Mysterious cold radiator
We've lived in our single-family house for several years. I've become a well-informed steam heat user, so I understand most of the basic principles, e.g., that if air can't get out steam can't get in. Ours is a one-pipe steam with two main brances. The boiler is near new and was properly sized by the local steam expert with proper near-boiler piping (drop header, etc.). Pipes all insulated. The system runs great, though still trying to dial in the far radiators with the right air vents to balance the system perfectly.
The single radiator in our small den, however, is a mystery that driven me nuts for a couple of years. I want to solve it this winter so we don't need to use a space heater. This radiator is on the first floor about halfway down one of the main branches. At the beginning of the heating season, when everything is really cooking, it gets nice and hot. But then, when the system is maintaining temperature, it pretty much goes cold. It'll occasionally get just a little warm, like it's really struggling, but then go cold when the cycle ends. The radiator immediately before and after this one on the same floor get really hot with each cycle. For the life of me and I can't figure out why this radiator just poops out.
I thought it might be an air vent thing, but I tried putting on a Maid-O-Mist with the largest venting capacity and faced the same problem. When I go down and feel the riser (where the pipe leaves the main), I can feel good warmth through the insulation until I get to the elbow that turns up toward the radiator above.
Any ideas on what's going on? I can't imagine it's anything other than trapped air, but I have no idea how to determine whether that's so and, if so, how to get it out. Perhaps there's some debris blocking air, but I'm not sure how to determine whether that's so. Appreciate any help.
Comments
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The pitch of the pipe that is feeding that radiator may be incorrect. If there is a sag in the pipe then condensation that is trying to return to the boiler may be trapped in there partially blocking the path for the steam to get to the radiator. Look close at the pipe between the main and the radiator to see if the horizontal pipe maintains a constant pitch of 1" per 10 feet sloping downwards from the radiator to the main.
There are stories about how a home owner used the steam pipe to hang a heavy bag for working out or using it to hang all kinds of stuff like a swing for the 4 year old. When the kid grew up to be 16, and weight in at 190#, the radiator stoped working.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Check what Ed said, of course. You can also have a problem with the angle valve. They can fall apart internally and cause a restriction. And of course the pitch of the radiator. If I were troubleshooting this, I would use air pressure through the 1/8" vent connection into the radiator to see that the line was free of restriction. I'd pump with a hand pump and listen for gurgling or feel for blockage. The pressure in reverse direction would also quickly identify a disassembled valve face.
I'd also check my boiler sizing. This can be the problem with newly sized boilers. If the boiler isn't providing sufficient steam, it's possible that one radiator would remain cool. The ones condensing the most steam will draw more steam into them, while one on the sideline could go cold. Since the vents aren't closing on short cycles, there's no "encouragement" for steam to find that radiator. Fast vents in all the other radiators will not encourage steam to find this one.Try removing the vent from the cold radiator while closing one or two of the bigger ones. See if it heats up then. Unless there's some mechanical or condensate restriction, that will narrow your diagnosis down to venting. I'd use American-made vents, to remove Chinese defects from the equation.
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Thank you both.
EdTheHeaterMan: I should have mentioned it, but what you mentioned was one thing I thought might be the culprit and did check it. The pitch is pretty much perfect, so that's ruled out. Pitch of the radiator is also correct.
Long Beach Ed: Pretty positive the boiler sizing is not the issue. The boiler is definitely producing enough steam. I've put vents with the smallest venting capacity possible on each of the radiators. The close ones have super slow vents so that they don't in steam too fast (and cause the room to boil). I have had to increase the venting rate on some of the farther radiators in order to balance things out, and all of those work well. It's just this one that is really struggling if working at all.
I've also been suspicious of the supply valve (that's what you mean by angle valve, right?). The issue is that my radiators are actually convectors recessed into the wall. They look beautiful, but this also means I don't have full and easy access to repair/replace the supply valve. Please see the picture to get an idea. Is it possible to remove and replace the valve from the convector cutout? Pretty sure I'll need to remove trim to get a wrench in there, but perhaps there is a way to do the job in such a restricted space.
First I'm going to fiddle a little more with the vent to try and rule that out.
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You could try removing the air vent on that convector and then turn the system on, make sure someone is standing buy to shut the system down if steam comes out the vent hole
There may be a short horizontal pipe under the floor that is not pitched right. Does the radiator shutoff valve get hot or at least warm?
Bob
Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
Vaporstat with a 12oz cut-out and 4oz cut-in
3PSI gauge0 -
That valve would require quite a bit of trim removal to replace. But there are options and some tricks an experienced fitter could employ to solve a broken valve problem without ripping up the place. But diagnosis comes first…
From the manner in which the valve is mounted, I doubt it's causing your problem.
