Main air vents - how many, where, what

emk2badknees

Yep. You are right again. 225k BTU/hr was input, not net. The boiler is a Dunkirk PSB-7D. Looking up the information, it looks like net AHRI rating is 571 sq ft. or 137k BTU/hr. Like you said, oversized, but not as bad as I thought. About 38% over-capacity.

I'm glad you noticed the pipe size problem. That was a question I meant to ask. Unfortunately, that spot has the only tap at the end of the dry run. I might be able to remove the bushing to open it up to 3/4". There are some bosses before the dry run (see post and pictures from Dec 18th, 2015 above). I don't know how tough they will be to break loose. They look like they have been there a while.

I guess I have three choices:
1) See if I can remove the bushing at the end of the dry run. Is 3/4" enough for all the vents?
2) See if I can remove a fitting from the pipe before the dry run and relocate some of the vents to that location.
3) A combination of the two.

Any advice on which approach is better for an amatuer? Also, any advice on how to remove stubborn old fittings? My tools set is limited at the moment to an 18" and a 24" pipe wrench and a 12" cressent wrench. Will those do or do I need something larger?

EMK

Fred

In this case, The best approach is the one that is easiest for you. Either approach will work. I think the 3/4 tapping, if you can get the bushing out will work. I believe it has the capacity for four Gorton #2's.

ChrisJ

Glad to know I'll never fit into the "never tested their systems accurately and simply parrot what they have read on here" category.

Fred

ChrisJ said:Glad to know I'll never fit into the "never tested their systems accurately and simply parrot what they have read on here" category.


Me Too!

ChrisJ

Fred said:

Me Too!

Yeah...
We all know how much experimenting you've done.

Fred

ChrisJ said:

Fred said:

Me Too!

Yeah...
We all know how much experimenting you've done.

Sorry, I thought we were talking about "Testing" that's different from "experimenting", at least in my mind.

Jamie Hall

@Dave in QCA -- thank you! The voice of sanity... I've kind of kept my mouth shut on the whole question of how many main vents does one need, since my experience has been so radically different from the currently accepted rule of thumb -- I just figured I was working on a different planet.

I have a grand total of 150 feet of mostly 3 inch main, insulated. 3 50 footers. Each one vents through a crossover trap at the end into the dry returns, which parallel the mains and return to the boiler. The whole show is vented by one (1) Gorton #2 and one (1) Hoffman 75. It takes about 4 minutes from when steam rises at the boiler to when steam hits the crossover traps -- and almost all of that is the time it takes the steam to heat iron in the mains; the vents are inactive (but wide open) during that time. More vents would accomplish... ta da... exactly nothing.

The "rule of thumb" would require 16 Gorton #2s plus, by some comments, another 8 to vent the returns.

I don't think so...

Fred

@Jamie Hall , The excerpt from @Dave in QCA was taken from a thread that was posted several months ago and is here with the intent to be very misleading. Dave's comments in that thread was related to the fact that he has found the venting rate of the Gorton #2 to be incorrect because, after the first vent, the mains remain hot enough, especially if they are insulated, that they don't open all the way and the next cycle the venting rate is slower. Dave prefers Hoffman 75's because they open faster than the Gortons. Dave correct me if I am wrong or if I am mis-stating your experiences.
Also, Jamie, we are talking about a one pipe system here. You have the venting advantage of those cross over traps at the end of your mains which vent the air into the dry returns.
Referencing @gerry gill 's venting capacity study, he indicates that venting on the mains, of a single pipe system, should be fast but to determine the "fastest" venting you can get is to do an experiment to determine the fastest venting you can accomplish. That experiment entails removing the venting at the end of a main and timing how long it takes for steam to arrive there, after it leaves the header. Once you get that time, you can calculate how many vents of the various types avaiable it will take to come as close to matching the "open Pipe" time as possible. That's the best you are going to vent.
Does one need to vent the mains to that capacity, maybe not but there are some trade offs on effeciency/fuel use. Every Steaam system owner will have to decide for themselves what that means to them.
As for this particular OP, my comment to him was that he has four Gorton #2's and a Hoffman #75 on a 1/2" pipe whose total capacity is about the same as 2 Gorton #2's and that the additional vents were being wasted.
I am hopeful that both Dave and Gerry will chime in here and share their thoughts.
EDIT: I would certainly like to hear @Dan Holohan 's perspective on this subject as well. Between these three guys, they have a multitude of experience that none of us who have posted a response on this thread can match.

