Help with Steam Boiler Main Vent Sizing

mcvetyty

Hello -

I've learned a ton from this forum, and appreciate everyone's help! I am hoping someone can help give me an idea on what size main vents I need for a steam boiler, and then also help me with another question I have...

First, I have three main returns, but unfortunately I have no idea the length of one of them (more on this below). The other two are around 60 feet each, and begin at 9" circumference and step down to 7.5" circumference. What's strange is that although both of them are approximately the same length, one (let's call it return #1) heats up much quicker than the other (#2). My assumption is that #2 maybe has more branching that isn't visible than #1?

Which then leads to my question: I have no idea where return #3 actually originates from. The pipe comes out of the basement ceiling near the boiler and basically joins up with return #2. #3 currently doesn't have a main vent at all, and the one radiator that I believe is connected to it is the last to heat up, and usually cold most of the time.

The other two mains both have Hoffman 4A's on them, which from what I've read, are severely under-powered. Can anyone give me some recommendations on what I should use to vent #1 and #2, and then confirm my suspicion that I need to add a main vent to #3, and if so, what size?

Attached are some pictures as well. Thanks!

Abracadabra

run an open pipe with a ball valve at the vent location. start boiler cycle, when header has steam it in, start timing. See how long it takes for steam to get to the open ball valve before shutting off the ball valve. Shut off boiler. Add sufficient main venting to that vent station to get the steam there in about the same amount of time.

mcvetyty

Thanks for the response, and that sounds like a good trick, however, I don't think that necessarily informs me on which main vents I should use.

Let me ask another question.... Other than financial investment, is there a downside to over-venting? What would happen if I just slap Gorton #2's on all three of the mains?

HarryL

I've been advised to use one Gorton #2 per 20 feet of 2 inch main. 9" circumference is probably 2 inch pipe. The venting is only needed at the end of the main, not at the end of the return.

ChrisJ

As far as which main vents to use I would go by how much room you have above the pipe.

The vents should not be screwed directly into the main but rather 5+ inches above it as this keeps water and junk out of the vent. Sometimes, you can't quite even get this so choosing vents can be difficult. If you have limited room use multiple Gorton #1s. If you have plenty of room start with a Gorton #2 and add as necessary. I seem to recall someone saying a Gorton #2 is around 9" tall from top to bottom.

I've attached a picture showing multiple Gorton #1s on one of my mains. I had very little room to work with but did my best. Looking back on it, I'd make them all face the same way now for cosmetic reasons but at the time that seemed like it would work better.

KC_Jones

9" calculates to 2 7/8" OD which is the OD of 2 1/2" pipe. The 2 1/2" pipe would have roughly 1.5 times the amount of air of equivalent length of 2" pipe. By those numbers you would want to go more like 1 gorton #2 for every 13-14 feet of pipe. I only did a very quick calculation on that. Not sure if anyone has a "rule of thumb" for 2 1/2" pipe.

Abracadabra

mcvetyty said:

Thanks for the response, and that sounds like a good trick, however, I don't think that necessarily informs me on which main vents I should use.

I provided that as a solution because you said:

mcvetyty said:

unfortunately I have no idea the length of one of them

mcvetyty said:

Let me ask another question.... Other than financial investment, is there a downside to over-venting? What would happen if I just slap Gorton #2's on all three of the mains?

You cannot over-vent mains. I doubt a single #2 would be sufficient, and the downside is that if on one main a #2 happens to be sufficient and it's not enough on the other mains, your short main will heat up first and those radiators will heat up before your other mains and radiators off those mains.

Abracadabra

100 minute boiler cycle time seems a bit high to me. What kind of temp rise are you seeing in the rooms? What kind of control system do you have for the boiler? IOW, what signals the end of the cycle?

Abracadabra

I've found that using wireless sensor tags from CAO gadgets help to balance a large install. You can track temps and compare different units.

JStar

I would say that one Gorton #2 is adequate for 12ft of 2-1/2" main.

JStar

The whole idea is to vent air with very little pressure. Pressure costs money.

mcvetyty

Hello again -

All very helpful. Abracadabra, thank you for clarifying your suggestion, and I am really liking the idea of the ball valve test. I have a two new questions if you don't mind:

1) Currently, my main vents are attached via a 1/2 inch nipple that goes up six inches. Hypothetically speaking, if I were to hook X Gorton #2's up this, wouldn't their performance inevitably be hindered by the maximum air flow through the 1/2 inch nipple? Or is that not true?

