Hot Water Temperature Maintenance

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Hot Water Temperature Maintenance
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HWAT Simply Keeps Hot Water Hot
Heat lost through the insulation
Water provided from Water Heater
Air at 70F
Pipe
Insulation
HWAT heating cable
Heat provided by HWAT heating cable
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Movement of Water in HWAT System
Water heater is set to the desired maintain
temperature
Water in untraced section cools to ambient 70F
HWAT-Y2
HWAT maintains the hot water by replacing the
heat lost through the thermal insulation
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HWAT or Recirculation?
Recirculation
HWAT
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Typical Recirculation System
Return Piping
Balancing Valves
Water Heater
Recirculation Pump
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Typical HWAT System
HWAT Heating Cable
Water Heater
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HWAT History

• System developed by Raychem in 1976
• Installed in more than 300,000 buildings
• More than 2,500,000 feet of HWAT cable installed
  every year
• More successful in Europe due to a greater focus
  on water and energy conservation which is only a
  recent trend in North America

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Advantages of HWAT

• Easy to design
• Low installed and operating costs
• No flow-balancing issues
• Compatible with low-flow fixtures
• Easy to provide instant hot water to the point of
  use
• Water conservation/Reduced time to tap

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Time to Tap Water Conservation

• Water in 10 of ½ pipe 0.1 gallons
• Water in 40 of ¾ pipe 0.9 gallons
• Water between fixture and recirculation loop
  1.0 gallons
• If this fixture is used 5 times per day, the
  annual water waste would be 1,825 gallons per
  year!

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Disadvantages of HWAT

• Perceived as new technology
• May not be economical for certain building
  configurations
• Me-Too competitive systems fail to perform as
  expected on an HWAT design

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Typical HWAT Building
Why is this a good HWAT application?
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Typical HWAT Building

• No horizontal return piping
• No booster pumps or booster heaters
• No balancing
• Reduced supply piping

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Typical HWAT Building
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HWAT Performance Issues
Sections without insulation or power
Hot water heater continues to maintain the water
at 115F.
HWAT-G2
Heated water moves into pipes.
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HWAT Performance Issues
Cold to Hot water by-pass
Cold to hot cross connection at fixture.
Hot water heater continues to maintain the water
at 115F.
HWAT-G2
Heated water moves into pipes.
Heated water mixes with by-pass water
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Mixing Valves
Main Mixing Valves Main mixing valves are usually
flow dependent. There should be a low flow and a
high flow valve. If theres only one, be sure it
can function in a low/no flow situation.
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Typical Maintain Temperatures

• Temperature Application
• 105F Hospitals, Nursing Homes
• 115F Schools, Prisons
• 125F Hotels, Apartments, Offices
• 140F Kitchens, Laundries
• 125F Residential

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HWAT Heating Cables

• B2 - 105F
• G2 - 115F
• Y2 - 125F
• R2 - 140F

• Y2 or R2
• R2

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HWAT Selling Tools
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HotCAP

• Hot Water Cost Analysis Program
• Introduced in March, 2004
• Integrates HWAT-ECO
• Updated material costs
• Updated labor, electricity and fuel rates
• Download from web

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HWAT-ECO Electronic Controller

• Flexible temperature control
• Insulation schedule
• Energy savings
• 9 pre-defined programs
• Heat-up cycle
• Alarm events
• Water heater sensor
• BMS interface
• Master/slave function
• Power correction factor

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Flexible Temperature Control

• Maintain Temp
• HWAT-Y2 105F 125F
• HWAT-R2 105F 140F
• Depending on the ambient temperature and
  voltage

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Fiberglass Insulation Schedule

• Copper pipe size (in) IPS insulation size
  (in) Insulation thickness (in)
• ½ ¾ ½
• ¾ 1 1
• 1 1¼ 1
• 1¼ 1½ 1½
• 1½ 1½ 1½
• 2 2 2 2½ 2½
  2½
• 3 3 3
• Insulation thickness matches pipe diameter for
  equal heat loss
• Pipes 1¼ and smaller require oversized
  insulation to allow room for the heating cable
• For pipes 3 and larger, 1/3 the thickness of
  insulation can be used with 2 runs of heating
  cable

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HWAT-ECO Limits the Power Output

• 400 seconds duty cycle
• On time depends on the desired maintain
  temperature
• 4 Modes Off, Economy, Maintain Heat-Up Cycle

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9 Pre-defined Programs
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Programming Options

• (48) ½ hour time blocks
• Additional energy savings during Off and
  Economy

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Heat-Up Cycle and Cool Down

• Raise the water temperature of stagnant pipes
• Determine the amount of time required to reach a
  desired maintain temperature
• Program the number of hours required
• Allow time to cool down before hot water usage

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Alarm Events

• Water heater temperature too low (next slide)
• Water heater temperature too high (Y2 gt 150F, R2
  gt 185F)
• Loss of power relay closes
• Loss of power for more than 8 hours clock reset
• Internal controller temperature too high (gt
  185F)
• Master/slave error

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Water Heater Sensor (Optional)

• Ensures maintain temp does not exceed the water
  heater temp
• Controller stores highest water temperature
  measured over last 24 hours
• Delta between supplied water temperature and the
  maintain temperature setpoint selected between
  9F and 27F
• Connected to single or master controller only
• Sensor cable can be extended up to 328 feet

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BMS Interface

• BMS input is 0-10 Vdc
• BMS controls the temperature setpoint
• If water heater sensor is installed, it overrules
  the BMS temperature setting if necessary
• Loss of power alarms BMS

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Master/Slave Function

• Control up to eight additional controllers
• Total maximum length of cable between all
  controllers is 328 ft
• RS-485 connection
• Water heater sensor connects only to master
  controller
• Controllers on the same phase (max 3 controllers)
  have a delayed On and Off

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Multiple Circuits with Single Controller

• For controlling multiple circuits with the same
  parameters (i.e. voltage, maintain temp, ambient
  temp, economy temp), connect the heating cable
  output relay to an external contactor coil

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Power Correction Factor

• Fine tuning of system
• Increase or decrease the actual pipe maintain
  temperature
• 0.6 1.4 percent of duty cycle

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Legionella What is it?

• Received its name from a 1976 break out at an
  American Legion Convention in Philadelphia
• Bacteria common to warm water environments
• Cause of Legionellosis any illness caused by
  the bacteria (Legionnaires disease and Pontiac
  Fever most common)
• Attacks the respiratory system

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Legionella www.awt.org

• Legionella 2003 an Update and Statement by the
  Association of Water Technologies (AWT)
• raising water temperature to 122F a 90 kill
  of legionella in 2 hours, 140F a 90 kill of
  legionella in 2 minutes and 158F a 100 rapid
  kill of legionella.

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Hot Water Temperature Maintenance

• Questions?