Is it possible...

Discussion in 'Geothermal Loops' started by wigaloi, Aug 13, 2012.

  1. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I reviewed your other thread again.

    What still concerns me is the zone setup with bypass dampers, which will increase the return air temps and therefore increase the refrigerant pressure. This is definitely an issue.

    However, obviously your loopfield is too warm, too. Your delta T indicates that your flow is fine,so I am not sure the loop is airlocked.. WHAT kind of circulation pumps do you have? When you put a purge cart on it, you know immediately. When the water level in the drops more than 1-2" in the cart, you have air in the loop.

    There is also the possibility that your loop is not performing well due to dry sand. the combination of both would be killing your performance.
     
  2. wigaloi

    wigaloi Member

    Upstairs. 2 grundfos up26-116f
    Downstairs 2 grundfos up26-116u
     
  3. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Whenever I see 26-116 pumps, especially 2 in serial configuration, it tells me that the installer did not fully understand the concept of energy efficiency here. The 116 has only 10% more ft of head than the 26-99, but uses 60% more electricity. A 4 ton hp needs anywhere between 10 and 12 GPM to stay happy, a single 26-99 could do the job. That alone would reduce the pumping power from 700-880 watts when running down to 230 watts, and that is for each heatpump.

    You have good equipment, no reason that it should not work to your satisfaction, but the system design seems to be inefficient. You need someone with a purge cart, testing your loop, see if air is in there, possibly combining your loop, throwing out your circulation pumps (at least some of them), and then fixing your zoning issue, were the current bypass will increase refrigerant temperature and render the heatpump inefficient with lesser capacity.
     
  4. wigaloi

    wigaloi Member

    Hey all, I am back and still not a Geo fan. Just suffered through the hottest summer in western Washington in quite some time.

    I thought about starting a new thread, but all of the info is here.

    One thing of note I should add is that our supply/demand air delta T is never greater than 10* even on mild days. In fact, the unit will run all day long with 65-67* supply air and the system struggles to cool below 76 degrees....on an 80* day.

    Well I had a self pronounced geo expert over the other day. Ewt 95, lwt 98.5*. He drilled a whole in my supply and return and came up with the same low delta t as my probes. He Amp tested the compressor etc, etc. He said high supply temp was due to high ewt. Ok I can accept that but the downstairs unit air delta t is not much better but ewt is some 13 degrees cooler.

    As is par for the course, he said he will combine my loops, haven't heard back from him...shock. I even spoke with a user of this forum a year ago, he came out and cleaned the coil...he wanted me to go under the house to mark the header lines and would send a crew back to combine the loops...you guessed it, it didn't happen.

    Out of desperation, I've tracked down the original installer. He promises that he will come back with in the next week to combine the loops.

    Finally my question. ..I have 0 faith that anyone here(in my area) knows what they are doing. Can someone draw up a rudementary sketch of 2 heatpumps on 1 loop. will I continue to use both flow centers? Where would the check valves go...will water flow through the non calling unit when the other unit is running...if this is not supposed to happen, how should it be plumbed to prevent this.

    I would love to have something in hand to check his plan before letting him proceed.

    All the information is included in this thread, but I'd be more than happy to answer any missing info.

    As a bonus, does anyone have any idea why the air delta T might be so low? I measured the supply temp at my office and it was 46* on a 90* day. I know that it's relative to ambient/return air, but even when it's only moderately hot, supply air never goes below about 62.
     
    Last edited: Sep 17, 2015
  5. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    Did he compare the ewt/amp draw to the manufacture spec....what about refrigeration temp/pressures. Some of my commercial systems have these EWT and even a pond of mine, but performance of unit is spot on for specifications and design....with supply air temps of high 40's/low 50's....Your typically boiler/tower commercial loop runs these temperatures all day long.... Might be time for a set of gauges on the unit?
     
  6. wigaloi

    wigaloi Member

    No, he did not compare amp draw to ewt, nor did he refer to the shop manual.
     
  7. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    Time to get a qualified tech to the job before doing any loopfield work.
     
  8. wigaloi

    wigaloi Member

    I am starting to wonder if any actually exist.
     
  9. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Did you fix your bypass damper?
    You delta T is too low, either you have a lot of flow, or you have an issue with your refrigerant circuit.
    Combining loops will not help you here.
     
  10. wigaloi

    wigaloi Member

    Yes, bypass issue has been resolved by staging zone board to remain in stage 1 when only 1 zone is calling, and after a set time can go to stage 2 when more than 1 zone calls. With stage 2 only available with 2 zones calling, bypass is no longer needed.

    I don't think that too much air flow is the issue for 2 reasons. 1. The variable speed blower is hardly spinning with a one zone call. 2, we have returns in every room and we've shut them all down with the exception of one and opened all supplies and still no change.

    I agree delta t is too low which contributes to my excessive run times. It's amazing that I've had 5 techs out in the 5 years since we've completed our house and no one seems to know what they are doing.
     
  11. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    I wish i could agree with you but a good geo/hvac tech is hard to find. They are out there....but limited. Luckily we have a couple they take their time and care about geo!! but they are not cheap!
     
  12. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I did not say air flow is the reason, were were talking about water flow. Very high water flow rates can cause low delta T's on the water side, but your's simply seems out of spec. Very straight forward: Unless you have some extremely high water flow (4-5 times as high as normal, which is almost impossible, unless you have a huge pump) you have an issue with your refrigerant circuit.
     
  13. wigaloi

    wigaloi Member

    Got you Doc. The last guy calculated flow based on ew pressure vs lw pressure and said flow was fine. I can't remember the flow rate he calculated however.
     
  14. wigaloi

    wigaloi Member

    He did however mention that my 2 pump flow center was not necessary and disconnected one of the grundfos 26-116s.
     
  15. wigaloi

    wigaloi Member

    Since the techs don't seem to know how to go through the diagnosis procedure, is there a checklist that I can have them go through and report the results back here if they still can't figure it out?
     
  16. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Every time I see a 26-116 pump in a geo system, it tells me that the designer is not evolved. A 26-116 pump uses 400 watts instead of 230 watts for a 26.99, but only adds 10% more pressure at the same flow. The consumer will pay the electricity price. Having (2) 116 pumps doubles the insult on the system's inefficiency.
     
  17. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Good point, Doc. The over sizing speaks volumes about the piping.
     
  18. wigaloi

    wigaloi Member

    I'm not sure that it does speak anything regarding the piping since the last tech disconnected one of the pumps because there was plenty of flow.

    It probably does however speak volumes about the installer's knowledge base.
     
  19. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    That is kind of what I meant.
     
  20. wigalo

    wigalo New Member

    I'm back and I'm pretty sure I know what one of my major problems is....air flow, or lack of it. I kept coming back to my winter problem of not being able to get the main zone to with in 4* of the set temp, but in 2 of the other zones we are able to do so with no problem.

    I read and read online hvac threads and pulled out my manual j and duct design plan. The main trunk for zone 1 called for an 18" round, and the hacks that did my install have a 12" with the sloppiest, leakiest (duct tape) connections in the history of man.

    I know what it's going to take to fix the supply, but have a question on the return plenum. The cold air plenum is 24x15 but they throttle it down to a 24x9. This is a 4 ton heat pump.

    Here is a photo...is there anyway that this is getting enough return air?

    Screenshot_2015-12-15-21-59-11.jpg
     
    Last edited: Dec 16, 2015

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