Good Day to you all. I've been lurking for the past few weeks on different sites and found this one to have some great information from some very helpful people.

So by the title of my post you'll see I am fed up with oil prices. I was an oil advocate and installation/serviceman for 18 years working for and running my family HVAC company before walking away from it all a few years ago. Now as just an Oil consumer...I hate it even more.

OK, here are the details...

I have a 2100 sq/ft Cape in Central MA. The house was built in 2001 and is fairly tight. The walls are all 6" (r19), the attic has of 12" insulation. The basement is unfinished, but has 1" poly foam installed on all basement walls. It is also studded, but that's it. Someday we will finish 500 sq/ft of it, so that will have to factor into the equation. I plan on downloading the program listed on many posts to do the proper heat loss calculations. I'll admit I used to be a "rule of thumb" guy, but I can see the sensitivity to details these systems require.

My current system is an oil fired hydro-air system. I designed and installed the system during the construction of the house in 2001. It all starts with an oil fired hot water boiler with 2 zones. The delivery system consists of two Unico high velocity air handlers, one zone located in the basement for the first floor, one located in the attic for the second floor. The ductwork for these units is 7" round metal ducts taped and insulated. The duct configuration for each zone is a 7" fully connected loop with thirteen 2" flexible ducts dropping/rising into the rooms. Both Unico units have a hydronic heating coil installed. The second floor zone has an evaporator coil connected to an outdoor 2.5 ton Ruud 10 SEER condensing unit for cooling. The first floor is heat only, no A/C needed. The second floor zone can cool the entire second floor to 62F and the first floor down to 70/72F when outdoor temps reach up to 98F with a 70F dew point. We just had a four day heat wave where these temps were reported on my weather station and only 2.5 tons did the job very nicely. I think the credit there goes to the high velocity ductwork helping dry the air out rapidly which promotes comfortable and efficient cooling. I think the only real DIS-advantage of this ductwork is the increased noise level compared to a conventional duct system. For my hot water I have a 41 gallon Amtrol tank with the heat exchange coil in it running on its own zone from the boiler.

I would like to use a horizontal closed loop system. I have a strip of land with trees and brush that is about 35' wide by 200' long I can clear and trench. My subsoil is silt/clay. I know it is at least damp, and possibly all winter it will be saturated. It is adjacent to a swamp and I had to use a raised septic system as the ground water rises to 18" from the surface. Yes I do have a high water table and wet land. The water seeps up in between hairline cracks in my basement floor all winter, so there is water there.

Before installing a wood stove in the basement, I burned about 1200 gallons of fuel oil per year for heat and hot water. Now I burn 4 cord of wood and consume about 500 gallons of oil for the year. The A/C cost is about $300 for the summer.

My goal is to install a GSHP that can handle 95% of my heating/cooling/hot water needs. I'll still plan to burn wood as long as I continue get some free, but I won't pay for it anymore if GSHP is cheaper.

Well there it is I think I have offered up some good details of my current situation and where I want to go. What I’m looking for is some opinions on how to get there.  I’m not worried about sizing right now. I’m more interested in options of how to retrofit a new GSHP into my existing footprint.

 

 

My questions about the indoor equipment…

I still need 2 zones, will one GSHP water unit be capable of heating and cooling 2 zones individually using the 2 existing air handlers I have? Or do I need 2 smaller GSHP water units, one for each zone.  Should I just take out the Unico air handlers and replace them with 2 new GSHP air units?

 

Now about the horizontal loop…

 Using a round figure of say 2000’ of HDPE pipe needed.  Instead of using 2000 feet of slinky buried in 700’*4’ wide trench, Can I just use 10 runs of strait HDPE in a 200’*9’ trench keeping each run 1 foot apart?

 

I have more questions, but my head hurts right about now…I’m just going to toss this out there and see what pops up.

 

Thanks!

ok,
first off starting with the load. I guess that you already know that your upstairs unit is oversized for the 2nd floor. thats why it can cool the 1st floor. this is a no-no in geothermal. the units should be sized for 90% of the heating load, and not 1 btu more.
there isnt a lot that you can do with your high velocity system. its not really compatable with geothermal heat. On the heating side, geothermal condenser temps cant go above 120. Ideally, the unit will run long cycles warming the house with 110 deg air. your HV system would probably be really annoying when it runs alot. You probably dont use cooling alot up there, but both units would be heating & cooling.
If you had to do it over, i would recommend 2- 1.5 ton air-water heat pumps. you would need to install low velocity ductwork & diffusers for each.