Fizz

Have a Richardson System with 2 main loops with dry return for each. The system called for a vent for each dry return but mine has common vent for each above the boiler. I notice that long loop which has 137 sf of radiation attached heats quicker and better than short loop which has 220 sf of radiation vented to same vent. My question is would adding another vent to short loop return improve the efficincy of the loop?

nicholas bonham-carter

Fizz--Try running it with the vent removed on the slow loop, and see if it speeds up.
Be ready to cut off the boiler when steam gets to the empty vent tapping. If there is a noticeable increase in speed, then get a bigger vent
Knees, remember that the main vents must be sized so that their resistance to flow (back-pressure) is lower that the aggregate resistance of the slower radiator vents. A good low pressure gauge will show you how many ounces the main vents are operating at-a couple of ounces at the most.
This will ensure that steam fills all the mains first (path of least resistance), and then begins to rise up into the radiators.--NBC

ChrisJ

And if you don't, you can always slow the other one down a bit.

It's a balancing act and faster isn't always better.

vaporvac

I'm reading that he only has ONE vent total for both mains. How would he test it in this case?

ChrisJ

Hatterasguy said:

Jamie Hall said:

More vents would accomplish... ta da... exactly nothing.

The "rule of thumb" would require 16 Gorton #2s plus, by some comments, another 8 to vent the returns.

I don't think so...

Exactly right.

The "rule of thumb" is wildly exaggerated.

Additionally, what exactly is saved if the time decreases by one minute? No fuel is saved. The rads at the end of the mains get steam one minute later. Easily manageable with radiator vents.

The entire concept of venting the mains at the equivalent of an open 1/2" pipe is simply over the top. Why use an open 1/2" pipe as your standard just because that is what you happen to have? You could make an even more ridiculous argument that you need a 1.5" hole to achieve the desired result.

All you accomplish is to enrich Gorton.

From my boiler to the radiators in an extra minute. An added minute is a shameful outrage. This is just an egg timer! What if it had been something else, like your paycheck, or poison berries, or adoption papers? An extra minute is an eternity, the cosmos was created in less time. Wars have been fought and nations toppled at a minute! Fortune made and squandered.


See if anyone gets it....

By the way Hat, my typical preheat time is 3 minutes, as fast as 90 seconds on a super cold day. An extra minute on a system like mine truly is an eternity.

Chris_L

I hesitate to jump into this one, but since I've been logging my header temperature and temperatures at the end of the two mains for most of this season, I thought I'd share what I've found. (This is a single-pipe, parallel flow system with the vents at the end of the dry returns.)

First, if you are going to talk about how long it takes the steam to get from the header to the end of the mains, you have to consider the starting temperature of the mains. On my longer main, the time can range from about four minutes, when the main temperature is about 53F to a minute or so when the temperature is 150F.

My mains cool at roughly 1 degree F per minute, so on cold days, if the heat comes on once an hour, there isn't much difference between an open pipe and a modest vent on the main.

This means if you are doing the "open pipe" test, be sure your starting conditions are the same. If you do the test with your normal vent and then repeat it with the vent off, you are guaranteed to get a misleading result with the vent off unless you let the system return to the same starting temperature.

I'm not yet sure what is the "right" amount of venting for my system, but one thing I've found is that by adjusting the relative amount of venting on each main, I can balance the time the steam reaches the end of each main pretty well.

Dave in QCA

My previous post from back in December has been quoted. I intended to answer the questions sooner, but I'm just getting to it now. It has been suggested that the repost was out of context. So, I am going to again repost both the first post in question and my subsequent answer, for the sake of clarity.

First Post:
Fred, I'm just jumping in here with a question. I was quite active on here in the past and have not been so active for the last year or so. Coming back on recently, I have been seeing reference to this "rule of thumb" of one Gorton #2 for every 20' of 2" main. Now... going back to the charts in Greening Steam, and the other information there from Gill and Pajek, if we are working at 1oz, which is half of the 2oz. that was usually used, a Gorton #2 would be good for about 95' of 2" main. Now, I'm all for proper venting of the mains, it is an absolute necessity to achieve even steam distribution. But, can you give me any idea where this new "rule of thumb" came from, and/or the rationale? I'm just trying to catch up here.

