Where should the TEV External Equalizer be installed and where should the TEV bulb be located?
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The purpose of the external equalizer is to sense the pressure in the suction line AT THE BULB LOCATION and transmit it to the TEV diaphragm.
This usually means installing the external equalizer immediately down stream from the bulb. This ensures the correct pressure is signaled to the TEV. In some situations this “ideal” location may not be possible.
In these cases, an alternate location, such as at B or C (see diagram), could be used. However, the pressure at these locations must be nearly identical to the pressure in the line where the bulb is located.In other words, locations B and C are acceptable as long as these pressures are essentially the same as A when the system is operating at full load.In the past there has been concern about installing the external equalizer “up-stream” from the bulb. This was due to the possibility of refrigerant leaking past the TEV push rods, passing through the equalizer line and into the suction line, thus falsely influencing the TEV bulb temperature. Today, with Sporlan’s TEV design, this Possibility is virtually eliminated.
In general, the TEV bulb should be installed on a straight section of horizontal suction line. Locate the bulb on a straight, horizontal line, pitched slightly down, immediately after it leaves the evaporator.
A short trap should follow before the vertical line rises to be connected to the compressor suction. With the line pitched down, any liquid refrigerant and/or oil will pass into the trap, away from the bulb. As the trap fills with oil, the velocity of the refrigerant will carry the trapped oil into the vertical section and be returned to the compressor.