ADSCO Radiator Valves and Venting

MikeDeLaurentis

Hi all,



This is my first winter in a 100 year old house that has a two pipe steam system. I've been told (by users on this site as well as a couple heating contractors who don't seem like knuckleheads) that it's an ADSCO vapor / vacuum system. We had some serious water hammer issues, which have gotten a lot better since we rebuilt a clogged drip loop. It runs mostly quietly now, with a few clangs here and there, but it doesn't feel like it's going to rattle itself apart like it used to.



There are a number of problems with the way the boiler was piped in (by a contractor for a previous owner). All the near boiler piping was done in copper. They didn't pipe in a mud leg, so there's no easy way to clean out the sludge. They used a pressuretrol rather than a vapor stat. I have it turned down to 1/2 psi with a 1 psi differential, but according to the gauge, it still gets up to 3 and sometimes 4 psi. Over the summer I will be getting someone to redo the near boiler piping, and I might end up replacing the boiler at that time depending on how much more that will cost. I have found a couple people that seem to be really good with steam, so I'm pretty confident they can de-knuckleheadify the boiler and near-boiler piping.



I have a couple questions about the venting on the system and the radiator valves.



There do not seem to be any air vents whatsoever on the system. I have heard that these systems sometimes had open-air vents that go up into the chimney or into the attic or something. As far as I can tell, there's nothing like that here. All the spots where there are risers that go up from the mains look basically the same. When we bought the house there was a vent on one of the radiators. It looked like it had been on there for a really long time. I took it off, to see if the system still worked, and it works fine without that vent. Or at least as fine as it did before.



We have 12 radiators, and the valves on about 9 of them leak steam. There are a few pictures attached. All the valves are basically the same, with a cylinder that turns, and a face that has the markings O, 3/4, 1/2, 1/1, and C on it. Most of the valves leak between the cylinder that turns when you turn the handle (is that called a stem on a packless valve?) and the face with the markings. In addition, one of them actually seems to have a small hole in the body of the valve that leaks quite a bit of air and steam (there's an arrow pointing to the hole in one of the photos).



So my questions are:



1. I would like to replace the valves that leak the most. I'm wondering if we can use standard steam radiator valves, or if we need to find valves like we already have, or rebuild the current ones.



2. Is it possible that there are really no vents anywhere in the system? I can't see how it would work at all without vents, but I really don't see any evidence of them. Is it possible that there's a vent going from one of the pipes in the third floor up into the attic space? I haven't gotten up there to check, because there are no stairs to it. It's just a tight crawl space on top of the ceiling of the third floor. The only access is through a small hole in a closet. Or, is it possible that someone removed the vents a long time ago, and now the system is just venting through the leaky radiator valves? I have a sneaky feeling that if I replaced those leaky valves it might not be able to vent at all.



Anyway, any feedback would be greatly appreciated.

Hap_Hazzard

I don't know much about two-pipe steam, but...

I don't believe they do use vents. They use what are called traps on the return side of each radiator that allows air and water to exit the radiator but prevents steam from leaving. I'm not sure where they are in your system, but those big discs on your radiators don't look like anything I've seen before. Main vents are usually at the end of the dry return, and there may be an F&T trap at the end of the main.



I am pretty sure the valves on two-pipe systems are different from those on one-pipe. You're supposed to be able to use the valves on two-pipe systems to throttle the steam supply in order to control the heat output of the radiator. One-pipe valves are strictly on-off controls. Some types of two-pipe valves have orifice plates in them. I get the impression that two-pipe valves tend to get rebuilt more often than one-pipe valves.



Hopefully somebody with more two-pipe knowledge will come along and give you the lowdown.

MTC

Orifice valves

I'm not really a pro either, but those look like orifice valves to me (the settings you see labeled are different orifice sizes). I could be wrong. If this is the case, the orifices in the valves were sized for the radiator they served, and this is why there are no steam traps. The largest orifice should be sized to let about 80% of the amount of steam that the radiator can condense pass through, and since steam is lighter than air and stays in the top of the radiator, even at full open, you should get very little or no steam passing through to the return lines. Put new regular valves on there, and you'll have all sorts of problems with pressurized return lines.



I'm unaware of any steam system that has no vents. 1 and 2 pipe systems do things a bit differently, but both are open to the atmosphere and have to "breathe out" air as steam is produced and pushing through the pipes, and then "breathe in" air again as it condenses back to its original volume (1/1700th the volume of the steam). Without any venting, you should have no heat in the majority of the house.



Does your system have a condensate return pump or anything like that, or does the return line go straight back to the boiler? Any condensation collection tanks will be vented with an open pipe, or they should be. If it isn't, it needs to be, or it can explode. That functions as the venting, or at least some of the venting, in any 2 pipe system that has a condensate tank of any kind.



You would be wise to add venting to the supply line just before the drip loop. While this loop is designed to allow air through (but the steam won't go through), it probably doesn't vent as quickly as you'd like a steam main to do so. You want it to vent out as fast as possible with as little resistance as possible. This will let the steam fill the mains before much goes up into the radiator take-offs. This in turn, helps to balance the system (your last to get hot radiator should get hot on first heating cycle).



