Vilter VSM 71-701 Operation And Service Manual Download

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BULLETIN 10-11 /

Page 3

recommended. In these cases the proper bulb location may be
determined by trial.

For satisfactory expansion valve control,

good thermal contact

between the bulb and suction line is essential. The bulb should be
securely fastened with two bulb straps, supplied with each expansion
valve, to a clean straight section of the suction line.

Recommended suction line piping usually includes a horizontal line
leaving the evaporator to which the TEV bulb is attached. This line is
pitched slightly downward, and when a vertical riser follows, a short
trap is placed immediately ahead of the vertical line, see Figure 3.
The trap will collect any liquid refrigerant or oil passing through the
suction line and prevent it from influencing the bulb temperature.

On multiple evaporator installations

the piping should be

arranged so that the flow from any valve cannot affect the bulb of
another. Approved piping practices including the proper use of traps

insures individual control for each valve without the influence of
refrigerant and oil flow from other evaporators.

For recommended suction line piping when the compressor is located
below the evaporator see Figure 5. The vertical riser extending to the
height of the evaporator prevents refrigerant from draining by gravity
into the compressor during the off-cycle. When a pumpdown control
is used the suction line may turn immediately down without a trap.

On commercial and low temperature applications

requiring

Sporlan Selective Charges C, Z, or X the bulb should be clamped on
the suction line at a point where the bulb temperature will be the same
as the evaporator temperature during the off-cycle. This will insure
tight closing of the valve when the compressor stops. If bulb insula-
tion is used on lines operating below 32°F, use non-water absorbing
insulation to prevent water from freezing around the bulb.

On brine tanks and water coolers, the bulb should be below the liquid
surface where it will be at the same temperature as the evaporator
during the off-cycle. When locating the bulb in a brine tank, paint it
and the capillary tubing with pitch or other corrosion resistant paint.

If, for practical reasons, the bulb must be located where its tempera-
ture will be higher than the evaporator during the off-cycle, a
solenoid valve must be used ahead of the TEV.

On air conditioning applications

having TEVs equipped with

VCP100 or VGA elements, the bulb may be located inside or outside
the cooled space or duct. The valve body should not be located in the
air stream leaving the evaporator. Avoid locating the bulb in the
return air stream unless it is well insulated.

External Equalizer Connection

For a complete explanation of when an externally equalized valve
should be used, refer to "equalization method," Bulletin 10-9. Valves
supplied with an external equalizer

will not operate

unless this

connection is made.

The equalizer connection should be made at a point that will most
accurately reflect the pressure existing in the suction line at the bulb
location. See Figure 6. Generally, the connection is immediately
downstream of the bulb. However, equipment manufacturers
sometimes locate them in return bends or suction headers that are

Compressor
ABOVE
Evaporator

Short as possible to minimize amount of oil.

Liquid and oil drains

away from bulb...

Figure 3

Multiple Evaporators

Above and Below Main Suction Line

Flow from upper valve cannot
affect bulb. . . . line free draining.

Inverted trap to
avoid oil draining
into idle evaporator.

Free draining.

Figure 4

Compressor BELOW