Wire Connectors

Wire Connectors

The content we provide is meant to inform you and help support the proper selection and use of electrical connectors. We recommend you consult a licensed and competent electrician to help you with the sizing and selection of parts for your particular application.

Barring sizing errors and damaged insulation, the most common cause of equipment failure in the field is the failing of components that make connections (e.g. switches, contacts, connectors, potentiometers, etc.). Therefore, when selecting wire, it is important not only to choose the right size wire but also a suitable connector to ensure a solid link between the conductors in your cable and the equipment terminals.

There is nothing particularly special about connectors for SOOW wire, except you may want flex nut strain relief as opposed to a dome nut. The guide below summarizes information from UL White Book section ZMVV and applies to the general selection of connectors. Please see general information on connectors and the vital role they play in electrical circuits.


The following ratings should be marked either on the connector itself or the unit container.

Wire Gauge

Unlike strain relief devices that fit onto the outside of the cable jacket, and thus require a nominal outer diameter (nom. O.D.) specification, connectors must form a solid connection with the conductors themselves, so the wire gauge (size) is required instead.

Conductor Material

A marking on the connector or the unit container will indicate what type of conductor material it can be used with.

Marking For use with
CU Copper Only
AL Aluminum Only
AL-CU or CU-AL Copper-Copper
Direct physical contact between copper and aluminum conductors are not permitted
AL-CU (intermixed - dry locations) Copper-Copper
Intermixed and direct physical contact between copper and aluminum conductors are allowed

Current (Ampacity) and Voltage

The fastest way to damage your equipment is to undersize some part of the electric circuit powering the equipment. Make sure to get connectors that can handle the amount of current and voltage the circuit will be conducting. Current affects the amount of heat generated due to resistance, and voltage affects electric arcing.

Also, remember the weakest link rule when sizing conductors.

Conductor Strand Class

All the SOOW wire we offer exceeds class C copper conductor stranding. Thus, to be NEC compliant, you will need connectors identified for the specific strand class (i.e. class D, G, H, K, or M) of the wire. Connectors without any marking to indicate the strand class can only be can only be safely used with class B stranded conductors.

Table 10 in chapter 9 (shown below) is a new addition to the 2011 NEC, and is reproduced from UL Standard 486 A-B.

Conductor Size Number of Strands
Copper Aluminum
AWG or kcmil mm2 Class B Class C Class B
24 - 30 0.20 - 0.05 a - -
22 0.32 7 - -
20 0.52 10 - -
18 0.82 16 - -
16 1.3 26 - -
14 - 2 2.1 - 33.6 7 19 7b
1 - 4/0 42.4 - 107 19 37 19
250 - 500 127 - 253 37 61 37
600 - 1000 304 - 508 61 91 61
1250 - 1500 635 - 759 91 127 91
1750 - 2000 886 - 1016 127 271 127

aStrand counts vary.

bAluminum 14 AWG (2.1 mm2) is not available.

Number of Conductors a Connector Can Hold

Since all SOOW wire has multiple conductors, you will want to pay attention to this specification unless you are planning to terminate all the conductors in your wire to the same contact point (i.e. single-pole connector).

Torque Tightening Rating

Some connectors will also have a manufacturer recommended torque rating for connections to terminal bolts or studs.

Insulation Temperature

Insulated connectors will have a temperature rating on the insulation or unit container.