Attempting to understand two-pipe system without steam traps or orifice plates

wentam

I moved in with my parents late last year (very old house built around 1870), and they've got a poorly-functioning steam heating setup. The radiator in my room does not heat at all, so I have a significant motive to try to understand this system .

This forum has been a great resource for learning about steam heating, but I just can't understand how this system is intended to function.

• There are no steam traps anywhere. Radiators just have an elbow on the return.
  
• All radiators have vents
  
• Returns are dry returns running around basement ceiling, and multiple radiators run into the dry return lines with no steam traps etc in the basement. Nothing to seal/separate radiators on the return.
  
• I've opened up two radiators, one working, and found no orifice plates or anything else interesting. Just a valve on one end and an elbow leading out on the other.
  
• There's one random radiator set up as a one-pipe (no return line)
  
• Most radiators work (though heating is quite uneven)
  
• Some radiators get extremely hot throughout, presumably feeding steam into the return before it condenses?
  

For the non-working radiator in my room:

• It was an addition that never worked from the day of installation.
  
• It has what appears to be a valve designed for hot water and not steam. Not sure if this is an issue or not. See photos.
  
• On particularly cold days (or if I turn the thermostat up enough for the system to run a long time), the radiator will heat up a little bit starting from the return side. Not the valve side.
  
• The return line leading to it heats up with every use a while after the pipe leading to the hot-water valve. Both pipes leading to the radiator get scalding hot, but radiator stays cold.
  

My non-working radiator, valve side: https://us.v-cdn.net/5021738/uploads/editor/vd/cg7g5nxlxywt.jpg
My non-working radiator, return side: https://us.v-cdn.net/5021738/uploads/editor/z3/5zb3340ejbp0.jpg
Working radiator, valve side: https://us.v-cdn.net/5021738/uploads/editor/o3/nfr4a0jhyh6t.jpg
Working radiator, return side (that nut thing isn't a trap, just a connector): https://us.v-cdn.net/5021738/uploads/editor/le/0r33rsd4da5l.jpg
Boiler (was originally coal): https://us.v-cdn.net/5021738/uploads/editor/xn/a7c65ag9bx54.jpg

So yeah, I'm pretty much lost at this point. Any help on this would be greatly appreciated!

Edit: system was set to 7psi for some reason, but seems to work just as well at 1/2psi, so I have left it set as such.

Jamie Hall

Are you sure this thing was originally steam? And not gravity hot water?

wentam

I suppose anything is possible, but there was at least one point in it's history where there was a coal-fired steam boiler in the basement so I feel like it's probably always been steam.

When my stepdad moved in, the coal-fired steam boiler had been converted in a bodge-y way to a gas-fired one. He had it replaced with a normal gas-fired boiler.

Edit: I also know nothing about hot water systems and would not know what to look for here.

retiredguy

On what floor is the working and non working radiators. If this is truly a steam system the vents on the radiators were probably added by someone not versed in steam. Is the boiler steam or hot water ? It could be either. Show a picture of the front of the boiler and the controls that are installed. Also show more pictures of the return piping on the right side.

wentam

It's a steam boiler, PSB-4D. There are working and non-working radiators on both floors.

Ironman

You probably have a 2 pipe air vent system. Steam traps weren't invented until about 1904.

The return pipe should be one diameter smaller to prevent steam from backing up in it or sometimes there's a restrictor in th e return elbow.

More than likely you have a vent problem on one or more radiator.

From the one boiler pic, it looks like it's not piped correctly. That would also cause many issues.

More pics of the boiler, please.

Here's an article about 2 pipe air vent systems:

https://heatinghelp.com/systems-help-center/two-pipe-air-vent-steam-heating/

wentam

Some radiators have a larger pipe on the valve side and a smaller pipe on return side -- others have both the same size.

My understanding was that a 2 pipe air vent system still required some mechanism to retain steam in the radiators, such as an orifice plate or a wet return to separate them. I have neither.

Boiler pics:

Ironman

It's hard to decipher what's been done there, but your near boiler piping looks wrong.

wentam

Ironman said:

It's hard to decipher what's been done there, but your near boiler piping looks wrong.

Well that's good to know.

Yeah, really hard to understand from photos. I'll try to diagram/3d model it or something.

wentam

Alright, I think I've got all the pipes here - here's a crude 3d model of near-boiler pipes: https://sketchfab.com/3d-models/boiler-pipes-04b3c4dfd1f746d9aa9dba82304fb6eb

Ignore any pipe pitch in model, I did not match that to reality

Left click and drag to rotate, right click and drag to pan.

