Watlow WATROD Screw Plug User Manual

WATLOW IND. WATROD Screw Plug Installation & Maintenance Manual

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I&M NUMBER: 316-42-10-1 Page: 1
Date:6/11/2008 Rev: 3.00

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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 UL, CSA, and CE LVD dielectric requirements, it may be necessary
due to atmospheric conditions / humidity, to perform a dielectric test prior to startup. (Refer to megohm

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 "National Electric
Code" 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.

functional hazard which could affect your equipment or its performance.

The Caution Symbol (exclamation point) alerts you to a "CAUTION", a safety or

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. Megohm precheck

During shipping and/or storage, the possibility of moisture absorption by the insulation material within the
element is possible. To ensure proper megohm values a minimum 500 VDC megohm meter (Megger)
should be used to ensure that the megohm reading between the heater terminal and the heater sheath is
more than 10 megohms when the unit is at room temperature.

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 a low megohm value exists, two alternative methods can be used to remedy the situation. The best
method is to remove all terminal hardware including thermostat if provided, and bake out the heater at no
higher than 250°F (120°C) overnight or until an acceptable reading is reached. The second method is to
energize the unit at low voltage in air until the megohm is at an acceptable reading. Care should be taken
to prevent the heater sheath from exceeding 750°F (398°C) for INCOLOY or equivalent elements, 750°F
(398°C) for carbon steel elements, and 400°F (204°C) for copper elements.

2. Protection of heater elements from over temperature

The use of temperature controls to regulate heating process and prevent heater over temperature is highly

recommended to ensure safe heater operation. It is the users responsibility to ensure safety of the
installation.

WARNING: Install high temperature control protection in systems where an over temperature fault

condition could present a fire hazard or other hazard. Failure to install temperature control
protection where a potential hazard exists could result in damage to equipment and property, and
injury to personnel.

WATLOW IND.n # 6 INDUSTRIAL LOOP RD. n HANNIBAL MO, 63401n PHONE [phone] n FAX [phone]

WATLOW IND. WATROD Screw Plug Installation & Maintenance Manual

I&M NUMBER: 316-42-10-1 Page: 2
Date:6/11/2008 Rev: 3.00

________________________________________________________________________________________________________________________________________________________________________________________________________________________

Failure of components in a temperature control loop, such as the sensor, heater control relay or main

temperature control, can result in damage to a product in process, a melt down of a heater, and / or
damaging fire.

To protect against this possibility, over temperature protection must be provided to interrupt or remove

power from the heater circuit. A bulb and capillary thermostat is not recommended for this function

since it may not respond quickly enough to adequately protect the heater. In cases where the
thermostat bulb gets too hot before the system is turned off, the thermostat bulb could rupture.
This could result in the thermostat remaining in the "ON" condition since there is insufficient fluid
to move contacts apart. We recommend the temperature protection have appropriate third party

approval, and be applied in the classification for which it was tested and approved.

In order to help prevent premature failure and a potentially hazardous condition in cases where

consequences of failure may be severe, use an appropriate third party approved liquid level protection
device. The liquid level should be such that the entire heater is fully submerged with enough liquid above
the heater to adequately dissipate heat from itself as under normal operating conditions. Consult your local
authorized sales representative for specific recommendations for your application.

3. Terminal Enclosures

Terminal enclosures should be selected to be compatible with the environment in which the heater will be

located. It is the users responsibility to determine the need for correct rating of the electrical housing. This
should be based on appropriate national and local electrical codes. Failure to use a compatible enclosure
could result in heater damage and personnel danger.

Standard terminal enclosures are designed for general purpose use and are rated NEMA 1. These

enclosures should be applied where there will be no danger of spilled liquids, dampness, dirt, and gaseous
conditions. Enclosures for wet or hazardous locations are also available, but must be installed at the
factory. One 3/4" conduit entry is supplied as standard on all NEMA 1 enclosures. Location of conduit entry
can be rotated by removing enclosure base from screw plug for NEMA 1 enclosures.

Although enclosures are supplied over the terminals, units should be located in an area that will minimize

the chance of being hit by falling or moving objects. The terminals must be protected at all times from
moisture or vapor.

In hazardous locations, (as defined in NFPA 70 NEC, Article 501) appropriate hazardous location electrical

enclosures must be used.

In order to maintain termination integrity, the terminal enclosure should be kept below 400°F
(204°C).

4. Orientation / Mounting

Heater orientation is important in order to ensure efficient heat transfer and safe operation. Care should be

taken to allow enough room for heater expansion without compromising heat transfer. When installing the
heater through the header on the tank, care should be taken to avoid bending the elements. If possible
elements should be inspected to ensure that they are not touching. Failure to do so could result in shorter
heater life due to higher heater temperatures.

The location of an immersion heater in a process is of prime importance. To take advantage of natural

convection, the unit should be located as low as possible; similar to the "X" position in Figure 1.
Consideration should also be given to sludge build-up in the bottom of the tank and the need for heater
removal (replacement or maintenance). Location of the heater in the sludge area will cause premature
failure and lower heat transfer efficiency.

The "Y" position (Figure #1) is not recommended, but can be used if properly controlled. The heated

section must be immersed during operation or premature failure may result. The use of an approved

WATLOW IND.n # 6 INDUSTRIAL LOOP RD. n HANNIBAL MO, 63401n PHONE [phone] n FAX [phone]