Then Fred answered and explained:
@Dave in QCA The 1 Gorton #2 per 20 feet of 2" pipe has been the topic of debate for a long time. Some feel it it over kill, others feel it works out well when one measures the time it takes to vent an "open" 2" main compared to the number of Gorton #2's necessary to vent that same main in an equal amount of time, realizing that the Gortons start to close at somewhere around 120/140 or so degrees. I haven't done that testing myself but others have. I guess the fool proof way to vent any main, as fast as possible and similarly to an open pipe (give or take a few seconds/minute), is to run through that exercise before investing in main vents but for those who don't want to take that time, the rule of thumb has been a relatively reasonable one. I happen to use Hoffman 75's on my mains and i have to say, in my case, the number of 75's comes very close to that rule of thumb when I consider that it takes 2 Hoffman 75's to equal one Gorton #2. If that means anything.

Second Post:
@Fred Thanks for clarifying. It is nice to know that the "rule of thumb" is a result of actual performance to the Gorton #2 in real world conditions. My observations are similar. That is to say, while the G2 performs amazingly well on the test bench as well as a cold start up, its performance on a system with insulated mains running at 1 cycle per hour is far less than the 1.1 cfm @ 1 oz. rating. The rule of thumb suggests that in practice, the performance is in the area of 0.23-0.46 cfm @ 1 oz. In my application, the performance was closer to zero. It all depends on the temperature of the mains (and the air inside of them) when the boiler begins its cycle. But, this is probably a subject for another thread.

March 3, 2016 summary:
The critical issue is the balanced distribution of steam. If distribution is not balanced, it will result in hot rooms, cold rooms, increased run times to compensate, and a generally unsatisfactory performance with increased cost of operation.

The open pipe method of determining the number of main vents necessary works, but with varying results. In some cases it may indicate that the number of vents necessary is less than the charts would dictate. In other cases, more vents than necessary. Keep in mind that when the main vents create a minor restriction resulting in a small amount of back pressure, some stream travel into laterals and risers will occur. This will slow down the "arrival time" of the steam at the main vent. However, as long as steam is not producing any measurable heating of the radiators before the main vents closed, the system will operate in a balanced manner. Heating laterals and risers will consume some of the steam and make it appear as if steam has been lost, but obviously, this is not the case.

Dave in QCA

Jamie Hall said:

@Dave in QCA -- thank you! The voice of sanity... I've kind of kept my mouth shut on the whole question of how many main vents does one need, since my experience has been so radically different from the currently accepted rule of thumb -- I just figured I was working on a different planet.

I have a grand total of 150 feet of mostly 3 inch main, insulated. 3 50 footers. Each one vents through a crossover trap at the end into the dry returns, which parallel the mains and return to the boiler. The whole show is vented by one (1) Gorton #2 and one (1) Hoffman 75. It takes about 4 minutes from when steam rises at the boiler to when steam hits the crossover traps -- and almost all of that is the time it takes the steam to heat iron in the mains; the vents are inactive (but wide open) during that time. More vents would accomplish... ta da... exactly nothing.

The "rule of thumb" would require 16 Gorton #2s plus, by some comments, another 8 to vent the returns.

I don't think so...

Jamie, I do certainly agree that the "rule of thumb" is an over exaggeration and I believe it points to a serious operating flaw of the Gorton G2 vent. I have invested in flow meters and intend on recreating Gill & Pajeck's flow tests, but with the added factor of temperature of the air being vented. I had fully intended to have that done a while ago, but some foot surgery has slowed me down temporarily.

For the benefit of other readers, Jamie is venting the condensate return lines of his system. All venting takes place at this point because main venting is done by crossover traps. Many systems can have the condensate lines vented with an open pipe or a float type air eliminator, because steam is never present in the returns. However, Jamie's system has a Hoffman Differential Loop on it and in certain conditions it will actually allow steam to flow into the returns. Thus, the return main vents must protect against steam.

The only thing I would consider doing differently is to experiment with one Hoffman 76 vacuum vent. While a single vent may be too slow initially, once you have the air out, the vacuum vent will prevent it from returning and thus on subsequent cycles there is much less air to be vented. It all depends on how tight your system is otherwise, especially your radiator inlet valves.

