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Water feed location.

JStar Member Posts: 2,752
I went to a warranty call today to replace a leaking hydronic boiler. Noticed the guy who originally did the install from our company piped the water feed like this because "It works better when you fill it from the bottom" (Quote from the guy he was with that day).

I tested pressures in a couple of different spots:

1. A boiler drain right where the feed ties in, between the pump and boiler. : 15psi

2. Tank air pressure - empty: 12psi

3. Tank air pressure - cold filled: 14psi

4. (Not pictured) Return purge-drains with pump running:  10psi

Is this not that big of a problem because the feed is on the supply side of the pump? There's also no hope of convincing this guy that anything he does is wrong. I would just like to know for my own well being, and maybe one day he'll acknowledge a second opinion, with some cold hard facts behind it.


  • Charlie from wmass
    Charlie from wmass Member Posts: 4,314
    no he will not

    But long as you do as you know is correct that is all you can do. He likes the pumps on the returns too I see.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • JStar
    JStar Member Posts: 2,752
    To top it all off.

    I had to go back to this job today because I left the Taco zone valves in the manual On position when I was purging. I swear...you can try as hard as you want to be a good student of heating, and all it takes is one little lever to knock you right back down a notch.
  • wuarhat
    wuarhat Member Posts: 2
    circulator location

    Isn't the circulator on the wrong side of the expansion tank?
  • EricAune
    EricAune Member Posts: 432
    Buy him a book

    Your time and headache are worth more than the $25.00 you will spend on one of Dan's best written books.  Pumping Away, find it when you click on the SHOP button above.  Or click here:

    "If you don't like change, your going to like irrelevance even less"
  • Chadio
    Chadio Member Posts: 4
    pumping away!!!!!!!

    A little education goes a long way. Definitely invest in the "Pumping Away" book. 
  • Pump Location

    So, that pump will not be able to add it's differential pressure to the system because the x-tank is just in front of it.  Instead, it will subtract it's differential pressure from the return piping.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • JStar
    JStar Member Posts: 2,752
    At the risk of offending anyone,,,

    ..."Go read a book", is not the service answer I was looking for. I've read Pumping Away. It's a great book, but it doesn't cover the parameters of every piping situation you see in the field.

    Thinking about my original post, it now makes sense that his set-up will work, for two reasons:

    1. The pump can't change the pressure between itself and the expansion tank, so feed water can't be added when the system is running. My only concern was the cold fill pressure. If the feed is maintaining 12 psi at the bottom of the boiler, how much would that affect the system pressure at the topmost loop in the house?

    2. Doing the wrong thing in heating always works for those who don't know it's wrong.
  • EricAune
    EricAune Member Posts: 432
    edited July 2010
    Got lucky this time

    The concept in the book does cover all situations, when sized properly and properly installed.

    That being said, the reason his install may be working is his circulator is likely oversized.  Alan is right, the circulator differential is added to the pressure differential through the system piping.  If, for example, the circulator is sized properly and will only create a differential large enough to overcome the head loss in the piping circuit then the pressure at the "top most" loop will be the product of the head loss and differential subtracted from the fill pressure.

    This type of installation, when the circ is sized close to the system parameters, can result in a no-flow situation very easily by having a zero or negative pressure at the highest area in the system.

    Circulator sizing is easy at best, circulator placement is even easier. 
    "If you don't like change, your going to like irrelevance even less"
This discussion has been closed.