Does the entire system employ convectors, or are there other types of radiators too?
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"At the beginning of the heating season, when everything is really cooking, it gets nice and hot. But then, when the system is maintaining temperature, it pretty much goes cold. "
Could you elaborate on this statement? So on a long call for heat, it does warm up? Or, as the system gets further into the heating season it dies? Or, never gets warm during a shorter call for heat?
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What @EdTheHeaterMan sid improper pitch on the branch piping feeding the rad or a defective valve (maybe the disk inside the valve fell off and is blocking the pipe but the pitch is the most likely culprit.
There is probably a low spot in the pipe that fills with water. Over the summer some of the water evaporates and the rad heats at first.
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Also possibly some sediment ended up in the runnout and is creating a dam that is holding water. The internal parts of the valve coming apart also could form a one way valve that lets steam in but does not let water out. If the valve is installed up side down it could potentially not let condensate drain. What does it look like compared to the other valves?
I assume you checked that the valve is all the way open.
Condensate doesn't have to block the pipe to stop the radiator from heating and it usually doesn't block the pipe. You just need a pool of condensate sitting in the pipe. When the steam hits the liquid water it condenses in to water until it has more or less evaporated the water. Steam won't progress beyond the water until it has heated the water to steam temps
Those are Trane in wall convectors or a copy of them.
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Thank you all. Will try my best to touch on many comments/questions without responding to everyone in turn.
About the convectors: They are all Capitol Fincast Style L.B. I actually have the original home specs, and I checked my convectors against the Capitol catalog posted here on Heating Help. It has the same metal enclosure and everything. In the interior of the house there are no other kinds of radiators. (Note: There is one gigantic wall-mounted radiator in the garage, but I have that one shut-off, since it struggled to get hot all the way across and because cars today don't need conditioned space, and I am planning to have it removed.)
The radiator shut-off valve is indeed getting warm/hot, and yes I've made sure all of the valves are all the way open. As many of you suspect, I don't think the valve is the issue. The boiler guys were here for annual cleaning just yesterday, and they said they can feel the normal resistance when turning the handle and therefore, like you, don't think the issue is a defective valve. It was just a maintenance call so I couldn't put them to work finding on solving this problem.
As you all suggest, this seems to leave either (1) faulty venting or (2) some kind of pooling water from a low spot or sediment built-up causing the incoming steam to prematurely condense. I'll go hunting but I just really haven't seen a spot missing the right pitch. First, I'm going to do some experimenting with the venting to ensure air is coming out. I was told that sometimes vents are duds and just require replacing. On most of the units I use Hoffman 43 convector vents and they work great.
If it is sediment blockage is there any way to test for this and, if found, remove it?
Finally, addressing what I mean by the statement about starting hot and then going cold. When the cold comes on strong, I usually bump the thermostat up to our desired setting (say 70 degrees when it used to be 65 or 68). To get up to temperature, the system runs a lot of longer and the problem radiator gets nice and hot. But then, as the system has its normal-length cycles to maintain the temperature, the radiator fails to warm up. So my experience has been to walk in during the middle of January and find the room freezing and the radiator cold all the way across.
Grateful for any further thoughts in light of all this. Thanks again.
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Might want to keep the radiator in the garage but keep it shout off, can be convenient if you need to work on something in winter.
Does it get hot to the valve at the same time as other emitters or does it take longer?
If it heats on a long cycle either there is a pocket of water somewhere that is eventually getting evaporated or the air can't get out and the boiler builds enough pressure to compress the air enough that some steam gets in to the emitter. Did you see what happens if you remove the vent altogether?
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Thank you, @mattmia2. Regarding the garage, I considered that but am still going to have it removed. When I do run it, it just doesn't get hot enough, perhaps because when I got the new boiler I had the steam contractor size it to not include the BTUs required for this mammoth radiator. It's a smallish garage, and the radiator block traffic when the car is parked, so it has to go. I don't use or plan to use the garage as a workshop (I have a small shop in my basement). If I want consistent heat in the future I'll just have a mini split installed. I appreciate the suggestion.
Hmm, not sure on the timing. I'd have to specifically test for that when I have some time to stand by for a full cycle. (That's hard with three little kids :-) ) What I can say, though, is that when the radiator is in "struggle mode," I've found at times that the run-out pipe feeding it is hot (warm under the insulation) up till about the last foot, which is cold, along with the valve of course.
