Uneven main venting

Oldslowandugly

Hello. My first post, so bear with me. I have several of Dan's wonderful books and I enjoy applying his wisdom to my steam system. I have a 94 year old colonial wood frame house that was originally coal fired steam. Over the years the coal boiler was adapted to oil, then replaced with a Peerless 5 section oil fired boiler, then replaced with a Burnham gas fired 5 section boiler, now 3 years old. The piping is original and consists of 2 mains, 1 on each side of the basement. The first floor has 4 identical thin tube radiators and the 2nd floor has 4 identical column radiators, so each main has the same load, 2 of each type on each floor, each on it's own riser, all original. Every radiator has a Hoffman #40 vent. Both mains are 23 feet from the boiler to the last riser. The short side has 8 feet of dry return and the long side has 23 feet of dry return. Both mains had a Dole #4 quick-vent main vent located at each end of the dry returns right at the boiler. They are thermal only, no floats. The mains still have the original asbestos insulation from the boiler header to the last riser, dry returns are bare. The thermostat is on the long main side of the house. Heating was good, but the long side seemed to lag behind the short side a bit. I decided to try and balance them by adding another main vent right after the last riser on the long side. That made that side a bit faster than the short side so I added another main vent to the short side at the last riser. Now that side was faster. Finally I decided to use 2 main vents on each side thinking they would just have to balance out, and they did, each around 2 minutes . So now I have a total of 4 Maid-o-Mist #1's on 3/4" nipples 10" long plus 2 of the #4 Doles and it was like the boiler was tossing a coin each cycle to decide which side closed first, they were that balanced, within seconds of each other. Then it got winter cold. All of a sudden the short side is taking 10 minutes to vent, and it's radiators barely heat up. Meanwhile the long side is still at 2 minutes and it's radiators are plenty hot. Adding another vent on the short side did nothing, removing all the new vents on the long side did nothing. I even removed everything and put it all back the way it was and that did nothing. The long side vents quick and the short side still takes forever to vent. I even completely removed the Dole #4 main vent on the short side thinking the open pipe should then vent first, but it didn't. Oddly, both boiler risers get hot at the same time, both sets of main vents begin venting at the same time. Then the long side heats up and shuts off while the short side just keeps on venting and venting until the steam finally gets there. I'm not sure what insulation is in the walls, probably not much, but the first floor radiator risers have insulation right up to the underside of the floor. Pipe pitch is good, no sags, well insulated, no hammer, no leaks. The pressure is always less than 1 pound, no cycling, thermostat shuts off on temperature. Heating cycle used to be around 20 minutes, now it's 30 minutes. I'm guessing the steam is collapsing on the short side, as I can hear lots of condensate draining back before the vents close, but why? What am I missing? What should I look for?

Captain Who

So you say you still have the vents at the ends of the dry returns, in addition to the ones you added at the ends of the mains? I somehow think that is part of the problem, especially since your dry returns are not insulated. Just for fun, try removing and plugging the vents at the ends of the dry returns and see what happens. You might consider moving them to the ends of the mains after that, if there is improvement. It is best to have them all located at the ends of the mains. I don't see any advantage to having them at the end of the dry returns also.

BobC

Are you saying that each main is fed by a boiler riser? This sounds like you don't have a header on the boiler. Please post pictures of the boiler and the piping around and above it.

Bob

Oldslowandugly

Thank's for the quick replies! Yes, I capped those old main vents that were back at the boiler. I thought the returns may be causing this. No difference. I now have just 2 main vents on each main after the last riser. The boiler riser does go to a header, but I think it could have been done better. I will get a pic up.

BobC

Do the two dry returns join together before going below the boilers water line?

Bob

Captain Who

Do each of the mains have their own take off from the header? Or are they fed by a tee on a single takeoff on the header?

Oldslowandugly

OK I figured out how to post pics . The header is exactly 28" above the boiler water line. The left pipe that goes straight up is the short main with the problems. I wonder why only 1 hole was used when there are 2, but it worked well until I added the vents. I was even thinking of re-piping a drop header using both holes, just to make sure the steam was as dry as possible.

Oldslowandugly

No, both returns drop to the floor and then join up there. A Dole #4 was at the top of each drop, on the T, for almost 40 years that I know of.

Captain Who

For all intents and purposes, that short main doesn't even have a header. That could be getting all the wet steam. As far as why it worked previously, I'm not getting that right now, but you must have set up a path of least resistance in the other main and the dry steam is preferring that. If the only thing that changed is your venting, have you tried putting it back the way it was as an experiment to see if that is all that changed with the system? You never had any insulation? When did you paint the piping silver?

Mark N

Short main comes off a bullheaded tee. Needs to be repiped.

Oldslowandugly

"that short main doesn't even have a header. " I get that, and I was going to put the rest of it all back, but that goes against all I've read. Don't they say it's impossible to over-vent? Or is that what I did?

Captain Who

There was an article by Dan where he had a strange situation where he had a pair of radiators that were on the same riser off of a common tee where even when he removed the vent on the one radiator, it still didn't get any steam and the other one with a vent got it all. I think his solution was to slow down the venting.

