American Water Heater Commercial Light Duty Electric Water Heaters Lowboy Standard and Upright Series User Manual

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Instruction Manual
PRINTED 1215 323289-005
PLACE THESE INSTRUCTIONS ADJACENT TO HEATER AND NOTIFY OWNER TO KEEP FOR FUTURE REFERENCE.
COMMERCIAL LIGHT DUTY ELECTRIC WATER HEATERS 
Thank you for buying this energy efficient water heater. 
We appreciate your confidence in our products.
Lowboy 6/10/15/20 Models Series 102
Lowboy 30/40/50 Models Series 110
Tall 30/40/50/66/80/120 Models Series 110
INSTALLATION - OPERATION - SERVICE - MAINTENANCE  
						

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SAFE INSTALLATION, USE, AND SERVICE
The proper installation, use and servicing of this water heater is extre\
mely important to your safety and the safety of others.
Many safety-related messages and instructions have been provided in this manual and on your own water heater to warn you and 
others of a potential injury hazard.  Read and obey all safety messages \
and instructions throughout this manual.  It is very important 
that the meaning of each safety message is understood by you and others \
who install, use, or service this water heater.
This is the safety alert symbol.  It is used to alert you 
to potential personal injury hazards.  Obey all safety 
messages that follow this symbol to avoid possible 
injury or death.
IMPORTANT DEFINITIONS
•  	 Qualified	Installer	or	Service	Agency:
  Installation and service of this water heater requires ability equivalent to that of a Qualified Agency (as defined by ANSI below) in the 
field involved. Installation skills such as plumbing, electrical supply are required in addition to electrical testing skills when performing 
service.
•  	 ANSI	Z223.1	2006	Sec.	3.3.83:  
  “Qualified Agency” - “Any individual, firm, corporation or company that either in person or through a representative is engaged in and is 
responsible  for  (a)  the  installation,  testing  or  replacement  of  gas  piping  or  (b)  the  connection,  installation,  testing,  repair  or  servicing  of 
appliances and equipment; that is experienced in such work; that is familiar with all precautions required; and that has complied with all 
the requirements of the authority having jurisdiction.”
 DANGER 
 WARNING 
 CAUTION  
DANGER indicates an imminently hazardous 
situation which, if not avoided, will result in 
death or injury.
WARNING indicates a potentially hazardous 
situation which, if not avoided, could result 
in death or injury.
CAUTION  indicates a potentially hazardous 
situation which, if not avoided, could result 
in minor or moderate injury.
CAUTION used without the safety alert 
symbol indicates a potentially hazardous 
situation which, if not avoided, could result 
in property damage.
CAUTION
All safety messages will generally tell you about the type of hazard, what can happen if you do n\
ot follow the safety message, and 
how to avoid the risk of injury. 
						

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GENERAL SAFETY INFORMATION
When servicing this unit, verify the power to the unit is turned off pri\
or to opening the control cabinet door.
PRECAUTIONS
DO NOT USE THIS WATER HE ATER IF ANY PART HAS BEEN 
E X P O S E D   T O   F LO O D I N G   O R   W AT E R   D A M A G E .  I m m e d i a t e l y  
call  a  qualified  service  technician  to  inspect  the  water  heater 
and  to  replace  any  part  of  the  control  system  which  has  been 
under water.
If  the  unit  is  exposed  to  the  following,  do  not  operate  heater 
until all corrective steps have been made by a qualified ser vice 
technician.
1. External fire.
2.  Damage.
3.  Firing without water.
GROUNDING INSTRUCTIONS
This  water  heater  must  be  grounded  in  accordance  with  the 
National  Electrical  Code  and/or  local  codes.  These  must  be 
followed in all cases.
This water heater must be connected to a grounded metal, permanent 
wiring system; or an equipment grounding conductor must be run with 
the  circuit  conductors  and  connected  to  the  equipment  grounding 
terminal or lead on the water heater.
HYDROGEN GAS (FLAMMABLE)
Hydrogen gas can be produced in a hot water system served by this 
heater that has not been used for a long period of time (generally two 
weeks or more). Hydrogen gas is extremely flammable.
 To reduce the 
risk of injury under these conditions, it is recommended that the hot water 
faucet be opened for several minutes at the kitchen sink before using any 
electrical appliance connected to the hot water system. If hydrogen is present 
there will probably be an unusual sound such as air escaping through the 
pipe as the water begins to flow. 