As far as the ground loop, its not really about the feet of tubing, but more about the amount of ground that the tubes come in contact with. The next problem with the field is that horizontal loops are affected by outdoor temperature. this will negatively impact performance. the loop will be cooler in the winter, and hotter in the summer. Also, your soil, clay and silt, is a poor conductor.
I am more famillar with vertical wells. a rule of thumb is 200 ft of well per ton, so 600 ft of well, in your case.
If you go horizontal, you need to add to it for the temperature effect, and add for the poor soils. You would really need to get the tubing in a trench 5 foot or below.

Hi Bill,

Thanks for your insight. You are correct, I did oversize my 2nd floor A/C unit, but that was planned. We were on a limited budget and had no more $$$ for 2 evaporator coils and condensing units. However, The Unico high velocity performs unlike conventional units, it fires the air out so fast that the room air moves and definately dries out far quicker than conventional ducts.

Anyway, I wonder about those ducts not being compatable. On the heat side, right now I only send 140 degree water to the coils. Before we burned wood, that temp was fine. Even on cold 10F degree days, the system cycled 60/40 on off. I am sure that 120F water will cycle much longer, maybe 85/15? Whatever, the noise is no problem with this system. It is better steady on all day and night than on and off. We actually turn on the fan only so our kids can take naps during the day. It is not at all annoying, this is not a loud system at all. My comparisons to conventional ductwork is accurate, the conventional systems I installed you could hear the blower motor noise more than the air flowing out of the ducts. Currently, my duct system does not even require me to turn up the volume on my television, so there is no annoyance there.

Regardless of so called noise, if I have a coil heated to 120F, and blow that out high velocity, what won’t work? What is the difference? I still have the same CFMs pumping, right or wrong? Please tell!

Please do not misunderstand me, I do have access to large ductwork. You know, 20*8-16*8-12*8-8*8 with the 6” and 7” runs to the registers. I can replace the high velocity at any time. However once I started using a more condensed, high velocity ductwork on my jobs, I noticed a much superior system if properly engineered. The only caviatt was the slight increase in air noise.

So forget noise, can anyone tell me why it will not work? GSHP will be 20-30F cooler at the register, but so what, the conventional ducts will be 20-30F cooler too, right? The on cycle is just longer so to keep a steady flow of warmer or cooler air to the rooms.

The last 2 winters I burned wood in a 70K BTU wood stove in the basement. The entire house heated up in the dead of winter as long as I kept feeding it every 3 hours. Now, the efficiency on the stove tops out at 73%, so at best I have a 50K net BTU wood stove heating an unfinished basement, 1st and 2nd floor, as long as the wood keeps burning at top efficiency.

So my guess is that Bill, you are pretty darn close. You think that 3 tons will heat my home. Well I agree, but I’ll wait for the program calculations for the final on that.

Let’s talk about the horizontal loop again. I will be digging a trench that will ultimately be 6’ deep minimum. So whatever the pipe length required…my question still is…Can I run straight lines 1 foot apart rather than slinkys?

WOW, There is a lot to this, but I am just trying to learn at this point.

Yes,  we have done this several times and it works great

On a new air-water unitary geo heat pump, its the fan thats the problem. Its small compaired to what you need for your hv system.
If your HV system in place....
check the hot water coil performance and see what it will do with 120 deg water. If it will work then you can get a geo water-water heat pump, and run the 120 deg water to the existing coils. This heat pump will also produce chilled water, but I dont think that the exist. hw coil will work with chilled water. you really need a 4 or 5 row coil for cooling with a drip pan. for cooling, maybe you can get a water cooled condensing unit and connect it to the existing DX coil. or just leave your existing ac in place.
another option is to see if you can replace the existing DX coil with a chilled water coil that you can also use for heating.

Even if it needs help on the coldest days you could fire up your wood boiler.

For the field, yes, straight piping will work. the field piping needs to be designed for your system and conditions. I assume that you have access to a backhoe, and thats easier than vertical wells.

Bill,

OK I see what you are talking about. So a water to water system will both send warm water to the water coil for heating and cold water to the coil for cooling. Same coil right?

