Specifications

WATLOW IND. WATROD Duct Heater Installation & Maintenance Manual
I&M NUMBER: 316-42-6-1 Page: 1
Date:6/11/2008 Rev: 3.00
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WATLOW IND.n # 6 INDUSTRIAL LOOP RD. n HANNIBAL MO, 63401n PHONE [phone] n FAX [phone]
Pre Installation
• Check to make sure that heater received is the same as that ordered.
• Elements may come in contact with each other during shipment. Minor adjustments to elements may be
required prior to installation to separate them. Extensive bending of elements should be avoided since
dielectric strength between coil and sheath may be compromised.
• Watlow heaters are built to comply with global dielectric requirements, it may be necessary due to
atmospheric conditions / humidity, to perform a dielectric test prior to startup. (Refer to Insulation
Resistance (megohm) precheck test under Installation section)
Safety
Electric heaters are inherently dangerous!! Care should be taken to read and completely understand the
Installation and Maintenance manual before installing and wiring the heater. Any installation and
maintenance performed on the heater shall be done by a qualified electrician, in accordance with the
governing and other electrical codes as they apply. It is the users responsibility to ensure that the heater
being used is properly selected and installed in the application.
!
The Caution Symbol (exclamation point) alerts you to a "CAUTION", a safety or
functional hazard which could affect your equipment or its performance.
The warning symbol (lightning bolt) alerts you to a "WARNING", a safety hazard which
could affect you and the equipment
Installation
Proper heater selection and installation will result in efficient heat transfer, safe operation, and long heater
life.
1. Insulation Resistance (Megohm) precheck
The insulation resistance was tested to the applicable standard(s) at the Watlow manufacturing facility
prior to shipement. During shipping and/or storage, moisture absorption by the insulation material within
the element is possible. The insulation resistance value is reflective of the product volume resistance.
The measured value in ohms at a given temperature can be used to estimate the current leakage when
a voltage is applied. The user should assure the the volume resistance is adequate to keep current
leakage at or below desired levels during startup and operation. Some products have ends seals that
allow water vapor to enter and exit the product. It is normal for the current leakage to change with time
and temperature on products with “breathable” end seals. The current leakage may be lower after the
product reaches equilibrium temperatures due to loss of water vapor from within the product. If the
insulation material is “dry” the volume resistance will decrease with temperature, and the current leakage
will increase with temperature. To test the volume resistance use a 500 VDC megohm meter (Megger)
and connect to any heater terminal and the heater sheath that is part of a load circuit. A suggested good
practice is to achieve a value of more than 10 megohms when the unit is at room temperature. The
actual required value depends on the allowed current leakage when voltage is applied to the product.
If several units are interconnected, the megohm of the heater is obtained by taking the reading and
dividing by the number of interconnected elements. This reading should be greater than 10 megohms.
If an undesirable megohm value exists, two alternative methods can be used to remedy the situation.
One method is to place the product in an oven and raise the entire product temperature to remove
moisture. Contact Watlow to determine what temperatures your product can safely be baked out to
avoid damage to components.