Converting From Steam to Hot-Water Heating

Steam-based heating has a long history as a reliable source of heating for commercial and residential applications. However, in some cases, converting from steam to hot-water heating may be a better choice. If you’re considering making the switch, here are some important points to keep in mind.

Common Reasons to Convert from Steam to Hot-Water Heating

Converting from steam to hot-water heating is not a trivial process. It will require a significant investment in planning, system modification and new equipment, including a boiler. There are three major factors that usually drive the decision to change to hot-water heating:

  1. Cutting annual operating costs: Hot-water heating can be much cheaper and more efficient than steam heating. Newer high-efficiency boilers can reduce operating costs by a significant percentage, making hot-water heating a much more economical choice.
  2. Uneven heating: Steam heating can be inconsistent and uneven. This results in areas that are either hotter or cooler than expected and desired. Adjustments at the thermostat may not be able to resolve the inconsistencies.
  3. Safety for building occupants: Steam is a potentially dangerous source of heating. Steam radiators can get extremely hot, often over 200 degrees. Accidental contact with these radiators can cause serious burns, especially in children or the elderly. Hot-water heating is, in general, a safer alternative.

Calculating Heating Load and Heat Loss

To properly size a new boiler, it’s necessary to know the amount of heat loss that occurs in the building. Sizing a boiler is the process of determining how much heating is needed and selecting a boiler that can consistently produce that amount of heating.

Heating load calculations
are most reliably performed using industry-standard resources such as the Air Conditioning Contractors of America (ACCA)’s Manual J, “Residential Load Calculation.” This manual contains all the procedures necessary for performing a heating load calculation or, in the case of steam to hot-water conversion, the amount of heat loss. Manual J calculations are usually performed using specialized computer software that handles the complex mathematics of the procedure.

When converting from steam to hot-water heating, the heat loss is calculated for each room containing a radiator. When your HVAC professional knows the amount of heat loss, he can determine the water temperature required for the radiators to make up for the heat loss. From there, he can help you decide the make, model and size of boiler that will most effectively and efficiently provide the right amount of hot water.

Modifications to Existing Radiators

A steam to hot-water conversion usually will require some modifications to existing radiators:

  • The upper vent plug should be drilled out and the threads chased.
  • The steam trap should be removed and replaced with a union-elbow (or “ell”). Alternatively, the interior of the steam trap should be removed to allow free flow of water.
  • The radiator valve should also be replaced.

Contact your local trusted HVAC service provider to perform these modifications.

Recommended Efficiency Factors

Newer boilers and associated equipment are much more efficient than their older counterparts:

  • Use a circulator with an electrically commutated motor (ECM). These motors use up to 90 percent less power than more common induction motor circulators. This level of power consumption reduction can result in significant monthly savings on energy bills.
  • Use a modulating condensing boiler. These types of boilers offer increased efficiency and better performance because they adjust their firing rate to compensate for outdoor temperatures. For example, if you need water at 120 degrees at 10-degree outdoor temperatures, the water will not have to be as hot when outdoor temperatures are 40 or 50 degrees.

Our goal is to help educate our customers about Plumbing, HVACR, Fire Protection, and Alarm Systems in Mechanical, Commercial, and Residential settings. For more information about converting from steam to hot-water heating and to view projects we’ve worked on, visit our website! We serve clients in Delaware, Pennsylvania, New Jersey and Maryland.

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  1. Posted August 29, 2014 at 2:32 am | Permalink

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  2. Mariam
    Posted August 31, 2014 at 9:41 am | Permalink

    John, thanks for this post. I have a situation where my steam radiators and piping were ripped out. I need to determine if hvac or hot water radiators is the way to go. Per your post, i see this as an opportunity to upgrade to something better. I have an old home with poor insulation and single pane windows. I’m hoping I can buy new radiators and reuse the passages where the old piping was to install pex for a water system to minimize the work. It seems that radiators are better for heating an old house than forced air. But hvac obviously gives me an option for cooling. Would appreciate any guidance

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