Carrier Gemini 38AU Series Installation, Start-Up And Service Instructions Manual page 17

38AUZ(A,B) unit is a single-stage cooling unit. If no economizer
function is required, select a single-stage cooling thermostat. If an
integrated economizer function is required, select a two-stage
cooling thermostat.
38AUZ(D,E) is a single circuit, two-stage cooling unit. Select a
two-stage cooling thermostat.
The 38AUD is a dual-circuit, two-stage cooling unit. Select a two-
stage cooling thermostat.
Select a thermostat cable or equivalent single leads of different
colors with minimum of four leads for 38AUZ(A,B) or five leads
for 38AUD/38AUZ(D,E) unit. Check the thermostat installation
instructions for additional features which might require additional
conductors in the cable.
For wire runs up to 50 ft. (15 m), use no. 18 AWG (American
Wire Gage) insulated wire (35°C minimum). For 50 to 75 ft. (15
to 23 m), use no. 16 AWG insulated wire (35°C minimum). For
over 75 ft. (23 m), use no. 14 AWG insulated wire (35°C mini-
mum). All wire sizes larger than no. 18 AWG cannot be directly
connected to the thermostat and will require a junction box and
splice at the thermostat.
PREMIERLINK (ACCESSORY INSTALLATION)
Refer to Installation, Start-Up and Configuration Instructions for
PremierLink Retrofit Rooftop Controller for details on connect-
ing the PremierLink controller and its various sensors.
If the unit will be operating at 208-3-60 power, remove the black
wire (BLK) from the transformer primary connection labeled
"230" and move it to the connection labeled "208". See Fig. 19.
Fig. 19 — Control Transformer Wiring
EXTERNAL DEVICES
The 38AU control transformers provide 24-v NEC Class 2 power
sources to energize external control devices. These devices will in-
clude the indoor fan motor contactor (or control relay). These de-
vices may also include liquid line solenoid valve (two on 38AUD
model), economizer control relay, supplemental electric heater
contactors or control relays and other devices selected by system
designer.
Control transformer TRAN1 provides control power through ter-
minal R to C on the field connection terminal strip TB for supply
fan motor interlock. This source may also be used to energize
economizer control relay and electric heater contactors or relays.
Maximum available power is 20 va. Check concurrent loadings by
external control devices. If the maximum concurrent loading ex-
ceeds 20 va, purchase and install the accessory Transformer-Relay
package (available for 208/230 and 460-v units).
38AUD Only
Control transformer TRAN3 provides control power through ter-
minals A1 (9) and A2 (10) to C for liquid line solenoids. Maxi-
mum available power is 75 va. These outputs are switched ON/
OFF by the Solenoid Valve Relays.
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