User manual

Maintenance
Liebert
®
DS
™
146
13.7 Air-Cooled Condenser and Drycoolers
• Clear coil surface of all debris that will inhibit airflow.
• Check for bent or damaged coil fins and correct.
• Do not permit snow to accumulate around or under outdoor unit.
• Periodically consider commercial cleaning of coil surface
• Inspect fans, motors and controls for proper operation.
• Check all piping and capillaries for proper support.
• Inspect for leaks.
13.8 Reheat—Electric Reheat (Three-Stage and SCR)
• Inspect and clean reheat elements.
• Inspect and tighten support hardware.
13.9 Thermostatic Expansion Valve
The Thermostatic Expansion Valve (TEV) performs one function: It keeps the evaporator supplied
with enough refrigerant to satisfy load conditions. It does not effect compressor operation.
Proper valve operation can be determined by measuring superheat. The correct superheat setting is
between 10 and 20°F (-12 and -6°C). If too little refrigerant is being fed to the evaporator, the
superheat will be high; if too much refrigerant is being supplied, the superheat will be low.
13.9.1 Determine Suction Superheat
To determine superheat:
1. Measure the temperature of the suction line at the point the TEV bulb is clamped.
2. Obtain the gauge pressure at the compressor suction valve.
3. Add the estimated pressure drop between the bulb’s location and the suction valve.
4. Convert the sum of the two pressures to the equivalent temperature.
5. Subtract this temperature from the actual suction line temperature. The difference is superheat.
13.9.2 Adjust Superheat Setting with the TEV
To adjust the superheat setting:
1. Remove the valve cap at the bottom of the valve.
2. Turn the adjusting stem counterclockwise to lower the superheat.
3. Turn the adjusting stem clockwise to increase the superheat.
NOTE
Make no more than one turn of the stem at a time. As long as thirty minutes may be required
for the new balance to take place.