Watlow Thermostat Control User Manual

WATLOW IND. Thermostat Control Installation & Maintenance Manual

I&M NUMBER 316-42-4-1 Page:1
Date: 6/11/2008 Rev:4.00

________________________________________________________________________________________________________________________________________________________________________________________________________________________

Pre Installation

• Check to make sure that the thermostat received is the same as that ordered.

• Check capillary for kinks and damage to the bulb

Safety

Fire and electrical shock may result if thermostats are used improperly or are installed by unqualified
personnel !! Care should be taken to read and completely understand the Installation and Maintenance

manual before installing and wiring the thermostat. Any installation and maintenance performed on the
thermostat 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 thermostat 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

Installation

Proper thermostat selection and installation will result in safe operation, and acceptable heater control.

1. Locate the thermostat in an area where ambient temperatures do not exceed 150°F (66°C)

. If thermostat is not already enclosed in an electrical housing, then enclose the thermostat to:

2

• prevent electrical shock to personnel through accidental contact

• if applicable, prevent fire or explosion when flammable gases or vapors, flammable liquids, combustible

dust, or ignitable fibers or flyings are present in accordance with articles 500 through 504 of the
"National Electric Code" (NEC)

• prevent contact with falling objects that might damage or cause electrical short

3. Locate sensing bulb in the process fluid so that the entire bulb is exposed to the heated media, but a
sufficient distance from the heating element to negate the influence of the sheath temperature. Care

should be taken not to kink the capillary tubing of the thermostat while installing the thermostat.

It is not recommended that the thermostat be attached to the heater sheath for high limit protection.

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.

Failure of components in a temperature control loop, such as the thermostat, and heater control relay

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

could affect you and the equipment

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

WATLOW IND. Thermostat Control Installation & Maintenance Manual

I&M NUMBER 316-42-4-1 Page:2
Date: 6/11/2008 Rev:4.00

________________________________________________________________________________________________________________________________________________________________________________________________________________________

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 for thermostats

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

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 thermostat damage and personnel danger.

Although enclosures may be supplied with the thermostat, units should be located in an area that will

minimize the chance of being hit by falling or moving objects.

In hazardous locations, (as defined in NFPA 70 NEC, Article 501) explosion resistant housings must be

used.

5. Wiring

Electrical wiring to the thermostat must be installed in accordance with the National Electric Code and

any state and local electrical code by qualified personnel.

Thermostats supplied have been pre-calibrated by the manufacturer and require no adjustment other

than desired temperature setting prior to use. Thermostats are not recommended for high accuracy
sensing. For high accuracy sensing, the use of a thermocouple and a solid state temperature controller
is recommended.

When using thermostats as a Watlow heater control the succeeding factors should be considered:

1. The thermostat may be interconnected with the heater only if the following apply:

a) the heater only has one circuit
b) the ampere draw of the heater is lower than the rated ampacity of the thermostat at the prescribed

voltage.

c) if the thermostat interconnected breaks enough power supply lines to cause the heater to

discontinue operation.

2. Either a single or double pole thermostat may be interconnected with a single phase heater where the
supply voltage does not exceed 277 VAC for SPST, and 480 VAC for DPST. Only DPST may be
interconnected to a three wire three phase heater. This includes delta connections and 3 wire wye
connections. See Figure 1 for more details.

3. In pilot duty situations (where the thermostat is not interconnected with the heater) a single pole
thermostat should be used. See Figure 1 for more details.

4. When installing the thermostat maintain electrical clearance between the capillary and live conductors.

5. Thermostats should not be used as a power switch. The use of a disconnect switch or circuit breaker to
shut down the heater for servicing or maintenance is necessary.

6. All Watlow thermostats contacts open on temperature rise.

7. Refer to specific wiring schematic shipped with heater for interconnection with heater. If one is not
provided, contact the factory for the applicable wiring diagram.

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