Residential/Commercial Gas
Ultra-Low NOx Tankless Water Heaters
Fully modulating, gas fired, tankless water heater with sealed combustion and power
vented flue. Indoor and outdoor models available for residential applications.
Supplies hot water to domestic hot water systems (directly or indirectly) can be used
with water storage tanks, recirculation systems, hydronic heating systems, radiant
floor heating systems, and/or combined domestic & heating applications.
FEATURES
COMPLIES WITH ULTRA-LOW NOx REGULATIONS
MAXIMUM FLOW RATES UP TO 10.0 GPM
PRIMARY HEAT EXCHANGER
I Stronger than standard copper and more resilient against erosion
INDOOR AND OUTDOOR MODELS AVAILABLE
OUTDOOR MODELS INCLUDE REMOTE CONTROL AS A STANDARD FEATURE
INDOOR MODELS INCLUDE BOTH A REMOTE CONTROL AND POWER CORD AS
STANDARD FEATURES
®
ENERGY STAR
AVAILABLE IN NATURAL GAS
QUALIFIED
INDOOR MODELS
ATI-110U, ATI-310U,
ATI-510U
EASY-LINK UP TO 4 UNITS (510U MODELS ONLY)
I With no additional parts or accessories needed
MULTI-LINK UP TO 20 UNITS (510U MODELS ONLY)
COMPLIES WITH LEAD FREE STANDARDS
ATI-510U AND ATO-510U CAN BE USED IN BOTH RESIDENTIAL AND
COMMERCIAL APPLICATIONS
SAFETY FEATURES:
I Built-in Freeze Protection
I Manual Reset Hi Limit (Up to 194°F)
I Overheat Cutoff Fuse
I Inlet and Outlet Thermistors for Constant Temperature Monitoring
I Air Fuel Ratio Rod
I Flame Sensor
VENTING AND COMBUSTION
I 4” Category III Stainless Steel
I Vertical or Horizontal Installation
I 50’ Max Length, 5 Elbows max (90° elbows = 5’ equivalent length)
I Power Vent
I Electronic Ignition - No Pilot Light
I 3” Combustion Air Intake (with optional kit)
OPTIONAL ACCESSORIES
I Complete Line of Stainless Steel Venting
I Recess Box (outdoor)
I Pipe Cover
I Direct Vent Conversion Kit (indoor)
I Isolation Valve Kits
I Backflow Preventor
I Concentric Termination Kits
WARRANTY
I 12-year limited warranty on heat exchanger in residential applications
I 5-year limited warranty on heat exchanger in commercial applications
I 5-year limited warranty on all parts
OUTDOOR MODELS
ATO-110U, ATO-310U,
ATO-510U
®
(510U models only)
ANSI Z21.10.3
CSA 4.3
Page 1 of 4
AOSBG45100
Residential/Commercial Gas
Ultra-Low NOx Tankless Water Heaters
ULTRA-LOW NOx TANKLESS MODELS
GAS CONSUMPTION
INPUT
MODEL
NUMBER
ATI-110U-N Natural 15,000 140,000 0.82 5.0 10.5 6.6 20-1/2 13-4/5 8-1/2 120 0.54 4” O.D. 3.0” O.D. 3/4” NPT 37
ATO-110U-N Natural 15,000 140,000 0.82 5.0 10.5 6.6 20-1/2 13-4/5 8-1/2 120 0.54 4” O.D. 3.0” O.D. 3/4” NPT 37
ATI-310U-N Natural 15,000 190,000 0.82 5.0 10.5 8.0 20-1/2 13-4/5 8-1/2 120 0.83 4” O.D. 3.0” O.D. 3/4” NPT 37
ATO-310U-N Natural 15,000 190,000 0.82 5.0 10.5 8.0 20-1/2 13-4/5 8-1/2 120 0.83 4” O.D. 3.0” O.D. 3/4” NPT 37
ATI-510U-N Natural 15,000 199,000 0.82 5.0 10.5 10.0 20-1/2 13-4/5 8-1/2 120 0.86 4” O.D. 3.0” O.D. 3/4” NPT 39
ATO-510U-N Natural 15,000 199,000 0.82 5.0 10.5 10.0 20-1/2 13-4/5 8-1/2 120 0.86 4” O.D. 3.0” O.D. 3/4” NPT 39
All dimensions in inches.
15-150 psi water pressure. 40 psi or above recommended for maximum flow.
* Category III required
**Current numbers based on factory testing, 0.4 GPM required for continuous fire after initial ignition.
Pressure only relief valve required (Min. 200,000 BTUs. 150 PSI). Min 50 PSI or above recommended for maximum flow.
Complies with Ultra-Low NOx regulations (SCAQMD Rule 1146.2) effective January 1, 2012.
Freeze protection draws 1.1 AMP
Indoor models are certified from sea level to 8,000 ft. elevations.
FUEL
TYPE
MIN.
BTU/H
MAX.
BTU/H
ENERGY
FACTOR
(EF)
INLET GAS
PRESSURE
MIN.
W.C .
MAX.
W.C .
MAX
HEIGHT WIDTH DEPTH
GPM**
DIMENSIONS
IN INCHES
VOLT AMP FLUE*
INTAKE
(OPTIONAL)
HOT/COLD
GAS
CONN.
