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SECTION II____________________________________OUTDOOR
Only certain versions of the HPT 100 are recommended for outdoor locations. Under the
Electrical Connection Suffix on the model code structure in Section I on page 1-1, the
suitable letters are "N" or "C".
Electrical Connection Suffix "N" or "C" is used when an outdoor location is planned as
the unit is compensated for outdoor temperatures and all seals are checked for leak rate.
Both styles employ a type of pigtail termination.
For Electrical Connection Suffix "N", when used in a Div 2 location, the use of a
secondary protective enclosure is required(gas cabinet for example). This is to protect the
exposed pigtail cable. An alternative is to use an approved safety barrier.
For Electrical Connection Suffix "C", when used in a Div 2 location with conduit, the use
of a secondary protective enclosure is not required as the pigtail cable is contained within
the conduit.
In an effort to provide long term operation in a harsh outdoor environment, Ametek has
designed the HPT 100 to resist the introduction of moisture to the internal circuitry. The
use of conformal coating on the circuit boards(outdoor models only) also aids the
rejection of the outside elements. It is essential that the potentiometer access cover be
properly tool tightened after any check or adjustment. Periodic checking of the
potentiometer access cover for a snug fit is recommended. To avoid damage to threading
and seals do not over tighten.
Since the unit is a gauge referenced unit, a path for "breathing" must be maintained. In
the HPT 100 pigtail models, the breathing path is maintained through the pigtail cable.
For this reason it is mandatory to terminate the cable in a dry, temperature stable
environment. It is also essential that the cable remain without any nicks or cuts and that
splicing cable lengths not be utilized. It is further recommended that a slight positive
pressure be applied to the pigtail termination (Z-purge). This method is often used to
keep outdoor gas cabinets dry under any weather condition. A suitable pigtail cable
crimp seal located at the gas cabinet may be used to allow the pigtail to enter a Z-purged
gas cabinet. The slight positive pressure entering the cable will be enough to allow the
transducer to function with any type of weather phenomenon for very long periods. The
pressure must be kept low enough to avoid affecting the measured pressure. A few tenths
of an inch of water pressure is adequate to protect the transducer and small enough not to
significantly affect pressure measurement accuracy.
The use of a Bendix connector outdoors should not be attempted because of the difficulty
of sealing the termination. Further, the low pressure models utilizing the Bendix
connector are vented locally through the transmitter itself and not the electrical
termination.
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