Fred

@Dave in QCA Thank you for your response. I apologize for wasting your time, and hate that others would take excerts from others and try to make them appear other than intended. What puzzles me is why Brian, AKA Hatteras Guy would make such an issue out of the open pipe venting approach when I can go back to multiple posts, of his over the past several months and demonstrate where he has advised other posters to take that very approach. I guess, maybe I do understand. For whatever reason, he has chosen to become my own personal Troll and it's ashame he can't spend his time in more productive ways but it is what it is.

EDIT: Maybe it would be in my best interest to report this Trolling issue to the site admin and let them monitor/handle it so we can do what we come here to do.: Help others as best we can and get help when we need it.

Fred

@Hatterasguy And, as far as being "your personal troll" Fred, that inferiority complex is going to kill you.
It's not an inferiority complex , on my part Hat. I took it as a compliment for a while that you found my comments that significant that you needed to do your best to discredit me, in favor of your "all knowing" wisdom. But now, it's boring and wasting everybody's time. The Pro's that come here, deserve better when they spend their time trying to help us HO's for free.
For a while, I thought maybe you just get up some mornings feeling especially inadequate and, on those days you just needed to lash out. Then, I began to think maybe you were just a mean drunk and when under the influence, your behavior changed. Unfortunately, I can't decide what the problem is but I know you aren't qualified to evaluate my "Condition".

vaporvac

And here I thought you guys were just joking. The nice thing about this forum is that we can use our experience, limited though that may be in my case, to help others with a similar dilemma. I don't mind at all when people disagree and it highlights the complexity of these issues. However, the venting issues associated with one-pipe systems sure make me appreciate my trapless, two-pipe vacuum!!!

Fred

Hatterasguy said:

What the pro's deserve, and what the HO's deserve is information that is factual and can be substantiated with personal experience and data.

What they do not deserve is anecdotal evidence from a single 40 year old steam system that the homeowner believes is the defacto standard for all steam systems in existence since the beginning of time.

What is extraordinarily unbelievable is that you feel qualified to determine what the pro's believe, despite the fact that you've never spoken with any of them.

The inferiority complex stems from your misguided belief that I have a personal vendetta against you when nothing could be further from the truth. The data or just plain physics tell the tale and in many situations, your statements simply conflict with it.

And, BTW, I am not the only individual on here who has observed the same behavior, of that you can be assured.

Did I touch a nerve? Keep trying to discredit me and everyone else on here Hat. That hasn't gone un-noticed by the vast majority on this site either. My system is not a defacto standard and I never said it was but at least I OWN a system. Do You?

Fred

Given the fiasco you had a few weeks ago, with your insults of a PRO, who by the way does excellent installs, and finally admitting who you are and what you do, I have to assume you aren't a licensed Tradesman. Let the Buyer Beware!

Fred

Hatterasguy said:

You know what they say about people who assume..................

That sometimes they are right? Answer the question. Are you a licensed Tradesman?

ChrisJ

Guys, chillax.

Fred

Yea right. If I were wrong, you'd have no problem stating that you were licensed and you proudly spell out in which trades. I know enough and I'll spend the rest of my time trying to help others on this site. However, Don't take that to mean you can make other insults that I won't address. You, Sir are a Fake, and a phony who continues to try to present himself as the only one on this site who can solve a problem or who could possibly design a functional boiler, system and even proper venting. Be respectful of others on here and try to help. That's the goal of this site.

Fred

One of your best tactics, Hat is to try to divert from the subject at hand, when you are cornered. I have seen that repeatedly and others do too. Stop the BS and try to be helpful to others on this site or shut up. If you are licensed, at anything, prove it. Yes, I know these people who you speak of but, I also know, if you could, you would have told each of them how to do it better (meaning your way). That's what got you in trouble a few weeks ago when you were challenged to step up and tell others on this site who you really are.

Fred

Thank you. You do the same. Post some pictures of all those installs when you get a chance so that others on this site can benefit from your expertise.

Dave in QCA

Hey you two!!

I had no idea that me posting some thought in this thread would create such a fire storm! I truly regret it now. You know, it takes two to fight, but it takes only one to stop it.

PLEASE! STOP!! NOW!

Fred

I said, over a year ago in several posts that I thought a 20% Pick-up factor would probably work but that I wouldn't go less than that. If it were worth the time, I'd go back and pull those threads up for you to review. Maybe you somehow missed those??? In any case, I think circumstances in every house is different. When my boiler gives up the ghost, I will do what 98% of the Pros do and replace it with a boiler that has a standard 33% Pick-up factor. I have a lot of Mains and run-outs and no reason to do otherwise, unless the Industry standard changes downward. I'm not interested in being a "trend setter". That may be a lot of the reason there is so much disagreement on boiler sizing. IDK.

