Carrier 19DA - Manual (Page 11)

Calibrating Pneumatic Transducer - Pneumatic
control is accomplished by a transformer which
converts a 3-15 psi pneumatic signal regulated
by a thermostat sensing chilled water temper­
ature into an electrical signal. The electrical
signal is transmitted to either a Barber-Colman
or Honeywell Electronic Chilled Water Module
to provide chilled water temperature control. The
same transducer is used for both Barber-Colman
(Fig. 5) and Honeywell (Fig. 4).
MOTOR OVERLOAD MODULE - Calibrate as
outlined under the motor overload sections under
Barber-Colman or Honeywell.
CHILLED WATER MODULE - Calibrate the
Chilled Water Module as outlined in Table 6 for
Barber-Colman or Honeywell.
Table 6 - Chilled Water Module
RESISTANCE COIL WIPER
ARM
SEQUENCE PROCEDURE
1. Supply fixed air
signal to trans­
ducer (Fig. 6)
Use either air signal from
control thermostat or sep­
arate air supply (such as
a medical aspirator) to
introduce 9 psi signal to
transducer diaphragm and
hold.
Coil wiper arm (Fig. 6),
should be in center of re­
sistance coil.
2. Preset chilled
water thermostat
set point
Turn thermostat dial (4)
Honeywell (Fig. 4), or (3)
Barber-Colman (Fig. 5) to
center of scale (vertical).
3. Add throttling
range
Turn the throttling range
screw (19) Honeywell, or
(17) Barber-Colman 1/3
of total clockwise travel.
4. Place machine in
manual control
and start the
compressor
Turn switch (8) Honeywell
to MANUAL position.
Place the capacity con­
trol switch (15) Barber-
Colman on HOLD.
5. To complete the
electro-pneumatic
chilled water con­
trol calibration
Refer to Table 5- Barber-
Colman, perform steps 1
(E thru H), and 3 (A and
B) or refer to Table 4 -
Honeywell, perform steps
1 (D), 2 (B), 3 (A thru D),
and 4 (A and B).
CONTROL AIR
SUPPLY
Fig. 6 - 19DA Transducer Assembly
(For either Honeywell or
Barber-Colman)
Trimming Refrigerant Charge - After the ma­
chine has been placed in operation, it may be
necessary to adjust the refrigerant charge to
obtain optimum machine performance.
When a machine full load is available, add the
remaining refrigerant slowly until the difference
between the leaving chilled water temperature and
the cooler temperature reaches design conditions
or becomes a minimum. Shut the machine down
and allow refrigerant to drain to the cooler, mark
the level indicator and maintain that shutdown
refrigerant level.
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