Small residential system main venting times for reference

ethicalpaul · November 10

No one asked, but here are venting times on my system for a Gorton #1, a Gorton #2, and an open 1/2" pipe. I hadn't really timed it accurately before.

My main is 30' at 2" (.69 cu ft) and then it goes down to 1-1/2" for 26' (.364 cu ft) for a total of 1.054 cu ft

I ran the test with the pipes fully steam hot (most of the main is insulated, but regardless, I only let a minute or two lapse between speed tests.

In between tests, I cooled the vent and the antler with a cold wet rag.

To start the time, I turned on the boiler and waited for condensate to show up in the steam supply, then wait a few seconds for it to also appear (as a thin film) in the riser to the main, then I would start it. If you're new here, I have sight glasses on my near boiler piping. If you're not new here, I apologize you had to read that again.

To mark the end time, I would hold the cooled vent until the steam hit it and burned me then shut the vent. The Gorton #2 is so massive that I couldn't use this method (it took too long to get heated by the steam, inflating the time). Instead I held the antler just before it until the steam burned me there. The open pipe I could see the steam condense at the exit so I knew it had arrived. I tested each configuration 3 times and took an average.

Gorton #1 (my normal vent): 24 seconds. This is much faster than I thought based on casual observation. For more about that, see below.

Gorton #2 (I got a deal on eBay): 20 seconds. Apparently a 1 cu ft main doesn't need a Gorton #2. I'll probably switch back to the #1 because it closes so much faster. The Gorton #2 is really ridiculously large and heavy.

Open 1/2" pipe: 15 seconds

*a note about venting rate. I always say the #1 really punches above its weight for venting. I stand behind that. This test is the most severe test that can be run for a vent. It is a main that was full of steam only one or two minutes ago. This does not happen in normal use.

In normal use, a boiler runs like once per hour at most. It runs for maybe 30 minutes, maybe more, maybe less, then it's off for 30 minutes, maybe more, maybe less. During that rest time, the main is cooling off (yes even if it is insulated).

A pipe that is cooler than 212 degrees has to be heated by the steam to 212 before it will let the steam pass. Try it. You can follow the steam around your basement with your hand. It's not fast. It's like a foot every 5-10 seconds, depending. With my hot main it was going like 2 feet per second.

With the cool or warm pipe slowing the steam down (which it always does), you don't need nearly as much venting rate. Gerry Gill and Steve Pajek's really nice venting chart and document touches on this in the intro writing where they do talk about testing your main with an open pipe and trying to match that with vents installed. I think this is the way to do it. But I would do the test about 1/2 hour after a call for heat ends to simulate the cooling that occurs during the heating season. In other words, use your main itself to determine how much venting you need.

If you strictly follow venting rates and main pipe calculations, I think you will be buying too much main venting. This is why I cringe when people just ask how long someone's main is and recommend like three #2 vents. You don't know how fast that main will vent until you time it.

Steamhead · November 10

@ethicalpaul , there are other things that figure into this too, such as:

1- How much capacity does the system have? How big is the boiler? A smaller boiler will produce steam at less static pressure (still in ounces though) as opposed to a larger one going into the same main. A 2" main can handle up to 386 square feet EDR, but I've seen 2" mains with much less. Since we size steam boilers to the radiation they serve, this will affect how much steam they make and at what pressure it will distribute.

2- How much resistance is in the main? This is one of those things we would need X-ray vision to see, unless we're taking pipe apart. But I've seen cases where, for example, the pipe was not properly reamed. This will impede the flow of steam through the main. The ASHVE Guides I have make a big deal about this.

3- Is the pipe insulated? Steam will distribute more slowly in an uninsulated system since more steam is condensing in the pipes.

And so on. When I make vent sizing recommendations, they are based on a lot of experience. I stand by them.

ethicalpaul · November 10

Your experience is massive and you are smart. I don't blame you for standing behind your recommendations, but I'm sorry, I'd take a simple test of an actual main anytime. Your #1 point above makes this point for me. So do your number 2 and 3 points as I think about it. All those variables are hashed out by simply timing it.

I will assert there is no pipe reaming situation in a residential low pressure steam system that can possibly make any measurable difference to the pressure in the main or the travel of the steam. Are the ASHVE Guides talking about residential pressures and residential rates of steam production in their concern about reaming?

Thank you for your reply!

Steamhead · November 10

Of course they are. They mention a trend toward lowering operating pressures generally, and in the 1947 Guide (chosen at random) in chapter 23 on page 416, we see the following quote: "All of the capacity tables in this chapter include a factor of safety. However, the factor of safety referred to does not cover abnormal defects or constrictions nor does it cover pipe not properly reamed (italics are theirs).

