2 pipe steam vapor system - possible help with venting issues

OldSteamPipesRI

I am hoping for some help troubleshooting a two pipe steam system that is not heating a few radiators in my house. To summarize, I have a two pipe steam system. The house is from 1870s and I am pretty sure was a coal system originally. I believe it was a two pipe vapor vacuum system. Currently it has an older HB Smith boiler (260 MBU) using heating oil, which runs without any issues. I have 2 cold radiators in the house upstairs (end of the lines) that do not get steam heat in supply lines while other radiators have warm supply lines. When I called repair companies, they want to replace the boiler and system which would be a project for next summer according to scheduling. The boiler appears to be sized correctly, as the recommended replacements (calculated based on number of radiators, height, tube numbers) are the same size. 

Currently, when the boiler fires, 2 radiators do not get any warm steam supply lines on our upper floor. The radiators on the lower floors have hot supply lines and get steam to the tops of the radiators near supply inlet. The bottom of the radiators stay cold. The steam traps throughout the house also stay cold, both where they exit the radiators at the bottom and the return line after the steam trap. I changed all the cage units on the steam traps (with some help from Barnes and Jones), as I thought perhaps the steam traps were failed closed. After replacing the cage units, no change in the heating issues at the radiators.

When I am in the basement, I can only find one vent on the main return line. There are no vents on the main supplies (one main line has a crossover line with a steam trap that connects to the main return). When the boiler is firing, there are small short sounds of the air coming out of one vent on main dry return (there is a small steel ball that gets pushed out on the vent, as shown in the photos below). This continues for at least 10-15minutes intermittently while the boiler is running with a few seconds of air coming out, then nothing for another minute or so, then another short air burst of venting. I think this vent is a remnant of the old vacuum system. There is also an old barnes and jones condensator, which I don’t understand the function of. The glass appears dry, so I don’t even know if the condensator is functional. 

I am wondering if my issue is a lack of venting. Basically, I think there may not be enough venting of the air, so that I am getting cool air stuck in the radiators, return lines, etc.  Then, the steam can’t force the air out of the pipes and thus won’t heat the radiators fully. I am trying to figure out an easy way to temporarily try to increase venting to see if that helps my steam supply issue. On the main return, before the vent, there is a small plug which is screwed closed. I don’t know if this can be opened to atmosphere for venting? If I unscrewed this and left it open for a few minutes, to allow venting, would this help? Obviously that would only be a quick temporary attempt to see if it helps. Would this damage my system in any way?  Or is there an easy way more main venting can be added to see if it improves the functioning of the system. I am hoping for some DIY help to see if I can make the system work/vent for this winter before doing bigger replacement project next spring/summer.

Thank you so much for your help!

Boiler

Vent

plug on main return line

Condensator

Steamhead

That looks like pretty standard Vapor. The Condensator is a "return trap", but despite that name it is actually a pressure-powered pump that makes sure the condensate can return to the boiler if its pressure rises above a pound or so.

The vent in the pic is probably the only vent in the system. The steam mains are vented thru the "crossover traps" piped between the ends of the steam mains and the dry (overhead) returns.

Post some pics of the crossover traps and a couple radiators that don't have covers on them. See if you can find any names on the radiator shutoff valves and traps.

mattmia2

don't replace the system, just figure out what is wrong with it. could be worth flooding the boiler to see if it is leaking and not making enough steam to fill the whole system . the boiler could be replaced but unless it is leaking it isn't your problem. did you replace the crossover traps or just the radiator traps? there are a lot of possible problems and you have to work through them to figure out the problem.

109A_5

Hello OldSteamPipesRI,

As a test you could back the screw out a bit and remove the ball to see if it makes a difference.

Since the radiators are at the far end I'd check for a sag in the pipes trapping condensate either cutting off the steam or the air leaving the radiators, no air leaving no steam getting in. If that trap at the end of the main is not working correctly the condensate may be puddling there blocking the steam flow to the radiators. With the Main and the pipes to the cold radiators where does the heat stop ?

I would not replace the boiler unless there is something seriously wrong with it. It seems like it is never good when they want to replace things that work, things seem to get worse, they introduce more issues to the system. If you need Pro for help find some one that wants to repair the system not just try to replace it, often making things worse.

KarlW

Do the radiators ever heat up when you've been running for a long time?

I had that at the end of line radiators in my attic - they'd take 45+ of boiler on time before they heat up. I installed a small air vent on the supply in the attack and it did the trick.

Jamie Hall

Sort of a summary here…

Problem isn't the boiler. So don't worry about that.

First thing to check is the crossover traps — there should be one at the end of each steam main connecting to the associated dry return. A quick and dirty way to check them is to fire up the boiler and follow the steam out each steam main. The mains should get nice and toasty all the way out to the crossover traps. If not… problem with the trap (or, remote possibility, condensate getting trapped — see below).

Next thing to check is how does condensate get out of the steam mains and the dry returns? Find all the low points on both the steam mains and the dry returns. There must be a drip at every low point to a wet return — unless the low point you find is a pipe which has sagged. If it's a sag, fix it.

Now go back to your problem radiators. Again, follow the steam in the runouts. Both the supply runouts and the returns must drain back freely — the supplies to the main and the returns to the dry returns. If they have sagged, fix that.

Now main venting. All the dry returns must join together at or near the boiler, and you do need adequate venting there. The existing vent should be enough — if it's working. If there is a dry return which got knuckleheaded and doesn't get back to the boiler, figure out how to reconnect it.

OldSteamPipesRI

Thank you all for the help and suggestions. I removed the steel ball on the main return vent but unfortunately that did not improve my issues. That would have been a great easy fix.

So apparently on to the steam mains and crossovers. There are a total of 3 main steams in the basement. At the end of 2 of the steam mains, there are cross over traps. Unfortunately the previous homeowner put dry wall on ceiling to make the basement look pretty which made the two crossover vents very difficult to find (as you see from my attempt to cut the drywall). Unfortunately due to this, I cannot get access to remove the covers and check these two crossovers or change the cage units.

The third main does not seem to have a cross over vent (as shown).

All three mains have drip lines to the floor that do not appear to be backing up. Though it is hard to see as parts of the drip lines are buried in cement (another challenge). So I am not exactly sure how to tell if they are draining or not.

Since I couldn’t change the cage units in the cross over vents due to access, I tried measuring temps across the traps. The supply line is as hot as the main, and the temp on the return side of the traps is lower. How much lower should it be? I am just trying to figure out if they are working before cutting open the entire ceiling.

Thank you all!

1. End of steam main #1 with cross over vent
   

2. End of steam main #2 with cross over vent

3. End of steam main #3 - no cross over vent found (yet…). Drip line drops into the cement.

Jamie Hall

Even as little as a 5 to 10 degree difference across a trap is OK, although the temperature on the outlet pipe should drop off pretty fast with distance. At least you know they are open to vent!

mattmia2

The main missing the crossover trap will have to vent through the radiators which will make it slower to heat.

OldSteamPipesRI

Understood. Installing a crossover line and tying into the main return is a bit outside my DIY abilities. Is it possible to remove the cap above the drip line and install an air vent there? That I could probably do myself. But not sure how much trouble that will cause the system?

thank you!

109A_5

Is this the Main that has the radiators with the problems ?

Before you buy a vent I would remove the plug and and manually vent it to see if it makes a difference.

Also if it helps and you were to put a normal (non-vacuum) vent there you may loose any benefit of vacuum enhancing the performance of your system. If your system is tight this lets the air out and not back in so with each subsequent heating cycle you are not burning as much fuel to push the air out of the system. The ball is a check valve.