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5.  When installing multiple water heaters in the same gas supply 

system it is recommended that individual positive lock-up gas 

pressure regulators be installed at each unit.

power supply

The water heaters covered in this manual require a 120 VAC, 

1Ø (single phase), 60hz, 15 amp power supply and must also 

be electrically grounded in accordance with local codes or, in the 

absence of local codes, with the national Electrical Code, AnSI/

nFPA 70 or the Canadian Electrical Code, CSA C22.1.

water temperature control and mixing ValVes

Water temperature over 125°F (52°C)

can cause severe burns instantly

resulting in severe injury or death.
Children, the elderly and the

physically or mentally disabled are at

highest risk for scald injury.
Feel water before bathing or

showering.
Temperature limiting devices such as

mixing valves must be installed

when required by codes and to

ensure safe temperatures at fixtures.

Water  heated  to  a  temperature  which  will  satisfy  clothes 

washing, dish washing, and other sanitizing needs can scald 

and  cause  permanent  injury  upon  contact.  Short  repeated 

heating  cycles  caused  by  small  hot  water  uses  can  cause 

temperatures at the point of use to exceed the water heater’s 

temperature setting by up to 20°F (11°C).
some people are more likely to be permanently injured by 

hot water than others. These include the elderly, children, the 

infirm and the physically/mentally disabled. Table 5 shows the 

approximate time-to-burn relationship for normal adult skin. If 

anyone using hot water provided by the water heater being 

installed fits into one of these groups or if there is a local code 

or state law requiring a certain water temperature at the point 

of use, then special precautions must be taken.
In addition to using the lowest possible temperature setting 

that  satisfies  the  demand  of  the  application  a  Mixing  Valve 

should be installed at the water heater (see Figure 10) or at 

the hot water taps to further reduce system water temperature.
Mixing  valves  are  available  at  plumbing  supply  stores. 

Consult a Qualified Installer or Service Agency. Follow mixing 

valve manufacturer’s instructions for installation of the valves.

taBle 5.

water temperature 

°f (°c)

time for 1st degree Burn

(Less Severe Burns)

time for permanent Burns

2nd & 3rd degree

(Most Severe Burns)

110 (43)

(normal shower temp.)

116 (47)

(pain threshold)

116 (47)

35 minutes

45 minutes

122 (50)

1 minute

5 minutes

131 (55)

5 seconds

25 seconds

140 (60)

2 seconds

5 seconds

149 (65)

1 second

2 seconds

154 (68)

instantaneous

1 second

(u.S. government Memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15, 1978)

gas supply systems

Low pressure building gas supply systems are defined as those 

systems that cannot under any circumstances exceed 14” W.C. 

(3.48 kPa) (1/2 PSI gauge). These systems do not require pressure 

regulation.  Measurements  should  be  taken  to  insure  that  gas 

pressures are stable and fall within requirements stated on the water 

heater rating plate. Readings should be taken with all gas burning 

equipment off (static pressure) and with all gas burning equipment 

running at maximum rate (dynamic pressure). gas supply pressure 

must be stable within 1.5” W.C. (0.37 kPa) from static to dynamic 

pressure to provide good performance. Pressure drops that exceed 

1.5” W.C. (0.37 kPa) may cause rough starting, noisy combustion 

or nuisance outages. Increases or spikes in static pressure during 

off cycles may cause failure to ignite or in severe cases damage to 

appliance gas valves. If your low pressure system does nOT meet 

these requirements, the installer is responsible for  corrections.
High Pressure building supply systems use pressures that exceed 

14” W.C. (3.48 kPa) (1/2 PSI gauge). These systems must use field 

supplied regulators to lower the gas pressure to less than 14” W.C. 

