Air vent recommendations
It appears that I have a couple of radiators whose air vents keep hissing even after the radiator has reached max heat. They eject steam.
The type I have are the pointy curved cone type. They have some kind of bimetallic diaphragm that bends at some threshold temperature and blocks the steam. Some work and some don’t in my house. So I plan to replace the faulty ones and maybe get a couple extra to swap out later.
I see there’s a few different types on Amazon and elsewhere are any especially good and reliable?
FWIW, I got 2 pipe radiators where steam comes in on one side at the top and the condensate pipe is at the bottom on the other side. The weird thing is that my air vents are not in the middle like you see in the texts, they’re mounted at the top (on the other end from the steam input). Is this a problem?
Comments
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Are you sure you have 2 pipe as 2 pipe usually doesn't have air vents on the rads? Can you snap a few pictures of some radiators and of the boiler and piping around the boiler from 10' away so we can see what is going on.
There was a two-pipe air vent system but it is a very old early 1900s system. How old is your house?
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Almost all of my radiators are like the photo i just added to post. The boiler is a modern Columbia, about 10 years old. The piping adjacent to the boiler is a mix of cast iron and copper segments. I just insulated the long runs of the copper this weekend.
The house is 100+ years old, no idea when the steam heating was originally installed!
I should add that the only vents are on the radiators, there is NO additional vent near boiler at all (is it called an “air trap”)? I expect that my system has had some bad decisions made upon it over the years!
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is this the european system that was posted a few months ago?
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@mattmia2, this is Philadelphia.
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this may be a vapor system that has been knuckleheaded. if it is supposed to have radiator valves they should be about 2/3 down but i suspect the screwed up the vapor specialties at the boiler that let the system vent the air out and instead of fixing that, someone put vents on the radiators in the hot water bleeder tappings.
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oh, ok, i seem to remember a similar radiator that was in europe a little while ago.
what brand are the radiator valves, that might help with the "is it vapor". what is the device at the boiler, can you take some pictures?
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then there is the gravity hot water system where someone went in the basement, saw huge pipes, incorrectly though it was steam and someone puts a steam boiler on a gravity hot water system.
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Post a pic of this air trap- let's have a look.
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
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@Steamhead , yeah, what I am saying is there is no air trap in the pipes going to the boiler, only pipes! The radiator vents are the only way air gets out in the whole system.
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I think @angelotrivelli is saying he has an air trap as in no vents in the basement, not that he has a steam trap in the basement.
We need pictures of the boiler and all the piping around the boiler from 8-10' back
That system doesn't look like a two-pipe air vent system
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@EBEBRATT-Ed, Yes, those are copper pipes, and yes, the installer did not configure the pipes in the way recommended in the installation manual.
The steam supply comes up from both sides of the boiler and then joins together before going up into the single steam supply line to the house. The condensate return goes down behind the boiler and a up through a hardford loop before entering the boiler.
I got confused about the name for the mechanism which I read about that is supposed to be somewhere on the condensate line. I called it an “air trap”, but it might be called “steam trap”. Whatever it is, I don’t have one in my system!
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can you show us what happens at the end of the mains and roughly what happens with the returns between a radiator and the boiler?
can yu show us another radiator, maybe one that hasn't been moved. that radiator in your picture has been moved or added or something, that piping is really weird.
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Without seeing more of the system I would say you would benefit from a main vent at the far end of the steam main. That way the steam propagation to fill the main is not restricted by the smaller vent rate of the radiator vents. Your system may have parts missing from typical or they were removed over the years, may never know.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
it looks like a gravity hot water system that someone stuck a steam boiler on, but we need to see more.
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here’s another radiator, this one is on first floor. It has a steam line and a condensate return, like the others. Also like the others it has a vent at the top and not the middle. The basement has 2 main pipes the larger one feeds steam to the radiators, the smaller one carries condensate back to the boiler. I will try to make a drawing later.
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@mattmia2 , since the return is smaller than the supply, it was not a hot-water system.
Since there are no traps or other special elbows on the return, it's probably a variation of the Tudor system:
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting2 -
@angelotrivelli , you need to look for air vents on the return lines in the basement, most likely near the boiler. It's possible someone removed them during a boiler replacement- not the first time I've encountered this.
