Application guidelines
13
FRCC.PC.002.A5.22
Electrical connections and wiring
Wiring diagram without
pump-down cycle
Control device
TH
Optional short cycle timer (3 min) 180 s
Control relay
KA
Compressor contactor
KM
Safety lock out relay
KS
H.P. switch
HP
Fused disconnect
Q1
Fuses
F1
Compressor motor
M
Discharge gas thermostat
DGT
IP rating
The compressor terminal boxes IP rating
according to CEI 529 are:
IP55 for NTZ048-136 except NTZ136-1
IP54 for NTZ136-1 & NTZ215-271
The IP ratings are only valid when correctly sized
cable glands of the same IP rating are applied.
Internal motor protection
Voltage unbalance
Motor protection
Three phase compressors are internally protected
by a temperature / current-sensing bimetallic
protector, connected to the neutral point of the
star-connected stator windings. This internal
overload line break protects the motor against
overheating, current overload and locked rotor
conditions. If the motor were to be overloaded
and the protector trips, all 3-phases are cut out.
It might take up to several hours to reset and
restart the compressor.
Operating voltage limits are shown in section
"Voltage application range". The voltage applied
to motor terminals must lie within these limits
during both start-up and normal operation.
The maximum allowable voltage unbalance is
2%. Voltage unbalance causes high amperage
on one or more phases, which in turn leads to
overheating and possible motor damage.
The voltage unbalance is given by the following
formula:
Vavg = Mean voltage of phases 1, 2 and 3
V1-2 = Voltage between phases 1 and 2
V1-3 = Voltage between phases 1 and 3
V2-3 = Voltage between phases 2 and 3.
|V
avg
- V
1-2
|+|V
avg
- V
1-3
|+|V
avg
- V
2-3
|
2 xV
avg
% voltage unbalance:
x 100
KM
L1
L3
L2
Q1
CONTROL CIRCUIT
F1
F1
KM
KA
KA
KS
KS
KS
LP
HP
DGT
TH
180 s
85 52 019 - A
T1
T2
M
T3
KA
KA
A1
A2
A3