New house w/two pipe steam - no traps anywhere in sight

srmaietta

Hey all, I've been lurking around here for the past month reading up as much as I can (on top of Dans great book) in anticipation of buying a home that has steam heat. Great place for info!!

So I got the keys two days ago and want to describe the system to you guys and gals, it is not really fitting in with any of the types of systems I've been reading up on. Overall it all works, every radiator gets hot and there is only minimal clanking throughout the night. This house is in Bergen County NJ..

Overall description: Small natural gas boiler 35 yrs old, feeding directly up into the main (No header), the main splits immediately and each branch feeds 4 radiators (8 in total throughout the two story house) Each radiator has an inlet hand valve, an outlet hand valve and each radiator has a single pipe style vent on it. There is an old Hoffman 76A vacuum valve on each return about 5 feet from the boiler, no vents on the main, no traps between the main and return. No insulation anywhere.

So basically the steam can travel right through the radiators into the returns! On the biggest radiator you can hear the vent letting air out and then after things cool down a bit you can hear air being sucked back in (the vent whistles a bit) We stayed there one night so far tonight will be night two.

I'm thinking there should be trap on each radiator, but there is no indication of any connection/trap between the mains and returns. How common were two-pipe air vent systems like this: https://heatinghelp.com/systems-help-center/two-pipe-air-vent-steam-heating/

thanks all keep warm
~Steve

BobC

Post some pictures of one of the radiators and show the input and output of one of them close up in separate photos.

Bpob

srmaietta

WIll do Bob, I'll get some tonight and measure/map out the piping. House was originally built in 1910..
~Steve

Jamie Hall

1910 is a bit late for two pipe air vent systems, but not unheard of. They work fine; just not as easy to handle as the later ones. Your link reference is a good one for systems like that.

They balance in the same way as a one pipe system -- making sure that main and return venting is adequate, and then using the radiator vent sizes to control how fast and how much each radiator heats.

More venting on the return will help -- as usual!. But a big improvement will be insulation on all the pipes you can get to. Every single one. We generally suggest 1 inch fiberglass; one can get it in snap-on sections. It's not that cheap, but it will save money -- and the system will operate much better.

Steamhead

On that type of system, you should not have vents on the return lines- unless it's a Moline system, in which case it should not have air vents on the radiators. Pics of some radiators will help.

gerry gill

To answer your question, they were popular enough that most of us have run across them but not so popular as to dominate a neighborhood. There will be a few here and there kind of thing.

JohnNY

Last year, with a referral and some good guidance from Señor Holohan, I did a total TRV retro-fit of a 14-story 2-pipe air vent system in Manhattan. It was difficult to control because each branch had multiple radiators which meant multiple valves and vents and dealing with a lot of condensate.
Definitely a learning experience, but the building owners are calling me for lots of other work now. It seems like everyone's happy with the results.
I'm glad I had the opportunity to get my hands on this one.
Just saying.

Dave in QCA

We find that these two-pipe vented systems were quite popular in Davenport, Iowa very early. There were a LOT of them installed in 1881 and quite a few of those remain. By 1885 there seemed to be a change to one-pipe with bigger radiator valves, mains, and risers, but less piping over all. Just like today, I suppose that what the customer got was mostly what the installer recommended.

srmaietta

Hey guys, still working on getting pics of the rads and valves up, but a few observations from the past few days.
-When the system is completely cold, the water level is up past the top of the sight glass and upon first steam I can hear water boiling up inside the boilers vertical outlet pipe. Near boiler piping is kind of a mess.

The only wet (below waterline) section of the returns is a short 2.5' section of pipe right at the hartford loop.

I think I found remains of a buried return as I was popping up loose cement around the basement floor...

I found all the paperwork for the boiler, LWCO, and old Honeywell thermostat today so that is nice to have.

Sloooow drip from two of the spigots near boiler.

Sight glass leaks a bit when completely full.

Ordered a ton of insulation for the pipes, look forward to getting that installed.

Mapped out the steam piping using Sketchup, will get more of the returns on there soon.

~Steve

Dave in QCA

That can't work.... Uhh...wOW

Dave in QCA

What happens at the ends of you steam mains? The low point is the end as I recall. Is that correct? Do they connect to the return lines?

srmaietta

It definitely doesn't match anything I've read about, but it gets the house warm and no water hammer!

The mains do not connect to the returns except through the radiators. They are pitched towards the boiler. No venting on the mains, just on the returns -a Hoffman 76a per side, a few feet from the boiler. Vents on all the radiators. Inlet and outlets are on the bottom of all radiators, no high inlets like you'd usually see on two-pipe.

One radiator in particular allows steam to pass right through, its on the shorter of the green(1-1/4") pipes in the diagram above. I can feel the steam progress through the returns starting from that rad.

I attached pics of some of the valves that I could make out any logo..

thanks for any thoughts!

~Steve

Dave in QCA

Two pipe vented have both connections at the bottom. I was thinking the pipes pitched away from the boiler, but I had it wrong, so it is a counter flow system. The connections at the boiler are wrong for a counter flow, but almost sorta right. HA!

So, you say you are finding evidence of that the return piping used to run under the floor? Having the return piping down below the water line would sure make it work a LOT better. Let me find a diagram of a 2-pipe vented. It will make more sense to you when you see it.

