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pex on condensate loop

I went on job today. General contractor had steam "guru" move around steam radiators on remodel job and he couldn't figure out why one rad would stay ice cold. Turns out that the guru ran about 40 feet of 1" black horizontal pipe to the rad. To me this WAY too long for a runoff using 1" pipe. I am convinced that the steam is dying in the pipe due to its mixing with the condensate. There plain and simply isn't enough room in the pipe for the steam and condensate. That's the background. The rad is on the second floor.I told GC that he can run a hot water loop directly off the boiler for that rad.I have done this before following Dan,s instructions in "How come". I told him that he could use pex as long as he blends the the supply water and return water to insure that the water that hits the pex is never more then 200 degrees.However after thinking about some more I am having second thoughts. I am not confident that the pex joints would do an absolute job keeping air out of the loop(critical for any condensate loop above the water level). Any thoughts on the matter would be greatly appreciated. Are the pex joints tight enough? That is the question. The difference in price between using pex and copper is fairly large. Thanks again


  • SWEISWEI Posts: 7,356
    PEX joints

    if properly done will hold 100 PSI for a week.  Don't worry about them.  A thermostatic mixing valve might be in order - set as low as needed to heat the zone.  I'd probably use copper from the hot port back to the boiler.
  • pipekingpipeking Posts: 252
    the pex joints

    is not whit's at u have to worry about, it's the pex. as long as u make sure use a heatpex (it's pex with an oxygen barrier) and do not exceed the temp/pressure limits u will be fine. pex is being used on residential heating systems more than anything else, so all the r&d is taken care of.
  • pex

    How important is the type of pex if anyway the boiler is open to endless oxygen? Again this is a steam boiler. I am aware that pex is being used for endless heating systems. My only concern is with particular application because the slightest bit of air in the system will cause the water to drop out of the loop and flood the boiler. Thanks again for the insights
  • Charlie from wmassCharlie from wmass Posts: 3,872
    edited March 2013
    the O2 infiltration

    means gas in the water. Even though your system is open O2 matters. I avoid installing hot water loops above the water line. I also usually do not leave the room the boiler is in. If I need to go further I use a heat exchanger. Brazed plate would be fine here  and you could run it no problem with pex. Why not just change the 1" to 1 1/4"? And provide a drip before the riser to keep the condensate out of the horizontal pipe.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • SteamheadSteamhead Posts: 11,157
    What size is the radiator

    If it's not too big, you could re-pitch the runout downward and run a drip line from the riser back to the wet return.  
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • non issue

    General contractor didn't like my price so he will give the job to someone cheaper. Dripping the runout would have been an option but access was an issue. Radiator is about 30 or 40 feet from the main and on the second floor. The radiator is certainly not too big. The room in question has estimated heat loss of 8-10 thousand btu(just did rough guess) and radiator has aprox 3500 btu!! Not kidding. Whatever!
  • SteamheadSteamhead Posts: 11,157
    I'm sure

    the HO will call you when the "repair" doesn't work. 
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • icesailoricesailor Posts: 7,265

    I doubt he'll cal YOU back when the radiator doesn't work. I find that most potential customers that give a job to your cheaper competitor will never call back because they don't want to admit that they were wrong for the second time in their life. The first was the time they thought they were wrong. And came to find out that they were right.
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