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Insulation for Pex?

lzalza Member Posts: 40
I'm going to be ripping out the old oil furnace in my new home and replacing it with a cast iron hot water boiler.  I've decided to use Pex (Raupex), but I was wondering about insulation.  Is the closed-cell foam Armaflex typically used on reefer and plumbing pipes rated for constant 180 degree water?  Is there a high temperature variant more suitable for hydronic systems? 



  • ZmanZman Member Posts: 6,338

    That insulation will work just fine.

    Be sure to use the pex with the O2 barrier.

    I have to ask why on the cast iron boiler? If you are doing it over, why not make some real leaps in efficiency.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • NRT_RobNRT_Rob Member Posts: 1,013
    if you're running temps like that

    I'd recommend PAP (Pe-Al-Pe) to avoid excessive tubing expansion and sagging. the aluminum core will help its stability.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • lzalza Member Posts: 40
    CI boilers


    To each her/his own.  But several reasons: 





    I am installing a mix of old and new cast iron radiators with a cast iron boiler and indirect hot water tank (so mod-con is not really appropriate), no primary/secondary, and a minimal amount of digital, satellite-linked, mp3 playing, video streaming, gadgetry.  KISS.

    A cast iron will greatly outlive an aluminum or ss heat exchanger. 

    Less parts means less can go wrong.

    The Burnham ESC/ES2 is what I'll be picking up, is partially condensing, so it is a bit more efficient than CI boilers of old.   

    Working as a steamfitter for the Seattle School District, all of our steam boilers have been around for sixty years or more.  They are simple to understand and maintain.  We've had steam boilers replaced by mod-con hot water boilers that haven't worked since day one.  As an environmentalist and a bit of a Luddite, I am extremely skeptical of "green" technical solutions.  There are many technologies that provide the image of energy efficiency, but don't factor in the waste of old products, dependency on limited  and exotic resources, planned obsolence, etc.  You want energy efficiency?  Put on a sweater for god's sake. 
  • lzalza Member Posts: 40

    Thanks, NRT_Rob.   The supply house I am working with on my little home project only supplies Rehau, and they apparently don't manufacture Pex-Al-Pex.  I may consider the competing supply house for my Pex, since I know they carry Uponor.  
  • SWEISWEI Member Posts: 7,356

    Outdoor reset will help either of those -- you can add a module to the ESC, but it costs 3x what an aftermarket ODR control does.

    Triangle Tube Prestige is what I'd be looking at for this.  Low head loss stainless HX, no need for primary-secondary in many systems.  Good track record for longevity, great company to deal with.
  • ZmanZman Member Posts: 6,338
    Too bad

    It's too bad you have had bad experiences. I think the early mod/con models have given the industry a black eye, as have knucklehead installers.

    I would second swei's recommendation. I have had one for 6 years without incident.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • NRT_RobNRT_Rob Member Posts: 1,013
    not necessarily

    I had a cast iron boiler in my house that died after 12 years. New school cast iron isn't like 50's cast iron, they have been value engineered for 50 years since the earlier "overkill design" days.

    a new mod/con with firetube, stainless steel HE should last a good long time and will easily cost justify itself over a cast iron, on any significant heating load. they are installed routinely with few problems these days. looking at the triangle tube as one example, it's basically got seven parts in it. service is not complicated. other firetubes are likely to be similar in that regard.

    the only app I can see where cast iron is justifiable is if you have a sealed combustion option for it and you have a fixed, high temperature heat demand. as soon as you bring in reset, the mod/con should be a clear winner in any comparison. sealed combustion is good for some efficiency bump regardless of any other benefits as well, and it's one that isn't captured in AFUE.
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
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