Mueller E-Star OESE 3.5 and 5 HP HFC Condensing Unit
Installation and Operation Manual, Part No. 8828747
Effective April 13, 2020
5.2 CHECKING AND ADJUSTING SUPERHEAT
Take the following readings with the cooler’s evaporator completely covered with milk or water, or with the chilled
water solution circulating through the chiller, at a temperature below 45°F.
1. Take an accurate suction pressure at the evaporator outlet.
IMPORTANT: The suction pressure must be taken at the evaporator outlet, rather than the suction
service valve, due to the unknown pressure drop in the refrigerant line between the evaporator and
compressor. The technician should also make certain the system is properly charged with refrigerant as
described in Section 3.
2. Using an accurate electronic thermometer, take the actual suction line temperature near the TEV sensing bulb.
3. Utilizing the pressure temperature chart, convert the suction pressure reading from step 1 to the saturation
temperature (dew point).
4. The superheat value is calculated by subtracting the saturation temperature (dew point) determined in step 3
from the actual suction line temperature taken in step 2.
5. If the superheat is not in the proper range, 4–6°F (2.2–3.3°C) for milk coolers and 10–12°F (5.6–6.7°C) for
chillers, at conditions as described above, adjust the TEV.
6. If the superheat is below the proper range, turn the TEV’s adjustment stem clockwise
1
⁄
8
to
1
⁄
4
of a turn. Allow
the system to operate for five minutes before repeating the test.
7. If superheat is above the proper range, turn the TEV’s adjustment stem counterclockwise
1
⁄
8
to
1
⁄
4
of a turn.
Allow the system to operate for five minutes before repeating the test.
8. Any time adjustment is made to the TEV, the refrigerant charge should be checked as described in Section 3.0.
9. Check the superheat setting and make final adjustments at a product temperature near setpoint for best
performance.
FIGURE 4: CHECKING AND ADJUSTING SUPERHEAT
11
40°F
60 PSIG
Example (R-507):
• 60 psig converted to saturation temperature on
refrigerant pressure temperature table equals 34°F.
• Actual suction line temperature equals 40°F.
Results:
• 40°F – 34°F = 6°F (4.4°C – 1.1°C = 3.3°C)
superheat at evaporator.