2) I did some testing over the weekend, and the master bedroom radiator takes 36 minutes before heat hits the FIRST fin. My assumption is that's way too long, but I am curious to hear what other members are averaging (in terms of time to heat the furthest radiator).

Thanks!

KC_Jones

36 minutes seems excessive. Your mains are roughly twice the size of mine and I am still under venting, but I can get steam to every radiator in my house in less than 10 minutes.

mcvetyty

Hatterasguy said:

You are limited.

The best you can do is a pair of #2's and a single #1. Anything more and the 1/2" opening becomes the limiting factor.

Thanks for the insight. I guess I'll start there, and see what that gets me!

KC_Jones said:

36 minutes seems excessive. Your mains are roughly twice the size of mine and I am still under venting, but I can get steam to every radiator in my house in less than 10 minutes.

I'd love to be in that position.... It currently took 17 minutes to just get the main returns heated.

Abracadabra

Properly insulate all your mains with 1.5" fiberglass and you'll get steam moving along more quickly. It won't condense in the mains and it'll end up in the radiators where you want it.

mcvetyty

They're currently all insulated in asbestos... I'm planning to go through the process to have it removed and re-insulated either next year or the year after. Is fiberglass' insulating factor equivalent to asbestos, or better?

PMJ

Way cheaper to just have the asbestos encapsulated. It is actually a good insulator. All my piping in the basement is insulated with the original asbestos. I had it encapsulated years ago and have been very happy with that result both functionally and aesthetically.

Abracadabra

mcvetyty said:

They're currently all insulated in asbestos... I'm planning to go through the process to have it removed and re-insulated either next year or the year after. Is fiberglass' insulating factor equivalent to asbestos, or better?

I might be missing something, but a lot of the piping I see in your pics is not properly insulated. Some looks uninsulated and some looks like it's insulated with foil faced pipe wrap.

mcvetyty

OH! You are right.. The boiler is new and they had to remove all of the asbestos within 5 feet of it, so yes, there is definitely an opportunity to insulate those pipes with something better than the foil stuff.. I was just planning to wait until I had the rest of the asbestos removed and do it all at once, but that's a good idea!

PMJ said:

Way cheaper to just have the asbestos encapsulated. It is actually a good insulator. All my piping in the basement is insulated with the original asbestos. I had it encapsulated years ago and have been very happy with that result both functionally and aesthetically.

Interesting! Does the encapsulation material add a lot of girth around the pipe?

PMJ

mcvetyty said:

Interesting! Does the encapsulation material add a lot of girth around the pipe?

Hardly any increase in dimension. It was almost like a paper mache process where they dipped strips of paper in a white paste and wrapped up the pipes. The stuff hardened and total sealed in the asbestos. It really came out nicely, has lasted really well and looks great.

mcvetyty

Ok guys, I am back with results I am not so inspired by... I did the test that Abracadabra recommended (basically attached a ball valve to return #2 to see how fast the main return heated up). The positive news is that the nipple is actually 3/4" and not 1/2. The not-so-positive news is that with a 3/4" ball valve attached, the pipe only heated up 6 minutes faster than it did with the Hoffman 4A on it.

The time-to-heat with the Hoffman 4A was 17:31, and the time to heat with the opened ball valve was 11:31.

So, if I understand this correct, even if I invest a ton in Gorton #2 valves, the most I'd get is a six minute gain. Is that accurate?

Does this mean my dream of getting heat to all radiators in less than 10 minutes is probably never going to be realized? Any options?

KC_Jones

I would say unless you can get a bigger opening that is as fast as you can go. Look at it this way you are basically saving 6 minutes worth of gas every single time your boiler fires if you increase your venting. If you go by the firing rate of the boiler you should be able to calculate how much money that will save you with every firing of the boiler. Don't forget this isn't just money savings, in all likelihood it's a comfort increase as well.

Fred

What is the pressure running on the boiler? The lower the pressure, the faster the steam will move down the mains. Do both mains currently have the same amount of venting on them? If one has more venting, it may be getting steam faster than the other. The third return you see, that drops down from the ceiling, what size is that? Is it just a drip leg, 3/4 to 1 inch in diameter or is it a full size return? From the pictures you posted, I only see one main coming off of your header. If you actually have three mains, they should all be fed directly off of the header. I'm not sure you are going to achieve optimim system performance feeding all three mains off of the one riser coming off of that header.

mcvetyty

Fred said:

What is the pressure running on the boiler? The lower the pressure, the faster the steam will move down the mains. Do both mains currently have the same amount of venting on them? If one has more venting, it may be getting steam faster than the other. The third return you see, that drops down from the ceiling, what size is that? Is it just a drip leg, 3/4 to 1 inch in diameter or is it a full size return? From the pictures you posted, I only see one main coming off of your header. If you actually have three mains, they should all be fed directly off of the header. I'm not sure you are going to achieve optimim system performance feeding all three mains off of the one riser coming off of that header.

