Vents on steam mains vs. dry returns

wsdave

Daniel

I had/have the same system for years with the vents on the dry return just before it dropped to the wet returns.

Last summer I repiped my boiler and installed vents at the ends of my mains and left the vents on the dry returns.

I have very even heating throughout the three floors, very little noise other than the occasional expansion/contraction,and have realized a 30% savings in fuel this season. I see no problem(s) with leaving vents on returns.

Dave

Dave_4

Will there be any issues by moving the vents to the end of the steam mains rather than keep them on the ends of the dry return at the boiler? According to Hoffman Specialty they say on parallel flow one pipe steam systems with dry returns the vents should be on the end of the return. If I put the vents on the end of the main what might happen to the dry returns concerning condensate/air in the return before the boiler. If the Dead men set up this sytem as it is why should the change be made? It may be that the system was fired by coal, I'm not sure. I understand the dry returns don't need to be filled with steam and the purpose is to get steam quickest to the end of the main and henceforth the radiators. It sounds more efficient but there's no information around regarding what ramifications may be attributed by taking away the vents from the dry returns. Thanks guys!

Big Ed

vent

There is no reason to charge the dry return with steam . You can locate them on the dry return as long as you have more then 25" above the water line .

Dave_4

I agree and the vents are well above 25". I am only concerned with what may happen over time with not having the vents on the dry returns.

Noel

related service call

On an old vapor system that had a non-working vent at the far end (the low end) in the original position on the system, and a vented boiler feed tank at the boiler, with the high end of the dry return connected to the vented tank, the system would hammer like crazy on start-up.

For other reasons and at a different time, the tank was removed and the air vent restored to it's original location. It seems that the water left the supply mains and radiators much easier when both the water and the air move in the same direction (downhill). The air "helps" the water along.

In your case, the water will be "on it's own" if you relocate the vent. Also, on the return, it never sees steam. On the supply, it'll be opening and closing all of the time. I think it'll last longer on the return, if it doesn't get dirty inside.

Those fellas knew how to build a steam system.

Noel

Dave_4

That makes sense Noel. Thanks for the response. Upon inspection whenever my system was at full capacity the returns did not feel hot but rather warm to the touch so there doesn;t seem to be too much steam entering the dry returns at all. Mkes me think the purpose is to vent air and get the water along rather than bring steam to themselves to close the return.

EBEBRATT-Ed

I would put thwm at the end of the dry return. Make sure they are sized correctly. They may not be large enough.


ED

Joe K_2

10 pounds at return vents

Hello,
On my new 1 pipe steam system I have a vaporstat running at 10 ounces pressure....I have 2 Gorton #2 vents 1 foot back from the end of each of the 2 dry returns before they drops down to the boiler (total of 4 vents)...plus a pressure gauge on one of them...the pressure goes up to 10 pounds on the returns when the boiler is running at supposedly less than 11 ounces on the vaporstat.

Does anyone know how the pressure could be 10 pounds? As soon as the boiler stops firing...it drops down to 0 pounds at the return.

Thanks for any insite.
JK

thfurnitureguy_7

vents

Forgive my ignorance but isn't your dry return is just a drain back to a wet return? If you vent at the end of it with a vent large enough to give you a fast even start up, your dry return will fill with steam. Also, if your vent never sees steam, chances are it is not large enough. I would place the vent at the end of the heat line (after the last radiator on the main) any further down the line you are paying to heat the basement. If you have vents at the end of the main make sure you have no drips going into a dry return with out a U seal. Remember, steam will travel toward an open vent, it will not care if it is a main or a return. a U seal keeps it from backing up the return and closing the vent from the back side. I'm sure that there are cases that you may need steam pressure to blow water back down the return but if the thing is not plugged up and the return pipe is pitched back to the boiler why pay to heat it?

thfurnitureguy_7

JK this is a crazy amount of pressure. are you sure that this is not a OZ calibrated guage? at 10 psi your radiator vents will lock shut and not open or hiss wildly. re post under your own thread.

Daniel_3

To be sure, yes the dry return does return to a short "U" water filled portion connecting the returns immediately behind the boiler but I wouldn't call it a wet return except that below the boiler water line is is filled with water. You speak truly concerning what steam likes to do yet there are various types of one pipe systems with parallel flow/counter flow and any with wet returns will automatically need a main vent since everything after the end of the main below the a dimension will be water filled. With my one pipe system with dry returns there is no hartford loop and no real need for one since obstructions or leaks will not block the system's condensate causing a dry fire and explosion. If that were to happen then a serious water hammering would give me a huge warning signal. My concern is why did the Dead-men insist on the vent at the end of the dry return instead of placing it at the end of the main? I haven't found any information on why they did it and why is should be undone.

Daniel_3

To add, my basement stays quite cold as all my lines are insulated very well. The vents at the end of the dry returns certaintly need to be changed and I have two gorton # 1's waiting to be placed somewhere. There's no hammer, the rads all get evenly heated, and it's fairly quiet for a steam one pipe system. I do get the occasional bump from the rads due to expansion //contraction and contact with the subfloor. The worry comes from not knowing what will happen if the vents will be placed on the main ends. Will there be a newly conceived water hammer problem? Maybe a problem from the lack of proper condensate return and air evacuation from the return? Will there be a pressure gradient produced by air not being vented from the dry returns which will in turn hinder condensate flow?

thfurnitureguy_7

Dan, from my handle you can see that I am a hobbiest when it comes to steam. If I understand the piping, your system is basically a main that starts at the boiler and wraps around, all the way back to the boiler. I guess yours just isn't feeding any radiators in the part where your pipe drops in size and goes back to the boiler. Yours will Im sure heat just fine. just for kicks post a picture of the near boiler piping.

Daniel_3

See Linky

http://forums.invision.net/Thread.cfm?CFApp=2&&Message_ID=304278&_#Message304278

thfurnitureguy_8

If this is you. Your Hartford loop is at the bottom right. Your wet return is where the dry one gets wet and your dry return is the pipe below the vent and above the waterline of the wet return, by definition. What you have infront of the vent is a main. Now if you have no drips going into the "dry return" (really a main)I don't see why you cannot place your vent after the last radiator on the main and stop steaming your "dry return". When the vent closes the steam will stop at the vent. The condensate, if the pipe is pitched back to the boiler, will flow just fine. Like I said before is just a drain back to the boiler. It uses gravity, and not wind to move it back to the boiler. The only benefit I see in moving the vent to the end of the real main is a lower heat load by the amount of edr being used to heat the "dry return". It is a radiator. If it is insulated, it may not be worth the time and money to add fittings. Nice looking drop header job by the way. Thanks for posting the link

Joe K_2

You were right

Hello,
I check the guage and it reads "inches of water" not "pounds"....so it is going up to 7 inches of water at the return when the boiler is running and then immediately dropping back to 0 when the boiler shuts off.
Do you have any idea of the conversion from inches of water to ounces of pressure?
JK

Noel

28 inches is one PSI

Noel