How to Create Hydronic Zoning on Steam Boilers

Many Long Island and New York City homeowners have gas fired steam systems and often call on us to create hot water hydronic zones they want to install in their basements or extensions on their homes. Offering a solution sounds simple but requires complex piping, controls and even a new boiler in some cases.

The best and preferred method to add a hydronic zone in a steam house is by adding a separate boiler installed with all the typical components. Air separator, expansion tank, circulator, pressure reducing valve, backflow valve, flow checks, relief valve and low water cut off to name a few. Plus venting, gas piping, water, etc. adding in the expense of actually running the copper or pex tubing then the actual baseboard. The costs add up quickly, but it’s the preferred and proper permanent solution.

Another solution is to use the existing steam boiler water that sits below the water line visible in the sight glass. Again, not so simple. Piping and plugged taps on the sides of the boiler may not easily break free to allow for reconfiguration and modification. If the system has been properly maintained (draining monthly, treating the boiler, etc) and is younger than 5-8 years it’s likely a plumber can install proper piping and temperature limit controls to harness that water for hydronic heating purposes.

This second method will provide years of reliable heating for that basement zone, extension or addition as long as it is installed properly and the boiler size can handle the additional load. Therefore a proper heating calculation must be performed by a competent and experienced plumber.

First, as anyone with steam experience knows, the boiler is constantly getting debris from the slowly eroding steam piping that returns back to the boiler with the condensate. This water shouldn’t be traveling by means of a circulator to the baseboard via the copper or pex tubing. Picture sandpaper slowly eating away at the tubing and fin tube baseboard. Eventually something will fail, clog up flow checks or destroy circulators. The best means to protect the zone or zones is by using a brazed plated heat exchanger or similar type keeping steam on one side and hydronic water on the other. Installing piping from opposite sides of the boiler with a circulator, valves and high temperature limit to one side the the heat exchanger. This piping essentially becomes an external part of the boiler along with the water residing below the water level in the sight glass. The opposite side of the heat exchanger becomes the hydronic side.

The hydronic side of the heat exchanger will contain all the standard components, piping configuration of a traditional hydronic boiler less the boiler itself.

When properly installed and configured here’s how it will work….
Let’s say, for an example, the basement thermostat calls for heat. The basement zone relay will receive signal from the tstat. If the high temperature limit on the boiler side of the heat exchanger says it’s under 180 degrees, it fires up the boiler and powers the circulator on that side. Once temperature reaches 180 degrees the boiler turns off and the circulator still runs. This 180 degree water is now circulating across the heat exchanger. At the same time the basement zone circulator powers up and circulates until the thermostat is satisfied. It’s important to note the high temperature limit. Without this limit the boiler will continue to run until the basement zone tstat is satisfied. This will result in steam being created and the steam zone heating up the house even though the steam thermostat is not calling for heat. So don’t forget this vital limit or you will have a very hot home.

Again it’s important that you use a competent and experienced plumber familiar with steam heat. Make sure your plumber explains the monthly service that must be done with the boiler. Monthly draining to remove the debris is imperative as well as confirming operation of the low water cut off and water feeder if one is installed. Our Long Island plumber highly advises all homeowners who have steam to purchase and read this book. It’s available for purchase on Amazon for a list price of $25. You will understand the gentle giant residing in your basement and respect it. Treat him well and he will deliver years of quiet and reliable service.

If you reside in the NYC – Long Island metropolitan area within our service area we’d love to help. Give us a call at 516-348-6300 or email us at Homeowners outside can refer to this website for a referral to a licensed professional in your area who would also love to help you understand your steam system and make any necessary boiler repairs or perform general service.

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