Fred

Dave in QCA said:

Hey you two!!

I had no idea that me posting some thought in this thread would create such a fire storm! I truly regret it now. You know, it takes two to fight, but it takes only one to stop it.

PLEASE! STOP!! NOW!

LOL, @Dave in QCA , your post did not start the firestorm. This one may rekindle it though .

ChrisJ

ChrisJ said:

Hatterasguy said:

Jamie Hall said:

More vents would accomplish... ta da... exactly nothing.

The "rule of thumb" would require 16 Gorton #2s plus, by some comments, another 8 to vent the returns.

I don't think so...

Exactly right.

The "rule of thumb" is wildly exaggerated.

Additionally, what exactly is saved if the time decreases by one minute? No fuel is saved. The rads at the end of the mains get steam one minute later. Easily manageable with radiator vents.

The entire concept of venting the mains at the equivalent of an open 1/2" pipe is simply over the top. Why use an open 1/2" pipe as your standard just because that is what you happen to have? You could make an even more ridiculous argument that you need a 1.5" hole to achieve the desired result.

All you accomplish is to enrich Gorton.

From my boiler to the radiators in an extra minute. An added minute is a shameful outrage. This is just an egg timer! What if it had been something else, like your paycheck, or poison berries, or adoption papers? An extra minute is an eternity, the cosmos was created in less time. Wars have been fought and nations toppled at a minute! Fortune made and squandered.


See if anyone gets it....

By the way Hat, my typical preheat time is 3 minutes, as fast as 90 seconds on a super cold day. An extra minute on a system like mine truly is an eternity.

Just so we're clear,
That was a modified Cast Away quote from Tom Hanks.

Dave in QCA

Ha ha! Nope, I don't think anyone got it.

But... here's one that is easier.

"The problem with steam heat is that we need more vents. But not just any vents, we need really big vents. I mean like I'm going to get the biggest hugest vents there are and when we get through, its gonna work so well that you're going to get bored with it. But that's OK cuz were gonna keep making in better anyway."

Fred

@emk2badknees , I apologize that your tread got off track but I did want to get back to you and let you know that, yes, by the way the Industry and virtually all of the Pro' s size a boiler, yours is about 37% to 38% over-sized. You might want to have a professional come in and see how much it can be down-fired to get you closer to your connected EDR or, better yet, you may want to investigate having a two stage gas valve installed.

Fred

Hatterasguy said:

Apparently some individuals are not good with mathematics so I'll repeat it again:

The gross output of the boiler is 180K. Your rads are a total of 100K. This is 80% oversized. We generally prefer something around 20% oversized to account for the piping and pickup.

Consider a Vaporstat and a two stage gas valve to save significant fuel and keep the pressure down without cycling.

Don't start with me again Hat. His boiler is rated at 571 sq. ft of steam and he has 417 sq. ft of EDR. That's 37% over-sized. The pick up factor is at the boiler design of 33% and that is an industry standard for Pic-up and not to be included in the EDR sizing calculation. The 20% you suggest is a Hatteras preference and not anything that is factual or industry accepted. Even if it were, your 80% over-sizing would still be wrong as it relates to boiler over-sizing.

Fred

Hatterasguy said:

Fred said:

Don't start with me again Hat. His boiler is rated at 571 sq. ft of steam and he has 417 sq. ft of EDR. That's 37% over-sized. The pick up factor is at the boiler design of 33% and that is an industry standard for Pic-up and not to be included in the EDR sizing calculation. The 20% you suggest is a Hatteras preference and not anything that is factual or industry accepted. Even if it were, your 80% over-sizing would still be wrong as it relates to boiler over-sizing.

That's a factually incorrect statement and you are deliberately misleading the OP into believing his problem is minor.

My calculation stands.

The boiler output is 80% above the EDR.

Well, your calculations are wrong. Go figure it out and stop talking about "factual". That coming from somone who deliberately takes another person's text and misrepresents it to support your position speaks volumes about your interpretation of "Factual" and to your character.

Fred

I'm done with you ,Hat. I've got better things to do. Even by you own admission above, you agree the boiler is 35% (actually about 37%) above the the connected EDR. Move on to someone else. There is no "Collective" proof. You aand one or two other people don't make up the majority or change the industry accepted standard, and that's a Fact.

