Fuzzy language

Hap_Hazzard

So when did everybody decide to change their minds about this? Not only does Dan talk about dry returns in one-pipe systems in TLAOSH (pp. 84 & 91), but, about ten years ago, I started visiting this site to get some help replacing a wet return that had rotted out, and I wanted to convert it to a dry return so it wouldn't rust out again. (https://forum.heatinghelp.com/discussion/137010/converting-a-wet-return-to-dry-return#latest) A number of the pros here were very helpful in advising me how to turn my wet return into a dry return. No one even suggested that I would be turning it into a steam main. In fact, Steamhead advised me to put the main vent at the end of the main because there is "no point in filling a dry return with steam."

EBEBRATT-Ed said:

I suggest holding your hand on the unvented pipe and see what happens when the boiler runs

You must think I'm stupid. Seriously? Do you think I don't know the pipe gets hot, or do you just want me to burn my hand? Just because it gets hot, that doesn't mean it's filling with steam. Condensation is just a process of turning 212° steam into 212° water, and that water remains scalding hot all the way back to the boiler. What makes you think steam could be entering a dry return when there's no place for the air to escape?

ChrisJ

Hap_Hazzard said:

So when did everybody decide to change their minds about this? Not only does Dan talk about dry returns in one-pipe systems in TLAOSH (pp. 84 & 91), but, about ten years ago, I started visiting this site to get some help replacing a wet return that had rotted out, and I wanted to convert it to a dry return so it wouldn't rust out again. (https://forum.heatinghelp.com/discussion/137010/converting-a-wet-return-to-dry-return#latest) A number of the pros here were very helpful in advising me how to turn my wet return into a dry return. No one even suggested that I would be turning it into a steam main. In fact, Steamhead advised me to put the main vent at the end of the main because there is "no point in filling a dry return with steam."

EBEBRATT-Ed said:

I suggest holding your hand on the unvented pipe and see what happens when the boiler runs

You must think I'm stupid. Seriously? Do you think I don't know the pipe gets hot, or do you just want me to burn my hand? Just because it gets hot, that doesn't mean it's filling with steam. Condensation is just a process of turning 212° steam into 212° water, and that water remains scalding hot all the way back to the boiler. What makes you think steam could be entering a dry return when there's no place for the air to escape?

The hot water will obviously get the pipe hot, but steam probably won't.

I have an 18" vertical length of 1/2" pipe screwed into the top of my boiler and it never gets hot more than a few inches up, most of it stays cold. It's what my gauges and low pressure control are connected to instead of a pigtail. The trapped air protects everything.

Jamie Hall

Look. In some ways it doesn't really matter what one calls any given pipe or fitting in a system. What matters is what it does and how it needs to be connected to other parts of the system. That is, within any one particular job, or for any one particular person. However, when we try to communicate with others -- whether they are other knowledgeable people or perhaps less knowledgeable ones, it can matter a lot.

I can usually (not always!) determine from context and other clues exactly what is being talked about, but not everyone can -- or should be expected to. In some situations, it doesn't matter. In others, such as the distinction between how dry returns in two pipe systems should (indeed must, in some cases) be treated and how the steam main extension, which some of us call a dry return, in one pipe systems should be treated, the difference is absolutely critical to the correct functioning of the whole system. There are other instances.

I'm not pleading for strict conformity, rather for clarity in discussion.

Hap_Hazzard

Well, Jamie, since TLAOSH defines the pipe in question as a dry return, and we recommend this book, I don't think it helps to tell people that the terminology used in that book is wrong.

Jamie Hall

With regard to the pipe in question, so long as we all remember and make clear when we are dealing with a one pipe system it or they have to be handled in one way, and when we are dealing with a two pipe system they have to be handled in completely the opposite way... particularly when we are telling some hapless homeowner or plumber what to do...

EBEBRATT-Ed

@Hap_Hazzard
So we agree the pipe has air in it. When the condensate enters the pipe because it is heavier than air the air is displaced....where does the air go?

The air being compressed by steam pressure only has two choices down to the boiler (we both know that's not happening) so it goes to the only place it can...back to the air vent.
So now we have a "steam main" that's vented (poorly vented I agree) which will allow steam to enter the pipe.

Air going against the flow of steam and condensate strikes me as the wrong thing to do so I would put the air vents at the top of the drop down to the boiler

Your not going to waste any steam. The pipe has no take offs and you agreed the pipe is hot at 212 degrees. so the pipe is radiating heat and btus are lost especially if uninsulated weather its steam or water

Having a vent located near the drop at the boiler means the pipe will be lower due to pitch allowing the vent to be installed higher above the main and along with the nearby vertical drop will keep water out of the vent....better than a tee up on the main

JMHO

Hap_Hazzard

Since the condensate starts running down the return before the steam even reaches the end of the main (I can hear it.), and the water level at the bottom of the drip at the end of the dry return doesn't change much, I don't think there's that much air getting displaced into the main after the vent closes. Certainly not enough to cause any trouble as far as I can see.

Fred

@ChrisJ , Don't think I didn't catch that:
"I mean, in the end it doesn't matter to me. You can call them Fred for all I care."
Besides, I don't know what you'd do with 20 ft of 1" main that's probably at least 50% full of condensate. I'd call that an extension of your drip.

ChrisJ

Fred said:

@ChrisJ , Don't think I didn't catch that:
"I mean, in the end it doesn't matter to me. You can call them Fred for all I care."
Besides, I don't know what you'd do with 20 ft of 1" main that's probably at least 50% full of condensate. I'd call that an extension of your drip.

I didn't mean you specifically.

jhrost

This question is probably above my pay grade , but it seems like calling the steam main the Main Return after it passes the last radiator runout would be a fairly descriptive term since the main is now just returning condensate to the boiler. On the topic of terminology what is that section of pipe called after the steam main return drops down below the boiler water line - is it a wet return or just a mud leg, as I think I've heard it referred to here?

Maybe a question for another thread but since it has been brought up here, I'm wondering if anyone here has ever tried to quantify the difference between putting the main vents just after the last radiator runout as compared to putting them just before where the main return drops down to become wet? Like putting plugs in one location and vents in the other, then vice versa, and comparing time for vents to work , for rads to become hot, or whatever relevant measurable effects it could have.

This may be a dumb question, but would there be any value or any effect from having main vents at both locations ( leaving out the consideration of the extra cost for more main vents). Sorry for all the questions, but if you don't ask them how are you going to learn anything? I try to apply principles I've learned to make deductions , but actually I just absorb most things here by osmosis, based on the majority of prevailing opinions.

Hap_Hazzard

If you put a vent at both ends, it would still fill the return with steam, and that's not necessary, unless you want to use it as a radiator. You can quantify the amount of steam it uses by calculating the surface area of the return piping up to the last vent as squre feet of steam.

Jamie Hall

If. And ONLY if. You two are talking about one pipe steam systems!

EBEBRATT-Ed

I think we have beaten this one to death