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting1 -
@Steamhead, thanks that's very interesting. There are distinct similarities to my system. I've annotated the main differences below and also annotated the differences between my system and the installation manual for my columbia boiler. I am sure that I have no air vents (I've looked carefully). The only venting in my system are the radiator vents.
This is the best I can do to describe the system without taking measurements! I started this post asking about air-vent recommendations, but it seems my whole system is now in question 🤣That's OK, it's never too late to understand what's going on in one's own house! Appreciate all the wonderful knowledge sharing here!
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Your vents are probably Hoffman 40's, a good relatively slow vent. You can still get those. Regardless of how incorrect the near boiler piping is and whether the system is as originally intended or not it is going to need main venting now to take the load off the radiator vents. Look for a place to add them either right after the last takeoff from the main or at the end of the return before it drops down. If you can give us the total length of your main and the pipe size we can suggest a main vent. Also, do the normal things like making sure your pressuretrol is set sufficiently low (cutout ~1.5psi and cut-in 0.5psi) and that you pigtail is clean so actual pressure can be seen by the pressuretrol and gage.
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The new rad picture looks like it has a copper return. Probably easier to add the vents at the boiler before the returns drop down.
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@dabrakeman Thanks, yes, they're Hoffman 40's. The pressuretrol lever is all the way down, the gauge reads just under 1 psi. Gauge goes all the way down when the system is cold, so that's a sign that it's OK. Unfortunately I can't clean it because I can't untwist the pigtail from the gauge and I don't want to muscle it and risk breaking the gauge and or pressuretrol ! Will have to try some WD-40 next time (or get a spare gauge/pigtail/pressuretrol in case I destroy mine).
The approximate length of the main (if I understand correctly) is 35 feet. It is a 42mm (1 5/8 ") OD copper pipe that extends from the riser above the boiler to the extreme end of the basement, where it u-turns and becomes a narrower (29mm, 1 1/8 ") copper pipe that collects the condensate.
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I have to agree with others on this one. There is such a thing as 2 pipe air vent systems, but they have differences from yours. First, the radiators are connected at the bottom on both ends. Second, they typically use larger piping than you have. In addition, the air vents on your radiators are in the wrong location, indicating addition at a later date. For me the top feed connection is a dead giveaway of this being a 2 pipe system.
The pipe running to outside could have confused an installer so they disconnected it on boiler replacement and eliminated all air venting, then the system wouldn't heat and in their infinite wisdom they added vents to all the radiators instead of in the basement where it should have been.
The circle you labeled as the pipes are simply connected at the end. Does anything in that area appear newer? That is a trap meant to hold water to keep steam out of the returns. That would be notorious for rusting out and needing replaced. Again a less knowledgeable installer may have not understood it as other steam systems are simply connected at the end, so they did that when pipes rusted out. Sometimes the presence of pipe dope or PTFE can indicate newer piping.
The boiler piping as you've already noted is incorrect. Appears to be a colliding header which is one of the worst offences in near boiler piping. At this point I'd have it low on my list of issues. Getting the rest of the system sorted would be my priority.
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If his entire main is copper then I would say it is all newer with all the original main and returns gone..
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@KC_Jones , @dabrakeman , yes, the piping in the basement is mostly copper, but the vertical pipes (risers?) that go through the floors are still cast iron. I suspect that the copper piping was installed ~20 years ago.
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This i believe is just a water seal with some cleanout fittings at the bottom, it allows condensate to run from the supply to the return while blocking steam (and air).
It sounds a whole lot like someone who knew nothing about steam tried to rip out and replace the mains (or scrappers got to the house and stole the mains). Stream mains should never be plumbed in copper.
Might need to add steam traps to the radiators to make it work right, hard to know what was there originally. If the radiators are original, the brand and other information on the valves might give us a clue.
None of us normally more or less ever say this, but this system might be a candidate for a hot water conversion, that might be the easiest way to make it work well.
What is with the grate under the radiator? Is there anything connected to it? I wonder if there were indirect radiators under the floor that were removed and replaced with radiators in the room.
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We all have heard the dreaded question from homeowners that "the pipes in my basement are too low".
I would suspect that in this case they repiped the basement in copper and maybe threw the vapor stuff out not knowing what it was. since the risers are the original black pipe.
