Hot Water Recirculation Pumps.
Tim Pehl
Outside Sales Rep For Dawson
Company.
Topics
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Scenario.
How a recirculation Pump works.
History of recirculation Pumps.
Latest technology.
2
Scenario.
We get up in the morning and we turn on the
hot water to take a shower.
we put our hand into the stream of water to
check the temperature, and it is cold.
We may wait for a full 60 seconds, or longer,
before we can step in and take our
shower.
Why??
We don’t have a recirculation pump!
3
Scenario.
Dead end piping
Traditional non-recirculated system
Traditional non-recirculated system
Normal Hot Water Operation:
Normal Hot Water Operation:
Last hot water use at night time around
11:00pm
Following morning at 7:00am
Water heater output:
Water heater output:
130°F Hot Water
None – Existing water cools to 60°F
DHW Pipe run:
WH
100 feet ¾” Copper Pipe
WH
DHW Pipe run:
100 feet ¾” Copper Pipe
Scenario.
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Residence is three bedroom with four occupants and two baths.
Water heater is approximately 60’ from master bedroom
Hot water supply line from water heater is un-insulated ¾” copper
pipe
Assume the following volume of hot water wasted per day:
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Master lavatory
1.5 gal fixture
2.625 gal wasted/day
Second bathroom lavatory
1.5 gal fixture
7.5 gal wasted/day
Master Shower
2.5 gal fixture
15 gal wasted/day
Second bathroom shower
2.5 gal fixture
2.625 gal wasted/day
Kitchen Sink
2.5 gal fixture
12.5 gal wasted/day
Water consumption is based on the system operating 350 days per year
Total water wasted in a year is 14,087 gallons based on total water
wasted of 40.25 gallons per day
Scenario.
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How Much Water is 14,000 Gallons?
Scenario.
Return line added with Circulator.
System with hot water recirculation
Normal Hot Water Operation:
Following morning at 7:00am
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60psi
WH
How a pump works
SYSTEM CURVE
Recirculation pump with ECM technology
Standard Induction Motors
ECM ( Electrically Commutated Motor) Technology
Induction Vs Permanent Magnet
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Induction Motor
No magnet on rotor
• Stator coils create magnetic
field which induces current
into rotor
• The rotor currents interact
with the rotating magnetic
field which causes a
rotational motion on the
rotor.
• Because the magnetic and
electric fields are out of
phase (slip), there are
greater current
requirements and current
losses.
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Permanent Magnet Motor
Permanent magnet on rotor
Eliminates the requirement for input
power to magnetize rotor
Stator coils generate a rotating field
to induce the permanent magnet to
rotate
Motor is microprocessor controlled
to keep the stator current in phase
with the magnets of the rotor.
The lower current requirement
and no “slip” result in greater
efficiency.
Comparison: Spherical Motor vs. Canned Motor
Key Advantages
• Simplicity – just one high precision part
• No shaft, no bearing bushings
• Self-aligning rotor
• Long term quiet and trouble free operation
• No start-up problems
SYSTEM CURVE
System Curve
S
y
s
t
e
m
C
u
r
v
e
System
Curve
Recirculation pump with ECM technology
Variable speed option can reduce smallest pump energy consumption even further..
10
System
Curve
10
Head (FT)
e3-4
8
5
4
2
2
Flow (GPM)
Duty Point 5 Watts
System
Curve
6
1
2
3
4
5
6
Flow (GPM)
Duty Point 40 Watts
88% LESS ENERGY CONSUMPTION
One Switch - Two Options
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Every ECM circulator has a switch installed- you
have the choice
A.Variable Speed Control
B.Variable Temperature Control(68 to 158 Deg.F.)
Variable
Speed
Control
NEED
PIC
Variable
Temperature
Control
Options
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Most pumps come standard with constant speed.
Power cords are sometimes optional.
Variable speed.
Temperature control.
Time clocks
What if I don’t have a return line?
Autocirc 14 watts
But I have a Tankless water heater
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Sizing a pump for Tankless water heaters is the
same as a tank type. However, a larger pump
will be needed as the Tankless units have a heat
exchanger inside that produces a higher pressure
drop.
Questions?