Should this pipe be attached to the main steam pipe and main vent capacity questions.

SteamInWellesley

Hi, I am relatively new to steam heating and need help on a couple of things. Thank you in advance for your help!

1. Am I using the right main vents? I just got my hands on a couple of Big Mouth vents and was planning to replace the current main vent. The length of the longest run, starting from the boiler, is about 57' with 2.5" pipes. This is where a pipe tees off to the last radiator on the line. Then the 2.5" pipe continues another 5' before it reduces to a smaller pipe and goes another 29' to where the current main vent is before it heads back to the boiler. Do I need to calculate the pipes from this main that goes to up to two radiators on the second floor? If so, I should add another 12'. So on the conservative side I used the 2.5" pipe cubic feet of air per foot of 0.03 and multiply that by 103' (57'+5'+29'+12') of pipe to get 3.09 cubic feet of air. So should I use one or two Big Mouths?

2. Should this pipe be here? In the pictures below you can see a main pipe (upper left first photo) that comes out from boiler's header and goes over the white waste stack before heading to the first radiator on the line. Now my question is this. The pipe that drops below from this main pipe and runs back to the return pipe just below the main vent (the one I plan to replace with 1 or 2 Big Mouths). It looks like this pipe is also bringing condensate water back. Is this a correct set up?

Thanks!

Fred

That lower pipe is a drip. I assume the Main (upper pipe changes pitch at that location or the pipe diameter changes there and would cause water to pool in that area if the drip wasn't there?
To your question about the vents. One bigmouth at the end of that 57' main should do a good job for you. The 12' riser to the second floor will be vented by those radiators. I assume this is a one pipe system? (One supply pipe to each rad and a radiator vent on the opposite end of the rad?
You do not need a vent on the end of that lower pipe, in your picture. There is no need to move steam into that pipe.

EDIT: On closer look, I see there are two mains. Both need a bigmouth at the current vent locations will work.

New England SteamWorks

We need some more photos of the piping, but so far the only thing I see that I like is the Big Mouth box on the boiler...

JUGHNE

Is the main headed towards the camera sloped to drain back towards the boiler or towards the camera. If the high point of the main in not at the boiler then that would probably be a counterflow main. The steam goes out the condensate comes back to the boiler in the same pipe. The lower pipe would catch this condensate and put it into the return rather than it running down the steam riser. If this is the case then you need a vent at the end of that main. Let us see the end of that main.

The other side could be a parallel flow with separate returns piped back to the boiler returns.

Fred

Hatterasguy said:

Fred said:

One bigmouth at the end of that 57' main should do a good job for you.

****, somebody please help up off the floor.

@Hatterasguy, What's the problem with a Bigmouth at the end of a 57 ft. Main?

Fred

@Hatterasguy ,If I were suggesting Gorton #2's I would have suggested maybe five or six. That way he could be sure half of them would be open by the next cycle.

MilanD

@Hatterasguy @Fred @RI_SteamWorks

What's the general speed of steam coming out of the boiler? I know it has to do with volume of water/btu (how quickly steam is made) and pipe diameter. So how fast is good (is it a range), and how fast is too fast so that it creates wet steam?

Reason I ask is that Big Mouth venting capacity equals max volume gotten at 18ft/sec speed of air (or steam) through and at the 3/4 mpt vent opening at 3oz (differential at 1 psi is negligible). Isn't max venting speed limited to whatever the opening of 3/4 would allow? Anything faster than 18ft/sec would create excess pressure at the opening and would need another vent but mounted on a separate 3/4 opening (not an antler), as 3/4 hole can vent only so fast. Is this correct?

Fred

@MilanD I believe Dan's book, The Lost Art of Steam Heating has some velocity charts in it based on pipe size. The velocity out of a boiler is going to be dependent on piping out of it. Hatt can probably quote you specifics about ideal velocities. I want to say 15 to 20 PSI is good, to allow water to drop out of the steam but again, hopefully Hatt will chime in.
Based on Vent testing done by Gerry Gill, a BigMouth can vent at about 3.6 CFM at 3 ounces of pressure and a 3/4" open pipe can vent at 9.5 CFM at 3 ounces so that pipe isn't a limiting factor. That pipe could support almost 3 BigMouths. The other factor is the fact that, on start up, the system pressure is probably an ounce or less with the main vents open.