Maybe there are orifices in the valves?
Either way it needs vents on the mains to be able to get it to heat.
Thankfully the op is not complaining about water hammer
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that's because the steam can't get far enough to find water and hammer.
why are you (the OP) asking about air vets, what problem are you trying to solve?
The mismatched radiators and copper return make me wonder if the radiators were missing too and were replaced with salvaged ones.
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@mattmia2, @EBEBRATT-Ed, I am 100% sure every imaginable mistake has been made in my house at one time or another.
And yes, I got water hammer too! Nonetheless the system more or less works.
I did notice that a couple of the radiator air vents are always hissing even when they're hot, so I wanted to replace them. That was my original objective. But I am willing to research what it would take to make a better system.
I understand that it's bad to have copper piping for the boiler header because the cast iron and copper have different thermal expansion coefficients. But why is it a problem on mains? I have asked plumbers about this and they just say that copper is "better".
FWIW, it's really, REALLY hard to find competent plumbers with steam experience willing to work on residential where I live (Philly). I basically feel like I am on my own.
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The conductivity of copper is a lot higher than black iron. It cools and condenses the steam in the mains a lot more than black iron.
The bigger concern with seeing it is all replaced with copper it that it was clearly done by someone that didn't understand how steam works so they wouldn't have installed it to properly manage steam, condensate, and air.
The find a contractor section of this site shows 4 contractors in PA.
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@mattmia2 Thanks, I've already contacted the ones which are close to Philly (unfortunately, they don't service the city). I KNOW there are plumbers who are expert at steam in the city, but I suspect they're fully engaged in commercial and institutional jobs (not residential). Maybe if I bribe the right person, I can get one of these. 😆
I did actually insulate the main supply and condensate lines this weekend (it made a huge difference).
However, it would be good to replace the header and supply tappings on the boiler with cast iron. I would also consider to eventually have the main runs replaced as well. Unfortunately, I don't know anything about cast iron and it's probably illegal for me to do it myself.
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I would not tackle repiping during the winter. Check the pitch on all the piping and do what you can to see if it is pitched properly and add air vents as needed.
Copper is what it is. It would be better if it had been steel pipe. Just live with it and hope it doesn't become an issue you can deal with it down the road.
If you can get the pitch and vents done the system should work. Then you can deal with replacement. Maybe you can entice @Steamhead to fix it or consult.
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it isn't as much that it is copper that concerns me but that anyone that would know how to make steam work properly wouldn't use copper.
The main shouldn't connect directly to the return, it needs to have a crossover trap or water seal and vent or some other method to keep the steam out of the return and let the air out of the main.
The main needs to be pitched and dripped so that it doesn't hold water.
The return needs to be able to vent the air from the radiators and get the condensate back to the boiler and the condensate can't block the air.
The radiators need to not send steam in to the return. It could be with radiator traps on the outlet or with orifice plates or vapor valves on the inlet and controlling the pressure.
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If you have vents on the radiators and put main vents at end of main and insulate the copper (guess you did that) I don't see why this shouldn't work. In essence would be no different from my one pipe system that has drip legs back to the main extension from each radiator.
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…put main vents at end of main…
My apologies that I'm not fluent with the jargon or that I mis-use the terminology…
I understand that "main" is the long pipe that carries steam from the boiler and which has "tributary" pipes coming off it that feed the radiators steam.
My main pipe has a u-turn at the far end of the basement and "becomes" a long (but smaller diameter) return pipe. This return pipe has tributary pipes that collect condensate from the radiators. The return ends up at the boiler and then turns down to the hartford loop.
Two questions about the main vent(s):
Should it go on the return pipe, right before the pipe turns downwards towards the hartford loop, or should it go at the "u-turn" where the main pipe "becomes" the return pipe?
Folks have alluded to the notion that there's a way to calculate the specs of the main vent depending on other aspects of the system. Is there a formula somewhere? Also why did you say main vents (plural)? I've seen pics on this website of multiple main vents ganged together— why is that? Redundancy? Do I need multiples? Are the multiples just a way to meet the calculated venting capacity if I can't find one vent that can do the job?
I also read about a "cross-over trap". This is a device that blocks steam but allows air. Should I have a cross-over trap at the "u-turn" where the main becomes the return and put the main vent at the return before it turns down to the boiler?
