Wire and Cable for Solar Electric Systems

Note: Wire and cable is usually cut to order, and may take an extra 1-2 days before shipping. Please check our online store for current pricing.

Wire and Cable Factoids

The single most important component of a wire or cable is its insulation. The selection of an insulation is governed by a number of factors such as: stability and long life; resistance to sunlight (ultraviolet); dielectric properties; resistance to ionization and corona; resistance to high temperature; resistance to moisture; mechanical strength; and flexibility. There is no single insulation that is ideal in every one of these properties. It is necessary, therefore, to select a cable with the type of insulation which most fully meets the requirements of the particular installation involved.

These are some general rules and common practices when wiring solar systems. They are not meant to be all inclusive, only general guidelines.

1. Almost all wiring is done with stranded wire or cable. Solid wire is occasionally used for long runs, but in most cases it is not suitable for wiring panels, controls, pumps, batteries, or other components. If used, you run the risk of breaking the terminals and/or screws if the cable is flexed. It is also difficult to get a good connection with some types of terminals.

2. All outdoor wiring should be of type XLP/XHHW, TC (Tray cable) or similar outdoor UV (sunlight) resistant insulation. Other types, such as THHN, may be used, but should only be run in conduit if it is used. Metallic or NMC (non-metallic conduit) may be used in most cases.

3. When wiring batteries, inverters, or other high current devices, crimp/solder type lugs, or cable clamps designed for good connections with large cable should be used. Do not attempt to wire the stranded wire directly to battery terminals. For most purposes, welding cable is a better choice than the more common PVC battery cable, due to it's much tougher insulation and higher temperature qualities. Welding cable is more expensive than PVC cable, but PVC will melt at fairly low temperatures.

4. Do NOT use the commonly available "Romex" type solid house wire for anything BUT house AC wiring. It is not suitable for outdoor, direct burial, or water pump wiring. The insulation will fall off within a year or two if used in direct sunlight. It is also difficult to get good solid connections with solid wire on most components used in solar systems.

5. Size the wire gauge properly - the best components will not work properly if undersized wire is used. For panel and general wiring, see the wire loss table. We sell quite a bit overseas, and most of the world uses metric wire sizes. For conversion, see the metric to AWG wire size conversion table on the same page as the wire loss table.

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Wire Loss Table  Insulation Characteristics Chart
 

Specialty Cable

2-conductor outdoor wire
(USE-2, type TC)

2A-1603: 3 conductor #16 stranded, for use with float switches and water level sensors. We can get #18, but it is only one cent less per foot.

10-2/TC: 2-conductor #10 stranded

12-2/TC: 2-conductor #12 stranded

8-2/TC: 2-conductor #8 stranded

THHN Insulation, PVC Jacket. UL Listed Type TC 90°C dry, 75°C wet VW-1, (THN/THWN Only) IEE383. 70,000 and 210,000 BTU.

Welding Cable

Available in Red, Black - other colors available on special order, colors may be 5 to 10 days extra. Discounts of up to 20% for larger quantities - see our online store for quantity pricing.

All prices are per FOOT. The #4 and #2 minimum order is 25 foot per color.

For #4, and #6 XLP outdoor wire, see the XLP listing near the bottom of the page.

Submersible pump cable for use with both AC and DC powered pumps

Manufactured with welding cable.

High quality SAE flexible cable with copper ring lugs for 3/8" bolt connections. Lugs are professionally double crimped and sealed to cable with inner-wall melt shrink tubing (red or black) to prevent moisture and battery fume entry and corrosion. Custom sizes and lengths are available for larger quantities. The number of * indicates the most popular items. The #4 jumpers are most commonly used for series (positive to negative) connections in multiple series battery banks.

Current ratings are the safe maximum allowed by NEC, and DO NOT take voltage drops into consideration, only wire temperature. For current pricing, see our webstore.

Battery to Inverter Cables

Non UL listed. For UL listed versions see the Trace price list. Except for the UL listing, these are practically identical in construction, but are much cheaper. Most installations do not require UL listed inverter cables.

High quality flexible multistrand welding cable with copper ring lugs for 5/16" or 3/8" bolt connections. Lugs are professionally double crimped and sealed to cable with inner-wall melt shrink tubing to prevent moisture and battery fume entry and corrosion. The number of * indicates the most popular items. All are priced for one RED/BLACK pair.

Part Number	Size & Description
49075	4/0 AWG, 5 foot, 3/8" lug, pair ***
49080	4/0 AWG, 10 foot, 3/8" lug, pair **
49050	2/0 AWG, 5 foot, 5/16" lug, pair ***
49100	2/0 AWG, 10 foot, 5/16" lug, pair *

XLP Heavy gauge wire for PV arrays and other circuits.

Available stock in sizes #4 AWG through #12 AWG - any size on special order.

"XLP - This insulation has the best balance of all needed cable properties of any of the general-purpose insulations. It is a chemically cross-linked polyethylene compound. It combines the best properties of both rubber and polyethylene to provide a thermosetting material with excellent thermal, electrical and physical properties. It is recognized for its outstanding resistance to moisture and chemicals. XLP insulation is normally rated at 90°C at most voltages with higher temperature ratings found in a few UL listed types. Its excellent properties reduce the need for a protective jacket over the insulation on non-shielded non-jacketed cables. A specially compounded, filled cross-linked polyethylene insulation is available on XLP flame resistant control cable for important control circuit applications where the ability to withstand flames for short periods of time is a primary concern. A wide range of wires and cables for power, lighting and control circuits and for equipment wiring is available with various formulations of XLP insulation to meet the specific requirements of the wires and cables for which they are used." - From the manufacturers information about insulation types.

Nearly all the wire that we stock is XLP or XLPE based, with the exception of welding cable. We do not recommend PVC, although it is cheaper.