Sailah

The orifice in the big mouth is 5/8", the hex is 5/8" as well so the hex dimension is probably smaller in area but I can't look it up on phone

MilanD

Thanks @Fred and @Sailah. I was curious if in general one big mouth would be all that's needed as a main air eliminator. I have the Lost Art book at work, I'll look tomorrow what venting capacity is for 5/8 opening. I'm still a little murky on how this is calculated and when one decides that one big mouth vent is not enough, if ever.

Fred

@MilanD I think the main driver is the amount of air that needs to be vented with the minimum amount, if any, back pressure. Longer the main, bigger the diameter, the more air that needs to be removed. All of us have opinions on how much venting is required and when you reach a point where an extra few seconds or an additional minute, relative to an open vent pipe/tapping in the main, to vent that air, has significant value. You're never going to vent a main faster than that open vent pipe will allow.

Steamhead

Fred said:

That lower pipe is a drip. I assume the Main (upper pipe changes pitch at that location or the pipe diameter changes there and would cause water to pool in that area if the drip wasn't there?

HOWEVER- that drip ties into the returns above the boiler's waterline, which means that steam will travel back thru the return and close the main vent on both the returns. These three pipes will need to be repiped to connect below the waterline, otherwise those brand new Big Mouths won't do you any good.

MilanD

Is there some larger version of Hoffman 17c that can be added there instead of having to repipe them all individually to wet? Something like the old Webster 78?

MilanD

> @Fred said:
> @MilanD I think the main driver is the amount of air that needs to be vented with the minimum amount, if any, back pressure. Longer the main, bigger the diameter, the more air that needs to be removed. All of us have opinions on how much venting is required and when you reach a point where an extra few seconds or an additional minute, relative to an open vent pipe/tapping in the main, to vent that air, has significant value. You're never going to vent a main faster than that open vent pipe will allow.

@Fred, so in theory, one could do 2 or more Big Mouths on separate tappings and would benefit from even faster venting?

(sorry, I've yet again hijacked a thread with a question tangentially related to OP question)

Steamhead

A radiator trap there would slow the returning condensate and turn the "A" dimension after the trap into a "B" dimension. This might cause banging.

The Dead Men figured out long ago how to seal drips from each other, without using any moving parts. Once it's repiped, you don't need to do anything more with it.

SteamInWellesley

Steamhead said:

Fred said:

That lower pipe is a drip. I assume the Main (upper pipe changes pitch at that location or the pipe diameter changes there and would cause water to pool in that area if the drip wasn't there?

HOWEVER- that drip ties into the returns above the boiler's waterline, which means that steam will travel back thru the return and close the main vent on both the returns. These three pipes will need to be repiped to connect below the waterline, otherwise those brand new Big Mouths won't do you any good.

Thanks everyone for your responses, I really appreciate the help. Can anyone else chime in on Steamhead's assessment on the need for me to have the three pipes re-piped to connect below the waterline. Is it as simple as having a plumber come out and have him basically move the three connections below or well below the water level on the site glass or are there other details I should be aware of?

I am still getting heat in my radiators despite the three returns that are piped above the waterline. So wouldn't replacing the current main vents still help with getting the steam into my radiators quicker because the air is now getting pushed out faster? Please explain like I am 5. Thanks!

Steamhead

Nope. Steam would follow the drip from the steam main toward the vents and quickly close them.

You are right- all the plumber/pipefitter would need to do is extend those three pipes down below the waterline, then up into the Hartford Loop (which we can't see in your pics- should be below the present drip connection) so water would stand in them. Also, add a drain valve for future cleaning and servicing.

SteamInWellesley

Below are a couple photos of the Hartford loop. The first photo shows the loop end at the t-fitting about 30" from the ground. Now is this the water line? The water in my sight glass is around 35" off the ground. So I need to have the three return pipes connected at least below 30" on the second photo. Thanks.

Steamhead

Correct. The simplest way is to simply extend the horizontal pipe that goes in back of the boiler, over enough so it can catch the three drips. This pipe looks like it's 17" off the ground, so its height is fine.

New England SteamWorks

Took awhile, but, -a happy ending!