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HVACR216 - Hydronics
Circulator pumps
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Circulator Pumps
• The circulator pump is the heart of the
Hydronic system
• Although smaller and less expensive then
the heat source, the pump is just as vital to
a heating systems performance.
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Circulator Pumps
• Pumps come in a wide variety of designs, sizes and
performance ranges.
• In a closed loop, fluid filled hydronic system, the
function of the pump is to circulate the fluid
throughout the piping.
– In a closed loop system the pump is made out
of cast iron. (heating circuits)
– In an open loop system the pump material is
bronze. (potable water circuits)
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Circulator Pumps
Taco 006 bronze pump
Taco 007 cast iron pump
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Circulator Pumps
• The type of pump used in hydronic systems
is known as a centrifugal pump.
• Most smaller circulator pumps utilize a
permanent split capacitor (PSC) motor
attached to an impeller.
• As the impeller rotates, it adds mechanical
energy (Head) to the fluid.
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Circulator Pumps
• As the impeller rotates, fluid within the center
opening (the eye) of the impeller is rapidly
accelerated through the passageways formed
by the impeller vanes
• As the fluid exits the impeller, the mechanical
energy converts to a pressure increase.
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Circulator Pumps
• Most impellers are constructed of stainless
steel, bronze or synthetic materials to
prevent corrosion.
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Circulator Pumps
• Impeller
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Circulator Pumps
• A circulator pump does increase pressure at
its outlet.
• A circulator pump does not create a suction
at its inlet.
• All circulators require the entering water to be
pushed into the inlet port of the pump by the
system pressure upstream.
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Circulator Pumps
• The chamber surrounding the impeller is
called the Volute.
• Circulator pumps can be built with different
shaped volutes.
• The volutes shape determines how the
pump will be installed on the system piping.
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Circulator Pumps
• Volute
Motor
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Circulator Pumps
• Inline type circulators have their inlet and
discharge ports along a common centerline.
• The inline type circulator is by far the most
common type used in residential and light
commercial hydronic systems.
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Circulator Pumps
• Inline Circulator
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Circulator Pumps
• By modifying the shape of the volute, a
design called an end suction pump is
created.
• End suction pumps create a 90 degree turn
in the system piping.
• End suction pumps are usually floor
mounted and are more common in larger
hydronic systems.
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Circulator Pumps
• End suction pump
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Circulator Pumps
• End suction volute
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Circulator Pumps
• The modern, smaller circulator pump is
known as a wet-rotor circulator.
• The rotor, shaft and impeller are combined
in a single assembly and housed in a
chamber filled with the system fluid.
• The motor is cooled and lubricated by the
systems fluid.
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Circulator Pumps
• Wet rotor circulator
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Circulator Pumps
• The wet rotor circulator does not require
oiling.
• There is no leakage from worn seals.
• They are small in size which makes it easy to
locate and support.
• They are relatively inexpensive.
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Circulator Pumps
• Another common pump design is the three
piece circulator.
• It consists of pump body (Volute), coupling
assembly and a motor assembly.
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Circulator Pumps
• Three piece circulator
Pump body Coupling assembly
Motor
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Circulator Pumps
• Unlike wet rotor circulators, the motor of a
three piece circulator is totally separate
from the wetted portion.
• This allows the motor or coupling to be
serviced or replaced without the need to
open the system piping.
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Circulator Pumps
• Most three piece circulators utilize a split phase
motor.
• The design of the coupling varies among
manufacturer's.
• A common design employs a spring assembly
that absorbs vibration or high torque between
the two shafts as the motor starts.
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Circulator Pumps
• Some of the disadvantages of using the three
piece circulator are:
– They are heavy and large
– Must be oiled periodically
– Noisier
– Potential maintenance of seals and coupling
– Motors are not as energy efficient
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Circulator Pumps
• Overview of circulators
– All circulators have an arrow showing the
direction of flow stamped on the Volute.
– Most circulators should be installed with
the shafts mounted in the horizontal
position.
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Circulator Pumps
– The weight of the circulator should not be
supported by the system piping unless it is
relatively light and the piping itself is well
supported.
– All circulators should be installed with some
sort of isolation valves to permit servicing.
Circulator Pumps
– Always install the circulator so that its
inlet is close to the connection point of
the systems expansion tank.
– Always install circulators to pump away
from the point of no pressure change.
• The point of no pressure change is the
area near the expansion tank
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Circulator Pumps
– If mounting several circulators on one
common header, support the added
weight using rod, clamps, chain, etc.
– If utilizing multiple circulators, you must
also install check valves in each circuit.
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Circulator Pumps
– Circulators are available in multiple
speeds.
– Some circulators are available with
internal flow checks.
– Most currently produced wet rotor
circulators are rated for continuous
operation at fluid temperatures up to 230
degrees Fahrenheit.
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Circulator Pumps
• The 3 piece type circulator typically has
maintenance issues that need to be
addressed.
• The seals will need to be replaced if leakage
occurs.
• The bearings needs to be oiled annually.