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Ceiling Radiator doesn't heat

gtomr Member Posts: 4
I have a ceiling radiator in the basement of an 1920s house that doesn't heat. It is likely original. The rest of the radiators in the house heat quickly including the other ceiling radiator. The steam makes it just past the radiator valve to 1 or 2 fins out of 40 or so, but most of the radiator is cold.
There is a steam trap body but no trap mechanism.
The return runs 30 feet and "T"s in to the other ceiling radiator return which then "T"s in to the dry return
Best I can calculate return slope is about 1" for 30 feet.
I assume it worked at some time, but not in my time.
Any ideas what is wrong, and how to fix it?


  • Steamhead
    Steamhead Member Posts: 15,331
    edited December 2019
    @gtomr , this is a Vapor system. The dry (overhead) return probably has pressure in it from another leaking or gutted trap, or a main air vent that isn't working or too small. It is supposed to be at zero pressure, otherwise the steam cannot flow into the radiator.

    Where are you located?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    EBEBRATT-Ed Member Posts: 11,992
    Also, you have to keep the system pressure low or the radiator will water log through the return + what @Steamhead said
  • gtomr
    gtomr Member Posts: 4
    edited December 2019
    System pressure is 8oz/sq inch cut in to 28 oz/sq inch cut out.
    So how do I diagnose which trap? No other radiator has an issue. I would assume I need check the return temp of each radiator when the boiler is running. That could be difficult. The system is running well and I get heat before I get positive system pressure. That means relatively low temperatures.
    @Steamhead - I am in the Chicago North suburbs.
  • Jamie Hall
    Jamie Hall Member Posts: 18,923
    First off, pressure is too high for a vapour system. It should be more like 4 ounces cutin and 8 to 12 ounces cutout, depending on the system. That's not helping.

    Second, what is your venting like? Most vapour systems (not all) have crossover traps from the ends of the steam mains to the adjacent dry returns. These must be functioning correctly -- that is, closing promptly on steam, but open when cool. Then there must be adequate main venting on the dry returns -- commonly at the point where the dry returns join prior to dropping to the boiler. A small number of vapour systems did have vents on the steam mains, but this was much less common. So check those dry return vents!

    Also check around your system for water line problems. The most common setup, again, had drips at the ends of the steam mains and corresponding drips from the dry returns at the same location. These went into a wet return. A not uncommon problem is that a new boiler was put in without regard to the water line, and one or more of those wet returns is now too high and not wet any more -- thus there is no water seal at that location between the steam main and the dry return, which will pressurize the dry return. So -- using a very good level (laser or water) check all such locations to be sure that the wet return at that location is adequately below the water line. If you are running vapour system pressure, as little as 13 inches should work. At the pressures you are running, you need at least 40 inches.

    Finding a failed trap -- either crossover or radiator -- isn't really that hard, since you are looking for one that is failed open. The temperature of the outlet from the trap should be at least 5 to 10 degrees cooler than the inlet. Don't try to estimate by hand! A good IR thermometer aimed at a dark surface -- say friction tape -- on the pipe is the simplest.

    The trap giving you grief is probably toast by now... but failed closed.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • gtomr
    gtomr Member Posts: 4
    edited December 2019
    It looks like I have a bunch of research and testing.

    The pressuretrol is wildly inaccurate and can't go any lower. I may put the vaporstat that "maybe the problem" (long story) back in. That will wait until spring.

    Steam traps at the end of the mains look to be working. They seem backwards, that is the lower connection is in the steam main and the upper is in the dry return. From what I have read that is ok.
    I will check the main vent model number to see if it is large enough. I know it is working.
    Water line for wet returns look right, But I will need to measure to be sure.
    The distance you specify (13" to 40"), is that water line in wet return to steam main?

    Testing 20 radiators will take a bit
  • Do you have an accurate low pressure gauge, graduated in ounces, so as to verify the operation of the Vaporstat?
    The traps you describe are probably the crossover traps, so check the radiator traps first, as one failed open one can close down the entire line, by letting steam into the returns. Are the crossovers steam hot or condensation hot? Steam hot could indicate a failed radiator trap.—NBC
  • Jamie Hall
    Jamie Hall Member Posts: 18,923
    No, that 13 plus inches is from the point at which the drips attach to the wet return UP to the boiler water line. And that's for vapour steam pressures -- 8 ounces or less.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • gtomr
    gtomr Member Posts: 4
    The gauge I have is in gram/sq cm, but I convert to ounces as that is what you are used to.
    I don't understand the "Are the crossovers steam hot or condensation hot? " question