Is it possible...

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

  1. wigaloi

    wigaloi Member

    To combine two separate ground loops?

    I have two 4 ton climate master heatpumps. 1 servicing the upstairs and the other servicing downstairs. We live in the Seattle area so summers are not taxing on the system and winters are not too severe. We have 4x100 foot slinky loops in the back yard for down and the same in the front yard for up.

    Our problem is that in the winter, the downstairs unit's supply air temp is 5-8 degrees cooler than the upstairs unit (of course the downstairs unit has a larger heating load in the winter). During the summer, the downstairs unit's supply air temp runs 9-11 degrees cooler when cooling. (of course the upstairs unit has a larger cooling load)

    Based on the unit having the largest load not performing as well as the "off load" unit, I'm thinking that the loops may be undersized. My question is....would it be possible to combine the two loops into one? The heatpumps are on two different levels, but both sets of header lines enter In the crawl space.

    Another piece of info. In the winter, the downstairs unit ice's heavily, upstairs barely any frost. In the summer the upstairs entering coupling is warm to the touch. The downstairs unit barely has a perceptible difference between the incoming and outgoing connections in cooling mode.

    Since the "off load" pump tends to run roughly 10 and 20% of the time in the summer and winter respectively, the extra capacity will feed the main heat pump and not let the combined loop over cool or heat.
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    Yes it is. But I'm hoping the 4x100' is the trench size vs. slinky size.

    There are some other potential issues and fixes, but you can tie the loops together. You just have to match pressure drops to ensure balanced flow.

    But look in to air flow and refrigeration charges first.
  3. wigaloi

    wigaloi Member

    Yes, the 100' is the trench legnth.

    We've had 2 heating seasons and this is the 2nd cooling season. For as much as we spent on the system, I have been more than disappointed with the performance. (unable to maintain temp in winter unles electric strips are running. Extreme power consumption. 200-250 kwh/day to keep house less than comfortable during coldest part of winter.

    It's bad enough that my wife and I have talked about yanking the geo units and replacing them with high efficiency gas units.

    I hope has been just a matter of an undersized loop. We are living in our dream house and can't keep it comfortable.
  4. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Your units performance is only patially based on your ewt. You need to determine what your ewt is at a given load in time before you rush to the loops as the source of poor performance. Have you had a tech out to address your concerns? Check the units ect.?
  5. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    What is daily usage during times of little / no heating or cooling, perhaps May and October billing cycles would illustrate that.

    We always combine loops when serving two systems.

    Has this house had an energy audit or at least a blower door infiltration test?
  6. wigaloi

    wigaloi Member

    @waterpirate. Construction was completed and we moved in Thanksgiving Day 11. It's colder here then, but not freezing. Low 40s during day and mid to high 30's at night. We knew we had a problem when we couldnt get the downstairs to warm above about 65 deg with the pump running 24/7.

    The installer came out and determined that 1. There was a crack and we were low on refrigerant. Fixed under warranty. So they pull it out and weld it back in. ( more on that later)
    2. The back up heat strip breaker was turned off.

    After that, I was Leary about the strips. During the prior billing period, I recd close to a $2000 powerbill for 2 months. (we werent even living in the house)I used close to 20,000 kwh. My electrician said that was impossible, but it turns out the construction t stat is set to on or off. Yep, we got stuck paying it. People never believe me that we had "grow operation" type consumption, but I kept the bill to prove it.

    With out the strips, we were then able to get downstairs to about 67 tops. Keep in my that we hadn't even hit the teeth of winter yet. Upstairs unit worked just fine running about 20-30% of the time as unit 1.

    I then noticed water leaking from the bottom of the repaired unit. Turns out that my installer failed to order the clamshell insulation so it wasnt installed along with the repair, imagine
    the condensation inside the unit. I called him back out to fix it, but between then, he had been out so many times purging loop etc, etc to try and get it to work that he just blew me off.

    So I called the supply house and asked them to order the clamshell for me to install. They wouldn't, but refd me to another geo guy. He came out installed the clamshell. He seemed pretty competent so I had him take a look. He worked with climatemaster, but in the end stopped calling too. Well actually, he said that "it's all about airflow and I didn't have enough" downstairs.

