Watlow Thermostat Control - Manual (Page 2)

WATLOW IND.
Thermostat Control Installation & Maintenance Manual
I&M NUMBER 316-42-4-1 Page:2
Date: 6/11/2008 Rev:4.00
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WATLOW IND.n # 6 INDUSTRIAL LOOP RD. n HANNIBAL MO, 63401n PHONE 573-221-2816 n FAX 573-221-3723
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.