(3.48 kPa) (1/2 PSI gauge). Appliances require gas regulators that 

are properly sized for the water heater input and deliver the rating 

plate  specified  pressures.  gas  supply  systems  where  pressure 

exceeds 5 PSI (34.5 kPa)  often require multiple regulators to achieve 

desired pressures. Systems in excess of 5 PSI (34.5 kPa) building 

pressure should be designed by gas delivery professionals for best 

performance. Water heaters connected to gas supply systems that 

exceed 14” W.C. (3.48 kPa) (1/2 PSI gauge) at any time must be 

equipped with a gas supply regulator.

gas pressure reQuirements

Natural gas models require a minimum gas supply pressure of 

5.2” W.C. (1.30 kPa). Propane gas models require a minimum 

gas  supply  pressure  of  9.0"  W.C.  (2.24  kPa).  The  minimum 

supply  pressure  is  measured  while  gas  is  flowing  (dynamic 

pressure). The supply pressure (dynamic) should never fall below 

the  specified  minimum  supply  pressure.  The  supply  pressure 

should be measured with all gas fired appliances connected to 

the common main firing at full capacity. If the supply pressure 

drops more than 1.5” W.C. (0.37 kPa) as gas begins to flow to 

the water heater then the supply gas system including the gas 

line  and/or  the  gas  regulator  may  be  restricted  or  undersized. 

See Supply gas Regulator section and gas Piping section of this 

manual. The gas valve on all models has a maximum gas supply 

pressure  limit  of  14"  W.C.  (3.48  kPa)  The  maximum  supply 

pressure is measured while gas is not flowing (static pressure).

supply gas regulator

The maximum allowable gas supply pressure for this water 

heater is 14.0 inches W.C. (3.48 kPa). Install a positive lock-up 

gas pressure regulator in the gas supply line if inlet gas pressure 

can exceed 14.0 inches W.C. (3.48 kPa) at any time. Regulators 

must be sized/used according to manufacturer's specifications.
If a positive lock-up regulator is required follow these instructions:
1.  Positive  lock-up  gas  pressure  regulators  must  be  rated  at  or 

above the input Btu/hr rating of the water heater they supply.

2.  Supply gas regulators shall have inlet and outlet connections 

not less than the minimum supply gas line size for the water 

heater they supply. See Table 7 on page 22

3.  Positive lock-up gas pressure regulator(s) should be installed no 

closer than 3 feet (1 meter) and no farther than 8 feet (2.4 meters) 

of equivalent length from the water heater’s inlet gas connection.

4.  After  installing  the  positive  lock-up  gas  pressure  regulator(s) 

an initial nominal supply pressure setting of 7.0” W.C. while the 

water  heater  is  operating  is  recommended  and  will  generally 

provide good water heater operation. Some addition adjustment 

maybe required later to maintain a steady gas supply pressure.

installation reQuirements

Summary of Contents for BTC 151

Page 1: ...15 Low Lead Content Thank you for buying this energy efficient water heater We appreciate your confidence in our products WARNING If the information in these instructions is not followed exactly a fir...

Page 2: ...Troubleshooting 33 Water Piping Diagrams 34 Manifold Kits 49 Limited Warranty 50 Notes 51 2 Table Of Contents Safe Installation Use and Service 3 APPROVALS 3 General Safety Information 4 Precautions...

Page 3: ...ate of California to cause cancer birth defects or other reproductive harm and requires businesses to warn of potential exposure to such substances This product contains a chemical known to the State...

Page 4: ...ment trap in accordance with NFPA 54 Use joint compound or Teflon tape compatible with propane gas Fire and Explosion Hazard Turn off gas lines during installation Contact a qualified installer or ser...

Page 5: ...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...

Page 6: ...water heater will not operate properly It could cause DEATH SERIOUS BODILY INJURY AND OR PROPERTY DAMAGE This manual contains instructions for the installation operation and maintenance of the gas fir...

Page 7: ...manual resetting of high limit control preceded by higher than usual water temperature is evidence of high limit switch operation The following is a possible reason for high limit switch operation A m...

Page 8: ...60 F 33 C 70 F 39 C 80 F 44 C 90 F 50 C 100 F 56 C 110 F 61 C 120 F 67 C 130 F 72 C 140 F 78 C BTR C 151 150 000 NAT 32 Gal 80 GPH 727 485 364 291 242 208 182 162 145 132 121 112 104 44 kW Hr NAT 121...

Page 9: ...CONSTRUCTION MODEL A RIGHT SIDE B LEFT SIDE C BACK D CEILING BTR C 151 201 0 0 0 12 30 5 cm Locating the Water Heater Property Damage Hazard All water heaters eventually leak Do not install without ad...