KC_Jones

Fred said:

You aand one or two other people don't make up the majority or change the industry accepted standard, and that's a Fact.

So we shouldn't try? We should just accept things? That goes totally against innovation. What if we start realizing these boilers don't need to be that big? We have many discussions about the "inefficiency" of steam, but what if it could be made even more efficient? What if we determine the 33% is too much? Remember several decades ago it was more than that. Even some pros that now know better said they were taught to add 33% manually then compare the rating so they would be 66% not 33%. That is and has been educated out. What Hat is saying is when the boiler is oversized as it is you should work from the system EDR and calculate everything from that get the gross amount and calculate a pickup factor then compare to the boiler. 80% is the gross oversizing and the OP only needs 20-30% "oversized" or pickup factor. We shouldn't "downplay" the oversizing to people that come on here. Is it the end of the world? No it isn't, but the OP should be aware so if they ever need to replace the entire boiler they take the sizing very seriously.

Fred

KC_Jones said:

Fred said:

You aand one or two other people don't make up the majority or change the industry accepted standard, and that's a Fact.

So we shouldn't try? We should just accept things? That goes totally against innovation. What if we start realizing these boilers don't need to be that big? We have many discussions about the "inefficiency" of steam, but what if it could be made even more efficient? What if we determine the 33% is too much? Remember several decades ago it was more than that. Even some pros that now know better said they were taught to add 33% manually then compare the rating so they would be 66% not 33%. That is and has been educated out. What Hat is saying is when the boiler is oversized as it is you should work from the system EDR and calculate everything from that get the gross amount and calculate a pickup factor then compare to the boiler. 80% is the gross oversizing and the OP only needs 20-30% "oversized" or pickup factor. We shouldn't "downplay" the oversizing to people that come on here. Is it the end of the world? No it isn't, but the OP should be aware so if they ever need to replace the entire boiler they take the sizing very seriously.

@KC_Jones , I'm not suggesting that the Pick up factor should or shouldn't be changed but I am suggesting that one or two indivIduals, can't come on here and suggest it is anything different by just declaring it to be so. If we want to be factual, provide some proof and one or two houses with small; boilers and minimal mains and run-outs isn't proof. Can it work on less, in some homes probably, is the 33% pick-up required, in some homes maybe. As I said earlier, (WAY UP in this string) I'm not interested in being a trend setter AND that, when it came time for me to replace my boiler, I will use the Industry standard and what most Pro's on this site use. If, at that time, suffectient testing has been done , under enough varying conditions, that a new standard is set, That's what I'll use. I think you have a 33% pick-up factor on your boiler, because that is what the industry standard is/was when you made your sizing decision. i'm not the one who has to be convinced to move to 20%. Convince the boiler manufacturers and the Steam Pro's.
BTW, Over sizing is a condition that occurs when all requirements have been factored into the requirements. Telling a user that his/her boiler is 80% over-sized is misleading because you allowed nothing for the pick-up which is a requirement with each heating cycle, be it a requirement for 10%, 20% or 33% above the connected EDR.

emk2badknees

Attached is the information on the boiler. I see both numbers:
- 183,000 BTU/h is the heating capacity
- 137,000 BTU/hr or 571 sq ft is the Net AHRI rating

I was trying to educate me about what each one of these numbers represents and found this link:
https://heatinghelp.com/systems-help-center/boiler-ratings-explained/

My interpretation (please correct me if I am wrong) is that 183k BTU/h is the gross output, while 137k BTU/h is the Net output after accounting for heat loss to pipes, particularly during start up. I noticed that 183k is almost exactly 33% higher than 137k. Is that how the pick-up factor is calculated?

My conclusion is that I think that perhaps there is a difference in how people are using the term "oversized". Is it fair to say my boiler is 37% oversized relative to boiler sizing convention with a 33% pick-up factor (which may be too much safety margin as @Hatterasguy suggests)?

I appreciate the suggestions from both @Fred & @Hatterasguy regarding possible fixes: two stage gas valve & vaporstat.

