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Steam radiator slope (C) Carson Dunlop Associates Steam Radiator FAQs

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Questions & answers on how to diagnose & fix a too-cold steam radiator.

These frequently-asked questions about steam radiators that are not working, cold radiators or sometimes radiators that are too hot, will help you diagnose and fix the problem.

This article series describes the diagnosis & repair of cold steam heating convectors or steam radiators. We list less common causes of cold steam radiators in buildings and we describe how to fix these conditions.



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Cold Steam Radiator Diagnosis & Repair FAQs

Radiator control valve (C) Daniel FriedmanQuestion: 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

More information:

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

Our page top heating system illustration was provided compliments of Carson Dunlop Associates.

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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

Reply/comment:

Robert, Thanks for your comments, and I apologize that we didn't catch them sooner. Sometimes the volume of comments leaves us behind.

Your cold steam radiator diagnosis success will add a helpful item to check and I'll add it into the diagnostic text above.

Indeed if your steam boiler is using more water than usual, I usually suspect a leak somewhere - often a small leak in a condensate line can go unnoticed; On occasion we also find excessive water consumption because radiator steam vent valves are not closing when they should (when the radiator is hot).

But I had forgotten that an internal leak in the boiler and that is going unnoticed and is large enough to prevent building up adequate steam pressure to heat the radiators can result in low boiler pressure, increased water use, and failure to deliver heat to upper floors.

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.

Thank you again. We welcome and appreciate reader questions - it helps us find where to add or clarify our information. If in the future you do not receive a prompt reply to an urgent question left on a particular web page/article, just shoot me a personal email using the CONTACT information found at page top or bottom and I'll be sure to get to it. - Daniel

Question: still can't fix this cold radiator - what else can I try?

(Jan 15, 2012) Robert said:
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?

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 added:

If anyone has this problem check for leaks, cracks or holes in the sections of the steaam 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.

Reply:

Robert,
Thanks for your comments, and sorry we didn't catch them sooner.

Your diagnosis will add a helpful item to check and I'll add it into the diagnostic text above.

Indeed if your steam boiler is using more water than usual, I usually suspect a leak somewhere - often a small leak in a condensate line can go unnotices; On occasion we also find excessive water consumption because radiator steam vent valves are not closing when they should (when the radiator is hot).

But I had not considered an internal leak in the boiler that was going unnoticed and was large enough to prevent building up adequate steam pressure to heat the radiators. 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.

Thank you again. We welcome and appreciate reader questions - it helps us find where to add or clarify our information. If in the future you do not receive a prompt reply to an urgent question left on a particular web page/article, just shoot me a personal email using the CONTACT information found at page top or bottom and I'll be sure to get to it. - Daniel

Question: only one room getting heat

Steam vent on a radiator (C) Daniel Friedman(Feb 4, 2013) charles whalen said:
having the problem with radiator on first floor one room only getting heat to all other floors 4 in total 23 apartments checked vent valve tilt of radiator flushed the supply pipe back to boiler it's clear steam comes up to radiator but seems to just puter out?

Reply:

Look for a blocked valve or valve broken internally and check for a steam vent that's not openin g.

Comment: website kudos

(Nov 17, 2015) Anonymous said:
I did learn how to fix a steam boiler who as cold radiator !! That was great !! thanks to inspect Apedia webside

Reply:

Thank you for the nice feed-back. We work hard to provide useful information so are really happy when it works out well for our readers. We also welcome criticism, content suggestions, questions: working together makes us smarter.

Question: Fixing one cold radiator

(Feb 11, 2016) Anonymous said:

One of my radiators is cold The valve is new

(Nov 20, 2016) Karl said:

We have a steam heat system where all of the radiators are warm except one. We followed the pipe back from the radiator to the floor below. In the room below, the pipe is hot near the floor but have way up the way it goes cold. There is not connection point or valve in the pipe that could explain it. Is it possible that something is clogged in the pipe half way up the wall. If that is possible, how do we clear the clog?

Reply:

Anon: Check that the valve is open and that the steam vent is working. As it's just one radiator we know the problem is local to that heating device.

Karl: sure, if the radiator's steam vent is not working or its valve is stuck shut that could explain the situation you describe.

Start by close examination of the steam valve at the radiator to be sure it's open. Beware that a broken valve stem can turn without lifting the gate inside the valve: fooling you.

Next, replace the steam vent with a new one of the same model or capacity.

Last, check the steam trap at the radiator for clogging.

Watch out: Do steam radiator work with the heat off and the radiator cold. Otherwise rising live steam can cause big trouble when you've got the piping or radiator open.