Page 10: ...ion to come within 9 inches 23 cm of floor within 2 inches 5 cm of bottom cover to prevent blockage of combustion air flow to the burners DO NOT cover the instruction manual Keep it on the side of the...

Page 11: ...rating label under any circumstances Note Due to the input rating reduction at high altitudes the output rating of the appliance is also reduced and should be compensated for in the sizing of the equi...

Page 12: ...37 kPa from static to dynamic pressure to provide good performance Pressure drops that exceed 1 5 W C 0 37 kPa may cause rough starting noisy combustion or nuisance outages Increases or spikes in sta...

Page 13: ...al expansion tank installed See Water Line Connections on page 19 and the Water Piping Diagrams beginning on page 34 Temperature Pressure Relief Valve Explosion Hazard Temperature Pressure Relief Valv...

Page 14: ...ems and Thermal Expansion on page 13 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 back cove...

Page 15: ...which the appliances are installed through openings not furnished with doors are considered a part of the unconfined space Makeup air requirements for the operation of exhaust fans kitchen ventilatio...

Page 16: ...uare inches 645 cm2 Outdoor Air Through One Opening Figure 14 Alternatively a single permanent opening commencing within 12 inches 300 mm of the top of the enclosure shall be provided See Figure 14 Th...

Page 17: ...aggregate input rating of all appliances installed in the enclosure Each opening shall not be less than 100 square inches 645 cm2 Outdoor Air Through Two Vertical Ducts The illustrations shown in thi...

Page 18: ...Number of Heaters Combined Input btu hr Manifold and Common Vent Diameter Inches 2 300 000 8 7 7 7 7 6 6 6 3 450 000 9 9 9 8 8 7 7 7 4 600 000 10 10 10 9 9 8 8 7 MODEL 201 Input 182 000 and 199 900 b...

Page 19: ...nections The water piping installation must conform to these instructions and to all local code authority having jurisdiction Good practice requires that all heavy piping be supported Read and observe...

Page 20: ...eat to this fitting Do not allow pipe dope to contact the plastic tube during installation Tube Inlet Installation Figure 18 TEMPERATURE SETTING SHOULD NOT EXCEED SAFE USE TEMPERATURE AT FIXTURES SEE...

Page 21: ...LECTRICAL GROUND IS REQUIRED TO REDUCE RISK OF ELECTRICAL SHOCK OR POSSIBLE ELECTROCUTION If any of the original wire as supplied with the appliance must be replaced use only type 105 C thermoplastic...

Page 22: ...ne be sure that all gas pipe is clean on the inside To trap any dirt or foreign material in the gas supply line a sediment trap must be incorporated in the piping see Figure 20 The sedimenttrapmustber...

Page 23: ...Gas Line Leak Testing on page 22 and repair any leaks found Start Up Initial Start Up Required Test Equipment U tube manometer pressure gauge or digital manometer Recommended range 20 W C 5 kPa Note...

Page 24: ...ressure to each water heater within the minimum and maximum supply pressure requirements listed in Table 3 on page 8 with all gas fired appliances connected to a common gas main firing at full capacit...

Page 25: ...to the Silicon Nitride Igniter 11 From the time the Silicon Nitride Igniter s power is shut off the Ignition Control Board waits 3 more seconds to monitor the Flame Sensor 12 If the Flame Sensor does...

Page 26: ...26 Sequence of Operation Flow Chart Description of this flow chart can be found in the SEQUENCE OF OPERATION section found on page 25 Figure 23...

Page 27: ...er through the heater where the thermostat senses the drop in water temperature and activates main burner operation of the appliance If the storage tank temperature control is out of calibration repla...

Page 28: ...heater storage tank be drained and flushed every 6 months to reduce sediment buildup The water heater should be drained if being shut down during freezing temperatures See Features And Components in...

Page 29: ...ve handling instructions on label of product being used Tank Cleanout Procedure The following practices will ensure longer life and enable the unit to operate at its designed efficiency 1 Once a month...

Page 30: ...flush with cool water If irritation persists get medical attention If swallowed give 1 or 2 glasses of water or milk and call physician Get immediate medical attention for eyes Keep out of reach of ch...