    Even though I didn't really think he addressd the problem of the performance differences of the supply temp of the two units, we were desperate (i actually submitted a post on tstat staging that you both responed to, thanks by the way. I thought i had the problem fixed, but letting the strips kick in when needed netted a7400 kwh month) and asked him to work up bids on increasing flow. Well we are 4 months later and he must be busy, cause we are still waiting.

    Well now that I am seeing an opposite performance effect in the cooling season, I'm thinking it has to be the loop. The downstairs supply temp gets down to 49. Only runs about 10% of unit two. Unit two supply air, 60 degrees.

    @engineer. Yes, I have a Ted o meter installed on both panels. During may and June (0 to nominal heatpump rusage, just blower fan) we averaged 19 and 24 kwh/day.

    Haven't had a energy audit done yet, but am working on it with my local utility.

    We flat consume too much power and still are not comfortable most of the time.
  7. wigaloi

    wigaloi Member

  8. ChrisJ

    ChrisJ Active Member Forum Leader

    Just want to be sure. 4 trenches 100' long. each of those trenches has 750' of slinky loop, giving you 750' per ton of heat pump= 3000' of pipe per heat pump.

    "both have 750' of slinky loop", when you said that it is refering to one loop field in the front and one in the back.

    Must be all that pipe in the ground, with 2 pumps per loop field.

    Reading the manual J, seems like 4 tons per floor is oversized.

    Last edited: Aug 13, 2012
  9. wigaloi

    wigaloi Member

    Yes Chris J. There are 4 100' trenches in the back yard with 750' of slinky loop in each trench AND 4 100' trenches in the front yard with 750' of slinky loop in each trench.

    Total of 8, 100' trenches. x 4 slinky loops in back and 4 slinky loops in front for a total of 6000' of pipe. (+whatever the headers are) so yes, 6000/8 tons is 750/ton.
  10. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    Do you have ideas on how they headers are connected?
    Reverse return, in parallel, in series?

    All the information you have will help out more. I am not a HVAC guy, just a loop installer. So I will not have the technical advice others on this site can provide.

    The loop installer always get the blame first when I system under performs, and rarely is it the cause of the problem. ;)
  11. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader


    sorry you are having problems...

    I don't see any where that you have measured the EWT (Entering Water Temp). This would be the temp of the water as it enters your heat pump.

    If this temp is below 90° in the summer and above 30° in the winter, then the loop is performing fine.

    This is the only way to know if your problems are loop related.
  12. wigaloi

    wigaloi Member

    You are correct Palace Geo, I have not actually measured EWT and LWT. I don't have the tools.

    Maybe I'm simplifying it too much, but I don't see how it can be anything else considering the off load heat pump works so far superior above the major loaded heat pump in both seasons. So it's not like it's the upstairs unit under performing all the time.

    Before I decide to get someone to combine the loops, I'll get some stats and measure as you've indicated.
  13. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

  14. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    It could just as easily be that the heat pump under the load is undersized, or the ductwork is inadequate.
  15. wigaloi

    wigaloi Member

    Ok, I do have pt ports and the wife has a digital therm. Loop is hot.

    105 ewt and 109.1 lwt
  16. wigaloi

    wigaloi Member

    I could see that in the winter for the downstairs unit, but not in the summer when a mere 85 degrees causes a problem. In our area they size the pump for the heating load. 4 tons should be plenty big enough for our cooling load.
  17. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Well you definitely have a loop problem:eek::eek:

    I would try and tie them together. How deep are the loops buried and what is the soil like?
  18. wigaloi

    wigaloi Member

    They are 6' deep and we have sandy loam.

    Should be easy to access because all 4 of the header pipes are accessible in the crawl space
  19. ChrisJ

    ChrisJ Active Member Forum Leader

    "he had been out so many times purging loop etc, etc to try and get it to work that he just blew me off."

    Sounds like loop could still have air in it. 105* wow.

  20. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Air in the loop is a real possibility

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