Steam radiator slope (C) Carson Dunlop Associates Fix Cold Steam Heating Radiators & Convectors

  • COLD STEAM HEAT RADIATORS - CONTENTS: How to Troubleshoot & Fix Cold Steam Radiators in 5 Steps - a complete diagnosis & repair guide & checklist for cold steam radiators. Diagnose & fix radiators that are too cold or too hot.
  • POST a QUESTION or READ FAQs about how to troubleshoot cold steam radiators, baseboards, or convector heaters

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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 include warnings about other radiator or baseboard types that are too hot or that overheat.

And we list less common causes of cold steam radiators in buildings and we describe how to fix these conditions.

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How to Troubleshoot & Fix Cold Steam Radiators in 5 Steps

Ceiling mounted heating radiator (C) Carson Dunlop AssociatesOur page top heating system illustration and the sketch at left were provided compliments of Carson Dunlop Associates.

Article Contents

Cold Steam Radiator Diagnosis Step 1: Check the thermostat & the steam boiler

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.

Step 2: Check the radiator control valve

Radiator control valve (C) Daniel Friedman

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.


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.

Step 3: check the steam vent on the radiator

Steam vent on a radiator (C) Daniel Friedman

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)[2]

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.


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.

Step 4: Check which radiators are not getting hot - check radiator slope

Steam radiator slope (C) Carson Dunlop Associates

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.

Step 5: Check these other causes of cold steam radiators

Internal leaks in the steam boiler can cause cold radiators - diagnosis:

Steam boiler operating problems that can lead to inadequate heat - radiators not hot enough or distant radiators not heating up - diagnostic checks.

Heating convector unit (C) Daniel Friedman

Troubleshooting Radiators that are too HOT

If your steam radiator is too hot in a two-pipe steam system, according to the U.S. DOE, check the steam traps:

In two-pipe systems, older steam traps often stick in either the open or closed position, throwing off the balance in the system. If you seem to have problems with some radiators providing too much heat and others providing too little, this might be the cause.

The best approach is often to simply replace all the steam traps in the system.

If your electric heater is too hot or is not shutting off when you think it should

Watch out: an overheating electric heater is a fire hazard.

Also see HEAT WON'T TURN OFF for complete diagnosis of too much heat or heat that won't turn off.


Continue reading at RADIATOR STEAM VENTS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Or see COLD HOT WATER BASEBOARD / RADIATOR if your heat is by hot water baseboard or radiator or convector rather than steam heat.

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COLD STEAM HEAT RADIATORS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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