As for returns, there has to be some sort of vent on your returns if you're house is heating. Trace it out, look for an open pipe, an odd tank, a trap, something. It may be that you'll need more venting on the returns, but if the system is heating fairly well now, its probably not necessary. The steam main venting will help balance the system, and therefore is well worth it.



For those vents, you want to put them about 15" from the end of the main ideally, and up at least 6" from the top of the main if possible. In order to determine the best amount of venting, we'd need to know how much cubic footage of air is in the lines. This can be calculated if you give us the diameter size of the main piping, and the length, for each main. If it changes sizes along the way, tell us all of that. Then we can give you a good idea of what type of venting is required.



Insulating your steam mains will be well worth your time. I suggest 1.5" thick, 3' long fiberglass sections you can buy at a heating supply place, or online.



A vaporstat is a nice upgrade. If you do that, put it on its own pigtail, and I'd keep your current pressuretrol on its own pigtail as a backup. Just set it to like 5PSI or so and leave it there in case the vaporstat ever fails, to protect the system. If your pressuretrol is not kicking off at 1.5 like it should, you might have a clogged pigtail. Pull it off and blow through it, if it doesn't blow through easy, clean it out.



Lots of stuff in there... hope this is helpful. And hopefully someone more experienced than me with this type of system can confirm/deny that those valves are an orifice valve.

MikeDeLaurentis

Vents

Thanks for the advice. I figured those valves would be something special. Any idea where I can get new ones like it, or used ones in good condition? Most of the valves aren't leaking so bad that I would want to change them, but as I mentioned in the first post, one has a hole in the side that leaks and hisses even at low pressure. I wouldn't mind replacing that one if possible.



There's no condensate return tank. The only devices in the basement are the oil tank, the boiler, the things attached to it (site gauge, pressure gauge, pressuretrol, burner, auto-filler), and the pipes. The returns just go right back into the boiler. There's definitely nothing in the basement that looks like it could be a vent. I suppose maybe there are vents in the attic space or something like that. I'll have to crawl up there one of these days. It's just a crawlspace between the ceiling of the third floor and the flat roof, and I haven't gotten up there yet. I'm sure you're right and that there are vents somewhere, but I can't for the life of me find them. The steam guy we used has worked on other similar houses on our block, and said that ours probably had a vent pipe going up the chimney that was removed at some point. But he's mystified as to how it's venting now.



I think we're going to get the boiler piping replaced in the spring, and I'll probably add some main vents at that time as you recommended. The whole house does heat, but I wouldn't say it's balanced. Actually the room that's farthest from the boiler is by far the hottest room now. That radiator heats all the way through, and most of the other ones only get hot in the top half or so.



I actually did insulate the steam pipes since those pictures were taken. I suppose that helped, because the basement went from being the hottest room in the house to the coldest.

MTC

Not me...

Wish I could help you on the valves, but I'm not even positive that they are orificing valves... let alone where to get them. Hopefully someone here can help better than me on that.



Any capped pipes/plugged fittings near the chimney? How about near the end of the mains, if thats not near the chimney? Or on the return line just before it drops down to the floor and goes back into the boiler? If there were vents, there has to be some evidence of them, unless all the piping has been replaced, which doesn't look to be the case, other than near the boiler. And I have no idea how the system would be able to fully heat if the vents were capped...



Have you tried turning down the valve setting on the farthest radiator? Its ok for radiators to not fully heat if they're heating the room, in fact its better that way (you're not wasting fuel). If those are indeed orifice valves, you can keep adjusting the settings in each room up or down a notch to get the room temperature to where you want it. Don't worry about how much of the radiator heats, its supposed to limit it to only the top when you orifice it down. That means the valves are doing their jobs.



The radiators don't happen to have a large disc on the top at the end opposite the valve with the words "In Air Rid" stamped into them, do they? If so, you might just have yourself an odd variation of a 2 pipe system with radiator vents...

MTC

More on orifices

If you do indeed have orifice valves, and can't find suitable replacements, you could put standard valves on and then insert an orifice disc in the union between the new valve and the radiator. This may take a little more trial and error to get them sized correctly, then the valve will essentially become just an on/off valve. You can have Tunstall size the orifices for you, or you can just buy a bunch of 1/8" ones and put them in, then see how they heat, and drill out any that need a bit more heat to the next higher drill bit size. Its finicky, but once you have it, it shouldn't change unless you change something else in the system.



Which brings me to an important point... if you're going to do that, you need to handle all other changes first, as these will change the way the system behaves and therefore the sizing required for the orifice plates. You need a constant low pressure controlled by vaporstat. You will be greatly served by properly insulated mains and as many runouts as you can access. Main vents near the ends of the steam mains will make a huge difference in how quickly each radiator starts getting heat, and therefore the balance of the system, and the size of orifice you need. I'd get the whole system basically operating as you want it first, if you choose to go the orifice route. And then I'd probably only change the valves that are leaking, which may be fewer once you're operating on ounces of pressure instead of pounds. The adjustability of those valves is nice to have.



And def figure out the venting situation. If your venting is insufficient, you'll never get your best efficiency or even heating.



If your basement went from warmest to coldest room, you've made great strides in reducing your fuel consumption. Getting proper balance, low pressure, etc will make it even better.