Thermoswitch Adjustment; Low-Refrigerant Level Operation; Internal Service; Service Valve Diaphragm Replacement - Carrier 16JT Series Start Up & Operation Manual

Thermoswitch Adjustment —
switch while machine is operating.
1. A thermowell is located on the absorber spray supply pipe
near the thermoswitch sensing bulb well. Place heat con-
ductive compound or oil in the thermowell and insert a
thermometer with a range of about 0° to 300 F or about
0° 150 C).
2. Turn the thermoswitch adjustment knob fully counter-
clockwise and then slowly clockwise until the contacts
close. Note the difference (if any) between the actual ther-
mometer reading and the reading on the thermoswitch ad-
justment scale as the contacts close. Allow for this dif-
ference in setting the thermoswitch control point. (Example:
As switch contacts close, thermometer reads 110 F
(43.3 C) and thermoswitch scale reads 107 F (41.7 C), an
error of 3° F (1.6° C). To have contacts close at a selected
temperature of 118 F (47.8 C), knob must be set at scale
reading of 115 F (46.1 C).
Allowing for any temperature difference as described above,
set adjustment knob as required to make contacts close at
118 F (48 C) thermowell temperature.
NOTE: Special operating conditions may require other
thermoswitch settings. Check job data. Use same adjust-
ment procedure.
Low-Refrigerant Level Operation —
load operation, with low condensing water temperature, the
normal dilution of the solution will lower the refrigerant level
in the evaporator. If the level goes down enough to open the
low refrigerant level switch 33RL, the refrigerant pump stops
to prevent cavitation in the refrigerant pump and subsequent
pump motor failure.
To check the operation of the low-level switch, first place
the capacity control in MANUAL and
closes the steam valve) and the Cycle-Guard switch in
MANUAL. This will transfer refrigerant to the solution cir-
cuit, lowering the refrigerant level in the evaporator. When
the refrigerant level reaches the low-level switch, the refrig-
erant pump stops. Then return both the Cycle-Guard switch
and the capacity control to AUTO. positions. If the pump
becomes noisy, it might be in cavitation from a low level
switch malfunction. Do NOT allow the pump to remain in
operation with this condition.
Internal Service —
To prevent corrosion from air in-
side the machine, break vacuum with nitrogen when open-
ing the machine for maintenance or repair.
While the machine is open, it is good practice to mini-
mize the amount of air entering by continuously feeding ni-
trogen into the machine at approximately 1 psig (7 kPa) pressure.
Perform service work promptly and efficiently and close
the machine as soon as possible. Do not rely on the inhibitor
for corrosion protection unless all lithium bromide and re-
frigerant have been removed and the machine has been com-
pletely flooded with a lithium chromate inhibitor-water
solution prior to machine opening.
Leak test the machine thoroughly after the machine has
been closed up.
Check the 26SH thermo-
During low-
position (which
36
When flamecutting or welding on an absorption ma-
chine, some noxious fumes may be produced. Ventilate
the area thoroughly to avoid breathing concentrated fumes.
Never cut into the purge chamber unless the purge
has been exhausted to remove any hydrogen gas that
might be present in the chamber. Hydrogen can form an
explosive mixture in the air.
Service Valve Diaphragm Replacement —
place valve diaphragms:
1. Break machine vacuum with nitrogen. Solution and re-
frigerant can be transferred to opposite sumps within the
machine or removed from the machine. If removed from
the machine, store it in clean containers for recharging.
2. Remove old valve diaphragms and replace. Torque valve
bolts to approximately 3 lb-ft.
3. Test all affected connections for leakage (see Machine Leak
Test section, page 33).
4. Reevacuate machine after servicing (see Machine Evacu-
ation section, page 33).
5. Replace solution and refrigerant in machine (the same quan-
tity that was removed).
Hermetic Pump Inspection —
tional structural schematic of a typical refrigerant or solu-
tion pump used on the 16JT chiller. These centrifugal pumps
are hermetic and do not require seals. The rotor assembly is
enclosed in a thin stainless steel can, and some of the pump
discharge liquid (refrigerant or solution) is circulated around
the rotor assembly for cooling the motor and for lubricating
the bearings. The following instructions are general proce-
dures for a typical pump version. Details will vary slightly
for different pump models.
Never run hermetic pump motor dry. Even momentary
operation without machine filled with liquid will dam-
age bearings and overheat the motor. Use only the cur-
rent value specified in the control circuit diagram when
setting the pump starter overloads.

DISASSEMBLY

Disconnect all primary power to the pumps; lock and
tag all disconnect switches.
1. Break vacuum with nitrogen if not already performed.
2. Remove solution and refrigerant from the machine. Store
in clean containers until recharging.
To re-
Figure 31 is a sec-