Your browser is out of date.

You are currently using Internet Explorer 7/8/9, which is not supported by our site. For the best experience, please use one of the latest browsers.

Products Indirect Packaged Semi-Instantaneous Steam Fired Water Heater

Packaged Semi-Instantaneous Steam Fired Water Heater

Hubbell Synergy Steam STX

Space saving design
Provides 10,500 GPH

Request a Quote
Stainless Steel Instantaneous Steam Powered Water Heater


The Model STX Stainless Steel Instantaneous Steam Powered Water Heater is a fully packaged semi-instantaneous steam fired water heater which utilizes steam for heating potable water. The entire package is designed to be a reliable and long lasting source for hot water. Each component is carefully selected to ensure high performance in even the most demanding application. Whether you are heating potable water in a commercial building or process water in an industrial application, you can select a Hubbell STX model to do the job.

When you specify and install a Hubbell water heater, you will be provided with a quality product that is a long lasting and trouble-free source for hot water.




  • Only high grade materials used in construction to ensure long operating life
  • Non-ferrous pressure vessel provides superior protection and tank longevity
  • Heavy duty construction withstands demanding commercial/industrial use
Packaged System
  • Factory supplied with all steam controls saving time and money during installation
  • All steam operating controls are factory sized and selected to ensure reliable operation
  • Full range of styles, sizes, and optional features to meet your exact heating needs

Model STX Semi Instantaneous Standard Equipment

Vessel Construction


  • Solid 316L stainless steel vessel and built in strict accordance with the ASME Code Section VIII and stamped, certified, and registered with the National Board of Boiler and Pressure Vessel Inspectors
  • Designed for 150 psi working pressure and hydrostatically tested


Steam Water Operating Controls


  • Steam operating controls are factory selected, sized, piped and tested to ensure reliable operation
  • All steam components are factory plumbed with schedule 40 black iron pipe and ready for steam and condensate connections
  • High quality cast iron pilot operated steam control valve modulates the flow of steam through the heating coil to provide accurate water temperature control
  • Cast iron Y strainer with 20 mesh screen protects the steam controls and coil from dirt and debris in the steam supply line
  • Thermostatic drip trap removes condensate from the steam supply line
  • Heavy duty cast iron float and thermostatic main condensate trap for optimum efficiency
  • All bronze integral circulating pump
  • Direct mounted steam and domestic water temperature and pressure gauges


Heating Coil


  • Factory sized and installed copper heating coil with a generously sized heating surface designed to ensure reliable operation
  • U-Tube heating coil constructed from single wall copper tubing designed for a maximum working pressure of 150 psi
  • Heavy duty fabricated steel head with threaded NPT inlet and outlet connections
  • All wetted parts are non-ferrous for maximum longevity
  • Non-Ferrous tube sheet




  • Heavy duty 3" thick fiberglass insulation for maximum operating efficiency and minimal stand-by heat loss
  • Heavy gauge painted galvanized steel protective outer jacket
  • Heavy duty integrally welded steel supports and base for floor mounting
  • Full five (5) year Non Pro-Rated pressure vessel and a one (1) year component warranty
  • ASME rated combination T&P relief valve set at the tank working pressure and 210°F steam supply


Outline Dimensions - Model STX (Vertical)

Stainless Steel Instantaneous Steam Powered Water Heater Diagram

Product Overview - Model STXH (Horizontal)

Stainless Steel Instantaneous Steam Powered Water Heater Diagram 1

Overall Dimensions, Model STX Vertical Dimensions (Inches)

Stainless Steel Instantaneous Steam Powered Water Heater Chart
Stainless Steel Instantaneous Steam Powered Water Heater Chart 2
Stainless Steel Instantaneous Steam Powered Water Heater Chart 3


All dimensions are approximate and subject to change. Please reference the submittal drawing for actual dimensions.


  • Vessel
    • Alternate vessel construction: 90/10 Copper-Nickel construction
    • Alternate working pressure: Specify
  • Heating Coil
    • Double wall tubing with a leak detection port
    • Alternate tubing material: Stainless Steel, 90/10 Copper-Nickel, Admiralty
    • Fabricated head constructed from: Stainless Steel, Copper Allow
  • General
    • Type 304 stainless steel protective jacket
  • Operating Controls
    • A double solenoid safety system dumps over heated water in the vessel to drain in addition to closing the steam supply to the heating coil. Requires 120 volt 5 amp electrical service
    • Electric or Pneumatic operated steam control valve
    • Electric Control package for integration with Energy Management Software (EMS) and Building Automation Software (BAS). MODBUS communication to monitor the heater via RS-232 or RS-485


What temperature should I set my water heater?

For typical domestic potable hot water service the temperature of your water heater at 125°F is sufficient. This prevents wasted energy (which means cost savings for you) and also decreases the possibility of scalding water burns. If you run out of hot water on this setting, increase the temperature by five degrees incrementally until your hot water needs are met. The goal is to have the temperature set just high enough to meet your needs but within safe operating parameters. Please note that a water heater in and of itself should not be relied upon as the ultimate temperature controlling source for the hot water delivered to your fixtures. Please consult local and state codes for installation of the proper and code approved (ASSE 1016, 1070, 1017) mixing devices to achieve the safe delivery of hot water to the fixtures. For a more complete information please download the whitepaper PDF titled "Understanding Potential Water Heater Scald Hazards" developed by ASSE at the following link ASSE Whitepaper

Which is better for me, a tankless or storage type water heater?

It depends. A tankless water heater is sometimes referred to as a Point-of-Use (POU) or instantaneous water heater. Due to the relative small physical size of a tankless water heater compared to a storage tank water heater, a tankless option can be advantageous from a space saving perspective and can sometimes be installed closer to where you want hot water (hence the term POU). However, tankless heaters are not suited for many applications, so it is critical that before choosing to go tankless you have carefully considered all of the factors that sometimes make the tankless option more complicated and risky compared to a storage type water heater. In particular, you should understand the operational characteristics, maintenance requirements, reparability, and sometimes significant installation requirements of a tankless water heater before making a decision. Tankless units do not store heated water like a storage type water heater; they only heat water as there is demand and therefore must be sized to meet the maximum flow for the application. In some cases a tankless water heater may improve operating efficiency, but possibly at the expense of user comfort. Hubbell tankless water heaters are available inElectric Tankless or Gas Tankless.

How does my water heater ship?

All Hubbell storage type water heaters ship via common carrier and are classified by the Commodity Classification Standards Board under National Motor Freight Classification (NMFC) class 100. Each water heater is palletized and wood crated. All Hubbell tankless water heaters, when transported using common carrier, ship class 77.5. To provide the lowest transportation cost, in most cases the shipment is made on Hubbell’s account and the freight cost is added to the invoice, commonly referred to as “Pre pay and add”. For very large shipments, the most economical method (LTL or Dedicated Truck) for transporting the water heaters to the final destination will be analyzed by Hubbell's transportation department.

What is the R value of a Hubbell water heater?

Hubbell uses a blown-in polyurethane foam insulation for all cement lined water heaters and tanks up to 150 gallon capacity. This insulation has an R value of 7.2 per inch. Most Hubbell tanks have a minimum of 2 inches of insulation resulting in an R value of 14. Certain models are available either standard or as an option with 3 inch insulation and therefore have an R value of 21. Large storage water heater tanks over 150 gallon capacity and custom made stainless steel or alloy tanks have either 2" or 3" fiberglass insulation with an R value of 3.5 per inch.

Do Hubbell water heaters qualify as Low Lead?

Yes, all Hubbell water heater models qualify as meeting the low lead requirements of the “Reduction of Lead in Drinking Water Act” amendment to the “Safe Drinking Water Act” (SDWA) Section 1417(d) effective as of January 4, 2014. Hubbell certifies that its water heaters meet the following requirements of the SDWA and therefore are qualified and certified as Low Lead : (a)Hubbell water heater do not contain more than 0.2 percent lead with respect to solder and flux (b)Hubbell water heaters do not contain more than a weighted average of 0.25 percent lead with respect to all wetted surfaces of the water heater


The water heater manufacturer shall warranty all components against defects in workmanship and material for a period of one (1) year from date of start-up, and the pressure vessel for a full five (5) years Non Pro-Rated (Square Optional: Full ten (10) years Non Pro-Rated) from date of start-up, provided that the unit is started within three (3) months of date of shipment and installed and operated within the scope of the tank design and operating capability. Each water heater shall be shipped with a complete set of installation and operating instructions including a spare parts list and approved drawing.

Technical Support

Our Technical Support Reps are ready to assist you. Please contact us today.


Request a Quote or Get More Information About the Hubbell Synergy Steam STX