Question on vaporstat:
- Does the vaporstat replace the pressuretrol or it be used in addition to the pressuretrol? Will the vaporstat provide more accurate control of cut-in and cut-out pressure? Now that I have a 0-3psi gauge, I have monitored the cut-in and cut-out and found that my system operates between 2.5 psi and 1 psi despite the fact that the (brand new) pressuretrol is set at 0.5 cut-in with a 1 psi differential. I have been meaning to contact Honeywell and ask them why it is functioning higher than the commanded window. Do I need to go to a vaporstat to actually control to these low pressures or should I expect better from my pressuretrol? If the vaporstat is better and will save fuel, why is a pressuretrol the standard equipment used in these systems? I do not doubt the suggestion is a valuable one, but I'm trying to get a better understanding.
- Does anyone have a feel for the amount of fuel savings to expect with either of these changes? I'm not hopeful that someone does know, but thought I'd ask in case.
- Do you guys think that the boiler sizing is linked to the pressure spike and hissing during start-up on a cold cycle and that these fixes could help there?

That brings me back to venting. Unless the boiler sizing or something else is causing the pressure spike and hissing in my system, it appears that 2 Gorton #2 vents is not enough (I have more, but I'm assuming the 1/2" piping is restricting flow to be equivalent to the two Gortons). I'd estimate that my system has about 110' of 2" pipe based on the layout I shared earlier. I will try to experiment as I open up the vent tree a bit to restrict flow less to figure out how many vents provides low pressure drop on start up, which is my main goal for venting at the moment.

BobC

One of our members came up with this procedure to recalibrate a pressuretrol -


PROCEDURE FOR RE-CALIBRATING A PRESSURETROL:

Inside the Pressuretrol, right below the micro switch, there is a pivot arm. At the end of that arm you will see a screw pin that is activated by the diaphragm at the bottom of the Pressuretrol. If you look very carefully at that screw pin, you will see it actually has a tiny (I mean tiny) hex head on it. It takes a .050 hex wrench and you can turn it clockwise (Towards the bottom of the Pressuretrol to decrease the Cut-out pressure or counter clockwise to increase the cut-out pressure (which none of us want to do but who knows, your Pressuretrol may be really screwed up!). Turn the power to the unit off first. You may find the first attempt to turn that screw a little bit stubborn (relatively speaking) because it has some Locktite on it but it does turn. Don't turn too much, a fraction of a turn goes a long way towards getting it adjusted where you want it (maybe 1/32 inch turn to start with). You may need to play with it to get it exactly where you want cut out to be.

Bob

Fred

My interpretation (please correct me if I am wrong) is that 183k BTU/h is the gross output, while 137k BTU/h is the Net output after accounting for heat loss to pipes, particularly during start up. I noticed that 183k is almost exactly 33% higher than 137k. Is that how the pick-up factor is calculated?

My conclusion is that I think that perhaps there is a difference in how people are using the term "oversized". Is it fair to say my boiler is 37% oversized relative to boiler sizing convention with a 33% pick-up factor (which may be too much safety margin as @Hatterasguy suggests)?
That's exactly how it is calculated and your conclusion is correct.
The Vaporstat is much more acccurate at lower pressures. Will it save fuel, I can't answer that but I suspect not enough to make a significant difference. Maybe someone else on here can answer that question but I would say fuel savings is driven, more by other factors in your home. A two stage gas valve will save some fuel costs because it essentially reduces the fuel input requirement and consequently the energy output. Many add the vaporstat along with the Pressuretrol so that the Vaporstat actually controls the boiler Cut-in and Cut-out pressures and the Pressuretrol becomes a back-up in the event the Vaporstat fails.
Pressuretrols are typically provided with your cast iron steam boiler because it is less costly than a Vaporstat.
Your Pressuretrol can be recalibrated to be a bit more accurate. Here is the procedure:
Inside the Pressuretrol, right below the micro switch, there is a pivot arm. At the end of that arm you will see a screw pin that is activated by the diaphragm at the bottom of the Pressuretrol. If you look very carefully at that screw pin, you will see it actually has a tiny (I mean tiny) hex head on it. It takes a .050 hex wrench and you can turn it clockwise (Towards the bottom of the Pressuretrol to decrease the Cut-out pressure or counter clockwise to increase the cut-out pressure (which none of us want to do but who knows, your Pressuretrol may be really screwed up!). Turn the power to the unit off first. You may find the first attempt to turn that screw a little bit stubborn (relatively speaking) because it has some Locktite on it but it does turn. Don't turn too much, a fraction of a turn goes a long way towards getting it adjusted where you want it (maybe 1/32 inch turn to start with). You may need to play with it to get it exactly where you want cut out to be.