I have a 3 ton climate master unit that I purchased from someone who built an addition on their house and upgraded to a larger system.  I live in Des Moines, Iowa and have an 1800 sq foot house, all new windows, and I will also be adding more insulation before winter in walls and attic.  I also have an auxilary heater that goes with the furnace for emergency electric heat.  The house is on a walkout lot so if I do wells they will go in the front yard and if I do horizontal loops they will go in the back yard.   

I am looking at two options for the tubing install. 
1.  Pay up to $1800 per well, 3 wells, ran into the house, grouted, filled, and purged. 
2.  Install horizontal slinky's in my yard.  I have an excavator and bobcat so I can dig all the trenches as deep as I need to go. 


I think option two is the best option reduce the cost.  From the research I have done online I think I need to have 3 trenches with 750-800' of 3/4 tubing per trench and will need to run 3 trenches that are 3 feet wide and 6 feet deep.  My back yard is 90 feet wide and 60 feet deep behind the house.  The lines will enter the side of the house running uphill with a 10 foot change in elevation.

Here are some of my questions.

1.  Will 80 foot trenches 3 feet wide hold the length of pipe I will need? 

2.  Can I go deeper and do one loop 12 feet deep and bury it and then do another in the same trench at  6 feet deep? 

3.  How close can I place one loop trench to another?  One idea was to excavate one large wide trench 10 by 80 and layout all three loops in this large trench.  

4.  I don't have a way to fuse the pipes, but I think I can find a professional to do that part.  Should I run all three loops into the house to a manifold and not have any joints in the yard, or pay someone to fuse the loops to a single header?  If I go with a header would I use 3/4 or 1 1/4 tubing?

5.  With the loops in the back yard the furthest loop would start 60 to 70 feet from where it enters the house and there would be another 12 feet inside the house to get to the pump.  I had someone calculate I would need 9 GPM for wells, but I am not sure what pump GPM I would need if I went with the wells. 

6.  How much should I expect to pay for PE tubing?  Will local plumbing supply house carry the tubing in these lengths?  

7.  What is the best way to put the tubing in a slinky shape?  Does it need to be zip tied or can I just use the walls of the trench to hold it in place?

I am sure I am forgetting a bunch of stuff, but this is a good start.  Thanks for any assistance you can provide. 

Pete

Pete,
Here are some important questions you forgot to ask:
1) is 3 tons adequate for my home?
To find out a Manual J heat load must be performed.
2) is my duct work adequate?
restricted air flow will not allow heat pump to perform?
3) is there adequate electricity to my home?
must do current load calculation and determine capacity limitations of existing system.
To not do this job correctly will cause you to have a less than happy geo experience.
Geo excavators in my area charge about $1,600/vertical ton and provide all the pipe and flow center, do the connections and flush and charge the field. I suggest you find someone like this as they will be able to help answer the questions above and they might let you do the digging for a discount.
To answer your specific questions: Depending on the nature of soil (most important) we run trenches 100' to 150' of 3/4" 4'/foot slinky, with 10' between trenches. We manifold them underground and only bring 2, 1.25" pipes into home. We generally would use a single pump flow center for a 3 ton which will be available at the same unknown supplier as the pipe for I don't know how much (the loop contractor mentioned above will pay less than you as he buys more in a week than you will in a life time).
Please do not go 12' deep in a trench and try to build your slinkies there. That is an oppurtunity for disaster. One of the beauties of the slinky is minimal time in the trench vs 6 pipe systems. Using zip ties you will find setting up slinkies is no picinic (we use a custom built table).
Again for something in the neigborhood of $4,000 to $5,000 You could have most everything done for you. You'll drop most of that on parts and tool rental (if things go perfectly) without expert help, so it's worth considering. Pay back for the additional investment is likely you might check out IGSHPA for certified diggers in your area.
Good Luck,
Joe

Thanks for your response.

1. I have had two contractors out asking them to do the turnkey install with my sytem. The first quoted me enough to show that he didn't want the job, instead of just telling me up front he wasn't interested. The second said the system should be fine for my house and then never even gave me a quote. I have one other person who should be able to do the work so maybe I should just get him out here to look at it instead of waiting.

2. First two guys that were here said it should be ok on the ducts, but who knows.

3. I am planning on upgrading to 200 amp service and running additional circuits to the furnace room prior to the install.

That's interesting to hear they include the flow centers, the two people I have got prices from do not include the flow center. I should be able to get contractor pricing through some other connections I have so that shouldn't be a issue for the materials. I wasn't sure if I was going to do the work myself so I haven't spend much time on that part. We already own the excavation equipment so that only costs me fuel, no rental or rush.

Sounds like I need to get someone who can help me with the duct question and heat load before moving forward.

