Several Questions Reguarding Loop Design

Discussion in 'Geothermal Loops' started by 230-sean, Jun 19, 2012.

  1. 230-sean

    230-sean New Member

    Hello all, I am currently looking to have a system installed at my house. 3 quotes in and I have been told by 1 person they'll install a 5 ton and the other 2 would install a 6 ton.

    I live in the Chicagoland area. My home has 2,475 sq. ft. of living space above ground and roughly 1,400 sq. ft. of basement/partial walkout. The house faces east with that side of the house being floor to ceiling windows (pella thermopane). The ceiling on the main floor is 8 ft. at the house's perimeter and pitches up to 10.5 ft. at the center. Current HVAC system is old, gas forced heat and central air, 175,000 BTU on the furnace and 5 ton on the a/c.

    The 2 people that said 6 ton system would be using the electric strip as the 3rd stage aux heat. The 1 guy that would do a 5 ton would be using a 45,000 BTU 93% efficiency gas furnace as the 3rd stage aux heat.

    The only guy that went into depth about the loop design was the 5 ton bid. He said he'd do a "vorizontal" loop system started from the bottom of a 4 foot deep trench. He said they would go about 40' deep. He would use 1" pipe for the loops. My main concern here was that he said they would start in the same trench but fan out away from each other underground. I don't know how far away loops need to be from each other in order to remain efficient, so I would like to know that rule of thumb. Also, if they are less than this distance from one another on one end, but further on the other would this "balance things out"?

    I guess I'd like opinions on how many tons I'll actually need and I for sure would like to find out loop spacing requirements. I'm sure I have more questions but we'll start with this. Thanks in advance!

  2. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    the loop configuration will work fine.

    However, the idea of installing a gas furnace for backup needs to be investigated,

    Electric backup heater only costs several hundred dollars.

    With Gas, the heat pump has to shut off in 3rd stage, with electric the heat pump stays on.

    The only reason I can see for doing gas would be if the electric service is not big enough to handle the extra load.

    Any competent installer will perform a manual J heat load calculation to determine heat pump size.

    You need to ask if any of these guys did the calculation.
  3. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    Loop seems fine to me too. The distance between that we do is no closer then 10' between loops for vertical.
    "vortizonal" will be fine if In a fan lay out. You can also ask the driller to vary the depth too between loops if your concerned. 40'-30'-40'-30'-40'. That way you can be assured that they are far apart.
    Did they mention grouts?
  4. 230-sean

    230-sean New Member

    I'll double check, but my understanding is that they install with a way to run the geothermal and the gas furnace parallel at the same time. Natural gas is cheaper than electric here so that is why he suggests this route. The house has 200 amp service, so I can't imagine not being able to handle the extra load?

    As far as I know there has been no J heat load calculation, but I'm not sure if someone would have done that on just a preliminary estimate/quote? I will make sure they do one before starting the job though, thanks for that reminder!

    Ok, thanks for the confidence boost!

    Just to clarify a few things, in my first post I said they'd use 1" pe pipe, but they'll actually be using 3/4" for the loop. Also, if they start like 2-3 feet apart would this still be ok?

    I will ask about the staggered depth, I like that idea.

    As far as grouts are concerned, (please forgive me for know basically nothing about this) he said that they drill at a certain rpm (if I remember correctly its slower than standard?) with a drill that has water flowing at the same time (?) and basically they don't pull too much soil up, but temporarily liquify it so they can stick the loop down into it. I pictured kind of a milkshake of soil when he was describing it. Does this sound common?

    Thanks guys!
  5. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    Though I am a driller, we do not do horizontal boreholes, or vortizonal for that matter.
    I know the drilling is different than the horizontal, I know they use different MUDs than vertical drilling. Something called bore gel, which could very well be a slurry mixture left in hole that could act as a grout too.
    The starting 3' variation should be fine too.
  6. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    You are spending too much time worrying about the loops, but since you asked "vorizontal" is an attempt to mimic the "smaller footprint" of DX diagonal loops.
    Many states do not have guidelines for diagonal boring like they do for vertical drilling.
    If you have soil like MI that is often damp sand or gravel, the loops close up rapidly and do not require the same grouting.
    ALL loops start at a manifold somewhere and work out from there so ALL loops start inches apart not 3 feet apart (unless they are in series). For diagonal fields picture a teepee with 40 foot lodge poles, while the tops are merged, the bottoms are quite far apart. Surface damage is minimized because of the configuration.

    Now what should you worry about? The size of the heat pump. In mid MI a house your size would employ a 3 or 4 ton heat pump.
    What is the BTU loss/gain for your home.
    What percent of the load are they trying to achieve with geo.

    200 AMP service is likely inadequate for a 6 ton geo with a 15-20K auxiliary as that pkg might demand 125 or more amps itself. Do you have more than 200 amps to the house.

    I like 5 ton guy best so far and can't know for sure, but he may be suggesting propane back-up to avoid service up grade and may have the geo sized for 100% of the load to minimize auxiliary use. Loop design suggests higher education in geo as well......If you don't know what this paragraph means, then my point is made that you are worrying about the wrong things.
  7. 230-sean

    230-sean New Member

    Ok, thanks for that info, sets the mind at ease.

    I don't know the loss/gain of the house, nor do I know the load percent they're trying to achieve. The 5 ton guy is planning on installing an Envision NDV064, 5 ton loop system, 2 stage cooling, 3 stage heating, with an E.C.M. blower and 45k btu high efficiency gas furnace as the 3rd stage heating, aprilair humidifier, desuperheater, and high efficiency tankless water heater.

    I'm not sure if I have more than 200 amps to the house or not. There are several more vacant spots for breakers at the box. Would the above system (NDV064) require more than what is already in the room? The furnace in there now is from 1988-1989 and is rated at 175k btu, probably overkill but that is what is there. Also, I am having them install a desuperheater to offload into my current 40 gal water heater tank and have that pass through a high efficiency tankless that I'm having them install. You're making me wonder if I need an electrician to com out to see if I can add more. In the future I am planning on building a home theater in my basement, which I'm sure will also be power hungry, so I wonder if they can coexist? Also, if geothermal is so much more efficient, then why would it take so much electricity to run it? I was thinking it uses less electricity than conventional since it has such high eer and cop, no?

    I have settled on the 5 ton guy already, so I'm glad you say he sounds like the way to go. Its not propane for the back-up but natural gas. He said he was choosing 5 ton over 6 ton because 6 ton would be too much for cooling and we wouldn't be able to dehumidify. He said the 5 ton should be able to handle the heating, but is installing the gas furnace for the really cold days that it might need assistance on.

    Does all this sound right? Should I be upgrading my amp service? Thanks!


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