THERE SHOULD BE NO SMOKING 
OR OPEN FLAME NEAR THE FAUCET AT THE TIME IT IS OPEN.
Improper installation, use and service may
result in property damage.
CAUT ION
 Do not operate water heater if any part has been  
  exposed to flooding or water damage .
 Inspect anode rods regularly, replace  when significantly  depleted.
 Install in location with drainage.
 Fill tank with water before operation.
 Properly sized thermal expansion tanks are required on all
  closed water systems.
Refer to this manual for installation and service. 
						

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Thank You for purchasing this water heater.  Properly installed 
and maintained, it should give you years of trouble free service.
Abbreviations Found In This Instruction Manual:
• ANSI - American National Standards Institute
•  AHRI - Air-Conditioning, Heating and Refrigeration Institute
•  NEC - National Electrical Code
•  NFPA - National Fire Protection Association
•  UL - Underwriters Laboratory
PREPARING FOR THE INSTALLATION
1. Read the “General Safety Information” section of this manual 
first  and  then  the  entire  manual  carefully.  If  you  don’t  follow 
the  safety  rules,  the  water  heater  may  not  operate  safely.  It 
could  cause  DEATH,  SERIOUS  BODILY  INJURY  AND/OR 
PROPERTY DAMAGE.
  This manual contains instructions for the installation, operation, 
and maintenance of the electric water heater.  It also contains 
warnings  throughout  the  manual  that  you  must  read  and  be 
aware of.  All warnings and all instructions are essential to the 
proper operation of the water heater and your safety.   READ 
THE ENTIRE MANUAL BEFORE ATTEMPTING TO INSTALL 
OR OPERATE THE WATER HEATER.  
Be sure to turn off power when working on or near the 
electrical system of the heater. Never touch electrical 
components with wet hands or when standing in water. 
When  replacing  fuses  always  use  the  correct  size  for  the 
circuit, see page 12.
    The  model  and  rating  plates  on  page  6  interprets  certain 
markings into useful information. Both of these references should 
be  used  to  identify  the  heater,  its  components  and  optional 
equipment.
2.   The installation must conform with these instructions and the 
local code authority having jurisdiction and the requirements 
of  the  power  company.  In  the  absence  of  local  codes,  the 
installation must comply with the latest editions of the National 
Electrical Code, NFPA 70 or the Canadian Electrical Code CSA 
C22.1.  The  National  Electrical  Code  may  be  ordered  from: 
National  Fire  Protection  Association,  1  Batterymarch  Park, 
Quincy, MA 02269. The Canadian Electrical Code is available 
from the Canadian Standards Association, 8501 East Pleasant 
Valley Road, Cleveland, OH 44131.
3.   If  after  reading  this  manual  you  have  any  questions  or  do 
not  understand  any  portion  of  the  instructions,  call  the  toll 
free  number  listed  on  the  water  heater  label  for  technical 
assistance. 
  A  sample  rating  plate  is  shown  on  page  6  of  this  manual.  In 
order to expedite your request, please have full model and serial 
number available for the technician.
4.   Carefully  plan  your  intended  placement  of  the  water  heater.  
Examine the location to ensure the water heater complies with 
the “Locating the New Water Heater” section in this manual.
  Installation  and  service  of  this  water  heater  requires  ability 
equivalent to that of a licensed tradesman or qualified agency 
(page  2)  in  the  field  involved.  Plumbing  and  electrical  work 
are required.
