Determining if the Main Steam Vents are still working properly

davevarga

I have a 100 year old house with three floors and there are 13 radiators. It is a single pipe steam radiator system. I want to confirm the 3 Main Vents are working. There are 2 Gorton #2 Mains, and 1 Gorton #1 Main. It is my understanding that these vents are strategically placed and they speed enable the initial steam thrust and once the steam has reached these main vents and heated them up sufficiently, those vents will remain closed for the rest of that heating cycle.

I am thinking to test each vent: at the beginning of a heating cycle I could hold a lit incense stick up right at the vent hole to see if air is coming out signaled by the disturbance of the incense smoke plume. Once the steam has started to move from the boiler the the smoke should be disturbed . And then when the vent is hot confirm with the incense stick smoke that that vent is actually closed - signaled by the smoke plume not being disturbed. This all is how it should be if the vent is working. If any vent is not working I will replace it with an exact replacement.

Is this a valid test method? If not is there a better way to diagnose these main steam vents?

Thanks!
Dave

deyrup

Should work, you might be down there for awhile though

ethicalpaul

It’s a good method. I can feel the air come out of mine with my finger. A piece of toilet paper held up should also work.

And it shouldn’t take long. Like a couple minutes from steam start time

nicholas bonham-carter

A low pressure (0-3 psi) gauge should show less than 2 ounces of pressure as the air is escaping.
What are the strategic locations of which you speak? Is there more than one main?—NBC

acwagner

@davevarga you can also check the vents to see if they are closing by holding a small mirror to it. If it's not closing, the mirror will fog up.

deyrup

ethicalpaul said:

It’s a good method. I can feel the air come out of mine with my finger. A piece of toilet paper held up should also work.

And it shouldn’t take long. Like a couple minutes from steam start time

@ethicalpaul Feel free to correct my math if I missed something to heat a 10 gallon boiler from cold start at 60 F to 212 F takes
8.33*152*10=12,661 btus, if the boiler is at 80% efficiency and is a 140k boiler then just to get the boiler to boiling will take about 7 minutes. 12661/(140,000*.8/60); and then you need to put in the energy to turn to steam, which will take more time than that; steam moves fast though so once it is in the system it will close the main vent relatively quickly.

We might have different ideas of what a while means; I think spending 10 minutes in the basement holding an incense stick over a main vent as an eternity

KC_Jones

That’s only for a cold start.  The critical time is from header hot to steam at end of main.  I’ve always done testing with a warm or hot boiler.  Under normal operation mine will take about 3 minutes from boiler firing to steam at end of main.  This is timed by the ecoSteam system using a sensor at end of the main.  Long main is about 26’ of 2” pipe, with an additional 30’ of 1” return piping with a big mouth vent at the end of that.

deyrup

KC_Jones said:

That’s only for a cold start.  The critical time is from header hot to steam at end of main.  I’ve always done testing with a warm or hot boiler.  Under normal operation mine will take about 3 minutes from boiler firing to steam at end of main.  This is timed by the ecoSteam system using a sensor at end of the main.  Long main is about 26’ of 2” pipe, with an additional 30’ of 1” return piping with a big mouth vent at the end of that.

Good idea, maybe we saved the poster 7 minutes

ethicalpaul

Note I said “Like a couple minutes from steam start time”

for consistency, interrupt a call for heat with the emergency off switch for a few minutes then switch it back to “on”.

bburd

@deyrup In addition to the water in the boiler, you also have to heat the iron (or steel) in the boiler. As an example, let’s take a 300 pound cast-iron boiler:

0.132 Btu/lb/°F specific heat of cast iron * 300 lb * 152°F = 6,019 Btu. So with the other conditions stated in your post, in theory you are looking at nearly 11 minutes from a cold start until it starts steaming.

In practice some of the iron will be hotter than the boiling point as it transfers heat from the flame and flue gases, and localized steam production may begin before everything is fully heated.

Jamie Hall

Just an observation, directed at no one... in 50 years of engineering practice as a licensed professional (civil (structural and sanitary and rail) and agricultural), the hardest thing I've had to do with the men and women working for me is to keep them from over-thinking and over calculating everything. The advent of calculators and later computers has made it even more difficult. Or as an old engineering saying goes, "it's hard to remember that you're trying to drain the swamp when you're up to you a$$ in alligators".

davevarga

Hi Deyrup, thanks... is there a faster way to diagnose the Main Vents?

ethicalpaul

Your way is fast

davevarga

Thank you all for this, I am on the right track for certain and will do this separately for each of the three Mains on this system! Either mirror, toilet paper, or incense stick I could get a visual confirmation. I think I had previously tried the finger method but was not certain w that way.

SteamingatMohawk

An infrared thermometer can tell you when the vent is at steam temperature. You can use it for other purposes in checking out how fast mains and risers heat up. Also, temperature distribution in a radiator, etc. It has lots of uses in this day and age.

I use one for cooking pancakes every third Sunday, too.

JUGHNE

You can get a very useful FLIR gun for about $400, track the steam travel, check traps etc.

It would show invisible steam wafting from vents also.

deyrup

@davevarga @ethicalpaul I think your way is totally fine; I just wanted to set some expectations on how long it might take. I would be sitting there wondering why something isn't happening and thinking I did something wrong after a minute of turning on the boiler. You might be more patient than me.

ethicalpaul

My timings are always from "time the boiler starts to steam" so it's only a few seconds before you start to feel the main vent venting from that start time

Gsmith

Here’s how I time the steam to vent: turn the stat up to start the boiler; put my hand on one of the boiler risers or boiler header; start timing when it’s too hot to keep my bare hand on the pipe; walk around to each main vent (all in basement in my case) and recode time the base of the main vent gets too hot to touch. We’re not looking for precision here, just the approximate time for steam to travel from the boiler to the vents. If you’re off by 15 second to half a minute doesn’t really matter.

Jamie Hall

@Gary Smith 's approach works for crossover traps too, only there you are timing to the trap. In a setup with crossover traps, don't pay any attention to the vent -- it will probably never close (or at least it shouldn't!) so long as your pressures are OK. The only way to assess whether the main vent in such a setup is working is to observe the system pressure on a low pressure gauge, and see if it is stable somewhere in the 1 to 4 ounce range. If it is, you're fine.

SteamingatMohawk

@JUGHNE My pancake thermometer is around 30 bucks. FLIR is cool, but beyond my pocketbook, although I'm always looking for a tool to buy.

Jells

I've been using logging thermometers to figure out what's going on in my system. For example, you can put one on the header, and one on the end of each of your mains for a day. Download the data via bluetooth, import to a spreadsheet and graph it, and it's all there to see the time relationship of all your mains to the boiler and each other. When tenants complained of being cold I discovered bad vents causing rads to to miss heat cycles with these. I was using Engbird's, but just discovered these Govee's, 2 for $18, and they have a display!

https://www.amazon.com/gp/product/B08CGM8DC7