Heater Wire

Springfield Wire, Inc. is recognized worldwide for its expertise in the development of silicone and thermoplastic insulated resistance wire for refrigeration anti-condensate applications. These heating elements are available in resistances from .22 ohm/ft. to 5000 ohms/ft. with a tolerance of ± 5%.

Whatever your requirements for insulated resistance wire, you'll find Springfield Wire, Inc. an excellent source for quality material, competitive pricing and dependable service.

The majority of silicone and PVC heater wire that Springfield Wire manufactures is used in domestic and commercial refrigeration applications to prevent the formation of condensation on surfaces.

The successful use of either type of wire depends on three critical factors:

Proper selection of the resistance (ohms per foot) to provide the desired wattage.

Selection of the appropriate style of wire.

Proper installation in the application.

Proper Selection Of Resistance's

All Springfield Wire heater wire is made to order. Resistance is measured in ohms per foot. This resistance is based on the watts per foot and voltage in your application. The amount of heat (wattage) required to prevent condensation around doors will vary according to the design of the cabinet.

For walk-in and deep freezers whose ambient temperature is 30°F to below zero, 8-12 watts per foot is commonly used. Reach-in and walk-in coolers that operate at a higher ambient temperature generally need 3-6 watts per foot.

It should be noted that the above figures are only general recommendations. Each application is unique and careful testing, using thermocouples, should be done by the customer to ensure a proper and safe design. Varying cabinet ambient temperatures and mullion constructions (steel, aluminum, plastic) will all play key roles in the heat transfer between the heater wire and the surface.

Thermoplastic (PVC) Insulated Resistance (Heater) Wire
Springfield Wire's thermoplastic (PVC) insulated heater wire is an excellent choice for use in low wattage applications. This premium quality thermoplastic jacket material has passed the most critical odor tests of the domestic refrigerator manufacturers. In addition to being used in bulk form for harness, PVC insulated wire is widely used in the manufacture of foil bonded and sewn to foil heaters.

Conductor and Insulation Temperatures

For 1/32" wall 105°C thermoplastic insulated heater wire suspended in still air at room ambient.

Power, Watts/ft. Conductor Temperature

1.0
1.5
2.0
2.5
3.0
3.5 45°C
54°C
64°C
73°C
80°C
90°C

SPECIFICATIONS

INSULATION: Polyvinyl Chloride, S-14 Compound

TEMP. RATING: 105°C Maximum (221°F)

VOLTAGE RATING: 300 V Maximum

WATTAGE: 3 W/ft. Maximum; 8 W/in² Maximum

WALL THICKNESS: .031 (1/32) Standard,
up to .062 (1/16) Available

CORE MATERIAL: Polyester, .021" Diameter

FINAL DIAMETER: .095 Standard, ± .003

RESISTANCE: .22 ohms/ft. up to 5000 ohm/ft. ± 5%

LISTINGS: UL File E-20903, CSA File No. 12087

Silicone Insulated Resistance (Heater) Wire
Springfield Wire's silicone insulated heater wire is an excellent choice for use in high wattage applications of up to 15 watts per foot. This wire is constructed using electrical grade fiberglass core material and is insulated with our SW-200 silicone rubber. SW-200 is a UL Class 22 Underwriters' approved rubber compound that is rated to 150°C (302°F) and can go as high as 200°C (392°F) in some applications.

Heater wall thickness can vary with applications. Generally a 1/32" wall is sufficient where heater wire is used within cabinet walls, doors and display rails of refrigeration equipment, such as reach-in, walk-in and commercial coolers. In specialized applications, a heavier 1/16" or 3/64" wall insulation is available. Mechanical protection in the form of braided fiberglass or braided aluminum covering is available to meet specific requirements. Aluminum braid will provide extra protection where a channel is unfinished or has sharp corners.

SPECIFICATIONS

INSULATION: Silicone Rubber, SW-200 Compound
Class 22 Underwriters' Approved

TEMP. RATING: 150°C Maximum (302°F)

VOLTAGE RATING: 300 V Maximum

WATTAGE: 15 W/ft. Maximum; 20 W/in² Maximum

WALL THICKNESS: .031 (1/32) Standard,
up to .062 (1/16) Available

CORE THICKNESS: Fiberglass, .025" Diameter Standard
Larger Diameter Available

FINAL DIAMETER: .095 Standard, ± .003 (extruded only, no braid)

FINAL DIAMETER
BRAIDED: .115 ± .003 with Fiberglass Braid
.140 ± .003 with Aluminum Braid

RESISTANCE: .22 ohms/ft. up to 5000 ohm/ft. ± 5%

LISTINGS: UL File E-20903, CSA File No. 12087

Proper Installation

Many factors are to be considered when installing any heater wire in domestic or commercial refrigeration equipment. The most important of these is good thermal transfer between the wire and the surface to be heated. Installation of the heater wire may be done by taping the heater wire directly to the surface or by bonding to aluminum foil, and then securing the self adhering foil to the surface. The foil bonded design is generally used to ensure proper spacing of the heater wire, ease of installation and good heat distribution.

When laying wire in grooves or channels around door perimeters, sharp edges and corners must be avoided so that the wire is not cut or abraded. Fiberglass or aluminum braid over the wire is available as protection from abrasion. Metal or plastic channels can be used, and grooves that are cut into wooden door frames should be lined with aluminum tape to prevent abrasion and also to reflect heat outward toward the surface being heated.

It is important that heater wire be installed with a small amount of stack at the corners of the frame. When the wire is energized, it will move slightly, This "creeping" motion can cause abrasion if the wire is installed too.

If multiple passes of wire are used, it is important to keep them spaced 1/4" apart and not allow any contact. If the wire should cross itself, the effective wattage at that point is doubled and a hotspot or burnout could occur.
If the wire exits through the wall of the cooler or freezer unit, care must be taken to ensure that it does not become buried or encapsulated in foam or other types of insulation. This causes poor heat transfer and overheating which could result in failure.