Try the IGSHPA site for someone. If you want sweat equity, you are 2 months late or 3 months early. That means you could get help in a few months that's not available now.
J

It has been wet here for most of the summer so I have a feeling there wouldn't have been many people with extra time to help me so II am thankful for your assistance online.

I found an online heat load calculator, http://www.heatload.com/unico/heatloadpreform.htm. I have a two story house and ran it for the main floor and the upstairs.
TOTAL HEAT LOSS 53212 btu
TOTAL HEAT GAIN 26089 btu

What size of geo system would be a fit for these numbers?

When you do a heat load calculation do include the basement? My basement is finished so I probably should include it, but wasn't sure.

Thanks! I appreciate your help in learning about how this all works.

Probably between 2 and 5 nominal tons. To narrow it down would need loop design conditions and then application of ACCA Manual S to the units under consideration.

Unless there is about R50 insulation between the first floor and the basement and no interior access to that basement, than yes, the basement is within the building envelope, will pull heat from the upper floors and needs to be considered.

Doing this project without a room-by-room heat load calc and careful consideration of dimensions and layout of present ductwork is a recipe for near-certain despair. Multistory houses are tough to get right without either zoning or multiple units.

Generally speaking, air flow requirements for heating with geo are substantially higher, possibly double those of heating via fossil fuel. Most duct systems are marginal to begin with.

Please be careful digging a 12 foot deep trench - we'd rather continue hearing of the trials and tribulations associated with a rigged HVAC system than that you perished in a trench cave-in.

I will try to rerun the calc again with the basement.

My house was built in the 60's so it it pretty basic on the duct work. Feeds run to every room with one larger cold air return in the hallway on the second floor and on the main floor there are several runs to the living room, dining room, kitchen, and family room and on the main floor there are more cold air returns in the kitchen, hallway, and dining rooms. It's easy to get the upstairs warm, just hard to cool it down and keep the colder air upstairs in the summer months.

As for the 12 foot trench, I was thinking more like a giant long and wide swimming pool and not like a narrow grave... We can go dig 17 feet with our excavator so we could dig a big hole pretty easy that's why I was curious about stacking two runs of loops.

I appreciate all of your assistance and helping me lean more about my options!

I would like to see the basement load. When you have it we can run you on operating cost software if you provide current equipment and fuel cost as well as electric rates, nature of soil and size of auxillary heater. In my area it sounds like it would be a 4 ton application, but there's something to be said for equipment that's already paid for (extra auxillary operation for a few hundred each year trumps thousands for a heat pump you don't have already). Duct work is a major concern but with a 3 ton system the requirements are still fairly modest and as the homeowner, you don't have the same customer satisfaction concerns that we do....you could try it and spend money on ducts if you're not satisfied (it's never to late to spend more money), however, the 6sq"/thousand btu rule is pretty important for your return air (and code most places). If we like you for a 4 ton, it may pay to put a 4 ton field in the ground now and change the heat pump size later if dissatisfied (besides the extra ton of material it changes the flow center).
J

Cool thanks! I will try to get it done tomorrow and post the updates.

I was kind of thinking about it the same way and leaning towards putting 4 tons in the ground just in case I needed to upgrade later.

Florida code now wants returns in bedrooms - common sense dictates that any room whose door is frequently or often closed is gonna need a return air path. Door undercuts aren't much good unless you don't mind a 2" gap between door and floor.

If you are serious about DIY ground loop consider investing in loop design software - it'll allow you to run various scenarios for your soil type(s) ground temps, tube geometry, etc.

If you have a 3ton unit and ductwork will support good flow for that - Joe's guidance is good - let heat strips make up the difference. 4 tons of field may well be a good investment especially since you can DIY most of that part. A 4 ton field makes a 3 ton unit run more efficiently and with slightly higher capacity.

Infiltration and insulation improvements to bring loads down may compare favorably against ductwork and equipment tonnage increases.

Here are the new numbers including the basement.

TOTAL HEAT LOSS 76104 btu
TOTAL HEAT GAIN 34011 btu

My current furnace is a Coleman 120,000 BTU model G9t12020upd13c. The Geo that I have is a Climate Master Ultra Classic model 36. The performance data on this model are here http://www.climatemaster.com/downloads/RP128.pdf.

Here are the gas and electric costs from my august bill. As I understand it once I switch to electric for the GEO and water heater the rate for electric will also drop.

electric
Basic Service Charge 8.50
Energy Charge 1,549 x 0.08263 127.99
5.00 % Electric Franchise Fee 6.82

Gas
Basic Service Charge 10.00
Delivery Charge 11 x 0.20459 2.25
Pipeline Transport Charge 11 x 0.06873 0.76
Gas Supply Charge 11 x 0.99194 10.91
5.00 % Gas Franchise Fee 1.20
Total $25.12


When you look at the load numbers and compare to my current current furnace would you say that 120,000 BTU is the right size or is it more than I need? I sometimes wonder if that could be contributing to my heating costs. Is it better to have a furnace that runs more or runs less?

