One Pipe Steam No Main Vents

PhilDavid

After replacing a leaking 2" elbow in the main, I discovered this one pipe system with two mains has zero vents on them. Of course there is water hammer, spitting rad vents, short cycling, and uneven heating. The rad vents are currently the only way the air escapes from the system. My solution would be to add a vent to the end of each main.
Sounds like a no brainier right?
However I have a buddy who I've always regarded as well versed in steam, telling me that the system was designed to vent the air through the convection style rads. I'm sorry I don't have pics but these rads look similar to hydronic baseboard. He said this design allows the condensate to return to the boiler. I'm very skeptical as this doesn't jive with anything I've read in Dan's book The Lost Art Of Steam Heating. Maybe it's in one of the others I haven't read?
Would the steam gods please enlighten me.

ChrisJ

Maybe your buddy is right, however the system was also designed to burn coal and heat super slow.

What it was designed for is moot.

It needs main vents, probably multiple per main.

Dave in QCA

@PhilDavid If this system was working perfectly, your buddy's comments would be valid. But, on one hand the system is not working well at all, and he says, "it was designed that way."

Looking at the original intent of the design is always the best way to approach a system that has been knuckleheaded. But, when a system is not working well, there are two things that need to be considered. In addition to how it was originally designed, you also have to analyze why the system is not working well and determine what has to be done to correct it.

gerry gill

Dave in QCA is correct. There are other issues at play here besides the venting.

PhilDavid

It seems apparent that this system is prob as old as the house (turn of 20th century cape) as there is no wet return or Hartford loop. Only wet return is the equalizer where it drops below water line and then turns into the boiler. All condensate returns to the boiler via the two 2" mains that are pitched back to the boiler.
So to address the lack of a Hartford loop my buddy wants to drip the mains 5-10ft out from the header into a wet return to tie back into the equalizer.
Is this necessary?

Double D

Sounding like a counter flow system.

Dave in QCA

You are describing a counter flow system. The close boiler piping is different for these. Most manufacturers will show a recommended setup, and they generally are about the same. Generally, a Hartford loop is not required on a conterflow system.

Fred

If the mains are pitched back towards the boiler, it does sound like a counter flow. Putting drips and the end of the mains, if theose ends are the high point of the mains won't fix anything. You need to look at those mains from start to end and see if there are sags ythat might be holding water and causing hammer. Also look at all the radiator run outs and make sure they pitch back towards the mains. Check the radiators and make sure they are all slightly pitched back towards the inlet pipe.
Make sure the pressure is set so the the Cut-in is around .5PSI and the Cut-out is no more than 1.5 PSI. Take the Pressuretrol off and clean out the pigtail. They get clogged and that prevents the Pressuretrol from seeing the actual pressure. High pressure can push water up into the system and also push some out of the radiator vents, especially if things aren't properly pitched.
Also, vents at the ends of those mains will help get the air out of the mains a lot faster and save some fuel. Probably will help a lot with initial pressure. As far as short cycling, how short and how often? I suspect the boiler is probably over-sized for the attached radiator EDR. Have you looked at the total Radiator EDR and compared that to the Sq. Ft. of steam output of the boiler?

Jamie Hall

Counterflow, no pipes below the water line -- no Hartford loop.

However... if you have any banging or clanging, go through the whole system -- every single pipe, however long or short, and make sure that the pitch is in the right direction and adequate. Older houses sag, and pipes sag with them -- and bang.

Also, check your pressure. It should be no more than 1.5 psi at cutout.

Main vents -- as has been said, for coal you didn't need them (as much). For modern boilers, you need them at the outer ends of each main.

Then one can go back and work on the uneven heating by adjusting or replacing radiator vents (don't even try until you have the main venting in place).

Depending on the nature of the short cycling, the main vents may help. They may not, too, if the short cycling is caused by an oversize boiler.

PhilDavid

Ok so a counter flow system generally doesn't have/need a Hartford loop? I read about counter flow in Dan's book Lost Art but have never seen one.
One main was badly pitched and after correcting that the "man with a sledgehammer hitting the pipes" water hammer went away. However the spitting vents on the second floor are still an issue no matter how low the pressure. Must be because the air has no other way out other than the rads and is keeping condensate from returning.

Dave in QCA

What kind of vents are you using?

Double D

Are your pipes insulated or bare?

jumper

Those convectors also have to slope correctly. Some have dead end fin tube so it has to slope back to supply. Others are the opposite.

PhilDavid

There are no main vents. No plugged tees where there would have been one.
No the mains are not insulated. Found evidence that they once were covered with asbestos but the homeowners have no clue. They've owned it less than 7 years and have had issues since day one.
So the general consensus seems to be that I should install a main line vent at the end of each main. At least to start.

Double D

Main vents would be a great start. Seriously consider insulating the piping with a minimum of 1" fiberglass. Post some pics of the near boiler piping when possible.

PhilDavid

Yeah I'll have to go back and check the pitch on the radiators.
Feel a bit embarrassed I didn't take pics. I'll take a bunch next visit and post.
But I'm not sure how to figure the EDR on these convection style radiators. There are 3 rows side by side of finned 3/4" copper tubing just like hydronic baseboard. Like I was saying earlier the air vents on these rads are currently the only way this system breathes.
So how the heck do I get the EDR on these convection style rads?

Fred

Man hitting it with a sledge hammer?

PhilDavid

Def gonna suggest end of main vents AND insulating at least the near boiler piping.
Pics will be coming. But I gotta figure the EDR so I know if the boiler is over sized which I suspect it is.

PhilDavid

Lol. Yeah same thing my buddy said until he came to the house and I started up the boiler. It sounded like someone on the other end of the basement smashing the main with a mini sledgehammer.
It's been spooking her kids for years. After experiencing that I really felt for that family.
Imagine a noise like that at 1am

PhilDavid

We got rid of the worst of the hammer after correcting the pitch of one main that was perfectly level. Really happy to have at least corrected that.
But it didn't fix the uneven heating, spitting vents on the second floor, and boiler short cycling.

BobC

This might give you an idea if you can match the element size to one they have listed.

Bob

Fred

Check that the Pressuretrol is working and set at .5 PSI Cut-in and 1.5 PSI Cut-out and that the pigtail is not clogged. Then make sure the rads are properly pitched. Post a pic of the rads, maybe we can help determine EDR. Main venting is needed to help balance the system. Once the mains are properly vented, then you can adjust the rad venting to balance the rads better.

Double D

Measure height, length and depth of every convector. The link will give you an idea how it's done.Page 10 bottom RH and page 11 top. Take pictures of a couple of them with and without the covers.

http://www.modine.com/download/6b73bs2jc2mgmf50sve87u7dh4/13-111.pdf