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Radiator not fully heating up

Msteam1 Member Posts: 1

I have a two pipe steam system. Most of the building works fine. One radiator in particular is only heating up about 5 of the 12 or so “cells” the rest remain cold. Why? I have checked the steam trap, pitch etc, it seems to be draining fine, why would only a small portion of this radiator heat? And it is full temp, not like warm, it’s HOT!

also I want to buy a replacement steam trap insert. It’s different from the rest in my building (Hoffman 17-c) and so I’m not sure which insert to buy? These pics are of the trap and insert


  • Jamie Hall
    Jamie Hall Member Posts: 23,544

    Is the inlet valve open all the way?

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 9,840

    What kind of inlet valve does it have? Usually a radiator not heating fully on 2 pipe is steam getting in to the return from a bad trap elsewhere or a water seal that is no longer below the water line preventing the radiator from venting.

    Alan (California Radiant) Forbes
  • Big Ed_4
    Big Ed_4 Member Posts: 2,818

    Maybe that radiator was adjusted for a lower load .. The lower output does it work for the area ?

    I hate to see you throw the baby out with the wash water.

    There was an error rendering this rich post.

  • reggi
    reggi Member Posts: 522

    The  Barnes & Jones 3143 Cage Unit but check as suggested first

    One way to get familiar something you know nothing about is to ask a really smart person a really stupid question
  • Sylvain
    Sylvain Member Posts: 149

    either with a metering inlet valve or with an orifice.

  • mattmia2
    mattmia2 Member Posts: 9,840

    Also what is the pressuretrol/vaporstat set to? If the pressure is high it will heat some without venting at all because the pressure compresses the air and lets some steam in.

  • KarlW
    KarlW Member Posts: 110

    Could the trap have failed shut and the radiator is now filling with water? If this theory is correct, it hasn't filled all the way and you are still getting steam.

    I flooded a bathroom when I cracked open a failed shut trap I didn't know had failed (I was replacing all of my trap inserts).

  • Steamhead
    Steamhead Member Posts: 16,944

    @Msteam1 , this is what we call a Vapor system. It uses steam at ounce pressures. Milvaco was a major supplier of Vapor equipment back in the day.

    In this system, the air from the radiators is not vented into the room. It leaves the radiator thru the trap along with the water of condensation, and together they go back to the boiler thru the "dry" (overhead) return line. Near the boiler, the air is vented into the basement and the water is returned to the boiler. If that vent is too small or not working, some radiators won't heat well.

    There are also probably vents or traps at the ends of the steam mains. The most common configuration uses radiator traps piped between the steam main and the dry return. If these fail, radiators at the end of the main won't heat well.

    Here is a Milvaco we encountered a few years ago:

    Where are you located? We might know someone who can help you.

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