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Help identifying and balancing two pipe steam

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I'm looking for a little help in identifying my two pipe steam heating system so that I can troubleshoot a couple problems (balance issues, steam in the return lines, and some hammering). I bought the lost art of steam heating but my system seems unusual.

Home is was built in 1915, boiler replaced several years ago with a Utica gas unit (I've been in the house about a year so no idea what it looked like before). The input and return for the radiators are on the same side. The runs of radiators drop into a dry return and at the end of each run of radiators is a siphon loop. Above the boiler at the end of the return is a large drum shaped tank with one big vent (only one on the system). I'm guessing this is some sort of vacuum vapor system?

If the boiler runs for a while, the radiators fill with steam and the steam then immediately travels through the dry return lines and back to the boiler. If it's on a while, I can hear boiling in the tank near the boiler. I've looked for some kind of trap or orifice on the radiators but as far as I can tell there is none. The shut-offs are standard, checked union elbows, looked for orifice plates, shone flashlight into the radiators and everything is just wide open.

Based on this, should I be investing in a vaporstat to keep the pressure much lower (it is currently set at 2.5psi)?
What is a good solution for steam in the returns and restoring system balance? (orifice shut offs? adding traps?)
Will fixing the above two things help with hammer? (I did replace a bunch of insulation which helped a bit, but I think some of the hammering is in the return line as steam tries to go the wrong direction since pipe/radiator pitch looks good)

I've attached some visual aids for reference to what I'm trying to describe.

Any suggestions or reference to sources for further research would be greatly appreciated!

Thanks
Kris

Comments

  • Fred
    Fred Member Posts: 8,542
    edited February 2015
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    My first guess is that that Hartford loop may be above the water line of the boiler, allowing steam to enter the return. You're thinking steam is entering from the main/s and I suspect it is entering at the boiler. Check the heigth of the Hartford loop. It should be about 2" below the boiler water line. That will also cause hammer as the steam hits the returning water.

    EDIT: Defininely drop the pressure setting on thee Pressuretrol to a Cut-in of .5PSI and a Differential of 1PSI and but a Vaporstat on, as Mark n suggested. When you do, set the Main for 10 to 12 OZ and the differential for about 6 OZ.
  • Mark N
    Mark N Member Posts: 1,115
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    Make sure the loop seals at the end of the mains are below the water level of the boiler. Pressue needs to be low so as to not have the steam blow the water out of the loops.
  • Mark N
    Mark N Member Posts: 1,115
    edited February 2015
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    Also there may be orifices in the supply valves so only a certain amount of steam could enter the rad and keep the steam out of the returns. This seems to be a Vapor system so therefore you need a vaporstat.
  • Steamhead
    Steamhead Member Posts: 17,008
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    That's a Tudor system, the first orifice-type Vapor system. It was often called the French or German system since it was popular there.

    There were several variations of this simple system, some of which used tanks to separate condensate from air. Go here for more:

    https://heatinghelp.com/heating-museum/european-heating-systems-circa-1907/
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    Lovely! Another vapour system on its way to resurrection and wonderful comfort!

    Step 1. Get yourself a 0 to 16 ounce vapourstat and install it (you can connect it is series with the existing pressuretrol) and start off with 12 ounce cutout and a 6 ounce differential.

    Step 2. As has been suggested, check the water levels -- look for any wet returns and make sure they really are still wet. That sometimes happens.

    Step 3. Take a look at each radiator and feel them when the system is running for a while. If you fund that they are generally hot across, but the returns are warm or hot -- but not steam hot, OK. If the return from a radiator is steam hot, someone may have taken the orifice out of the valve assembly or otherwise futzed with it. Try closing the valve on any misbehaving radiators part way (not all the way!).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • pickles
    pickles Member Posts: 3
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    Wow thanks everyone! You guys are a great resource, thanks for your help so far!! You've confirmed my hunch about it being a vapor system and being at too high of a pressure. I turned the pressure down, and am shopping around for a vaporstat and another gauge to add.

    Fred- you mentioned checking the height of the Hartford loop. I've been able to follow the steam travelling out of the radiators, into the returns and back to the boiler via a infrared thermometer and a little patience. That is not to say the loop isn't a contributor too. I measured up from the floor and the water level in the sight glass is at about 30", which is about the center of the short nipple on the Loop. Am I measuring this correctly? I'm thinking this is bad...

    Mark- The loops seals are definitely above the water level (about 60" vs the 30" in the boiler) Will they still function once they fill with condensate? As long as they aren't blown clear by high pressure that is...

    All the pipes are up in the ceiling so I'm thinking they were always dry, minus the loops. You can see how the boiler used to be taller by where the boiler vents into the chimney.

    I had some fun on the patent office website and looked up the radiator valves that hadn't been replaced (attached). There doesn't appear to be any throttling capability built into them but I will definitely try slightly closing some of the smaller rads to see what happens. It seems as near as I can tell they have all been fiddled with if there should be orifice plates. I would hate to remove all the vintage shut offs (especially after I crafted some wooden replacement handles for a bunch of them), but would new valves with adjustable orifice be the way to permanently tune them into balance?
    1.pdf 30.2K
  • Fred
    Fred Member Posts: 8,542
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    Fred- you mentioned checking the height of the Hartford loop. I've been able to follow the steam travelling out of the radiators, into the returns and back to the boiler via a infrared thermometer and a little patience. That is not to say the loop isn't a contributor too. I measured up from the floor and the water level in the sight glass is at about 30", which is about the center of the short nipple on the Loop. Am I measuring this correctly? I'm thinking this is bad...

    That Hartford loop should be about 2" below the water line in the boiler. It is letting steam into the return. Get that dropped down and I suspect that will resolve the water hammer.
  • Steamhead
    Steamhead Member Posts: 17,008
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    Those loop seals will work fine as is. Once in a while we find a different type of loop seal where two pipes, one from the steam main and one from the dry return, drop below the waterline before tying together and returning to the boiler- at least, they did with the original boiler. This means water fills the drops above the level of the tee, so steam can't go from one to the other. But new boiler's lower waterline might expose the tee connecting the two drops, allowing steam to pass between the two.

    The loop seals on your system are essentially backups for the rather unreliable boiler safety valves then in use. There was no vent on the tank, rather an open pipe, and if the water in the loop seal blew out, the steam would get into the dry return and out the vent.

    Here is another example of the Tudor system:

    http://forum.heatinghelp.com/discussion/130735/tudor-vapor-system-in-easton-pa#latest



    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting