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Fully Packaged Steam Fired Water Heater Solutions

Hubbell Synergy Steam ST

Storage Type 80 - 5000 Gallon Capacity ASME Stamped

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Fully Packaged Steam Fired Water Heater Solutions


The Model ST Fully Packaged Steam Fired Water Heater is designed to be a reliable and long lasting solution for hot water. Each component is carefully selected to ensure 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 Model ST to do the job.

When you specify and install a Hubbell ST model water heater you will have confidence in knowing that the owner 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
  • Hydrastone cement lining 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 ST Storage Type Standard Equipment

Vessel Construction
  • All welded carbon steel vessel designed 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
  • All internal tank surfaces are lined with a minimum of 5/8" thick Hydrastone cement for superior protection and tank longevity
  • Designed for 125 psi working pressure and hydrostatically tested
Steam 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
  • Thermostatic drip trap removes condensate from the steam supply line
  • Heavy duty cast iron float and thermostatic main condensate trap for optimum efficiency
  • Brass vacuum breaker and dial steam pressure gauge
Steam Heating Coil
  • A high quality factory installed 2 pass U-Tube heating coil constructed from 18 gauge 3/4" O.D. single wall copper tubing designed for a maximum working pressure of 150 psi
  • All wetted parts are non-ferrous for maximum longevity
  • Heavy duty fabricated steel head with threaded NPT steam and condensate connections
  • Copper lined tube sheet
  • Reference Heating Coils for detailed heating coil construction features
  • Heavy duty 3" thick fiberglass insulation covers 100% of the pressure vessel for maximum operating efficiency and minimal stand-by heat loss
  • All wetted parts are non-ferrous for maximum longevity
  • Heavy gauge painted galvanized steel protective outer jacket
  • Heavy duty integrally welded steel supports for floor mounting
  • Full five (5) year Non Pro-Rated tank warranty and a one (1) year steam component warranty
  • ASME rated combination T&P relief valve set at the tank working pressure and 210°F

Model ST (Vertical)Convection Model Shown

Large ASME Steam Heater Diagram

Model STH (Horizontal)Convection Model Shown

Large ASME Steam Heater Diagram 1
Large ASME Steam Heater Chart
Large ASME Steam Heater Chart 2



  • All dimensions are approximate and subject to change. Please reference the submittal drawing for actual dimensions. The tank selections above are shown for convenience. A full selection of storage capacities is available.
  • * 80, 120, and 150 gallon tanks do not come equipped with a manway.


Model ST Optional Equipment</h3

  • Vessel

    • Alternate protective lining: Phenolic epoxy resin, Flame spray copper, Hot dip galvanizing, other
    • Alternate vessel construction: Stainless Steel Type 304 or 316L, 90/10 Copper-Nickel, other
    • Alternate working pressure: Specify
  • Steam Heating Coil

    • Double wall tubing with a leak detection port
    • Alternate tubing material
    • Fabricated steam head constructed from: Stainless Steel, Copper Alloy, Other
  • General

    • Skid mounting on heavy duty all welded I Beam
    • Type 304 stainless steel protective jacket
    • Manway 12" x 16" or Inspection Opening 3" NPT
  • Operational Controls

    • Steam control can be factory sealed and sized, but shipped loose for in the field installation by others.
    • Various steam control valves are available to meet the specific needs of your application: Self-operated type, pneumatic operated, electronic operated, separate pressure reducing pilot type
    • Single solenoid safety system closes the steam supply to the control valve should the water temperature in the tank reach the hi-limit set point. Requires 120 volt 5 amp electrical service
    • A double solenoid safety system dumps over heated water in the storage tank to drain addition to closing the steam supply to the control valve. Requires 120 volt 5 amp electrical service
    • Intra-tank circulation pump pacakage continuously circulates water within the tank in order to reduce stratification. All bronze fractional HP pump
    • Anticipator control system forces incoming water over the control valve sensing bulb in order to begin heating water immediately
    • Dial water thermometer and pressure gauge factory installed in the tank
    • Factory wrapped and baffled steam coil with integral pump package

Steam Component General Configuration

The steam control valve maintains accurate water temperature in a steam fired water heater by regulating the flow of steam through the heating coil. There are four types of steam control valves available for use on a steam fired storage water heater.

There are four types of steam control valves available for use on a steam fired storage water heater

Self Operating

  • The valve design includes a bulb and capillary assembly charged with a thermally responsive vapor. The expansion/contraction of the vapor acts upon the valve bellows in order to control the flow of steam through the valve. No external power source is required for operation.

Pneumatically Operated


  • In this configuration the building air supply feeds a factory installed temperature controller which operates the steam control valve. The temperature controller sends a precise air signal to the steam control valve which adjusts the flow of steam into the heating coil. The temperature controller is fully adjustable from 50-250°F and requires 20 psi air at a maximum consumption of 0.5 SCFM.

Large ASME Steam Heater Diagram 2

Pilot Operated


  • A pilot operated control valve is the most widely used type of valve for standard water heating applications. In this type of valve, a temperature pilot device utilizes steam to operate the main valve. No external power source is required other than steam. This is a highly dependable temperature control system which is suitable for most commercial and industrial applications. As an option, this valve may include a pressure reducing pilot which limits the steam pressure to a predetermined maximum.


Electronic Operated


  • This control valve is similar to a pneumatically operated system, except in this case the temperature controller is a PID digital display electronic temperature controller which outputs a 4-20mA signal to a compact motor mounted on the steam control valve in order to proportionally control the flow of steam to the heating coil. The temperature controller displays set point as well as actual water temperature and is available with an RS486 communications port for remote control.


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


Hubbell 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.

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