Hot Water recirculation

1. Hot Water Recirculation Pumps.
Tim Pehl
Outside Sales Rep For Dawson
Company.

2. 2
Topics
 Scenario.
 How a recirculation Pump works.
 History of recirculation Pumps.
 Latest technology.

3. 3
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!

4. Scenario.
Dead end piping
WH
Normal Hot Water Operation:
Last hot water use at night time around
11:00pm
Normal Hot Water Operation:
Last hot water use at night time around
11:00pm
Water heater output:
130°F Hot Water
DHW Pipe run:
100 feet ¾” Copper Pipe
WH
Normal Hot Water Operation:
Following morning at 7:00am
Water heater output:
None – Existing water cools to 60°F
DHW Pipe run:
100 feet ¾” Copper Pipe
Traditional non-recirculated system Traditional non-recirculated system

5. 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

6. Scenario.
 How Much Water is 14,000 Gallons?

7. Scenario.
Return line added with Circulator.
 60psi
WH
Normal Hot Water Operation:
Following morning at 7:00am
System with hot water recirculation

8. How a pump works

9. SYSTEM CURVE

10. Recirculation pump with ECM technology

11. Standard Induction Motors

12. ECM ( Electrically Commutated Motor) Technology

13. 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.

14. 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

15. SYSTEM CURVE

16. System Curve
S
y
s
t
e
m
C
u
r
v
e
System
Curve

17. Recirculation pump with ECM technology
Duty Point 5 Watts Duty Point 40 Watts
Flow (GPM)
1 2 3 4 5 6
2
4
6
8
10
Flow (GPM)
Head
(FT)
System
Curve
System
Curve
88% LESS ENERGY CONSUMPTION
e3-4
Variable speed option can reduce smallest pump energy consumption even further..
10
5
2

18. 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
Temperature
Control
Variable
Speed
Control
NEED
PIC

19. Options
 Most pumps come standard with constant speed.
 Power cords are sometimes optional.
 Variable speed.
 Temperature control.
 Time clocks

20. What if I don’t have a return line?
Autocirc 14 watts

21. 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.

22. Questions?