These OI Analytical FS3700 heaters are quite robust as the electronics are all contained in the board of the system not in the heater itself, which limits points of failure. However, over time the tubing can degrade or become clogged, this means that often many issues can be completely resolved with a simple rewrap, using kit E080133.

The rewrap procedure is very inexpensive and easy, you can find it detailed below.

Please see our videos here, that provide a detailed overview of the rewrap process.

1.     PROCEDURE

  1. Begin by loosening the set screw at the top of the heater spindle and removing the ¼ inch cartridge heater and thermocouple wire.         
  2. Remove the tubing, tape, and glue that is left on the heater spindle.                                                                           
  3. Using the provided rewrap kit (E080133) wrap once around the top of the heater spindle leaving about 8-12 inches protruding out from the top of the heater spindle.

Note: The tubing will not be able to thread through the holes in the top of the heater while  doing a field rewrap as the provided kit already has flanged fittings. However, this is fine and will not affect performance. Just be sure not to pinch the tubing against the edge of the top rim of the heater spindle. This is due to the flanged fittings on the ends of the tubes which can only be done in the field with a flanging device.

  1. Cover the top section of tubing on the heater with a 6-inch piece of foil tape to secure the tubing to the heater spindle.
  2. Continue wrapping a tight coil around the heater. (See diagrams below) the wrap should be snug but not completely immobile, this will prevent the tubing from coming loose. Once the tubing is wrapped all the way to the bottom of the heater, cover the bottom section with a 6-inch piece of foil tape to secure the tubing in place if needed, leaving another 8-12 inches protruding. (Note, there are two types of heater spindles; an angled/conical variety and a flat/cylindrical variety, the rewrap procedure and functionality do not change, only the appearance.)                                                                                                                                                      
  3. Slide provided blue insulation over the heater so that it completely covers the tubing.             
  4. Re-attach the ¼ inch heater cartridge and thermocouple wire into the top of the heater spindle and secure with the set screw.
  5. Remount heater in system and start flow to check for leaks.
  6. Enjoy your newly rewrapped heater.