Also, even though we may have mentioned in the past the a counter does not need a Hartford loop, in this case, if the return piping is running below the water line, (which it should), it should connect to the equalizer with a Hartford loop.

Abracadabra

sounds like water level in the boiler is too high

srmaietta

Dave QCA, the wet return does connect to the equalizer through a hartford loop. Thats the orange pipes in the diagram -you see the return that is cut off, that connects to all the radiator returns (not yet drawn in) then it goes down to the short wet section, which meets the hartford loop which cuts into the equalizer (orange pipe that goes up into the yellow main)..

Abracadabra, my gut feeling is that the water level is too high when everything has returned to the boiler, (sight glass totally full) but I'm just not sure how to tell . . . Gotta read the book again. A distance B distance etc etc.



So despite being some sort of frankenstein system, it all works. Thats the beauty of simple things like this I guess.

I would like to improve it though of course, without any major work this heating season. The boiler is 36 years old and I don't want to put much $$ into repiping it when who knows it could crap out any day now.

-I've got insulation arriving any day for all the steam pipes.
-Add a G 2 vent at the end of each 2" main, perhaps a G 1 at the end of the 12' 1-1/4" pipe (green) in the diagram above.
-Remove the vents on the returns, to discourage steam from getting to them. ?
-Balance the radiator venting. (Paid for the balancing E-Book)
-Get a better thermostat (PID) than the old old Chronotherm on there now.

Still no traps between the mains and returns, but if the rads and pipes are leveled correctly then... They shouldn't be necessary?

I've attached pics of a couple of the radiators. . . The first is in the front entranceway at foot of stairs, Second long and low is in the family room bay window behind my ez chair and the third is in the living room.

Thanks for listening

~Steve

Dave in QCA

Two pipe systems with traps do not have vents on the radiators. Air is vented and through the traps and returning piping as is the condensate. The return piping is vented to the atmosphere and the pressure difference that occurs between the boiler and the vented return lines creates a factor that is known as Dimension B.

Two pipe vented systems are much different. The return piping is NOT vented. Venting takes place at the main vents and radiator vents, but most of these systems that I have encountered do not have main vents, and thus all venting takes place via the radiator vents. Steam enters the radiators via the inlet coming from the steam mains. The return pipe is at the same pressure as the inlet, thus there is NO dimension B. Steam will not leave the radiator via the outlet pipe (if everything is working right), because the returns are not vented and there is no where for the steam to go. However, it is possible for steam to travel out of one radiator, travel through the return piping and into the outlet of another radiator. This is may happen if an inlet valve is turned off but the return is open on the second radiator, or in the case where one radiator has a very fast vent it may allow flow to come into the radiator through both the supply and return connection. Since the inlet and outlet connections have essentially same pressure, steam is allowed to enter via the supply connection as air is vented out through the vent. Water condenses and by gravity will flow out of the outlet connection.

In ideal setups, the return line in the basement will run at the floor level or even under the floor. Each radiator dropping to a wet return line will thus be separated from other radiator outlets by the water seal created. Since the return lines are not vented in any way, traps are not needed because there is no way for steam to travel in the return pips unless the air can get out.

This is a rambling description, but I hope it provides some help to you.

srmaietta

Dave in Quad - thanks for those descriptions.

Well, I have no traps anywhere and I have vents on the returns. So it is much more like a vented system... that I am assuming over the decades owners have added vents to the radiators for some reason. Or perhaps when (if) the rotted out wet returns were replaced with the current dry returns, the plumber installed the vents.. Who knows.

An interesting thing is that none of the returns get warm. (Except one where the steam was flying right through)
I'm tempted to close the return valves for a cycle or two to run it as a one pipe system to see if/what difference I get.

Take a look at the third radiator pic, it is tilted pretty drastically towards the inlet!! So that makes no sense either. I'll put a level on all of them and see whats up.

On a few of the radiators there are these tiny vents too small to have any thermostatic mechanism. Are these mini check valves perhaps? Was it at some point a vacuum system? The mystery deepens. . .

Having fun
~Steve

gcp13

All the returns from each radiator are supposed to run separately back down below the Waterlevel and tie into a horizontal wet return , then run along the basement back to the boiler and then up through the Hartford loop. I've also seen the returns pipes across the ceiling of the basement individually back to the boiler to an air vent then drop down into a wet return right next to the boiler. Either case you protect each radiator return by dropping it below the Waterlevel keeping a water seal on it.
Just make sure each return is separate until it gets down to below the water seal then they can tie together.
Some cases you may have to come back up higher than the water level and create a false Waterline to make sure that the return stays under the water at all times.
I service a couple of two pipe with air vent systems and they work very good.

Steamhead

The pics confirm it- this is a 2-pipe air-vent system. There should be no vents at all on the returns, but the steam mains should be well vented.

It's possible that Hoffman #76 is holding water up in the system with vacuum. remove the return line vents and plug the openings, vent the steam mains properly and see if that helps.

srmaietta

Thanks GCP and Steamhead.. I was thinking of venting the main and confirmation from the pros is reassuring. I added a 3 psi gauge yesterday and when underway all it does is bounce a tiny bit. So I'm getting heat with essentially zero pressure! ?

Post pics of my actual piping soon..

Enjoying the journey,
~Steve