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#20907 –
2/20/19
Thermowells (continued...)
Table 3: Pipe Insertion Recommendations using Carrier Thermowells
Thermowell Installation
To install a thermowell, a pipe fitter typically drills a
¾-inch hole into the pipe where the thermowell is
needed. A customer-provided fitting, called a
Threadolet or Weldolet, is welded to the pipe over
the hole. The Threadolet has a ½" NPT thread in the
center. Thread sealant such as Teflon tape or pipe
dope is applied to the ½" NPT threads of the
thermowell. The thermowell is then inserted into the
Threadolet and tightened.
Figure 6 shows a 4" thermowell and 4" immersion
sensor probe installed in a 12" pipe. In a properly
insulated pipe with liquid or steam, the temperature is
essentially the same across the entire cross-section of the
pipe.Usually thermowells are sized to extend to the center
of the pipe; however, shorter thermowells will give proper
temperature readings if properly installed. The shorter
thermowells are used in pipes with high flow velocities.
Since the wall thickness of the pipe commonly used
for HVAC plumbing is ½-inch, the thermowell sticks
four inches into the pipe. The four-inch distance is
from the inside surface of the pipe to the end of the
thermowell.
Catalog No. 11-808-632-01
6.5" Overall
Probe Length
Threadolet
Figure 6: Typical Immersion Probe Installed in a Thermowell
Specifications subject to change without notice.
Immersion Temperature Sensors
Installation and Operation
Weld
2" Thick
Pipe Insulation
1/2" Thick
Pipe Wall
(Schedule 80)
4" Thermowell
Insertion Length
4 of 7
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