Great questions.. Here are some answers to the best of my ability:

1) If the pressure is the Honeywell indicator on the front, then it appears to be set to about 1.5 PSI. I've attached a picture to verify.

2) The mystery return that's unvented from the ceiling has a circumference of 6.25",

3) I am starting to wonder if my terminology is correct or not. I've attached a different picture that shows the boiler setup better, but I am starting to believe I have only one main, but then three separate returns? Does that answer your question?

Fred

The Pressuretrol should be set at .5PSI. On top of the unit there is a screw. Turn it to turn the Cut-In pressure down to .05. In the center bottom front of the Pressuretrol is a screw. Loosen it and take the cover off. Inside you will see a white wheel. Set it to 1. That is you differential and will give you a Cut-out Pressure of 1.5PSI (.5 cut-in + 1 Differential). Your pressure is set too high right now. Make sure the pigtail that the Pressuretrol is mounted to is clean and open. If it is plugged, it will not allow the Pressuretrol to do its job.

That mistery return appears to be about 1.5 inch ID. It probably is a return and not a drip leg. My suspecion is that you have 2 or 3 mains being fed off of that one riser. We need to see a picture of the piping above the riser that goes up from the Header. I suspect that is also contributing to the long times you are seeing.

mcvetyty

Fred said:

The Pressuretrol should be set at .5PSI. On top of the unit there is a screw. Turn it to turn the Cut-In pressure down to .05. In the center bottom front of the Pressuretrol is a screw. Loosen it and take the cover off. Inside you will see a white wheel. Set it to 1. That is you differential and will give you a Cut-out Pressure of 1.5PSI (.5 cut-in + 1 Differential).

Done, thank you. The differential was set to 1 already, but I lowered the Cut-In down to .5. Any idea why the installer would have had it at 1.5? And then, can you confirm my understanding of this correctly in that this means the boiler will start releasing steam to the main sooner than it was set previously? And also it might impact how quickly the mains heat up?

Fred said:

Make sure the pigtail that the Pressuretrol is mounted to is clean and open. If it is plugged, it will not allow the Pressuretrol to do its job.

How do I do this? Detach it?

Fred said:

We need to see a picture of the piping above the riser that goes up from the Header. I suspect that is also contributing to the long times you are seeing.

Pictures attached. Basically (in my own terminology), I think I have one main riser (picture 1), and that goes for about 28 feet (picture 2) and then branches off into a T (Picture 3) which then starts feeding all of the radiators and the two T's come back to the boiler, where it is joined by the mystery return.

Fred

The boiler won't release steam any faster than it cn make steam but steam travels faster the lower the pressure so it should move through the mains a little faster but I doubt you will see and difference when starting from a cold start. The mains still have to come up to temperature. From what I see in the picture, you have one main with a couple branches off of it. In total you probably have 100 to 120 feet of main and 10 to 11 minutes is probably not that bad. Regardless of what you had hoped to achieve, you need those vents on there and it would be good to find out where that mistery pipe comes from.

As for cleaning the Pigtail, take the two wires loose inside the Pressuretrol, at the bottom of the Pressuretrol is a hex head that connects it to the Pigtail. Turn that to turn the Pressuretrol off, then you can turn the pigtail off and clean it really well inside.

mcvetyty

Fred - Thanks so much for all of your help! I'll attempt to clean the pigtail this weekend. Other than that, do you recommend I eventually try and increase the pipe size of the nipped in order to try and vent the main air quicker than the current 3/4" will?

Fred

That 3/4 inch pipe will allow you to vent up to four Gorton #2s. That should be plenty.

KC_Jones

I noticed in the one picture (white pipes) that the main appears to tee. It's possible this is one of the mystery returns. If it tees and both sides of the tee have a return that would explain 2, but the third is still perplexing. I wonder if it could be a drip off of a long run out to a large radiator? It's really hard to say without being there. It would be a good idea to try and map out your entire system as best as you can. This might answer the questions and in the long run it can be a useful tuning tool to know pipe size, length amount of venting etc. It's sometimes nice to be able to study what you have and you could post it here for more input.

mcvetyty

KC_Jones said:

I noticed in the one picture (white pipes) that the main appears to tee. It's possible this is one of the mystery returns. If it tees and both sides of the tee have a return that would explain 2, but the third is still perplexing. I wonder if it could be a drip off of a long run out to a large radiator? It's really hard to say without being there. It would be a good idea to try and map out your entire system as best as you can. This might answer the questions and in the long run it can be a useful tuning tool to know pipe size, length amount of venting etc. It's sometimes nice to be able to study what you have and you could post it here for more input.