The GEO also has a desuperheater so even if I have to spend a little more in electric in the winter I am guessing that lowering my hot water costs in the summer will help offset some additional cost.

Thank you for all your help.

I also found out during the heating season the electric rate will drop to $.03 per KWH after I switch to geothermal.

With those heating and cooling loads, your furnace is oversized, and the 3 ton geo unit you have is undersized. A furnace will get higher efficiency, or closer to its efficiency rating, when it has to run a long time to maintain temperature.

I agree with Joe's suggestion of a hybrid type system. You'd be better off than just with propane alone. However, I think you'd be a lot happier selling your 3 ton unit and doing the proper sized system on your house. With that load, you may be looking at needing 5 tons, too. Of course, you could probably do 2 systems to get to the 5 tons.

With that electric rate, you'd be crazy to pass on the opportunity for geothermal, too. Is that rate if the house is all electric and geo? or is it just geo?

I called and got more detailed information on the electric rates.

Current winter rate:
.08263 and after 1000 KWH it drops to .0712

With Geo and gas waterheater or gas emergency heat:
.07950 and after 1000 KWH it drops to .02962

With Geo and electric water heater:
.06802 and after 1000 KWH it drops to .02962

I was a off on my initial costs for the electric, but after the 1000 KWH it hits the $.03 price.

The aux heater I have is made by Warren technology. It says model AH10GM, 2 steps, 24.0 volts, 40 Amps, and is 9200 watts.
It sounds like this will need to be an important part of making up the difference in tonnage for the winter months and I better make sure it will be able to produce enough heat. This part says it was built in 1997 so maybe it would be better to update it to a newer model. How much does something like this cost?

I'll try to crunch this for you soon (already midnight here)......of course if any one else hase time.....:-)

I'm taking some things for granted.
1) that the "11" mentioned in your gas rates represents cubic feet making your cost about 1.37 per
2) that you have 4 people using hot water
3) that the furnace indicated is 90%
4) that you have a 3 ton a/c
Your heat load strikes me as heavy (I would have expected a 10K-ish additional loss for basement as our climates appear similar), but if we go with it:
Your job calls for a 5 ton.
Working with what you have and a lower loop design temp of 20 degrees the 5 ton calls for about 450 ft (4 ton almost as much, 3 ton 10% less) of 4'/ft slinky 5 feet deep and more than twice that for a 30 degree temp minimum. The three ton unit calls for a 17K auxillary heater and the 4 ton a 14K.
All that said, let's work the basement as unconditioned space and also the basement floor as 2' below grade.
Let's make sure we input the right numbers before you run out and buy a 5 ton.
I did not factor in a desuperheater as your 3 ton will not have a lot of wasted heat.
Narrow the numbers for me and we'll re crunch.
J

peter designing a geo system is not really a diy task, but if you must, check out geokiss.com they have a bunch of free software that will help you, i would consider trying to find a geodesigner(hopefully they will also be a licensed engineer) in your area
pay him for his knowledge and a detailed plan
i would also encourage any first timer to bring each loop (1per ton) into the house rather than burying a manifold

1. The '11' is total therms.
2. There are two of us with a baby on the way. But it is a 4 bedroom house. I only have a 40 gal water hater today.
3. Current furnace is 92%
4. I think it is 4 ton 12 seer.. Coleman model DRCS0421BE

The heat load program I used didn't have a way to indicate basement space so that would probably explain why it is higher than it should be. It just had a option for on slab. The house is a walkout and three sides of the basement are underground.

If the desuperheater won't make much of a difference would you still do electric water heater and hook it up or would you do a tankless gas?

Thanks again Joe. I am learning a lot and appreciate your help!

Okay,
Without properly calculating the basement, we are chasing our tails. I'm still guessing that you are in the 4 ton range, but we may find 3 ton works. Based on the numbers you gave me though you don't have enough equipment.
Does your gas company offer a break down in cubic feet?
Heat of the Earth has a great resource mentioned (geokiss), though I would rather see you keep the basement penetrations to two. So ensure you have the right help and tools for fusion.
Joe

The gas compay doesn't show cubic feet. I did some checking online and found this formula, 1 cubic foot = 1020 BTU, and 1 therm = 100,000 BTU. My 11 therms = 1078 cubic feet (1 Therm = 98 cubic feet). Not sure this is all accurate, but I found a couple of different places with similar formulas online so more than one person is at least sharing this formula. Does this work?

I was thinking I would get it all layed out and then have a professional fuse it together to the header that runs into the house so I can keep it to two penetrations into the house.

I will see if I can find a place to calc the basement. It's pretty basic 24 by 36. Wall down the middle. Laundry, bathroom, stairs on one side below grade with one 3x2 window. And on the walkout side there is a 6x6 double glass door and two double windows 6x4 that face south.

Thanks
Pete