Not sure if this offers any further clues. One question: Can water pool up in a properly pitched pipe? Perhaps in a section that has corroded and cause a little divot? Just speculating. You all would know better.
Will update you when I've tested the vent by removing it. Hoping to find time to do that today. If the vent isn't the issue, maybe I can talk to my steam contractor about replacing this line of pipe with a new one.
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Can water pool up in a properly pitched pipe?
Extremely unlikely
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Not sure if this offers any further clues. One question: Can water pool up in a properly pitched pipe? Perhaps in a section that has corroded and cause a little divot? Just speculating. You all would know better.
A mound of debris can sit in the pipe and hold water in the pipe. usually this only happens if that section of the pipe or emitter has been flooded so that the water can carry the debris there. The fix is to flush it with a hose from the emitter connection. that isn't easy in your case since the valve is buried in the wall.. i might try adapting a hose to the vent tapping and flushing it there if you think that is the issue.
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Mysterious cold radiator
OK we are close enough to October 31, so I Will propose that many mysteries can occur during this Halloween season. Perhaps there is a ghost in that radiator and just like AIR, Spirits and steam don't mix well, but spirits don't leave thru air vents.
To test this spooky theory, remove the air vent and see if the spirit leaves your radiator so the steam can get in.
YIKES ! ! !Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Perhaps a holy water additive would help. It could be obtained free (although a donation would be nice) at any Catholic church. Bring your own bottle.
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If you take the vent off, shake it so any water inside comes out, and replace the vent does the rad heat up properly?
I have a radiator that occasionally the vent gets water logged (i.e. surface tension prevents the water from draining out properly). It's intermittent, and hasn't happened for a while. But your symptoms sound similar.
Burnham IN5PVNI Boiler, Single Pipe with 290 EDR
18 Ounce per Square Inch Gauge
Time Delay Relay in Series with Thermostat
Operating Pressure 0.3-0.5 Ounce per Square Inch1 -
On a convector sometimes you need to put the vent on a riser to keep the condensate from getting carried in to it with the air.
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Thanks all for the suggestions. @acwagner I appreciate your sharing your experience. This never occurred to me. @mattmia2 good point. I noticed when moving in that most of the convectors have a little riser consisting of two small 45 elbows. The wall covers have a damper, so I thought these elbows were to allow the dampers to operated unimpeded, but maybe they are actually for the reason you suggest.
Been busy the last couple of days so haven't been able to work on this. Will report soon when trying some of these tests with the vent.
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water
the condensate is just a tiny trickle, it just takes a stream of water to move the debris back to the returns
I would use a straight vent on a 3" or so nipple unless there is a clearance issue with the damper. If you use angle vents you have to be sure they pitch toward the convector so whatever water gets in them can get back out.
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Update: I removed the existing vent and found that there was a little bit of the plumber's tape was in the opening. Not sure if that obstruction would slow the air flow enough to prevent even heating, but it's a start. With the system on, I held a thread over the vent opening and saw the thread dance, so I know the air is getting out, and of course the convector starting heating very quickly.
I got out the Hoffman vent I had initially used (and which is on all the working convectors) and, upon inspecting, found that the tongue was a little rusted. So perhaps some water did indeed get in there and prevent it from working. I blew in it to make sure air was passing through and put it back on just now.
I'll monitor over the course of the day to see how the emitter works. I'll also be ordering another vent or two to have on hand for present and future replacement, and I'll be adding a nipple to serve as a riser.
Question: Still not counting out the possibility that there might be some sediment—I would guess in the convector itself—slowing or stopping the trickle of condensate. If there is, my guess is that any trapped water would corrode and add more crud. Would there be any harm in trying to flush some water through from the vent? Can I add a little bit of vinegar to it? My understanding is that the water would just flow back to the boiler, so I can just remove some water there if the level is too high. And if it smells like vinegar I can just flush and add fresh water. Right? Just spit-balling here, so would appreciate input.
Will share any further updates. Thanks everyone.
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I wouldn't add anything but water into the vent hole to try and flush out any sediment. Perhaps the hotter the better…just be careful. I'd avoid vinegar because you will get a "fresh pickle" smell from all the radiators until 100% of that water gets flushed out of the boiler.
But the fact that you removed the vent, air came out and the convector heated quickly points to a poorly functioning vent. If there was an obstruction it wouldn't have heated much faster than with the vent on there.
Flush it out as best you can and put a new vent on there.
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The teflon tape could have kept the water from draining out of the vent if the resulting opening was small enough for surface tension to seal it off. Ideally the tape would not cover the first thread or so on the end.
If it heats in the situation that it didn't heat before with the vent removed the problem is with the vent in some way.
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