That's a great suggestion, KC. I'll try and put a map together, but I've tried to follow all of the mains I could and none of them make sense for feeding that mystery return. The two ends of the T at the end of the white pipe are actually the Return #1 and Return #2 pipes I illustrated in the first post, and both have Hoffman 4A vents on them.

I wish I could figure out that mystery return pipe because I am almost certain its connected to the radiator in the master bedroom which is the last to heat up and unless the boiler is running for an extended period of time (basically off of a 6 degree setback) it doesn't ever stay hot very long.

My plan as of now is to add a Gorton #2 to both of the main returns, and a Gorton no. C to the bedroom radiator to see if that improves anything. Then in the spring, I will get some antlers attached to the two mains and add additional Gortons.

KC_Jones

Ok this may sound crazy, can you start at the return end and trace the pipe back that way? I hate to say that as I would guess you already tried it, but figured I would throw it out anyway. It is possible it's some kind of drip or return pipe for a remote radiator...anything is possible with steam.

mcvetyty

Unfortunately it's not possible to trace. It goes directly from that image over to a corner and up through the basement ceiling. It's the same corner of the house that the master radiator is in, two floors up, which is why I assume they are connected.

Forgive my ignorance, but I am not sure I understand the difference between a drip pipe and a main return, and probably have mixed the two up throughout this thread. If a main return is defined by just the loop of pipes that happens in the basement, then I actually no longer think this is one of them as this seems to come straight down from the wall/ceiling in the corner of the basement.

But if that were the case, then why would a separate drop pipe exist? Wouldn't that negate the point of a one-pipe system where the condensed water travels back down to the mains themselves?

KC_Jones

This is going to sound crazy, but tap on it with a hammer and have someone go around the house listening for the tapping. If you tap lightly you can sometimes hear were that pipe is in a wall or floor. Hard to explain easier to show. Lol

Fred

That third return could well be a drip leg but we'll never know until you get a chance to explore further. I have a similar situation in my basement where one of my mains extends out to reach a single radiator. In my case, they tilted that branch down, away from the boiler and put a drip leg on the bottom of that branch to carry condendate back to the boiler. It drops down below the water line and ties into the common wet return, before the Hartford loop.

mcvetyty

Alright everyone.. I am hoping someone is still around on this thread. I've done some investigation, and I am pretty sure that 'mystery' main return/drip pipe/whatever that is referenced in my very first post, is actually the riser that goes to the master bedroom radiator (the one that is always last to heat up, etc.).

I've attached a picture of the configuration, and here is what I believe is happening:

"One" illustrates the end of one of my main branches, which has a main vent on it with a Gorton #2.

"Two" is where the end of the main branch heads back down to the boiler, but also where it forks off to this mystery pipe, which I am postulating is actually the riser to the master bedroom radiator.

"Three" is where the 'riser' disappears into the wall/ceiling (same corner of the house as the master radiator).

Is this setup an issue? Shouldn't the riser for that radiator be connected to the main closer to "Three" and before the main vent?

Thanks so much!

Fred

If that is truely a riser that feeds steam to the master bedroom radiator, it should be tied into the main, before the vents. If it is a return from that radiator, it should have a vent put on it. Is this a one oor two pipe system? Is there a pipe on each side of the radiators or just one?

mcvetyty

Thanks Fred - It's a one-pipe system.

Fred

Then it needs to be moved to the main, before the vent.

mcvetyty

Hey Fred - hoping you are still monitoring this thread. My installer is pushing back about this setup being an issue, and I'm hoping you can help me describe why it is. I'm confident it's leading to my latent radiator problem, but is there an explanation that can help me form my case? I appreciate it.

KC_Jones

Basically it is tied into your return lines and not your steam main. It's pretty simple and if your installer doesn't see that I would honestly be scratching my head about their abilities with steam. I am honestly not sure how else to describe it. By the pictures you posted and what you say is going on with this pipe that is a steam FEED to a radiator tied into the RETURN line so how is it going to get a good amount of steam to even work? Even if you have some small amount of steam in that line it probably isn't enough to feed the radiator, as evidence by your saying it doesn't heat well. What is your installer suggesting as a solution to the heating problem?