WEIGHT
INDOOR MODEL
3-5/8" (94 mm)
Front view
13-3/4" (350 mm)
10" (254 mm)
7" (180 mm)
∅4 (101 mm)
Side view
4-3/8" (113 mm)
UNIT
(LBS)
1-3/8" (36 mm)
2-1/4" (58 mm)
19-3/8" (493 mm)
20-1/4" (520mm)
1" (26 mm)
120 VAC 3" (75 mm)
GAS 5-1/4" (135 mm)
1-7/8" (47 mm)
HOT 4-5/8" (116 mm)
120 VAC 1-5/8" (40 mm)
COLD 1-5/8" (41 mm)
GAS 5" (127 mm)
CLEARANCES: Top 12”, Bottom 12”, Front 24”, Back 0.5”, Sides 2”
For Technical Information call 1-877-737-2840. A. O. Smith Corporation reserves the right to make product changes or improvements without prior notice.
COLD 6" (153 mm)
HOT 6" (153 mm)
9-1/2" (241 mm)
Page 2 of 4
www.hotwater.com AOSBG45100
Residential/Commercial Gas
Ultra-Low NOx Tankless Water Heaters
OUTDOOR MODEL
Front view
13-3/4" (350 mm)
10" (254 mm)
7" (180 mm)
20-1/4" (520 mm)
Side view
3-5/8" (94 mm)
7" (203 mm)
5" (128 mm)
19-3/8" (493 mm)
1-5/8" (43 mm)
1" (26 mm)
120 VAC 3" (75 mm)
GAS 5-1/4" (135 mm)
COLD 6" (153 mm)
HOT 6" (153 mm)
9-1/2" (241 mm)
1-7/8" (47 mm)
HOT 4-5/8" (116 mm)
CLEARANCES: Top 36”, Bottom 12”, Front 24”, Back 0.5”, Sides 2”
For Technical Information call 1-877-737-2840. A. O. Smith Corporation reserves the right to make product changes or improvements without prior notice.
120 VAC 1-5/8" (40 mm)
COLD 1-5/8" (41 mm)
GAS 5" (127 mm)
Page 3 of 4
www.hotwater.com AOSBG45100
Residential/Commercial Gas
Ultra-Low NOx Tankless Water Heaters
110U Indoor/Outdoor Pressure Loss
50
40
30
20
Pressure Loss (psi)
10
0
0.0 2.0 4.0 6.0 8.0
Flow Rate (GPM)
310U Indoor/Outdoor Pressure Loss
50
40
30
20
Pressure Loss (psi)
10
0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
Flow Rate (GPM)
120
100
80
60
40
20
0
120
100
80
60
40
20
0
110U Comparison of Flow Rate vs. Temperature Rise
7
6
5
4
3
Head Feet
2
Flow Rate (GPM)
1
0
0 20 40 60 80 100 120 140
Temperature Rise (°F)
310U Comparison of Flow Rate vs. Temperature Rise
9
8
7
6
5
Head Feet
4
3
Flow Rate (GPM)
2
1
0
0 20 40 60 80 100 120 140
Temperature Rise (°F)
510U Indoor/Outdoor Pressure Loss 510U Comparison of Flow Rate vs. Temperature Rise
Set temperature 125°F (52°C) or lower
Set temperature 130°F (55°C) or higher
80
70
60
50
40
30
20
Pressure Loss (psi)
10
0
0.0 2.0 4.0 6.0 8.0 10.0 12.0
Flow Rate (GPM)
120
100
80
60
40
20
0
Set temperature 125°F (52°C) or lower
12.0
11.0
10.0
9.0
8.0
7.0
6.0
Head Feet
Flow Rate (GPM)
5.0
4.0
3.0
2.0
1.0
0.0
0 20 40 60 80 100 120 140
Temperature Rise (°F)
Set temperature 130°F (55°C) or higher
Specification
Water heater(s) shall be Model_____________________ as manufactured by A. O. Smith. Water heater(s) shall be a copper coil integral fin and tube construction with quick
release brass or bronze waterways. Heater(s) will be factory assembled and tested.
The heater shall be vented with 4” stainless steel Category III vent pipe or Special BH type gas vent at a distance not to exceed 50’ (equivalent) for 4” vent, terminating vertically
or horizontally as prescribed. Intake air pipe may be of such material as ABS, PVC, galvanized B-Vent, corrugated aluminum or stainless steel, or Category lll / IV stainless steel
not to exceed 50’ (equivalent) for 3” vent.
The heater(s) shall be controlled by an onboard solid-state printed circuit board monitoring incoming and outgoing temperatures with factory installed thermistors, sensing
and controlling flow rate to set point temperature, controlling both air and gas mixture inputs to maintain thermal combustion efficiency. The heater(s) shall also consist of
inline fusing, a spark ignition and sensor system, aluminized stainless steel burners, an air-fuel ratio sensor, a hi-limit temperature switch, modulating and proportional gas valves,
a freeze protection sensor with ceramic heating blocks, and an overheat cutoff fuse.
The water heater(s) shall be CSA listed, exceed the
For Technical Information call 1-877-737-2840. A. O. Smith Corporation reserves the right to make product changes or improvements without prior notice.
energy efficiency requirements of ASHRAE 90.1b-2007, and shall comply with SCAQMD Rule 1146.2 Ultra-Low NOx Standards.
December 2012R
Page 4 of 4
www.hotwater.com AOSBG45100
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