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  1. #1
    Join Date
    May 2005
    Posts
    161
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    Geo loop maintenance

    Hey guys,

    I've been out of the loop (no pun intended) for a few years. I originally setup my geothermal about 9 years ago. I have a 4 ton FHP system with a single Grundfos UP26-116 loop pump. It's a custom setup, rather than a purchased flow center. Well, yesterday I went in the basement and noticed my loop pressure was approaching 30 psi, so I thought I'd lower it a little by dumping a small amount of liquid. When I did this, I noticed the water is looking pretty brown. So it has me thinking about some maintenance. I haven't really touched my system since I went to a sealed horizontal loop about 7 years ago. I originally tried an open loop setup, but it clogged with rust and sediment. When I did the switch, I flushed the heat exchanger as best I could, and it appeared to be fairly cleaned. However, after seeing that water yesterday I suspect over the years that there was still some leftover.

    My question is..... what's all this talk about nonpressurized systems now? I'd always kinda thought about bumping my system up to a dual pump arrangement since I am slightly underflow for a 4 ton system (I'm getting 10 gpm with a single pump). Is there a way to add my single pump to a single nonpressurized system to get the flow I need? In my brief searching it looks to me like the single pump nonpressurized system don't really expand to a dual pump setup. However, the old school flow center that have a push pump and a pull pump are expandable. So are people just doing the nonpressurized setups because it's safer with regard to leaking loops? Over the years my loop has proven solid with no leaks. The only thing I battle is pressure fluctuation because I didn't have any expansion chamber. I've recently added a bunch more clear tubing for compliance above my loop and that's helping to keep my pressure more stable. I may look into an expansion tank, but for now I like the clear tubing because I can see the liquid level.

    Additional info: I'm in michigan, and I use a 20% methanol antifreeze. If I were to service my loop and upgrade m flow center, I'd probably hire a loop company to come out, purge it, and fill with 20% glycol.

  2. #2
    Join Date
    Feb 2009
    Location
    Portland OR
    Posts
    2,081
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    I am personally not a fan of non pressurized systems and 30 PSI is in no way to high for your system so I dont' know why you decided to let water out.
    If the loop does have rust then you might just need to reflush and fill the system.
    I also don't know why you want to switch from Methanol to Glycol, Methanol is more efficient and does not gum up or loose as much viscosity at lower tempertaures. We do Methanol for all our systems and only use glycol if there is some odd need for it specifically.
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  3. #3
    Join Date
    May 2005
    Posts
    161
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    Ok thanks for the reply. I appreciate the honesty. What's your feeling on 10 gpm with a 4 ton system? Should I even bother with another pump?

  4. #4
    Join Date
    Feb 2009
    Location
    Portland OR
    Posts
    2,081
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    10 GPM is a little low, we shoot for 3GPM per ton, but even if you were getting 9 GPM flow I show about a 1-2% loss in efficiency at most.
    From my WaterFurnace NDV049(4 ton dual stage 5 series geo unit)
    9 GPM, 1550 CFM of air has a COP of 3.97
    12 GPM, 1550 CFM of air has a COP of 4.01
    Both at a 40 degree entering water temperature, I would not add another pump for a .04 COP difference IMHO.

    Cooling
    9 GPM, 1550 CFM of air has an EER of 15.5
    12 GPM, 1550 CFM of air has an EER of 16
    Both at a 90 degree entering water temperature in cooling mode.
    Check out my YouTube channel - http://www.youtube.com/user/skyheating1 We have customer testimonials, product reviews and more!
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