470
Modern Refrigeration and Air Conditioning
As the handle is turned, the ball bearing presses
into the tubing and compresses it against the die on the
bottom of the tool. A permanently pinched line is pro-
duced. See Figure 19-24. Care must be taken to avoid
over tightening the pinch-off tool. The tool should be
left in place until the tubing end is sealed by brazing.
Effect of Altitude on Refrigerator Temperatures
A refrigeration system with a sensing bulb ther-
mostat calibrated for use at sea level may run too
cold at elevations above 5000′. This is a result of the
decreased atmospheric pressure at higher elevations.
Changes in altitude do not affect bimetal and elec-
tronic thermostats.
As altitude rises, atmospheric pressure drops.
Beyond certain elevations, the reduced atmospheric
pressure lowers the pressure on the control diaphragm
or bellows enough to affect the settings. The altitude
adjustment and range control pressure for the bellows
or diaphragm should be increased if the system will be
operating at a high elevation. This adjustment compen-
sates for the lower atmospheric pressure.
Figure 19-25 shows one thermostat with an alti-
tude adjustment and its altitude adjustment table. To
adjust for altitude, the cut-in and cut-out adjustment
screws are turned the appropriate number of degrees.
Ritchie Engineering – YELLOW JACKET Products Division
Figure 19-22. Two styles of pinch-off tools. A—This type
of pinch-off tool resembles and operates like locking pliers.
B—On this type of pinch-off tool, the wing nuts are loosened.
The tubing is inserted through the rectangular jaws in the
center of the tool. The wing nuts are then tightened to deform
and seal the tubing.
Tubing Ball bearing
Goodheart-Willcox Publisher
Figure 19-23. Ball bearing–type pinch-off tool.
A
B
Inner tubing
wall
Original tubing
shape
Goodheart-Willcox Publisher
Figure 19-24. Deformations created by pinch-off tools.
A—Pinch-off made by the tools shown in Figure 19-22.
B—Pinch-off by a ball bearing–type pinch-off tool.
00
55
50
45
35
30
For altitude correction, both “cut-in” and “cut-out”
screws must be adjusted
Adjustment
Altitude
in Feet
Cold
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
This scale may be used as a guide for measuring degrees of
rotation required for altitude correction. The arrows indicate
direction of screw rotation.
7/60
13/60
19/60
25/60
31/60
37/60
43/60
49/60
55/60
Counterclockwise
Turns
25
20
15
10
5
40
Amana Refrigeration, Inc.
Figure 19-25. Thermostat equipped with an altitude adjustment.
The table indicates the correct setting for various elevations.