Watlow WATROD Screw Plug - Manual (Page 2)

WATLOW IND.
WATROD Screw Plug Installation & Maintenance Manual
I&M NUMBER: 316-42-10-1 Page: 2
Date:6/11/2008 Rev: 3.00
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WATLOW IND.n # 6 INDUSTRIAL LOOP RD. n HANNIBAL MO, 63401n PHONE 573-221-2816 n FAX 573-221-3723
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