TABLE OF CONTENTS
INTRODUCTION
SAFE INSTALLATION, USE, AND SERVICE .......................................2
GENERAL SAFETY INFORMATION  ....................................................3
Precautions  .................................................................................. 3
Hydrogen Gas (Flammable)  ......................................................... 3
INTRODUCTION  .................................................................................. 4
Preparing for the Installation  ........................................................ 4
DIMENSIONS AND CAPACITIES DATA  .............................................. 5
APPROVALS  ........................................................................................ 6
MODEL AND RATING  .......................................................................... 6
FEATURES AND COMPONENTS  ....................................................... 7
LOCATING THE NEW WATER HEATER  .............................................8
Facts to Consider About the Location  .......................................... 8
Clearances  ................................................................................... 8
INSTALLATION  .................................................................................... 9
Required Ability  ............................................................................ 9
General  ......................................................................................... 9
Contaminated Water  ..................................................................... 9
Circulating Pump  .......................................................................... 9
Insulation Blankets  ....................................................................... 9
Temperature-Pressure Relief Valve  ..............................................9
Closed Water Systems  ............................................................... 10Thermal Expansion
 .................................................................... 10
ELECTRICAL  ...................................................................................... 11
General  ........................................................................................ 11
Branch Circuit  .............................................................................. 11
Calculating Amperage/Overcurrent Protection  ............................ 11
WIRING DIAGRAMS  .......................................................................... 12
OPERATION  ....................................................................................... 13
General  ....................................................................................... 13
Filling the Water Heater  .............................................................. 13
Initial Start Up  ............................................................................. 13
Draining the Water Heater  .......................................................... 13
TEMPERATURE REGULATION  ........................................................ 14
Temperature Adjustment  ............................................................ 14
MAINTENANCE  ................................................................................. 15
General  ....................................................................................... 15
Anode Rod Inspection  ................................................................ 15
TROUBLESHOOTING CHECKLIST  .................................................. 16
Checklist  ..................................................................................... 16
Leakage Checkpoints  ................................................................. 17
NOTES  ............................................................................................... 18
Repair Parts List  ......................................................................... 20 
						

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DIMENSIONS AND CAPACITIES DATA
TABLE 2 - RECOVERY CAPACITIES
Element Wattage 
(Upper/Lower) INPUT 
KW  
U.S. Gallons/Hr and Litres/Hr at TEMPERATURE RISE INDICATED
F° 36F° 40F°54F°60F° 72F° 80F° 90F°100F° 108F°120F°126F°
C° 20C° 22.2C° 30C°33.3C° 40C° 44.4C° 50C°55.5C° 60C°66.6C° 70C°
NON-SIMULTANEOUS /1500 GPH17151110 8 8 76 655
1.5 LPH 64584338 32 29 2623 211918
/2000 GPH23201514 11 10 98 876
2.0 LPH 85775751 43 38 3431 282624
/2500 GPH28251917 14 13 1110 988
2.5 LPH107 967164 53 48 4338 363230
3000/3000 GPH34302320 17 15 1412 111010
3.0 LPH12811 5 8577 64 58 5146 433837
4000/4000 GPH45413027 23 20 1816 151413
4.0 LPH17015311 4102 85 77 6861 575149
4500/4500 GPH51463430 25 23 2018 171514
4.5 LPH19217312811 5 96 86 7769 645855
5000/5000 GPH56513834 28 25 2320 191716
5.0 LPH213192142128 107 968577 716461
6000/6000 GPH68614541 34 30 2724 232019
6.0 LPH256230170153 128 11 5 10292857773
SIMULTANEOUS OPERATION 3000/3000 GPH68614541 34 30 2724 232019
6 LPH 256230170153 128 11 5 10292857773
4000/4000 GPH90816054 45 41 3632 302726
8 LPH 341307227205 170 153 136123 11 410297
4500/4500 GPH101 916861 51 46 4136 343029
9 LPH 384345256230 192 173 153138 12811 511 0
5000/5000 GPH11 3101 7568 56 51 4541 383432
10 LPH 426384284256 213 192 170153 142128122
6000/6000 GPH135122 9081 68 61 5449 454139
12 LPH 5 11460341307 256 230 205184 170153146
Recovery capacities at 100° F rise equal: for non-simultaneous element operation = 4.1 gal. x KW of one element; for simultaneous element operation = 4.1 gal. x 2/3 KW of 
both elements. For other rises multiply element KW as previously explained by 410 and divide by temperature rise. Full load current for single phase = total watts : voltage.
 TABLE 1 - ROUGH-IN DIMENSIONS
Models
Dimensions No. of
Elements Tank Capacity
AB CDApprox. 
Shipping Weight 
US Gals. Litresinches mminches mminches mminches mmLbs.Kg.
