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2 pipe direct return (hydronic)

jbeckjbeck Member Posts: 15
edited February 2019 in Gas Heating
Would like some help troubleshooting my heating system.
  • Hydronic, 2 pipe direct return.
  • 100 years old, was previously a gravity system with big cast iron supply pipes.
  • Now has a B&G circulator on the return side.
  • Building is 2 floors with 2 supply / return loops. Each loop spans the front or back half of the building.
  • Each loops starts as a long horizontal branch (3" pipes) that eventually travel up 1st and then up to 2nd floor.
  • 3/4" T's split off the main branch to each cast iron radiator
  • Radiators have been bled.
1st floor radiators are 110F surface temp (Room temperature 68F)
2nd floor radiators are 140F surface temp (Room temperature 72F)

In a 2 pipe direct return + circulator, wouldn't the 1st floor rads get the most flow?

Why are my 1st FL rads not getting hot as upstairs? The problem may have started when I installed TRV valves on the 1st floor. I installed them to control 1st floor temperature. the 2nd floor radiators.

Note, the 3/4" supply / return pipe coming off the radiators are both hot.

BTW, I installed Honeywell V110 valves. The valves are not stuck. I also unscrewed the control to test if they were defective, but the rads don't get any hotter. Sheet.pdf


  • jbeckjbeck Member Posts: 15
    edited February 2019
    Any chance the Honeywell V110 TRVs were installed in the wrong direction? Would this cause underheating?

  • jbeckjbeck Member Posts: 15
    I confirmed that the TRV was installed backwards. What's lame is that the original plumber won't fix it without charging me
  • JohnNYJohnNY Member Posts: 2,443
    jbeck said:

    I confirmed that the TRV was installed backwards. What's lame is that the original plumber won't fix it without charging me

    Did the plumber install them or did you? Who provided the valves?
    For troubleshooting and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F Mechanical, LLC"
    Or email John at [email protected]
    John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
    John also oversees mechanical installations and maintenance for metro-area clients with his family's company, Gateway Plumbing and Heating along with his brother/business partner.
  • jbeckjbeck Member Posts: 15
    edited February 2019
    I bought the valves
    The plumber installed them. Backwards.

    To be somewhat fair, he simply replaced the original valves with these TRVs. And some of the original valves were on the RETURN side. He obviously never checked which pipe is which.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,051
    the trvs are adding restriction to the first floor. TRVs can't give you more heat. They will only prevent over heating. Converting a gravity system to forced can be problematic and will result in some trial and error. Hopefully when the valves are turned around it will work
  • jbeckjbeck Member Posts: 15
    edited February 2019
    Original Plumber refused to fix the work himself, so I personally replaced the backwards TRV with regular radiator valves. Also left him a valid review on Angieslist/Google/etc. Suffered with underheating for 2 years before finally self-diagnosing the problem. Other plumbers (including 1 on this board's FIND A CONTRACTOR) could not diagnose it.

    Of course, their lazy take was "your piping is all wrong" (which it is, but it wasn't fully responsible for the cold rads).

    Anyways, parding my venting. It's been a long 2 years.

    With regular valves, radiator surface temps are now 140F. Previously 110F. (Aquastat high limit is set to 175)

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