The 386 square foot rating for a 2" one-pipe main which appears in @DanHolohan 's "The Lost Art of Steam Heating" appears in this Guide also, and assumes a pressure drop of 1 ounce per 100 feet of main, which is typical for small systems. This means, for example, that a 50-foot main should have a total drop of half an ounce. Un-reamed pipe would definitely have an effect at such low pressure drops.

In a larger system which might use a slightly larger pressure drop, it is still important to vent the mains the same way. Steam distribution is just high(er) pressure going to low(er) pressure, and the vent location needs to be kept as low -pressure as possible.

ethicalpaul · November 10

I don't want to go too far afield here, I was just posting some real world timings for main vents on a small system, but there is no such pressure drop observable in a residential system.

I have put a high accuracy gauge at the end of my main, there is no measurable pressure drop. Every change in pressure at the boiler is nearly instantly reflected at the far end. Has anyone besides me actually measured this pressure drop, or is it theoretical, based on much greater flow rates and pressure?

My system operates at 1"-3" of water column (and yes higher after it fills), how could there be a pressure drop of 14" of water column (roughly 8 ounces/sq in)? (edit: I based this statement on my mis-reading of Steamhead's pressure drop—but I saw no drop at all).

If anyone can measure the reaming of pipe affecting anything in a residential steam system, I'd love to see it.

Steamhead · November 10

I'm going to assume that the ASHVE people found a way to measure that. I doubt they would have published it without some basis in fact. Keep in mind that your pipe length is much less than 100 feet, so it would show a smaller drop.

ethicalpaul · November 10

I did misread your drop value, sorry about that, but I saw zero drop…the entire system is the same pressure, even at the radiators.

I assume they saw something too, I just don't know anything about the pressures and flow rates they were working with so all I can speak to is what I have seen.

If anyone ever sees something different, please share it because I want to know the truth.

109A_5 · November 10

With a small system like Paul's or mine, if the atmospheric pressure inside the house is the zero pressure reference. And the measured boiler pressure is say 1" Water Column, I would suspect most of the actual pressure drop is across the vents (all of them), with the vents that flow better the pressure drop may be slightly less.

Pipe reaming is good practice (Steam, Plumbing and Electrical), any restriction to flow and subsequent unneeded turbulence should be minimized. With a very small system it may be hard to measure the effect, multiply it by many instances with many feet of pipe the effect will add up. Most inefficiencies like this are cumulative.

If you only have a dollar $ 1.00 and you only spend a penny per day (a 1 % restriction), you will be broke in 100 days. If you only spend 0.1 cents per day (a 0.1 % restriction) after 100 days you will have 90 cents left. 90 % of your original amount is much better than none.

ethicalpaul · November 10

systems much larger than mine distribute fine at those same pressures I see.

Steam isn’t pennies. The boiler is making x steam per hour. An un-reamed pipe can’t change that, nor a 100 foot pipe. The burners don’t care, and the water doesn’t care.
If there is any effect, it will appear as larger pressure at the boiler and lower pressure at the radiators.

Since even large residential systems distribute fine with tiny pressures at the boiler, I say the alleged pressure drop doesn’t exist.

It would be easy to see it existing. I look forward to that day, but until then I have real world behavior on my side and I seem to be alone in that.

But this post isn’t about that. It’s just showing the vent time of a 1 cu ft main and what should be an uncontroversial, unoriginal statement that with a simple test, anyone can determine how much venting they need.

PCapNJ · November 10

"But I would do the test about 1/2 hour after a call for heat ends to simulate the cooling that occurs during the heating season. "

What would be your prediction if you were to retest with 30mins of cooling in between? i guess actual time each takes is less important than the comparison between each against the open pipe.

#1 = 60% longer

#2 = ~33% longer

Open = 100%

My mind goes to your point of 20 v 24 seconds is very close but that is only true under this specific condition of back to back testing with 1-2 min between runs. I'm curious if we learn anything more about performance differences in other conditions (30mins between).

As usual, thanks for sharing! You have me thinking about establishing some formal baseline for my system.

ethicalpaul · November 10

I am going to run the tests again after 30 minutes of cooling, thanks.

What I expect will happen is that the size #1 vent is going to be even closer to the #2 and open pipe times

ethicalpaul · November 10

Here are the timings with 30 minutes of cooldown time between. My main is about 3/4 insulated with 1" fiberglass. After 30 minutes, the insulated pipe was still pretty hot, the uninsulated pipe was still pretty warm, and the vent antler was just slightly warm which made it easy for me to determine when the steam arrived there by touch.

Before the first timing, I ran the boiler to fill the main with steam, then shut it down and waited 30 minutes

Open 1/2" pipe: 2:19

(wait 30 minutes)

Gorton #2: 2:15

(wait 30 minutes)

Gorton #1: 2:32

Of course, the Gorton #2 shouldn't have a shorter time than the open pipe, so apparently there's at least a 4 second "noise" or margin of error due to whatever variances. The basement temperature overall might have been warmer for the Gorton #2 test, for example. Anyway that error looks to be about 5%.

