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SOLAR HEATING SYSTEM DESIGNS
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How to diagnose & fix a too-cold steam radiator? No steam system heat in some or all building areas? What to check first. Troubleshooting cold steam radiators: this article describes the diagnosis & repair of cold steam heating convectors or steam radiators.
We also describe how to fix a steam radiator that is too hot. And we list less common causes of cold steam radiators in buildings and we describe how to fix these conditions.
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Our page top heating system illustration and the sketch at left were provided compliments of Carson Dunlop Associates.
Make sure that your room thermostat is set to a temperature higher than the temperature in the room - so that it is calling for heat.
Make sure that your heating boiler is working, that is that the heating boiler turns on and off normally. A steam boiler will usually turn on right away in response to the thermostat being turned up or on a call for heat.
Make sure that the control valve at the heating radiator is "open" or "on" as we describe just below.
First check the radiator valve itself. At COLD HOT WATER BASEBOARD / RADIATOR we illustrated different types of heating radiator control valves and explained their operation.
Details are at RADIATOR VALVES & HEAT CONTROLS.
It's standard to ask first "is the radiator valve turned on or "open" (fully counter-clockwise)?
Experts warn that a radiator slow to heat could have a supply valve that is too small (the problem would always have been observed since date of installation) or a supply valve that is partly closed (the problem would have originated when the valve was closed and would go away when the valve is fully opened, provided the valve is undamaged and really opens internally when its handle is turned.)
We also see both radiators and other forms of steam or hot water heat that are not hot enough if the supply piping is undersized, a valve is partly closed, piping is clogged or blocked, or the hot water flow rate or for steam heat the rise of steam is too slow.
Other problems can cause a steam heat radiator to stay cold when you want heat as we explain next where after the above digression we continue our diagnostic and repair advice for cold radiators or convectors in steam heating systems.
If some of your steam heat radiators are not getting hot, the steam vent may not be working, may not be venting at all (radiator stays cold) or may be venting too slowly (radiator heats to proper temperature but too slowly)
If a steam radiator valve is open but the radiator is still cold, the steam vent may not be working.
Our photo at left shows a typical steam radiator vent.
When steam is first rising in the heating system, the steam heating radiator will be cool as will be the steam vent. The vent opens, allowing rising steam to enter the radiator by pushing air out through the vent.
When the steam radiator and steam vent are warm or hot, the vent closes. If a steam vent stops working, rising steam cannot enter the radiator and it will be slow to heat or may not heat at all.
See STEAM VENTS and
also STEAM HEATING SYSTEMS for details about the choice, installation, diagnosis & repair of steam radiator vents - a common source of cold steam radiators, slow to heat steam radiators, even overheating steam radiators and that incessant hissssssss or spitting condensate when a steam vent doesn't close as it should.
Steam radiator sloped the wrong way - steam condensate blockage
As our Carson Dunlop sketch shows (above, left), steam radiators can be sensitive to exactly how they are installed and pitched or sloped.
You'll want to learn if your steam heating system is a "one pipe" or a "two pipe" design, but in either case, if the steam supply or condensate return piping have been moved or settled so as to have lost the proper slope, correcting those conditions may be needed.
That's because condensate, produced by cooling steam in the radiator, has to be able to drain back out of the radiator.
A steam radiator that is sloped the wrong way, perhaps due to building floor settlement or a change made by an inexperienced re modeler, will become partly or even completely blocked by accumulated condensate, leading to loss of heat.
Steam heating system controls, inspection, diagnosis, and repair are discussed beginning at STEAM HEATING SYSTEMS.
Steam boiler operating problems that can lead to inadequate heat - radiators not hot enough or distant radiators not heating up - diagnostic checks.
If your steam radiator is too hot in a two-pipe steam system, according to the U.S. DOE, check the steam traps:
If your electric heater is too hot or is not shutting off when you think it should
Continue reading at RADIATOR STEAM VENTS or select a topic from the More Reading links shown below.
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Frequently-Asked Questions about troubleshooting steam heat radiators & convectors
Question: trouble finding the cause of cold steam radiators in two buildings - traced to internal leak in steam boiler
I have done all the above. Pitched the radiator, changed the air valve, even putting a larger orifice air valve and removing the radiator to check the open and closed position of the supply valve. I still get cold radiators. The larger steam supply valves are properly pitched in the basement and the boiler runs a sufficient amount of time to build up pressure. Is there anything else?? - Robert
This problem exists in both a private house and in a six family dwelling. Both have a one pipe system. In the private house, only the second fl rear (about 3 radiators) are cold. The radiators directly below are hot. In the 6 family, both apartments on the 2nd fl are cold or get hot on one side only. - Robert
Reader Diagnosis: cold radiators traced to boiler leaks caused by condensate return line leaks
If anyone has this problem check for leaks, cracks or holes in the sections of the steam boiler. Also check return lines for leaks. It seems if fresh water is constantly being fed to the boiler, a corrosive reaction takes place in the sections of the boiler.
In this case there were leaks undetected in the return lines which caused water to be added constantly.
The fresh water ate at the sections in the chamber causing two small holes. This in turn did not allow enough pressure to build up for steam to reach the radiators. After replacing boiler all radiators were very hot and also at a much faster rate. - Robert
Thanks for your comments, and I apologize that we didn't catch them sooner. Sometimes the volume of comments leaves us behind.
And your reminder that abnormal water consumption increases corrosion in the boiler is very important since, as you explain, the result can be leaks in the boiler itself.
Unfortunately the good news of a correct diagnosis can lead to the bad news of a costly repair - the need for a replacement of the steam boiler.
We're always smarter in hindsight - and now I also see that your observation that lower radiators got hot but upper level radiators all did not, could have pointed to a steam pressure problem. Too often an amateur "fixes" the problem by trying to set up the steam pressure at the control switch - not the right approach.
Questions & answers or comments about how to troubleshoot cold steam radiators, baseboards, or convector heaters.
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