Lowboy-6 162315 1/2 39414 1/4 36211279 --3515.9
Lowboy-10 110 3818 1/4 4641845712 1/2 318 --5424.5
Lowboy-15 115 5726660 1845720 1/2 521 --5826.3
Lowboy-20 120 7622 1/4 56521 3/4 55215 3/8 391 --7333.1
Lowboy-30 230 11 430 7/8 78421 3/4 55224 1/8 613 8203 10045.4
Lowboy-40 24015132 1/4 8192461025  9/16 6498203 12556.7
Lowboy-50 25018932  1/4  81926 1/2  67325  1/8  6388203 16675.3
Tall-30 230 11 434 1/2 87620 1/2 521 --8203 9844.5
Tall-40 24015145  1/8  114620  1/2  521--8203 11 351.3
Tall-52 25018954 7/8 139420 1/2 521 --8203 13159.4
Tall-66 26625060 3/4 154321 3/4 552 --8203 17679.8
Tall-80 28030359 3/8 1508 24610 --8203 2 1195.7
Tall-120 211 9 45062  7/16 158629 3/8 746 --8203 326147.9
FIGURE 1  
						

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APPROVALS
MODEL AND RATING
Lowboy-30/40/50 & Tall-30/40/52/66/80/120Lowboy-6/10/15/20
All models are listed by 
Underwriters Laboratories Inc. 
						

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FEATURES AND COMPONENTS
FIGURE 2
This page shows typical water heater installations by model designations.
† OVER CURRENT PROTECTION MUST BE SUPPLIED IN WATER HEATER CIRCUIT.  
CONSULT LOCAL CODE OR CURRENT EDITION OF NEC FOR PROPER INSTALLATION.
* INSTALL IN ACCORDANCE WITH ALL LOCAL CODES.
INSTALL VACUUM RELIEF 
IN COLD WATER INLET 
LINE AS REQUIRED BY 
LOCAL CODES.
INSTALL SUITABLE DRAIN PANS UNDER WATER HEATERS 
TO PREVENT DAMAGE DUE TO LEAKAGE. REFER TO WATER 
HEATER LOCATION ON 
PAGE 8.
INSTALL THERMAL 
EXPANSION TANK IF 
THE WATER HEATER 
IS INSTALLED INTO A 
CLOSED WATER SYSTEM. 
SEE CLOSED WATER 
SYSTEMS ON PAGE 10.
Lowboy 30/40/50 & All Tall Water Heaters Lowboy 6/10/15/20 
						

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FACTS TO CONSIDER ABOUT THE LOCATION
The  water  heater  should  be  located  as  close  as  possible 
to/or  centralized  to  the  water  piping  system.  The  water 
heater should be located in an area not subject to freezing 
temperatures.
The water heater should be located in an area where leakage 
of  the  tank  or  connections  will  not  result  in  damage  to  the 
area adjacent to the heater or to lower floors of the structure.
When such locations cannot be avoided, a suitable drain pan 
should be installed under the heater.
Such  pans  should  be  at  least  two  inches  deep,  have  a 
minimum  length  and  width  of  at  least  two  inches  greater 
than  the  diameter  of  the  heater  and  should  be  piped  to  an 
adequate drain.
Drain  pans  suitable  for  these  water  heaters  are  available 
from  your  distributor,  dealer  or  manufacturer  listed  on  the 
rating plate.
LOCATING THE NEW WATER HEATER
Water heater life depends upon water quality, water pressure 
and the environment in which the water heater is installed. 
Water  heaters  are  sometimes  installed  in  locations  where 
leakage may result in property damage, even with the use 
of  a  drain  pan  piped  to  a  drain.  However,  unanticipated 
damage can be reduced or prevented by a leak detector or 
water shut-off device used in conjunction with a piped drain 
p a n .  T h e s e  d e v i c e s  a r e  a v a i l a b l e  f r o m  s o m e  p l u m b i n g  s u p p l y  
wholesalers and retailers, and detect and react to leakage 
in various ways:
• Sensors  mounted  in  the  drain  pan  that  trigger  an  alarm 
or  turn  off  the  incoming  water  to  the  water  heater  when 
leakage is detected.
•  Sensors mounted in the drain pan that turn off the water 
supply to the entire home when water is detected in the 
drain pan.
•  Water supply shut-off devices that activate based on the 
water  pressure  differential  between  the  cold  water  and 
how water pipes connected to the water heater.
•  Devices  that  will  turn  off  the  gas  supply  to  a  gas  water 
heater while at the same time shutting off its water supply.
CLEARANCES
A  minimum  clearance  of  4”  must  be  allowed  for  access  to 
replaceable  parts  such  as  thermostats,  drain  valve  and  relief 
valve.
