ProLine® 40-Gallon Ultra-Low Nox Atmospheric Vent Tall Natural Gas Water Heater

Model GUC-40 450
4.2 out of 5 Customer Rating
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Capacity (Gallons)
Height Classification
UEF
Advanced Options
Limited Tank Warranty
Diameter

  • Delivers 83-gallon first hour rating
  • 40,000 BTU input atmospheric vent design delivers up to 0.64 Uniform Energy Factor
  • Ultra-Low NOX Green Choice® Gas Burner, meets or exceeds emission requirements in California & Utah

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    What to Expect from this Model
    modal-clock
    tooltip
    Number of minutes you can enjoy a shower before running out of hot water. Assumes a 2.1 GPM flow rate
    26.7 minutes
    single shower length
    modal-frame
    tooltip
    Number of back-to-back showers you can take without running out of hot water. Assumes a 2.1 GPM flow rate and an 8 minute shower length
    3.3 showers
    back-to-back
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    Number of showers you can take at the same time without running out of hot water. Assumes a 2.1 GPM flow rate and an 8 minute shower length
    2.7 showers
    at the same time
    modal-tank-capacity
    tooltip
    Biggest tub this water heater will fill without running out of hot water. Assumes a 5.0 GPM flow rate, and a 67% fill level
    68 gallons
    max tub size
    modal-cost
    tooltip
    The estimated annual cost to operate this water heater in your location
    $278/year
    est. energy cost
    Based on location results for Columbus, OH 43215
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    Edit Location / Advanced Settings
    Product Details
    • Delivers 83-gallon first hour rating
    • 40,000 BTU input atmospheric vent design delivers up to 0.64 Uniform Energy Factor
    • Ultra-Low NOX Green Choice® Gas Burner, meets or exceeds emission requirements in California & Utah
    • Push-button piezo ignitor makes lighting pilot fast & easy
    • Intelligent electronic gas control provides precise temperature control and LED status indicator
    • Patented Blue Diamond® glass tank lining protects against corrosion
    • DynaClean™ automatic cleaning system protects against sediment build-up
    • Stainless steel CoreGard™ anode rod protects against corrosion longer than ordinary anodes
    • Commercial-grade brass drain valve for durable and easy operation
    • 6-year limited tank and parts warranty

      • The ProLine® 40-Gallon Ultra-Low Nox Atmospheric Vent Tall Natural Gas Water Heater delivers an efficient, reliable performance and features an innovative design that protects against accidental ignition of flammable vapors. Featuring a 40-gallon (nominal) tank and a 40,000 BTU gas burner, the GUC-40 Standard Vent delivers a first hour rating of 83 gallons and a recovery rate of 41 gallons per hour. It carries a 6-year limited tank warranty, and meets Ultra-Low NOx emission requirements. Environmentally-friendly insulation and factory-installed heat trap nipples reduce heat loss for maximum energy savings. This ProLine® water heater is designed with A. O. Smith's superior commercial-grade tank protection. Advanced tank features include stainless steel CoreGard™ anode rod, Blue Diamond® glass lining and DynaClean™ automatic sediment-cleaning system, all designed to help protect the tank from the corrosive effects of water and extend the life of the water heater. A. O. Smith’s ProLine® water heaters are residential products built to commercial-grade standards and are only available for purchase through professional wholesalers and contractors.

    Specifications
    Tech Specs
    Nominal Gallon Capacity
    40 Gallons
    Rated Storage Volume
    38 Gallons
    UEF
    0.64
    Maximum BTUs
    40,000
    Power Source
    GAS
    Limited Tank Warranty
    6 Years
    Limited Parts Warranty
    6 Years
    T&P Relief Valve
    Yes
    Water Connection Location
    TOP
    Emissions
    Ultra-Low NOx
    First Hour Rating
    83 Gallons
    ASME Certified
    No
    Blanket Included
    No
    Destination Country
    US
    Flue Diameter
    4.00
    Fuel Source
    NATURAL
    Installation Type
    INDOOR
    Application
    RESIDENTIAL
    Product Tier
    ProLine®
    Shipping Height 
    62"
    Shipping Length 
    19"
    Shipping Width 
    22"
    Side Loop
    No
    Dimension & Venting
    Type
    Water Heater
    Height
    58.25"
    Diameter
    18 in."
    Shipping Weight
    125lbs
    Vent Type
    Atmospheric Vent
    Maintenance & Troubleshooting
    Maintenance

    Residential ProLine® Series Atmospheric Vent Application and Installation

    Residential ProLine® Series Atmospheric Vent Lighting the Pilot

    Troubleshooting

    Residential ProLine® Series Atmospheric Vent Draft Test

    Residential ProLine® Series Atmospheric Vent No Hot Water

    Residential ProLine® Series Atmospheric Vent Status Code 1 Flash

    Residential ProLine® Series Atmospheric Vent Status Code 2 Flash

    Residential ProLine® Series Atmospheric Vent Status Code 4 Flash

    Residential ProLine® Series Atmospheric Vent Status Code 5 Flash

    Residential ProLine® Series Atmospheric Vent Status Code Light Continuous

    Marketing Videos
    Residential ProLine® Series Atmospheric Vent Features and Benefits
    Residential ProLine® Series Atmospheric Vent How It Works
    Find a Replacement
    Current Product
    Option 2
    ProLine® 40-Gallon Ultra-Low Nox Atmospheric Vent Tall Natural Gas Water Heater
    ProLine® XE Ultra-Low NOx Indoor 180,000 BTU Condensing Natural Gas Tankless Water Heater
    GUC-40
    ATI-340H
    current Product
    option 1
    Rebates up to $300 +
    Rebates up to $300 +
    Nominal Capacity
    40 Gallons
    Rated Storage Volume
    38 Gallons
    Diameter
    18 in."
    Width
    17.75"
    Depth
    21.75"
    11.25"
    Height
    58.25"
    23.625"
    Shipping Weight
    125lbs
    70lbs
    Power Source
    GAS
    GAS
    Limited Tank Warranty
    6 Years
    0 Years
    Limited Parts Warranty
    6 Years
    5 Years
    T&P Relief Valve
    Yes
    Water Connection Location
    TOP
    BOTTOM
    First Hour Rating
    83 Gallons
    Thermal Efficiency
    0%
    0%
    All Reviews for ProLine® Ultra-Low NOx Atmospheric Vent (450 series)
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