Insulated Heater Wire

Backer-Springfield is recognized worldwide for its expertise in the development of specially fabricated silicone and thermoplastic insulated resistance wire for refrigeration anti-condensate applications. These heating elements are available in a broad range of resistances from .22 ohms/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:
  • 1. Proper selection of the resistance (ohms per foot) to provide the desired wattage.
  • 2. Selection of the appropriate style of wire.
  • 3. Proper installation in the application.

Proper Selection of Resistances

All Backer-Springfield heater wire is made to order to a resistance, as measured in ohms per foot. This resistance value is based on the watts per foot and voltage available 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 deep freezers whose ambient 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.


Backer-Springfield

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 and mullion constructions (steel, aluminum, plastic) will all play key roles in the heat transfer between the heater wire and the surface.

 

Ohms Piechart

Thermoplastic (PVC) Insulated Resistance (Heater) Wire

Backer-Springfield’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 insulation

 

Silicone Insulated Resistance (Heater) Wire

Backer-Springfield’s silicone insulated heater wire is an excellent choice for use in high wattage application 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 rated to 150C (302°F) and can go as high as 200°C (392°F) depending on application.

Conductor insulation

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 a 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 such surface 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.

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 type of insulation.  This causes poor heat transfer and overheating which could result in failure.

It is important that heater wire be installed with a small amount of slack 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 tightly and is under tension in the channel.

 

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