Adequate  clearance  for  servicing  this  water  heater  should  be 
considered before installation, such as changing the anodes, etc. 
						

							9
INSTALLATION
REQUIRED ABILITY
Installation and service of this water heater requires ability equivalent 
to  that  of  a  qualified  installer  or  service  agency  (page  2)  in  the 
field involved. Plumbing and electrical work is required.
GENERAL
The installation must conform with these instructions and the local 
code authority having jurisdiction and the requirements of the power 
c o m p a n y.  I n  t h e  a b s e n c e  o f  l o c a l  c o d e s ,  t h e  i n s t a l l a t i o n  m u s t  c o m p l y  
with the latest editions of the National Electrical Code, NFPA 70 or 
the Canadian Electrical Code CSA C22.1. The National Electrical 
Code may be ordered from: National Fire Protection Association, 
1 Batterymarch Park, Quincy, MA 02269. The Canadian Electrical 
Code is available from the Canadian Standards Association, 8501 
East Pleasant Valley Road, Cleveland, OH 44131.
Do NOT  test electrical system before heater is filled with water, follow   
the START UP procedure in the OPERATION section of this manual.
The  principal  components  of  the  heater  are  identified  in  the 
Features and Components illustrations on page 7.
MIXING	VALVE	USAGE: 
Water heaters are intended to produce hot water. Water heated to 
a  temperature  which  will  satisfy  space  heating,  clothes  washing, 
dish washing, cleaning and other sanitizing needs can scald and 
permanently injure you upon contact. Some people are more likely 
to be permanently injured by hot water than others. These include 
the  elderly,  children,  the  infirm,  or  physically/developmentally 
disabled.  If  anyone  using  hot  water  in  your  home  fits  into  one  of 
these  groups  or  if  there  is  a  local  code  or  state  law  requiring  a 
maximum  water  temperature  at  the  hot  water  tap,  then  you  must 
take  special  precautions.  In  addition  to  using  the  lowest  possible 
temperature  setting  that  satisfies  your  hot  water  needs,  a  means 
such  as  a  MIXING VALVE   should  be  used  at  the  hot  water  taps 
used by these people or at the water heater.  
MIXING VALVES  f o r  r e d u c i n g  p o i n t  o f  u s e  t e m p e r a t u r e  a r e  a v a i l a b l e  
and are to be set at a maximum of 120 degree F. Consult a qualified 
installer or service agency. Follow all manufacturer’s Instructions 
for installation of these valves. Before changing the factory setting 
on  the  thermostat,  read  the  “Temperature  Regulation”  section  in 
this manual.
CONTAMINATED WATER
This water heater shall not be connected to any heating system(s) 
or component(s) used with a non-potable water heating appliance.
Toxic chemicals, such as those used for boiler treatment shall not 
be introduced into this system.
CIRCULATING PUMP
Field  installed  circulating  pumps  should  be  of  all  bronze 
construction.
INSULATION BLANKETS
Insulation  blankets  are  available  to  the  general  public  for 
external use on electric water heaters but are not necessary with 
this product. The purpose of an insulation blanket is to reduce 
the standby heat loss encountered with storage tank heaters. 
Your water heater meets or exceeds the EPACT and ASHRAE/
IES 90.1 standards with respect to insulation and standby loss 
requirements, making an insulation blanket unnecessary.
Should you choose to apply an insulation blanket to this heater, 
you  should  follow  these  instructions  below.  Failure  to  follow 
these  instructions  can  result  in  fire,  serious  personal  injury, 
or death.
•  Do not cover the temperature  and  pressure  relief  (T & P) valve 
  with an insulation blanket.
•  Do  not  cover  the  instruction  manual.  Keep  it  on  the  side  of  the 
  water heater or nearby for future reference.
•  Do  obtain  new  warning  and  instruction  labels  for  placement  on 
  the blanket directly over the existing labels.
TEMPERATURE-PRESSURE RELIEF VALVE
This  water  heater  is  provided  with  a  properly  rated/sized  and 
certified  combination  temperature  -  pressure  relief  valve  by  the 
manufacturer.  The  valve  is  certified  by  a  nationally  recognized 
testing laboratory that maintains periodic inspection of production 
of  listed  equipment  of  materials  as  meeting  the  requirements  for 
Relief Valves for Hot Water Supply Systems, ANSI Z21.22 • CSA 
4.4, and the code requirements of ASME.
