Dawson Company
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Transcript Dawson Company
Hot Water Recirculation Pumps.
Tim Pehl
Outside Sales Rep For Dawson
Company.
Topics
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.
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:
•
•
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.
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
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
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.
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
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
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
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?