SERVICING
48
S-61A CHECKING HEATER LIMIT CONTROL(S)
Each individual heater element is protected with a limit control
device connected in series with each element to prevent overheat-
ing of components in case of low airflow. This limit control will
open its circuit at approximately 150°F.
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.
1. Remove the wiring from the control terminals.
2. Using an ohmmeter, test for continuity across the normally
closed contacts. No reading indicates the control is open -
replace if necessary.
IF FOUND OPEN - REPLACE - DO NOT WIRE AROUND.
S-61B CHECKING HEATER FUSE LINK
(OPTIONAL ELECTRIC HEATERS)
Each individual heater element is protected with a one time fuse
link which is connected in series with the element. The fuse link
will open at approximately 333°.
WARNING
Disconnect ALL power before servicing.
1. Remove heater element assembly so as to expose fuse link.
2. Using an ohmmeter, test across the fuse link for continuity - no
reading indicates the link is open. Replace as necessary.
NOTE:
The link is designed to open at approximately 333°F. DO
NOT WIRE AROUND - determine reason for failure.
S-100
REFRIGERATION REPAIR PRACTICE
DANGER
Always remove the refrigerant charge in a proper
manner before applying heat to the system.
When repairing the refrigeration system:
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.
1. Never open a system that is under vacuum. Air and moisture
will be drawn in.
2. Plug or cap all openings.
3. Remove all burrs and clean the brazing surfaces of the tubing
with sand cloth or paper. Brazing materials do not flow well
on oxidized or oily surfaces.
4. Clean the inside of all new tubing to remove oils and pipe
chips.
5. When brazing, sweep the tubing with dry nitrogen to prevent
the formation of oxides on the inside surfaces.
6. Complete any repair by replacing the liquid line drier in the
system, evacuate and charge.
BRAZING MATERIALS
I
MPORTANT NOTE:
Torch heat required to braze tubes of various
sizes is proportional to the size of the tube. Tubes of smaller size
require less heat to bring the tube to brazing temperature before
adding brazing alloy. Applying too much heat to any tube can melt
the tube. Service personnel must use the appropriate heat level
for the size of the tube being brazed.
NOTE:
The use of a heat shield when brazing is recommended to
avoid burning the serial plate or the finish on the unit. Heat trap
or wet rags should be used to protect heat sensitive components
such as service valves and TXV valves.
Copper to Copper Joints
- Sil-Fos used without flux (alloy of 15%
silver, 80% copper, and 5% phosphorous). Recommended heat
1400°F.
Copper to Steel Joints
- Silver Solder used without a flux (alloy of
30% silver, 38% copper, 32% zinc). Recommended heat - 1200°F.
S-101
LEAK TESTING (NITROGEN OR NITROGEN-
TRACED)
To avoid the risk of fire or explosion, never use
oxygen, high pressure air or flammable gases for leak
testing of a refrigeration system.
WARNING
To avoid possible explosion, the line from the
nitrogen cylinder must include a pressure regulator
and a pressure relief valve. The pressure relief valve
must be set to open at no more than 150 psig.
WARNING
Pressure test the system using dry nitrogen and soapy water to
locate leaks. If you wish to use a leak detector, charge the system
to 10 psi using the appropriate refrigerant then use nitrogen to
finish charging the system to working pressure, then apply the
detector to suspect areas. If leaks are found, repair them. After
repair, repeat the pressure test. If no leaks exist, proceed to sys-
tem evacuation.