Oldslowandugly

The insulation is original, asbestos, I wrapped it with duct tape to keep it from dusting. the installer painted the pipes. Would it be easier to move that riser over next to the other, maybe even raise the header higher at the same time. I'm not afraid of re-piping, if that's what it needs.

Captain Who

Yeah that is definitely what it needs. That header is all wrong, but since you know about drop headers, you know that. It looks like there is no reducer on the equalizer too. Can't see the Hartford Loop. In the meantime put the smaller venting back in so you can get some heat.

KC_Jones

Now that you have sped up venting (and the steam) what could be happening is you are getting a ton of wet steam into that main. Any water going up that pipe doesn't have a way to flow into the equalizer so it is shot straight into the main. That could be affecting what is going on. The water will slow the steam down. If the water got up there is it getting out? Have you verified the main is sloped and doesn't have any sags that could be holding the water? What size and brand is this boiler? What size is that riser pipe? 2"? If it is 2", unless that is a tiny boiler I suspect the piping is also inadequate which won't help matters. It is said often these are systems. Sometimes they work well despite the errors. Since it appears you have several issues it could be your changing of the venting is just bringing other problems to the surface. Just a couple things that popped into my head.

Fred

What pressure is the boiler running at? That equalizer that drops to the bottom of the boiler is filled with water up to the water line of the boiler. I'm wondering if the steam, headed to that short main is condensing before it even has a chance to move into that Main because the water in that equalizer hasn't gotten to boiling temperature yet and, of course, as the pressure, in the boiler rises, so does the water level in that pipe.

I can't figure out why the venting would have changed that except that the steam may have been moving so slow before that that the equalizer may have had a chance to get hotter and/or the water in it may haave had a chance to come to a boil. seems like if you put the vents back like they were, you'd get back to where you were with the steam (slow but there).

Under normal circumstances, you really can't over vent the system. You just get to a point with vents that they offer no additional value.

Mark N

You state you have Dan's books. Do you have the The Lost Art of Steam Heat? Read the chapter on boiler piping. The bullheaded tee in the supply piping is a major no no. It would seem you have an IN-5, you should use 2 risers into a 2 1/2" header, get rid of the bullheaded tee. The last fitting on the header should be a elbow into the equalizer that drops straight down. The equalizer should be at a minimum 1 1/2".

Oldslowandugly

Yup, it's an IN-5 with 2" mains, same size as the Peerless it replaced, small but adaquate. I just put everything back exactly as it was and called for heat. No change in the unbalance, just the long main took longer to vent than with the extra main vents. I guess I can put them back. However I'm hearing a waterfall in the return on the short side where it drops down to the wet return, so it would seem that a LOT of water is getting up in there. Yes, it looks like the piping is at fault. The heating is OK, but, I want to make it better. I have The Lost Art, Greening Steam, and Classic Hydronics. Based on them, I think I want to use a drop header that is a lot higher than what is there now, and use both ports to slow the velocity. I just am afraid of stressing the sections, so besides going higher for more "A" , I know I should use offsets. What is better for stress relief, unions or companion flanges?

Oldslowandugly

Heat came up. Short side is better without the extra vents, so as suggested I guess I aggravated a bad situation. Looks like I'll be fixing the piping after heating season ends. Thank's for all the help, this site is awesome!

Dave in QCA

I have just done a quick read through on this post. I don't see anything regarding your radiator vents. What kind are they? Did you change them? The old sage advice is "vent your mains fast and your radiators slow, but completely." Theoretically, you can't vent your mains too fast. But, if your radiators have vents that are too fast, it will through the system completely out of balance. I prefer the old time set up of a Hoffman 40 on every radiator with a substitution only where a space may be too warm or too cool. Most of the time, a system with Hoffman #40s and fast main vents will be very well balanced.

Regarding your near boiler piping, riser, and header, I also recommend that you get this straightened out in the spring.

Oldslowandugly

I too believe in the Hoffman #40's and I have them on every radiator. After looking again at the piping I was wondering if a simple fix would work for now. What if I were to remove that troublesome riser that is on the bullhead T, replace the T with an elbow, and move the T over to the other side of the other riser just before it turns to the equalizer, and use that for my riser. Then it would be a proper header, though a short one. It looks like I have enough room to do that and since the other main is not getting any water in it that should do it. All I would need to do is pipe it over from above a foot or so. Assuming that would work should I maintain the drop in the equalizer or keep it at the same height as the header? And since I'm disconnecting things, should I raise the header up higher than it is? I have lots of room above.

Steamhead

That piping is definitely wrong. But I'd check your boiler water quality- dirty water can cause the same symptoms.

Oldslowandugly

OK then that's what I'll do. I have the tools, the parts are available, and I have the time. Yes, the water is now dirty, but it wasn't before I started playing with the vents. I figured the large amount of condensate washed a lot of rust from the pipes. After I finish with the piping I'll clean the boiler and start fresh.