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13 - ELECTRICAL CONNECTION
13.1 - Recommended wire sections
Wire sizing is the responsibility of the installer, and depends
on the characteristics and regulations for each installation
site. The following should only be used as a guideline, and
does not make Carrier in any way liable.
After wire sizing has been completed, using the certified
dimensional drawing, the installer must ensure easy connec-
tion and define any modifications necessary on site. The
standard connections for the field-supplied power entry ca-
bles to the general disconnect/isolator switch are designed for
the number and type of wires, listed in the table below.
The calculations are based on the maximum machine current
(see electrical data tables), and standard installation practices,
in accordance with IEC 60364, table 52C have been applied
(38RM-N units are installed outside)
The calculation is based on PVC or XLPE insulated cables
with copper core. A maximum outside temperature of 48°C
is taken into consideration. The given wire length limits the
voltage drop to < 5%.
IMPORTANT: Before connection of the main power cables
(L1 - L2 - L3) on the terminal block, it is imperative to check
the correct order of the 3 phases before proceeding to the con-
nection on the main disconnect/isolator switch.
Power cable entry
The power cables can enter the 30RB control box from below
or from the side of the unit, at the bottom of the angle iron.
Pre-punched holes facilitate the entry. Refer to the certified
dimensional drawing for the unit.
13.2 - Power supply
After the unit has been commissioned, the power supply
must only be disconnected for quick maintenance operations
(one day maximum). For longer maintenance operations or
when the unit is taken out of service and stored (e.g. during
the winter or if the unit does not need to generate cooling)
the power supply must be maintained to ensure supply to the
heaters (compressor oil crankcase heaters.
14 - REFRIGERANT PIPE SIZING
WITH REFRIGERANT
14.1 - General and pipe sizing limits
The pipes must be as short as possible and have as few chang-
es as possible (bends etc.) to minimise pressure losses.
If there may be a risk of poor operation, adequate measures
(design, position, protection) must be taken to prevent this.
Refrigerant pipe sizing must be carried out, taking account
of the following constraints:
Oil return to the compressor for the majority of applications
must be ensured. Oil return is ensured by entrainment. A
minimum refrigerant velocity is required to ensure entrain-
ment. This velocity depends on the pipe diameter, refrigerant
and oil temperature (these are treated as being the same in
most cases).
A reduction of the pipe diameter permits an increase of the
refrigerant velocity. The problem of a minimum entrainment
velocity does not exist for the pipes that carry liquid refriger-
ant as the oil is fully miscible here.
The compressor suction line (pipes linking the evaporator
outlet with the compressor inlet) pressure drops must be
limited to avoid system performance losses (the compressor
power input increases, and the cooling capacity decreases).
The pressure drop in the liquid line (linking the condenser
outlet to the expansion device) must not result in a change
in phase. The estimate of these pressure drops must include
those for the possible accessories, such as solenoid valves,
filters, dehumidifier etc.
14.2 - Pipe sizing
The following procedure can be used for pipe sizing:
• Measure the length (in metres) of the piping under
consideration.
• Follow the pipe size as below for additional ref. meters
Unit
till 30 M
TR
Suction Line
Liquid Line
8
1 1/8
5/8
10
1 3/8
5/8
12
1 3/8
5/8
15
1 1/8 x2
5/8 x 2
20
1 3/8 x2
5/8 x 2
25
1 3/8 x2
5/8 x 2
30
1 1/8 x 4
5/8 x 4
35
1 3/8 x 4
5/8 x 4
40
1 3/8 x 4
5/8 x 4
45
1 3/8 x 4
5/8 x 4
50
1 3/8 x 4
5/8 x 4
• Calculate the equivalent lengths for parts included in the
piping under consideration (such as valves, filters,
connections). The equivalent lengths are normally available
from the component supplier. Add these lengths to the
length calculated.
31 - 50 M
Suction Line
Liquid Line
1 3/8
5/8
1 3/8
3/4
1 5/8
3/4
1 3/8 x2
5/8 x 2
1 3/8 x2
3/4 x 2
1 5/8 x2
3/4 x 2
1 3/8 x 4
5/8 x 4
1 3/8 x 4
3/4 x 4
1 3/8 x 4
3/4 x 4
1 5/8 x 4
3/4 x 4
1 5/8 x 4
3/4 x 4
21
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