Standard Mica Type Cylindrical Heaters are constructed in either one or two piece configurations using a low expansion alloy clamping strap(s) to provide optimum contact throughout the operating temperature range.

These bands are easily installed by slipping the heater over the cylinder and tightening the single clamping screw. Where obstructions prevent slipping the heater over the cylinder, two piece heaters may be used. When two piece heaters less than 3" wide are used, each half is normally rated at half wattage and half voltage for series connections. 3" or wider heaters are normally supplied with each half rated at half wattage and line voltage for parallel connections. Each half is appropriately marked. NOTE: Ratings should be carefully checked before installation.

Because of the extremely wide range of specifications and options available, most heaters of this type are CUSTOM MANUFACTURED. However, short production times of usually 7-10 days are maintained to accommodate the requirements of the plastics industry.

It is recommended that cylindrical heaters with width of 2" or less be used for most applications; however, any width or diameter within practical limits can be supplied.

A gap of 1/8 - 1/4" is standard on bands fitted with clamp straps. 3/8-1/2" gaps are most common on heaters having flanged clamping means. Wider gaps can be supplied where required.

Clearance holes, slots and cut-outs can be provided upon presentation of adequate drawing or instructions.

Flanged Type Cylindrical Heaters while usually not recommended, utilize turned up locking flanges in lieu of low expansion clamp straps.

Mica Type heaters of rectangular, hexagonal and other unusual shapes can also be provided to your specifications.

In view of current safety standards, metal terminal covers are recommended on heaters equipped with post terminals, which will not be otherwise enclosed or protected. Metal braid or metal armor protected leads are recommended on those heaters requiring flexible leads.

Unless otherwise specified, standard watt densities are in the 30 watts per square inch range. Other power ratings are available based on individual requirements.

Therm-Coil Mfg

Wiring Terminals

Wiring Terminals
  • Type P– POST TERMINALS with #10-24 threads
    are standard on Mica Heaters. Terminals have a
    thread length of 7/16" and a clearance height
    of 3/4" above the ID or bottom of the heater.
  • Type Q - POST TERMINALS with #5-40 threads are
    supplied on heaters 1-1/8" wide and narrower. 3/8"
    thread length with 5/8" clearance height.
  • Type S - BUTTON TERMINALS are available with a
    #10-32 screw, 1/2" clearance height.
  • Type R - BUTTON TERMINALS are available with a
    #6-32 screw, 7/16" clearance height.

Flexible Leads

For special clearances, exposed or simplified wiring, or other problems areas, flexible leads are often required. Standard lead length is 12". The following constructions are available.

  • Type A -Flexible leads with stainless steel outer
    braid. Two single conductor leads emit from ends of
    element at gap parallel to conductive surface.
  • Type C -Flexible leads with stainless steel outer braid.
    Two-conductor lead emitting perpendicular to conductive surface,
    wither near gap or 180° from gap. 1-1/4" minimum band width.
  • Type D –Flexible leads with stainless steel outer braid.
    Similar to Type A but with a two-conductor lead emitting from
    one end of the heater at the gap. 2-1/2" minimum band width.
  • Type J –Flexible leads without shielding.
  • Type K –Flexible leads without shielding. Leads emit from
    each end of heater thru the gap. Recommended on very narrow
    heaters only.
  • Type L –Flexible leads without shielding. Similar to Type A.
  • Type M –Extra-flexible stainless steel armor cable. For
    use where abrasion problems are serious. CAUTION –material is
    NOT waterproof.
  • Type U –Flexible leads without shielding. Similar to
    Type Y but supplied with 2-1/2" long spring at junction of
    lead and heater
  • Type Y –Flexible leads without shielding. Similar to Type C.