Page 31: ...e thermostat calling for heat It is possible that the high limit E C O has functioned to shut off the appliance See High Limit page 7 High Limit Switch for reset procedure Contact your service agent i...

Page 32: ...s bacteria is nontoxic to humans d An excess of active hydrogen in the tank This is caused by the corrosion protective action of the anode Hot water odor may be eliminated or reduced in some water hea...

Page 33: ...call a qualified service agency Delime heater Ticking or metallic sounds Expansion and contraction normal Pounding or water hammer Air chambers in piping have become waterlogged Thermal expansion tank...

Page 34: ...s operating thermostat should be set 5 degrees F higher than the Tank Temperature Control MULTI FLUE 1 UNIT WITH VERTICAL STORAGE TANK LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CI...

Page 35: ...ostat should be set 5 degrees F higher than the Tank Temperature Control MULTI FLUE 1 UNIT WITH HORIZONTAL STORAGE TANK LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP...

Page 36: ...and the storage tank s MULTI FLUE 1 UNIT WITH MIXING VALVE TWO TEMPERATURE LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL PORT BAL...

Page 37: ...mp between the water heater s and the storage tank s MULTI FLUE 2 UNITS LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL PORT BALL VA...

Page 38: ...tat should be set 5 degrees F higher than the Tank Temperature Control MULTI FLUE 2 UNITS WITH VERTICAL STORAGE TANK LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TAN...

Page 39: ...tat should be set 5 degrees F higher than the Tank Temperature Control MULTI FLUE 2 UNITS WITH VERTICAL STORAGE TANK LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TAN...

Page 40: ...t should be set 5 degrees F higher than the Tank Temperature Control MULTI FLUE 2 UNITS WITH HORIZONTAL STORAGE TANK LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TAN...

Page 41: ...EMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL PORT BALL VALVE TEMPERATURE GAGE WATER FLOW SWITCH CHECK VALVE WARNING THIS DRAWING SHOWS SU...

Page 42: ...VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL PORT BALL VALVE TEMPERATURE GAGE WATER FLOW SWITCH CHECK VALVE WARNING THIS DRAWING SHOWS SUGGESTED PIPING CONFIGURATION AND OTHER DEVICES C...

Page 43: ...LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL PORT BALL VALVE TEMPERATURE GAGE WATER FLOW SWITCH CHECK VALVE WARNING THIS DRAWING...

Page 44: ...than the Tank Temperature Control MULTI FLUE 3 UNITS WITH VERTICAL STORAGE TANK LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL PORT...

Page 45: ...r than the Tank Temperature Control MULTI FLUE 3 UNITS WITH HORIZONTAL STORAGE TANK LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL...

Page 46: ...RE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL PORT BALL VALVE TEMPERATURE GAGE WATER FLOW SWITCH CHECK VALVE WARNING THIS DRAWING SHOWS SUGGESTED...

Page 47: ...emperature Control MULTI FLUE 4 UNITS WITH VERTICAL STORAGE TANK LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL PORT BALL VALVE TEM...

Page 48: ...Temperature Control MULTI FLUE 4 UNITS WITH HORIZONTAL STORAGE TANK LEGEND TEMPERATURE PRESSURE RELIEF VALVE PRESSURE RELIEF VALVE CIRCULATING PUMP TANK TEMPERATURE CONTROL DRAIN FULL PORT BALL VALVE...

Page 49: ...49 Manifold Kits MANIFOLD KITS TWO UNIT MANIFOLD KIT PART NO 9003426205 THREE UNIT MANIFOLD KIT PART NO 9003427205 FOUR UNIT MANIFOLD KIT PART NO 9003428205 MODEL DIMENSIONS A 151 201 45 0...

Page 50: ...also installed at the heater s and operational at all times The relief valve installed on the heater is not an acceptable method 4 SERVICE AND REPAIR EXPENSES s t s o c r e h t o l l a r o f e l b i s...

Page 51: ...51 Notes...

Page 52: ...www hotwater com 500 Tennessee Waltz Parkway Ashland City TN 37015 Tech Support 800 527 1953 Parts 800 433 2545 Copyright 2012 A O Smith Water Heater Company All rights reserved...

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