If  replaced,  the  new  valve  must  meet  the  requirements  of  local 
codes, but not less than a combination temperature and pressure 
relief  valve  rated/sized  and  certified  as  indicated  in  the  above  
						

							10
paragraph.  The  new  valve  must  be  marked  with  a  maximum  set 
pressure  not  to  exceed  the  marked  hydrostatic  working  pressure 
of the water heater (15 0 psi = 1,035 kPa) and a discharge c apacit y 
not less than the water heater Btu/hr or KW input rate as shown on 
the water heater’s model rating plate.
For safe operation of the water heater, the temperature and pressure 
relief  valve  must  not  be  removed  from  its  designated  opening  nor 
plugged.  The  temperature-pressure  relief  valve  must  be  installed 
directly into the fitting of the water heater designed for the relief valve. 
Install discharge piping so that any discharge will exit only within 6 
inches (15.2 cm) above, or at any distance below the structural floor. 
Be certain that no contact is made with any live electrical part. The 
discharge  opening  must  not  be  blocked  or  reduced  in  size  under 
any  circumstances.  Excessive  length,  over  30  feet  (9.14  m),  or 
use of more than four elbows can cause restriction and reduce the 
discharge capacity of the valve.
No valve or other obstruction is to be placed between the relief valve 
and the tank. Do not connect discharge piping directly to the drain 
unless a 6” (15.2 cm) air gap is provided. To prevent bodily injury, 
hazard to life, or property damage, the relief valve must be allowed 
to  discharge  water  in  adequate  quantities  should  circumstances 
demand. If the discharge pipe is not connected to a drain or other 
suitable means, the water flow may cause property damage.
The Discharge Pipe:
• Shall not be smaller in size than the outlet pipe size of the valve, or 
have any reducing couplings or other restrictions.
•  Shall not be plugged or blocked.
•  Shall be of material listed for hot water distribution.
•  Shall  be  installed  so  as  to  allow  complete  drainage  of  both  the 
temperature-pressure relief valve and the discharge pipe.
•  Must  terminate  a  maximum  of  six  inches  above  a  floor  drain  or 
external to the building. In cold climates, it is recommended that the 
discharge pipe be terminated at an adequate drain inside the building.
•  Shall  not  have  any  valve  or  other  obstruction  between  the  relief 
valve and the drain.
The temperature-pressure relief valve must be manually operated 
at least once a year. Caution should be taken to ensure that (1) no 
one  is  in  front  of  or  around  the  outlet  of  the  temperature-pressure 
relief  valve  discharge  line,  and  (2)  the  water  manually  discharged 
can  cause  bodily  injury  or  property  damage  because  the  water 
may be extremely hot. If after manually operating the valve, it fails 
to  completely  reset  and  continues  to  release  water,  immediately 
close  the  cold  water  inlet  to  the  water  heater,  follow  the  draining 
instructions  in  this  manual,  and  replace  the  temperature-pressure 
relief valve with a properly rated/sized new one. 
If  you  do  not  understand  these  instructions  or  have  any  questions 
regarding  the  temperature-pressure  relief  valve  call  the  toll  free 
number listed on the water heater label for technical assistance.
CLOSED WATER SYSTEMS
Water supply systems may, because of code requirements or such 
conditions  as  high  line  pressure,  among  others,  have  installed 
devices such as pressure reducing valves, check valves, and back 
flow preventers. Devices such as these cause the water system to 
be a closed system.
THERMAL EXPANSION
As water is heated, it expands (thermal expansion). In a closed system 
the  volume  of  water  will  grow  when  it  is  heated. As  the  volume  of 
water grows there will be a corresponding increase in water pressure 
due to thermal expansion. Thermal expansion can cause premature 
tank failure (leakage). This type of failure is not covered under the 
limited  warranty.  Thermal  expansion  can  also  cause  intermittent 
temperature-pressure relief valve operation: water discharged from 
the valve due to excessive pressure build up. This condition is not 
covered under the limited warranty. The temperature-pressure relief 
valve is not intended for the constant relief of thermal expansion.
A properly sized thermal expansion tank should be installed on all 
closed systems to control the harmful effects of thermal expansion. 
Contact a local plumbing service agency to have a thermal expansion 
tank installed.