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State GTS-310U Indoor-Outdoor NG-LP UltraLow NOx Tankless Water Heater

Original price $919.00 - Original price $919.00
Original price
$919.00 - $919.00
Current price $919.00


State GTS-310U Indoor/Outdoor NG/LP UltraLow NOx Tankless Water Heater

Get an endless supply of hot water from a compact, wall-mounted tankless water heater that will afford you substantial savings in energy costs.

Ships configured for Natural Gas, with Propane conversion kit included

The State GTS-310U is the most popular and versatile tankless heater from State Industries. It features a maximum flow rate of 8.0 GPM to provide enough hot water for three showers at the same time. It comes with a standard remote control. Complies with Ultra-Low NOx regulations (SCAQMD Rule 1146.2 and other air quality management districts with similar requirements for Ultra-Low NOx emissions requirements of 14 ng/J or 20 PPM). Meets ASHRAE 90.1b-1992 energy efficiency requirements.

Indoor models include an integrated temperature controller.
Outdoor models include a remote control unit.

State Proline XE series tankless water heater features

Freeze Protection

Every tankless heater by State Industries has an internal freeze protection system, rated to protect the heaters in sub-freezing conditions. This prevents water temperatures in the heat exchanger from falling below a certain level, to prevent freeze damage.

Hi-Limit Switch

This ensures that the water temperature does not exceed dangerous levels. It disengages the gas valves, which effectively shuts down the water heater.

Air-Fuel Ratio Sensor

State's unique sensor monitors and maintains optimal combustion at all times. The onboard computer adjusts the fan motor speed to make sure that air and fuel are mixed in the proper ratio to minimize emissions and maximize efficiency.

HRS35 Copper Alloy

The HRS35 copper alloy is heat-resistant, with additive elements which make it much stronger than the standard C1220 copper alloy commonly used in other heat exchangers. HRS35 is 8 times stronger than regular copper, even at high temperatures. It's also resistant to the damaging effects of corrosion which is the leading cause of leaks in heat exchangers.

Drum Thickness

At every ignition cycle, thermal expansion causes heat exchangers to undergo heat stress. The thousands of ON/OFF cycles typical in commercial applications can be damaging to water heaters. This is why State Industry's commercial products utilize heat exchangers with drums that are 25% thicker to ensure durability. A thicker drum produces less strain for the heat exchanger.

316L Stainless Steel Secondary Heat Exchanger

The secondary heat exchanger, where the rest of the heat transfer happens, is made from high quality 316L stainless steel. Lower temperature causes acidic condensation, and stainless steel is needed to avoid corrosion. 316L stainless steel is more suitable in condensing heat exchangers because of the extreme environment (heat, chloride, acidic condensation) that the material is constantly subjected to.

Better Water Pathway Design

By redirecting and redesigning water flow, the heat exchanger drum and finned coil's temperature stay above dew point, making it more difficult for condensation to build up.

Fin Pitch

Widening the pitch at the heat exchanger fins not only improves durability by reducing blockage, but it also maintains higher temperature levels on the upper finned coils. Keeping an elevated temperature at these coils reduces the chances of condensation buildup.

Match the Unit to Your Needs

Warmer Climates

70°F Incoming
Groundwater Temperature

Colder Climates

50°F Incoming
Groundwater Temperature

Capacity - Number of Shower Heads
GTS-110/U 2 1
GTS-310/U 3 2
GTS-240H 2 1
GTS-340H 3 2
GTS-540H 4 3
GTS-510/U 4 2
GTS-710 4 3
GTS-910 6 4

Flow Rate Guide (values are in gallons per minute, "GPM")

Temp Rise 110/U 310/U 510/U 240H 340H 540H 710 910
30° 6.6 8.0 10.0 6.6 8.0 10.0 9.0 14.5
35° 6.6 8.0 9.3 6.6 8.0 10.0 9.0 14.5
40° 5.7 7.8 8.1 6.6 8.0 9.5 9.0 14.5
45° 5.1 6.9 7.2 6.6 7.6 8.4 8.5 13.5
50° 4.6 6.2 6.5 6.1 6.8 7.6 7.7 12.2
55° 4.2 5.7 5.9 5.5 6.2 6.9 7.0 11.1
60° 3.8 5.2 5.4 5.1 5.7 6.3 6.4 10.1
65° 3.5 4.8 5.0 4.7 5.3 5.8 5.9 9.4
70° 3.3 4.4 4.7 4.3 4.9 5.4 5.5 8.7
75° 3.1 4.1 4.3 4.1 4.6 5.0 5.1 8.1
80° 2.9 3.9 4.1 3.8 4.3 4.7 4.8 7.6
85° 2.7 3.7 3.8 3.6 4.0 4.4 4.5 7.2
90° 2.5 3.5 3.6 3.4 3.8 4.2 4.3 6.8
95° 2.4 3.3 3.4 3.2 3.6 4.0 4.0 6.4
100° 2.3 3.1 3.3 3.0 3.4 3.8 3.8 6.1


Gas type Ships configured for natural gas. Convert to LPG/propane with conversion kit included with the heater.
Installation Type Indoor, Outdoor, Direct Vent
Dimensions Indoor: 20.5" (H) X 13.75" (W) X 10" (D). Outdoor: 20.5" (H) X 13.75" (W) X 9.5" (D)
Weight 39 lbs
Electrical 120 V, 0.73 A (Operation), 0.05 A (Standby), 0.93 A (Freeze-Protection)
Ignition Electronic Ignition
Noise Level 55 dB at Max output
Min. Input 15,000 BTU/h
Max. Input 190,000 BTU/h
Energy Factor 0.82
Min Gas Pressure 4.0" W.C. for NG. 8.0" W.C. for LP.
Max Gas Pressure 10.5" W.C. for NG. 14.0" W.C. for LP.
Flow Rate 8.0 GPM. Values based on factory testing. 0.4 GPM required for continuous fire after initial ignition.
3/4" NPT
Coil Capacity ≈0.2 Gallons
Water Pressure 15-150 PSI. Pressure Only Relief Valve Requires (Min 200,000 BTUs. 150 PSI). 40 psi or above recommended for max. flow.
Easy-Link System N/A
Multi-Unit System N/A
Dipswitches 120°F (default) 140°F
Temperature Settings 120°F to 140°F (9 options), 120°F Default Factory Setting
Remote 9008172005 remote (max. distance 400’ from heater, non-polarized 18 gauge wiring.)



Residential Use: 15 yrs limited heat exchanger, 5 yrs limited parts


Product Guide
User's Manual
Spec Sheet

Frequently Asked Question ("FAQ")

Q1: What are the differences between the GTS-310 and the GTS-310U?
A1.1: The GTS-310U adds a 3" flue opening for fresh air for combustion intake. The GTS-310 took in fresh air from the grill at the bottom front of the heater.
1.2. The GTS-310U 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.

Q1: What are the differences between the GTS-110 and the GTS-110U?
A1.1: The GTS-110U adds a 3" flue opening for fresh air for combustion intake. The GTS-110 took in fresh air from the grill at the bottom front of the heater.
1.2. The GTS-110U 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.