold. When replacing it, be careful to seat the O-ring properly.

The outline drawing shown below illustrates the drier's operation.