WATLOW ELECTRIC MANUFACTURING COMPANY
Installation & Maintenance Manual for MULTICELL
TM
Heaters
I&M MANUAL No: 316-42-21-1
Page: 7
Date: 3/15/2017
Rev: 5.00
WATLOW ELECTRIC MANUFACTURING COMPANY - 6 INDUSTRIAL LOOP RD.
– HANNIBAL, MO 63401 - PHONE 573-221-2816
Original Instructions (English)
Insulation Resistance (Megohmmeter) Pre-check
Any products that have been shipped sealed in plastic should not have the plastic removed until
the product is ready for installation and use.
During shipping and/or storage, the possibility of moisture absorption by the insulation material
within the heater is possible. To determine if the proper insulation resistance value is present, use
a 500 VDC (minimum) Megohmmeter to measure the dielectric insulation resistance (IR) between
the heater terminal and the heater sheath. This value should be greater than 50 Megohm when
the unit is at room temperature.
If a low IR value exists, the following options may be used to dry the elements and return the IR
value to an acceptable range. In order to maintain termination integrity, the termination should be
kept below 222°C (400°F), or the maximum temperature rating of the lead wire insulation and end
seal. When needed, bake the heaters in an oven at 177°C (350°F) ± 27°C (50°F) for a period of
12 hours. After baking, repeat the IR test to verify the evaporation of sufficient moisture from
within the heater. If the heaters fail a second IR test, contact the factory at the phone number
shown on this manual. Regardless of the insulation resistance value, the heat up and cool down
rates in the Start Up section of this manual should be followed.
Protection of heater elements from over temperature
The use of automatic temperature controls to regulate the heating process and prevent heater
over temperature is highly recommended to ensure safe heater operation. All temperature limit
devices must have appropriate third party approval and be applied in the classification for which it
was tested and approved. The high temperature limiting device(s) should function independently
from the process temperature control.
High Temperature Limit controllers with temperature feedback and relays that are independent
from the heater control system can be used to provide an automatic means of interrupting the
electrical power circuit when/if excessive temperatures occur.
The Multicell heater transfers heat energy through the radiant mode. Heat transfer can be
significantly enhanced by thoroughly oxidizing the platen installation holes before running the
heaters above a temperature of 538°C (1000°F). This can typically be accomplished with a torch
head set with a low oxygen flame that leaves a sooty black residue inside the platen holes.
WARNING
– Risk of Electric Shock
The bake-out procedures listed below should only be performed by properly qualified
personnel. If the procedure calls for connecting electric power to the heater, this shall
only be performed by a qualified electrician, in accordance with applicable national
and local electrical codes.
