190,000 BTU tankless gas water heater for homes with up to 3 bathrooms.
The ATI-310U for indoor installation is A. O. Smith's most popular and versatile tankless model. It features a maximum flow rate of 8 GPM, providing enough hot water for three showers in warm climates, or up to two showers in colder climates at the same time.
New, Improved Features
• Heat-resistant copper heat exchanger tubing
• Thicker heat exchanger drum
• Includes a pump control port
• Easy-Link System for up to 4 units
• Set up for natural gas from factory, but field convertible from NG to LP with included gas conversion kit
• 190,000 BTUs
• Maximum flow rate of 8.0 GPM
• Non-condensing technology
• Ultra-Low NOx emissions (natural gas only). Complies with SCAQMD Rule 1146.2 for NOx emissions requirement of 14 ng/J or 20 ppm
• Complies with lead-free standards
• Built-in freeze protection
• Indoor models include factory-installed 120V power cord with plug
• Overheat cutoff fuse
• Inlet and outlet thermistors for constant temperature monitoring
• Can be used for radiant/hydronic/space heating as well as the usual running hot water (domestic hot water/DHW). See page 36 of the installation manual (download below).
• Horizontal, through-wall or vertical stainless steel venting kit
• Recess Box (for outdoor models)
• Pipe Cover
• Isolation Valve Kit
• Backflow Preventer
• Concentric Termination Kits
|Limited Heat Exchanger Warranty
||15 Years for residential installation
5 Years for commercial installation
|Limited Parts Warranty
|Water and Gas Connection Location
|Water and Gas Connection Size
||3/4" male NPT
||HRS35 Copper Alloy
|Secondary Heat Exchanger
||120V 60 Hz
|Uniform Energy Factor (UEF)
|ENERGY STAR qualified
||NSF/ANSI Standard 5
|Fresh air intake vent diameter
|Exhaust vent diameter, material
||4", Category III Stainless Steel
60’ Max Length, 6 Elbows max
(90° elbows = 5’ equivalent length)
Horizontal or vertical
|Minimum water heating flow rate
0.5 GPM initially, 0.4 GPM thereafter
||9.5" for outdoor model
10.0" for indoor model
• Ultra-Low NOx Manual
• Spec Sheet
Frequently Asked Question ("FAQ")
Q1: What are the differences between the ATI-310-N (ATI-310-I-N) and the ATI-310U-N (ATI-310U-I-N)?
A1.1: The ATI-310U-N adds a 3" flue opening for fresh air for combustion intake. The ATI-310-N took in fresh air from the grill at the bottom front of the heater.
1.2. The ATI-310-U complies with Ultra Low NOx standards.
1.3. The water connections at the bottom of the heater are in different locations. The gas connection remains at the far right side.