Steamhead

Are the air vents on the dry (overhead) return line near the boiler working?

wentam

Steamhead said:

Are the air vents on the dry (overhead) return line near the boiler working?

No clue. How would I go about testing this?

Steamhead

Remove them and try blowing through them. I'll bet they are stuck shut, and that's why some knucklehead added vents to the radiators.

AMservices

I like your 3D model. The piping is not perfect, but it's far better then some of the horror shows that get posted here.
I want you to perform a test.
Start the boiler, let it run 20 minutes and take the vent off a radiator that's not heating. Now listen and wait.
If steam starts to fill the radiator then all you need is better air vents. If you hear a panting, like the radiator is breathing, that pulsing sound is caused by waves of condensate cutting the steam supply to that radiator.
If that's the case (and it sounds like it is because you said it never heated from when it was installed) then there will be some work correcting the piping leading to that radiator.
Might need a drip added, might need a bigger pipe properly pitched.
Try the test first.

retiredguy

Let me start by saying that I have only seen 1 of this type steam system and only observed it during a summer walk through. That said, I think that the article posted by @Ironman probably explains the design of your system. The only idea I can add is that if this system was originally coal and is now fired by a gas boiler controlled by a thermostat that may be most of the non heating radiators problem. The gas boiler cycles on/off and the coal came on in the fall and usually ran all winter with no off cycle until warm weather arrived in the spring. My guess would be that to utilize an on/off boiler you will have to add a lot of main line venting or go back to a coal boiler. The sad part of this system is that the removal of the coal unit may have been the "death kneel" to this system.All the good intentions to fixing this heating system could be in vain. You may never get working as it should. (0ld meets new) my 2 cents

AMservices

Its true that with coal burning, steam moved through the pipes differently. It doesn't mean you can't get get the job done and have a balanced heating systems burning gas or oil.
What you need is enough steam to fill the system, good working vents that can be adjusted and to be sure that the piping hasn't changed in ways that condensate is collecting where it shouldn't and is able to drain out of the steams way into the radiator.
I've never seen a steam radiator not heat without explanations.

Jamie Hall

I missed the bit about all the radiators having vents. That sort of clinches it -- two pipe air vent.

There is a good discussion of these things in The Lost Art -- if you don't have it, get it. @AMservices nailed it with his comment "What you need is enough steam to fill the system, good working vents that can be adjusted and to be sure that the piping hasn't changed in ways that condensate is collecting where it shouldn't and is able to drain out of the steams way into the radiator. " Pretty mundane stuff -- but you need to check every pipe and think about how the condensate is going to get out of it and how the steam is going to move through it. The system works well enough if you get those things right.

mikeg2015

This system was the same way. I think it’s a Moline system. It needs to run under 1psi or lower and boiler needs to be sized correctly.

I think there is a water seal or supposed to be some sort of differential pressure device at the boiler.

retiredguy

To @mikeg2015, Are the valves on the rads you show equipped with a variable flow orfice device that allows you to control the flow of steam as compared to a gate, globe or flat seated valve that is usually installed today? If so, that would allow you to control the flow of steam to each rad to better control the heating of each room. If they are that type of valve, that may be something for @wentam to consider. He could then control the flow of steam to each rad so the cold rads would be allowed to also heat at the same rate. (Just a guess)

mikeg2015

I can’t remember. I think they did, otherwise what is the point other than preventing counter flow of condensate on laterals to radiators.

We only replace a loop seal where condensate pipe went uphill due to low basement beam.

wentam

Thanks for all the help so far!

When I get a chance in the next few days I'll do the following:

• Test all vents in the system
  
• Perform AMservices' test
  
• Potentially document the rest of the system with the 3d model
  
• Make note of pipe diameters -- I believe the non-working rads have two smaller pipes of the same size going to them, while the working rads have a larger diameter pipe on the valve side.
  
• look into getting the lost art book
  

wentam

The non-working radiator in my room most definitely is panting, and it's not subtle. Removing the radiator vent does not allow the radiator to heat up.

The pipes are visually obviously pitched towards the boiler, and a radiator connected to the same main lines inches away works just fine.

The air vent on the dry return for the branch this radiator is on near the boiler has a patent number from the 1940s on it, but is extremely seized onto the pipe. Heat+big pipe wrench is not enough to remove. It's got a line of rust going down the side from rusty water coming through the vent out the top. So it's likely that it's not working.