So for me, it doesn't seem worth it to install a Gorton #2. The #1 only took 13 seconds longer than an open 1/2" pipe after a 30 minute rest time for my 1 cu ft main.

These results are difficult to extrapolate out to larger systems because of the way my main changes from 2" to 1-1/2". But I could measure the time it takes 10 feet of insulated 2" pipe to let steam through following a 30 minute rest, and do the same with uninsulated.

But it's so easy for each interested party to just remove their vent and time their own system as I described in the first post in this discussion. Share your results here!

Steamhead · November 10

Now try it with a longer cool-down, say 2 hours.

ethicalpaul · November 10

you got it. What’s your prediction?

Steamhead · November 10

None.

ethicalpaul · November 10

What's the fun in that?

109A_5 · November 10

I'll take the 13 seconds of fuel savings per boiler cycle, that adds up to hours per heating season that the gas meter is not turning. Money I can spend on something else.

ethicalpaul · November 10

I’m not sure that adds up. You have to cough up an extra $100 for it, and as I mentioned it closes quite a bit slower than the much smaller #1 which I didn’t count in the time as I was only interested in the steam travel time.

Also it’s not like I’m throwing away that extra burn time. The BTUs are going into my house.

But the decision is every individual’s to make!

ChrisJ · November 10

My venting was based around performance when it's below 0 out and I run 3 cph. My off cycles are often only 5 minutes at a time and my vents need to be able to keep up with that rush of steam down the toasty mains.

Venting cool piping is easy.

Venting insulated piping that's only been empty for a few minutes isn't . Well it's easy but you need a whole lot more venting.

I believe I was roughly at a 70% duty cycle at -8f.

ethicalpaul · November 10

Yes, that's why I started with the test with only a couple minutes between timings! I didn't need a whole lot more (in fact no more) venting.

109A_5 · November 10

$100 ? Anyways I don't replace my main vent every heating season.

"Also it’s not like I’m throwing away that extra burn time. The BTUs are going into my house."

You are burning fuel to do the 'work' of pushing the air out of the main, the longer that takes the more inefficient the system is and not aiding in actually heating your home. Work is not free.

Also better system balance (fill the main as fast as possible) may heat the house more evenly and may result in a shorter call for heat.

ethicalpaul · November 10

I don't think a 13 second difference in filling the main with steam is going to result in any noticeable improvement in my heat balancing on a call for heat.

Work is definitely not free, but the boiler is burning, the water is boiling, the heat is getting generated. You can't prevent that—the BTUs are going into my house.

Yes, $100 is roughly the difference between a Gorton #1 and a #2. No one said you replace a main vent every season.

But as I said, we each get to decide how much venting to add. This thread is just to provide information. I'm not even arguing in this one 🙂

ethicalpaul · November 10

Two hour between timings test

I let the system cool off for two hours between timings. In that time, the exposed pipe became room temperature, and the insulated pipe was still warm. The times are from when steam appeared in the main supply to when it appeared in the vent antler.

Open 1/2" pipe: 4:20

(wait 2 hours)

Gorton #1: 4:45

(wait 2 hours)

Gorton #2: 4:15

As you can see, a cooled off main makes the steam take longer to travel, even with no vent. Test your own systems to determine how your vents are doing, and have a good heating season!

EBEBRATT-Ed · November 11

As far as reaming goes a pipe un reamed in theory should hold a little water although the amount may be negligible if the pipe is pitched but any water would have to be reevaporated which would probably slow the steam a little.

As far as steam flow with an un reamed pipe this will only hinder the steam flow if the pipe is loaded to capacity.

That being said it is always good practice to ream all pipe

109A_5 · November 11

It is interesting (so far) that the Gorton #2 seems to consistently out perform the Open 1/2" pipe . Is that not a full port valve or are the nipples not reamed out ?

"Work is definitely not free, but the boiler is burning, the water is boiling, the heat is getting generated. You can't prevent that—the BTUs are going into my house."

Sure you can, apparently by 30 seconds with your last test. An yes, you can choose where you spend your money, I rather not give it to the gas company.

ChrisJ · November 11

https://forum.heatinghelp.com/discussion/comment/1819278#Comment_1819278

Unless you ran the tests a hundred times you can just assume the #2 is doing the same as the open pipe.

There's no way it's outperforming it.

ethicalpaul · November 11

Not the reamed out nipple idea again. You’ll have to test that yourself.

I consider the time difference to be noise especially on my small system

ethicalpaul · November 11

https://forum.heatinghelp.com/discussion/comment/1819276#Comment_1819276

Thanks Ed— Since the guys who installed my main are no doubt dead, we know they must have installed it correctly with good reaming practice

Steamhead · November 11

https://forum.heatinghelp.com/discussion/comment/1819370#Comment_1819370

Maybe, maybe not. I've seen good reaming and no reaming on Dead Men's piping.

