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SERVICE HANDBOOK
Residential
Gas and Electric
Water Heaters
M O D E L S C O V E R E D
Residential Gas Water Heaters that
are atmospherically vented and use a
thermocouple as their electrical source.
Residential Electric Water Heaters
having one or two heating elements
and common wiring configurations
for these models.
Part No. TC-049R3 • $15.00 • Printed in the U.S.A. • 0505
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK TABLE OF CONTENTS Page Page Introduction Residential Electric Water Heaters Terms.................................................. 1 Installation………………………………23 Tools ................................................... 2 Standard Illustrations………………….24 Guidelines………………………………25 Residential
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK The information contained in this handbook is designed to answer commonly faced situations encountered in the operation of the Residential Gas and Electric product line and is not meant to be all-inclusive. If you are experiencing a problem not covered in this handbook, please contact the A.O. Smith Technical Information Center at 1-800-527-1953 or your local A.O. Smith Water Products Company representative for further assistanc
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK GENERAL SECTION MISCELLANEOUS INFORMATION Draw efficiency is the quantity of hot water available to the consumer before the outlet water temperature decreases 25 degrees F. A 40 gallon water heater will typically provide 70% (28 gallons) of this “usable” hot water. The burner or elements are allowed to operate during this test. Incoming, cold water mixes the remaining stored water below this 25 degree limitation. Energ
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK One gallon of (120 ° F, 49 °C) water weighs approximately 8.25 pounds. Pounds X .45359 = Kilogram Gallons X 3.7854 = Liters % of Hot = (Mixed Temp. – Cold) divided by (Hot Temp. – Cold) General Section – continued % Thermal Efficiency = (GPH X 8.25 X Temp. Rise X 1.0) divided by BTU/H Input BTU Output = GPH X 8.25 X Temp. Rise X 1.0 GPH = (BTU/H Input X % Eff.) divided by (Temp. Rise X 8.25) One cubic foot of Na
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK INSTALLATION OF RESIDENTIAL GAS WATER HEATER Water Exhaust Vent to Shut Off Outside of Building Valve Union Union Expansion Tank Pressurize to Equal Supply Water Pressure See Manual and Labels For Installation Clearances Temperature And Pressure Relief Typical Model Valve – Do Not and Rating Reuse Old Valve. Plate Location Temperature and pressure relief valve tube piped to within 6” Maximum Gas Supply
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK RESIDENTAL GAS WATER HEATER SERVICE This portion of this manual applies to the Operations and Servicing of Residential Gas, Tank Type, Water Heaters, which are vented atmospherically and use a thermocouple as their electrical source. Construction: See also “General” section of this manual. Control: There is one control on this style of water heater. The control has a main gas regulator, pilot gas regulator
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK Residential Gas – continued Burner: The burner assembly consists of the main burner, main burner orifice, main burner gas supply tube, pilot burner, pilot burner orifice, pilot burner gas supply tube and thermocouple. The pilot burner remains on once it is manually lit. When incoming cold water activates the thermostat, gas flows to the main burner. The pilot flame ignites this gas. The main flame burns until the tank re
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK Residential Gas – continued Temperature: Two metal probes mounted onto the back of the control are immersed inside the tank water. One probe (the shorter) acts as a temperature high limit. If water gets excessively hot, a sensor within the probe opens, interrupts the small electrical current to the gas valve, and gas flow through the control is interrupted. If this safety sensor opens, the entire control must be repla
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK Residential Gas - continued Water Flow: When a hot water faucet is opened, water pressure from the well tank or street main forces cold water into the water heater. This pushes hot water out of the tank. Operation: A residential water heater is not a precise operating appliance. Because the water heater relies on the expansion and contraction of a metal rod, when the thermostat dial is set at an indicated setting (“ σ” is re
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK Residential Gas - continued Service: Air: A gas burning appliance requires the oxygen contained in 12.5 cubic feet of air (at sea level) for every 1000 BTU of heat that is generated. If your water heater has a BTU per hour input of 40,000 BTU then a minimum of 500 (40 times 12.5) cubic feet of clean air must be available. This oxygen will mix with the gas for a clean, blue flame in the burner chamber and provide dilution ai
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK Residential Gas – continued The instruction manual gives guidelines under “Air Requirements” and “Unconfined “ or “Confined Space” sections. If you want to test for a lack of air: 1. Turn on every appliance and fan that exhausts air from the utility room and/or house. Make sure all windows and doors are closed, as well as chimney dampers. 2. Open a hot water faucet so that the main burner will ignite 3. Remove the outer doo
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK Residential Gas - continued Sooting causes: If … … then the burner is clean but the chamber and/or flue check for lack of supply air. are sooted the main burner, chamber and flue are sooted check the following: • incorrect orifice • excessive gas pressure • loose main burner • cross threaded orifice • gas control valve gas seepage • loose gas connection in burner assembly. Electrical Testing This type of water
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK Residential Gas - continued Electrical Testing– continued Millivolt dropout test through copper magnet winding and ECO (Emergency Cut Off) Procedure: Move meter probe to upper ECO solder joint and ground If … … then reading of at least 10 MV is not present replace the control valve. reading of more than 10 MV is present but, replace the control valve. gas to the pilot shuts off each time knob is released Safety drop o
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK Residential Gas – continued Condensation is a mild acid – it will corrode steel Condensation is usually noted when: • water dripping is heard (only) while the main burner is on, • there is “water” around the heater just after the heater has been operating, • there are small, black or red granules on the main burner or top of the heater or • corroded jacket or vent piping is noted. If … … then any of the above cond
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK Residential Gas – continued Exhaust Venting Notes Follow current National Fuel Gas Code requirements for proper installation. “D” – Typically, same or larger diameter as Draft Hood outlet “L” – Horizontal piping slopes upward ¼” per foot from heater to chimney or vertical vent Length of horizontal not more than 75% of “H” “H” – Not less than 5 feet Maximize vertical distance to first elbow
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK IMPLEMENTATION ANTICIPATED CLASS OF PRODUCTS CATEGORY INTRODUCTION INCLUDED IN THIS CATEGORY 30, 40, and 50 gallon atmospheric vented. (Manufactured housing Phase I July 1, 2003 models are excluded.) 30, 40, and 50 gallon power-vented models. (Manufactured housing Phase II January 1, 2005 models are excluded.) Phase III July 1, 2005 All other gas-fired models with inputs of 75,000 BTU or less. This supplement addresses th
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK FLAME ARRESTOR Made from Corderite, a fireproof ceramic material, the flame arrestor is built into the base of the water heater. Combustion air is drawn in through the LDO screen (s). After entering the bottom area of the water heater, this air passes up through the small ports of the flame arrestor and into the combustion chamber. In the event flammable vapors are introduced accidentally into the combustion chamber, the flam
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK If there has been a flammable vapor ignition, a qualified service agent needs to inspect the arrestor for cracks. The arrestor is not a replaceable part – the heater would need to be replaced. Possible service issues associated with the flame arrestor. • Poor combustion – yellow flame, sooting, possible carbon monoxide production. • Pilot outage due to lack of oxygen. Continued pilot outage or finding that the LDO screen(s) is
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER SERVICE HANDBOOK The TCO is an integral part of the thermocouple and not replaceable as a separate item. A pilot burner assembly must be reinstalled. On repeated calls of no hot water or pilot outage, a clogged/dirty LDO screen might be the cause and should be checked. Keep in mind this TCO will shut off the pilot and main burner when activated. With the different cutoff temperature set-points of TCO devices for different model water heaters,
