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This article describes the normal operating pressure range for residential steam heating systems and for commercial or high-rise building steam heating systems. We include citations of steam boiler explosions and describe probable differences in boiler explosion causes between early steam heat history and modern steam boiler use.
This article series provides an illustrated inspection and repair guide to Steam Heating Systems. The page top photo shows a modern steam heating boiler. Click to enlarge and you can see the actual pressure settings on the steam boiler control shown at left.
Watch out : If your residential steam boiler is operating at higher pressures that may be an indication that a service technician or owner was having trouble getting heat distributed through the building. Rather than finding and fixing the problem, someone is trying to "force" the steam around the system. According to a University of Idaho engineering text we cite below, a 30 psi high pressure steam system might provide sufficient pressure to deliver steam heat to a building 40 stories in height.
So we might see 15 psi for a 20 story building steam system. An experienced steam heat service technician will look at the operating pressure of your steam heating boiler and if it is not set to a normal level, the technician will look for the reason.
Examples of problems that can affect the flow of steam heat through the system, leading to attempts to over pressurized the system include.
Steam or Hot Water
Watch out : do not modify a steam boiler pressure control switch to try to force steam heat to cold radiators or to higher floors. Doing so makes the system less efficient, fails to find and correct the underlying problem, and in some situations it could make the heating system unsafe. The pressure control switch on a steam heating boiler is designed to shut the heating system down should unsafe high pressures develop. As we emphasize at our description of pressure gauges On a steam boiler, residential steam heating systems are almost always designed to operate at very low pressures, perhaps around.
You should see similar settings on the pressure gauge and on the steam pressure control switch the gray box our photos of steam pressure switches shown here on your boiler.
Because the operating temperature, pressure, and form of heat distribution are different from hot water heat typically psi of hot water , steam boilers typically less than 0. The gray box on my steam boiler is set low less than 2psi but the glass pressure gauge is reading 7 or8 at times.
Brian, One wouldn't expect a boiler to blow up at 14 psi, but I agree that the system is not set nor operating at safe normal pressures.
I suggest calling a service tech promptly. Usually residential systems operate at lower pressures, less than 1 psi, often around 0.
High Pressure Steam Boilers
Since your steam boiler pressure control valve is set under 2 psi and the boiler pressure is way over that, and assuming that your steam boiler gauge is working and not "stuck" at an abnormal reading , the problem may be the pressure control valve itself. You should see similar settings on the pressure gauge at left in our photograph and on the steam pressure control switch the gray box at right in our photo on your boiler.
These are not steam systems. Rick the exact pressure needed varies by installation but in a low pressure residential steam system the pressure range is usually between 0. Pressure on gas steam boiler was rising far too high, so high that the pressure relief valve released twice when it hit 15 psi as it was supposed to do. Good buddy who really knows his stuff checked everything from pressure valve to pressuretrol.
He then checked "pigtail" and found blockage. Problem solved!! Watch out : If your heater is a residential steam heating system it is operating at an abnormally high temperature and is unsafe. Turn the system off immediately and call your heating service company. If your heater were a residential hot water heating boiler hydronic heat its pressure might be close to the upper end of normal operating pressure - and the leak at the valve could be due to a valve problem or to any of quite a few other causes.
See the links just below for information on how the steam heating system pressure is controlled and set. In modern steam boiler explosions we are of the opinion that other forces might be at work, such as improper maintenance, tampering or work performed by inadequately-trained personnel.
All of the steam heating system controls described in our introduction are illustrated below and described in greater detail in individual articles found in this steam heat series.
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High Pressure Boilers: Features and Advantages
If you are a homeowner and are experiencing a problem with your Weil-McLain equipment, the first step you must take is to contact your installer or locate an HVAC contractor in your area.
National Fuel Gas Code Z Catalog XHO Reprinted Brumbaugh, ISBN v. Macmillan Publishing Co. Tel: Email: info carsondunlop.
Carson Dunlop Associates' provides extensive home inspection education and report writing material. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.