Question: diagnose odor coming from a radiator

(June 11, 2016) Claudia Thompson said:

Months ago, when I used to turn the control in the upstairs closet off at night that controlled the boiler and the radiators in the house, all of a sudden one day I started having trouble turning on the control downstairs that controls the temperature. It wouldn't come on, unless I would go back upstairs and turn the control switch off and on again. A repair man just told me not to turn it off anymore at night and put in a new thermostat upstairs. So I did what he said and stopped turning it off at night. My friend I am staying with thought it made his bedroom hotter so that was why I turned the switch off at night in the upstairs closet where the boiler is located.

Now all of a sudden there has been a smell coming from the radiator in the kitchen. THat is the new radiator that a company put in about a year ago, they removed the old one so we would have a larger radiator in the kitchen. This is completely different brand of radiator.

Then all of a sudden one day recently, I got up in the morning and the whole kitchen smelled just awful with that chemical smell. Right as you walk through the door you would get a waft of it right up your nose,and the radiator is right there on the left as you walk in. I just couldn't figure out what it was, and my friend and I thought it was the refrigerator giving out, so I bought a new one. But the smell was still there. Finally I went upstairs and discovered that without me knowing it, my friend had turned off the heating control upstairs again in the closet where the boiler is.

So I turned it back on and moved the thermostat downstairs to start the heat a little bit then turned it down to where it clicked off. The smell mostly went away but now I can still smell it a bit just as I walk into the kitchen so I leave the kitchen window open somewhat because I am worried about what the smell is.

Anyway, the people that put it in insist that smells cannot come from a radiator and will not do anything about it. I think that maybe there is something that happens when it is turned off at where the boiler is in the upstairs closet and that this one radiator in the kitchen doesn't have whatever safety mechanism in it that all the other radiators in the house do, that would keep it from leaking whatever it is that it is leaking.

It was a special different company that put in the new kitchen, they reconstructed the whole thing, flooring, cabinets, countertops and so forth and had also put in that new radiator.

So what could this be... any ideas? And what can I do about it? I asked them if they could just remove the radiator and install another one like what was there before but they won't. They told me they would send out someone to flush out the System, but they did not ever do that.

Reply:

Claudia

If you are absolutely sure the odor is coming from a specific radiator, look for

Detailed advice for tracking down an odor source begins at ODORS GASES SMELLS, DIAGNOSIS & CURE - home

Question: steam radiator not getting hot, water in the line

(Oct 11, 2016) bob said:
Steam radiator not getting hot line changed in basement sloping upward before downward slope to furnace that section has water in it can that be the problem.

Reply:

Agreed: an improperly-sloped steam supply or condensate return line can block the steam heat system.

Question: plan to cut and cap an old radiator off; asbestos insulation worry.

(Oct 25, 2016) David said:

I plan on removing a radiator in kitchen for various reasons. There is a spot in the basement to cut pipe and cap. However, there is some asbestos insulation I would love to avoid. Is it possible to simply cap it where the intake valve is? Is that a norm? Same size? Thanks for any help.

Reply:

If you can remove the piping with insulation intact that will probably be the least-disturbance.

Yes you can cap off an un-used steam riser as long as it was feeding just that one radiator.

See this detiled advice

 

Question: half the heaters on the first floor are not working

2016/12/17 Michael said:

I have a baseboard heating system in my home that I just purchased. The boiler is in the basement. I have discovered that half of the heaters on the first floor (none installed on second floor) are not working. The ones that aren't working are all on the far side of the house. I followed the pipes from the boiler and they are all hot to start with and then one just gets cold. I put my hand on it and it's hot and move my hand over a few inches and it's cold. What could be causing this issue? The other pipe is hot all the way to the wall/floor where it goes up to the first floor.

Reply:

I suspect a pipe that's waterlogged or pitched the wrong way.

Question:

2016/12/22 LZ said:
one pipe steam system. not super efficient but worked ok. somehow a couple days ago, radiators stopped heating up. followed the steps here. keep it short, checked the steam main pipe, hot. so steam did come out from the boiler. and all the branches were hot. then checked all radiators, valves are fully open. finally decided to twisted vents off, but still no steam. seemed like the steam in the main pipe magically disappeared somewhere before it reached any radiator... can any expert here take a good guess what's going on? thx.

Reply:

Please see your question and our answer at inspectapedia.com/heat/Heating-Equipment-Gauges.php GAUGES ON HEATING EQUIPMENTwhere we said

LZ:

Watch out: removing the vents will indeed let steam rise into radiators if they're not otherwise blocked, but once hot steam starts shooting out of the vent mounting opening you can get burned or have a difficult time replacing the radiator vents.

I would look for a system steam trap or control between the boiler and the first cold radiator.

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