Vilter VSM 71-701 Operation And Service Manual Download

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Page 10

/ BULLETIN 10-11

tions are not necessary. If hunting is severe with floodback to
the compressor, check the possible remedies shown in
paragraphs below.

2. Valve size

— An over-sized valve usually aggravates hunting.

Carefully check the valve rating considering all the factors
affecting its capacity. See Bulletin 10-9, or Bulletin 10-10.

Remedy

— Replace valve with one correctly sized. On

multiple circuit evaporators using a refrigerant distributor, the
capacity of the valve can be reduced, within certain limits, by
installing a smaller distributor nozzle. See Bulletin 20-10.

3. Bulb location

— If the bulb is located in a suction line trap,

its temperature will be affected by liquid oil and refrigerant
alternately collecting and evaporating at this point. This
condition frequently results in severe hunting.

Remedy

— As a temporary measure relocate the bulb away

from the trap, and any turbulent areas created by elbows, tees,
etc. Also remove the bulb from the air stream or insulate. Re-
pipe if necessary. Sometimes another position around the
circumference of the suction line will minimize hunting. Follow
the Bulb Location and Installation instructions given on Page 2
for the best TEV control.

4. Refrigerant and load distribution

— In addition to the

effects of poor distribution explained in paragraphs

D-1

and

D-

, hunting also frequently results. This is caused by liquid

refrigerant from the overfed circuits occasionally reaching the
bulb of the valve.

Remedy

— Correct the faulty distribution.

5. Superheat adjustment

— All Sporlan TEVs are preset at

the factory to give the best performance on the average system.
A valve should not be adjusted unnecessarily, but occasionally
another setting may prove to be better.

Remedy

— Turn the adjusting stem clockwise a turn at a time.

If the hunting stops or is reduced, turn the adjusting stem
counter clockwise a turn at a time to obtain the lowest superheat
with stable operation.

6. Moisture

— As ice forms in a TEV from excessive moisture,

a very erratic hunt may result.

Remedy

— Remove the moisture with the installation of a

Sporlan Catch-All Filter-Drier. A safe moisture level can be
determined by installing a Sporlan See•All.

Complaint "F"

“System won't perform properly.”

SYMPTOM:

■

Cannot get valve to react or regulate at all.

THE CAUSE MAY BE:

1. No refrigerant being fed to evaporator

. See Section

on Pages 6 & 7.

2. Too much refrigerant being fed to evaporator

. See

Section

on Page 8.

3. Too much refrigerant being fed to evaporator at

start-up only

. See Section

on Page 8.

4. Refrigerant control is erratic

. See Section

on Page 9.

5. System is hunting or cycling

. See Section

on Page 9.

6. The TEV has been physically abused in an effort

to make the valve work properly.

This is usually the

result of a mistaken analysis. It is frequently assumed that if a
valve does not feed properly, it is stuck (either opened or
closed). Beating the valve body with a hammer will only distort
the body and make it impossible for the valve to work once the
real cause is determined.

If a valve “sticks,” it is usually due to moisture freezing in the
port, dirt and other foreign material restricting or plugging the
internal parts, wax forming on the internal parts at low temper-
atures, or the valve has been physically abused so it

cannot

function.

Remedy

— Inspect the valve and its internal parts, including

the inlet strainer. If plugged or restricted in any way, clean the
parts thoroughly, oil the parts with a good grade of refrigerant
oil, and reassemble the parts. Complete details on this subject
are found on Pages 10 through 12.

If the valve is beyond normal cleaning processes, or if it is
physically damaged in any way, replace the valve with its proper
replacement model.

Field Assembly
Instructions

Sporlan valves my be opened easily for inspection.

Thermostatic
Element

Pushrods

Inlet

Body

Outlet

Seat

Pin Carrier

Spring

Spring Guide