RTW · November 11

To Paul:

I have close to fifty feet of 2inch main with an antler at the end with three ports for main venting. It now have a single #1 gorton and and single#2 gorton with an unused port on this antler furthest from the boiler ( and, its a challenge to get steam to the end compared to the other shorter main that has a single #1). Note two mains split off from the residential boiler - American Standard A3

Question: Do I change out the #2gorton and add two more #1gortons? or, do I just add another #1gorton to existing set-up.

Its a judgement call I know, I dont need the math, just your gut opinion please

Regards,

RTW

ethicalpaul · November 11

Hi @RTW

My gut feeling is that with 50 feet of 2" main, just the Gorton #2 alone should be fine. Since you already own the #2 I would keep using it. Your main is a little bigger than mine.

When you say you are having a challenge to get steam to the end of that main, do you mean that radiators on the front of that main are already getting heat before the steam gets to that main vent antler?

If so, then I would say either the Gorton #2 isn't working right, or you have really large venting on some of your radiators on that main, preventing the main from filling with steam first.

What kind of vents do you have on the radiators on that main?

See this thread where the radiators' massive vents are going to be taking steam from the main prematurely

Just to reiterate, it's good to make the main vent faster than the radiators so that the main completely (or mostly completely) fills with steam before the steam starts making its way generally evenly to the radiators.

RTW · November 11

Paul

I will boil the suspect #2 vent in white vinegar to see if that makes a difference ( its been there for many years). I tweaked the radiator venting on that main from smaller to larger with the largest - MOM D furthest away from boiler. I tried to even out system to get steam to all radiators on that main at the same time. The smaller venting on radiators nearest the boiler are old stock reliable vents with no issues and heat up properly

As another consideration, I may buy a #1 and add it to see if that makes a difference

Greatly appreciated your input!

Regards,

RTW

ethicalpaul · November 11

Oh you don't have to boil it right away. You can hold it upright and blow into the bottom to see if it lets air pass. It should be unrestricted. Form your fingers and hand into a kind of tube so you don't have to kiss the vent.

D is a very large vent on a radiator, I don't recommend it except is extreme extreme cases.

Adding a #1 to a #2 on your main shouldn't have a large effect—your #2 should allow steam to fill the main readily.

ChrisJ · November 11

https://forum.heatinghelp.com/discussion/comment/1819373#Comment_1819373

So,

Contrary to what many seem to think, much like today the deadmen had both good work and terrible work and everything in between?

RTW · November 11

This topic in above post referencing, "Maybe, maybe not. I've seen 'good reaming' and no 'reaming' on Dead Men's piping" brings to mind other interesting plumbing terms and wonder what they were thinking:

Ballcock, Diaphragm, Nipple, Rim holes, tailpiece, cock, plunger, rigid pipe, tail pipe etc.

Just sayin

Regards,

RTW

KC_Jones · November 11

https://forum.heatinghelp.com/discussion/comment/1819425#Comment_1819425

I'm sure the deadmen never notched joists to run pipes….oh wait, I've been in my basement. Never mind.

ChrisJ · November 11

https://forum.heatinghelp.com/discussion/comment/1819442#Comment_1819442

They notched them.

They also cut them out completely and didn't do anything to fix it. Just left them hanging.

Also known for knocking out bridging and crossbracing.

A joist in my bathroom has about 7" cut out of an 8" joist and that was done in 1910. Right next to it they notched the top of several to run a lead drain from I assume a tub.

delcrossv · November 11

Well, notching tops is better than bottoms. :-D

Segue:

I think the reason why the handbook is so insistent on reaming is not turbulence but rather each burr makes a pocket to collect condensate that has to be evaporated before steam will flow.

That could slow cold starts down markedly.

Theo_G · November 11

https://forum.heatinghelp.com/discussion/comment/1819442#Comment_1819442

In my basement all of the piping is hung at least a few inches below the joists. But it's a 200+ year old house that had no plumbing when it was built. Also nothing in the house is at a right angle to anything else, which was a huge problem when I was repairing/upgrading my system this year. Every single pipe was properly reamed/deburred and I did the same using one of those deburring tools you spin around the inside edge. Off topic but there were a lot of offsets using threads cut crooked at opposing angles, which I found interesting.

ChrisJ · November 11

https://forum.heatinghelp.com/discussion/comment/1819473#Comment_1819473

That suggests that single pipe systems cannot ever function because there's both water and steam in the piping at the same time?

ethicalpaul · November 11

https://forum.heatinghelp.com/discussion/comment/1819476#Comment_1819476

No, the hot water is OK

Small residential system main venting times for reference

Comments

Categories