Could insufficient venting on the dry return near the boiler be causing the panting? The other radiators connected to this line all work just fine.

clammy

It looks like the equalizer pipe off of the header is teed into the dry return drop above the water line ,it’s hard to tell between the insulation and piping .i also wonder if any of the dry returns drop into a wet return by them selves providing a water seal as to not to pressurize your return which will slow or stop your distribution ? I think I would take a closer look,at your near boiler piping size and make sure it done correctly .As some mentioned I would also look for long plugged drips in long mains .long mains with the drips removed can be a real issue to trouble shoot unless you see it and re use it again seen it done it fixed it . Are the rest of the piping on the system insulated and is the boiler properly sized just asking .from the looks of it you will hopefully get her fixed . Peace and good luck clammy

clammy

I looked a little closer and see you equalizer but your dry return must drop and form a water seal instead of tying together and dropping down .should be repipe and add more main venting .aside from closer look at the near boiler piping Peace and good luck clammy

wentam

Update: I decided to crawl under the non-working radiator in the crawlspace below with a level.

Most of the line is very subtly pitched the correct way (much less obviously so than the rest of the radiators, but pitched correctly nonetheless).

Right before the radiator, though, on the valve side, the pipe pitch reverses slightly, angled the wrong way for several feet.

Would a very small backwards pitch immediatly before the rad for a short distance like this be enough to create the panting behavior described?

If the answer is yes to that, all I would need to do is shorten the pipe leading up to the valve a bit, as that would lift up the pipe.

Jamie Hall

Yes. And it might create a water hammer now and then particularly on startup.

wentam

Thinking I may just give up on getting this to work and sticking with expensive electric heater...pretty lost at this point.

I hung a weight from a spot on the pipe as a test - got the pipe pitch very consistently pitched towards to boiler. No change in behavior: rad panting and no heat.

This is the return line that had pitch issues - not the supply. Incorrectly stated valve side before.

Mains vents seem to be working fine. There are no drips that I can find, only vents.

On all the non-working rads, supply and return pipes are both 3/4". All working rads have 1 1/4" supply and 1/2" returns.

Only thing I can think of is that the differing pipe diameters have something to do with it. I don't understand why it would make any difference - but it's the only difference I can find between this rad vs others and there must have been some reason that the working rads have the larger supply pipe.

AMservices

"Only thing I can think of is that the differing pipe diameters have something to do with it. I don't understand why it would make any difference - but it's the only difference I can find between this rad vs others and there must have been some reason that the working rads have the larger supply pipe."

You are correct. The 3/4 pipe is to small in this sanrio.
The pipe size needs to be larger enough for steam and condensate to move without getting in the way of one another.

The only way steam can make it to the radiator is if the pipe is at steam temperature.
As soon as steam hits cold pipe it will condense back into water.
What's happening is steam condensing in that 3/4 pipe and trying to drain backwards against the incoming steam.
Just like wind blowing over the surface of water, waves start to form within the pipe.
The painting you hear are waves of condensate sloshing around, pushing air out of the vent and sucking it back in.

The fix to your problem is not an easy one, but it's not completely hopeless.
You need a bigger pipe to supply steam to that radiator.

wentam

AMservices said:

You are correct. The 3/4 pipe is to small in this sanrio.

The pipe size needs to be larger enough for steam and condensate to move without getting in the way of one another.

Aha! I suspected something like this and touched on pipe diameter previously - but nobody here questioned further so I assumed it should be fine.

This 3/4" pipe is also not insulated for most of the route to the rad, which obviously is not helping reduce the condensation rate.

It's a pretty short run -- any chance insulating the pipe will give me a little bit of heat?

I don't have much in the way of plumbing skills/tools and hiring a plumber to re-run the pipe is almost certainly something we can't afford, but it's nice to understand what the problem is (and to know it was indeed the radiator installer's fault ).

I'm guessing that running this pipe, connecting to 100+year old galvanized pipe, is not in the realm of the DIYer.

Thanks so much for all the help, I've learned a ton!

AMservices

Find where the 3/4 Tee's off the main. If your lucky, the T might have a reducing first making it 3/4.
If so and you want to try some pipe fittings, 1-1/4 pipe and fittings are available at home depot.

If the T dosen't have a reducing fitting and increasing the piping size requires a new T installed on the main, then you would want someone with more experience involved.

Can't hurt trying more insulation first.
Does steam get close to the radiator?
If the valve is getting warm, then insulation might do the trick.

wentam

I'll remove insulation and look at the T soon when I get the chance. If it's a 1 1/4 thread I'll definitely consider giving it a go. Probably in the spring though, just in case I screw it up.

The supply-side pipe and valve do get hot after some time, yes. Takes longer than other rads of course.

Will probably try to insulate and see what happens.

Edit: Just checked. T is indeed 1 1/4 and converts down.