*** The reason I ask these questions is that I will eventually find a professional plumber to do this installation and I need to be "ready" when the plumber proposes something! The problem is that I lack a strong enough **** detector to be able to discern genuine "I-know-what-I'm-talking-about" confidence from someone who's just making stuff up as they go along. The horror pics I posted above were of a system that multiple plumbers worked on before I even got here, so it's hard for me to trust plumbers! 🤣
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it has to control air, water, and steam properly just like in your one pipe system and that is mainly in how the pipes are arranged.
the mains need to be pitched to a drip one way or another so the water can get out.
the connections to the return need to keep the steam out of the return one way or another, either they need to:
individually, one per radiator and one per main drip drop down to a wet return individually,
they need to have a steam trap,
or they need to have an orifice plate or metering valve that limits the amount of steam that can get in to the radiator to less than the amount it can condense.in the case of the mains a drip to a wet return or a steam trap are the only options.
if steam gets in to the returns it will follow the air out the radiator vent and in the return end of the radiator and close the vent with more or less only the last section of the radiator heating.
the mains need to be vented either directly through main vents or indirectly through crossover traps to the returns.
the radiator vents need to be about 2/3 of the way down on the radiator or the radiator will fill about 1/3-1/2 with steam when the steam gets to the vent and closes it trapping the air below the vent in the radiator(or the system is arranged to vent through the returns like normal 2 pipe and vapor systems)
Some of these options interact so the whole system has to be thought through.
The person that replaced the mains with copper almost certainly didn't account for these things.
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Agree the mains need to be pitched and since the OP did not mention that his system was different from the schematic he attached I assume they are pitched parallel flow. As far as keeping the steam out of the return if the main vent is right after the last radiator takeoff and the main extension eventually drops below water line back at the boiler then that creates a block against steam entering the main extension. Note, again I am not describing this system as a two pipe anymore since that was lost somewhere way in the past. The little pipe he has going from each radiator back to the return is truly no different than the drip lines I have from the supply side at each of my radiators (this over the last dozen years on this forum I have noticed is quite rare). Nonetheless, if I were to have main venting back at the boiler they behave as the OP's lines would allowing steam to pass though and make there way back to main vents back at the boiler. I go rid of this by moving my vents six or seven years ago and improved the performance of my system greatly.
The radiator vents indeed should be moved lower. The OP has not answered whether there are bosses or plugs present but with the correct drill and tap sizes this can be done either way with a little patience.
The entire NBP and mains could be replaced and traps and orifices installed but I'm trying to see a more financially feasible solution path here.
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@dabrakeman, the mains do have a downhill grade towards the boiler. Not sure if that tilt has to be a specific angle (I haven't measured it) but it is visible.
I am thinking about doing 3 things (I would probably have a plumber do at least the vent & trap):
- Add a crossover vent (aka steam-trap aka thermostatic trap?) at highest point of the main where it u-turns and becomes the return. A Hoffman 17C seems to be the right one for my 35 foot long main.
- Add a main vent at the end of the return right before it turns down to the boiler. I am thinking a Barnes and Jones "Big mouth air vent".
- If everything is still working, I will then replace all the radiator vents with plugs. I know that these are just 1/8 NPT fittings, so I would just use brass plug w/teflon-tap, after cleaning the threads with a tap.
At that point, it will be a "2-pipe" system with the difference that the one pipe is at the top of the radiator and one pipe is that the bottom. If there's problems, I can always put back radiator vents (1/3 from bottom on the radiators that have a flat I can drill on).
Does this sound like a sane plan?
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""Add a crossover vent (aka steam-trap aka thermostatic trap?) at highest point of the main where it u-turns and becomes the return."
I thought you had parallel flow mains (highest point is back at the boiler and they slow AWAY from the boiler (at least 1" per 20ft)?
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the connection to the returns with a vent is NOT the same as 1 pipe with a main extension. steam must be kept out of the returns because it can follow the return connection to the radiator and close the vent before steam has filled the radiator.
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you will also have to either keep the boiler pressure low with a vaporstat and add orifice plates to the radiators or add steam traps to the radiators to keep steam from passing through the radiators to the returns
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