STP SERIES Install, Operation, and Maintenance Manual
SECTION 3: OPERATION AND CONTROLS
Page
26
of
97
Diversified Heat Transfer, Inc.
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439 Main Road
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Towaco, New Jersey 07082
Rev-1
09/11/2019 PHONE: 800-221-1522
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WEBSITE: www.dhtnet.com
STP Manual
The LED will typically assume only the conditions in this table (continuously red or green,
flashing red or green, or off).
3.6 VARIABLE FREQUENCY DRIVE (VFD) PUMP OPTION
The optional VFD pump consists of two main parts: the centrifugal pump and electronic control
module on top. It is a self-sensing, close coupled, mechanically sealed, in-line pump that
exceeds industry and efficiency standards with an advanced hydraulic design. It features a high-
efficiency volute, permanent magnet motor with ECM technology and integrated frequency
drive. It has simple yet versatile control options. These standard features combined with the
intuitive user interface allow for quick start-ups achieving optimum system efficiency and
maximum comfort. It is available in standard Cast Iron material construction for closed loop
boiler water flow control through heat exchanger(s).
FIGURE 3-8: VFD Pump with Flange Connections
3.6.1 Performance Data
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STP Series water heaters include optional VFD pumps which are simple to install and easy
interface
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VFD pump modulates the flow of boiler/HTHW through the heat exchanger based upon the
signal from the controller to maintain domestic temperature to target set point inside tank
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Standard 1-1/2 inches 2-bolt flange connections (flange gaskets included)
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Max flow: 120USGM
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Max shut-off head: 65 feet
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Temperature of medium = 36°F to 230°F (2°C to 110°C)
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Ambient temperature range: 32°F to 104°F (0°C to 40°C)
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Max Operating Pressure = 175PSI (12bar)
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UL listed
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Minimum static inlet pressure at pump suction to avoid cavitation and mechanical seal
damage (NPSHR)
Fluid Temperatures
PSI / bar
112°F (50°C)
7.3 / 0.5
176°F (80°C)
11.6 / 0.8
230°F (110°C)
20.3 / 1.4