My Unico Air handler has 3 sections that snap together. The first section is the blower section. Next is the water coil for heating, and the final section is the DX cooling evaporator. I don't think my water coil is very big, but with this system I can just remove the cooling evaporator and snap on a second water coil and daisy chain them together so the two coils together will extract as much heating or cooling energy as posibble. There is also a drip pan installed so that is fine.

Remember, I don't think cooling will be a problem. Right now I have only one 2.5 ton cooling unit that can really freeze the upstairs. If I go with 2 GSHP units I will be spreading out the cooling, one source upstairs and one source downstairs. Al;so I would be using 3 or 3.5 tons now for the entire house. And we do use the A/C all summer, from May to October, pretty much every day and night.

It's the heating that I am worried about. For me, sure if I can get this system to heat the house to 70 on a 15 degree night, I'll be happy. I don't mind throwing the wood on the fire. However if I ever sell the house...would the prospective buyer feel the same way? So I would hope I could heat the house well down to 5 degrees without assistance.

I'll tell you what though, 1000 gallons of oil consumption during the heating season at $5 a gallon this winter is $5000 that I am not willing to spend. The other 200 gallons heats the water during the summer...Another $1000. So I am sure that I can shave a lot off of that, even with my tiny ducts. If it doesn't work, I'll just change them out, the money saved will pay for it anyway.

For the loop, I would love to go vertical, but I think the price may be too much. I will look at that option though. It would be nicer than digging up 200 + feet of yard. I know a guy who will come out with a big excavator and trench for me. It might cost $1000, but just one Oil tank fill is going to be close to that anyway.

One more question about the trench. If my silty soil is a bad conductor, would a 50/50 mix of sand in there help? The area I am going to dig in is 2-4 feet below the grade of my home. I would like to build it up and gently slope it. So I will have to buy material anyway. Why not add the effecient type of soil into the trench around the pipes? What would be good?

Thanks again for the advice...

Right, you could pull out the water coil and DX coil and replace them with a 4 or 5 row chilled water coil. This will do the heating nicely also with 120 deg water. Hopefully you could even use the existing piping to the systems, provided the pipes are big enough and insulated well.
I understand your concern about capacity. Typically a supplimental electric heater is used for the 1% cold hours.
But the capacity question ties into your well field. It has to be designed as a system. In the case of a shallow horizontal system like you describe, the coldest day of the year will also be the worst day to get heat out of your geo-source field. In a veritcal well, there is little or no influence from surface temperatures.
That said, its not impossible to do it that way successfully, but you will need more pipe & trenching. How much more? I dont know, but it has to be designed. There are computer programs that do this, but they are not for beginners.
As for your soil type, there isnt anything that you can do about it, except design for it. (more trench & tube)
Have you looked into contractors in your area ?

According to IGSPHA  at a depth of 5',   the high and low soil temp lags behind the surface temp by about 30 days.

  I have a horizontal loop installed at my house .   My loop temp swings from 40° in the winter to 60° in the summer.  If I had a vertical system the swing might  be 5° less.   Not hardly a reason to spend all that money on drilling.

Bill.
Yes I did reach out to 2 different contractors today. Hopefully they will return my inquiries. It would be nice if they would agree to size up the system, install the loop, and let me do the inside work. I understand if the hesitate on that, but I don't want to pay for the inside work that I had 18 years of experience in. We shall see.

Geodean,
I looked at your website, i see that a DX loop requires only 100 sq/feet for the loop? Can you elaborate? I am not against a copper coil in the ground as many are. I figure that if I am saving the world a little bit from my fuel oil and wood emissions for a trade off of any potentioal hazzard of copper coil in the ground...the copper coil wins. plus I can leave the rest of the yard un touched.


Thanks,
Dane

THERE IS ABSOLUTELY NO PROBLEM WITH COPPER GROUND LOOPS!!!!!!

COPPER COMES FROM THE GROUND. IT'S A NATURAL ELEMENT!!! IF IT NATURALLY CORRODES, WHERE DOES IT COME FROM?!

Sorry, but I'm sick of this concern. There is absolutely nothing to be concerned with using copper ground loops. They're more efficient systems (EarthLinked DX) and always require less footprint for the ground loop. It saves money on installation, and saves money on operation.

LOL, I completely agree, but some are concerned about potential leaks in the tubing, yadah yadah yadah. I'm not worried about it. Like I said i think the elimination of oil and wood emissions far out weighs the potential of any spillage of refrigerant IF there was a problem with a leak in the tubing.

Since I have you're attention, what is involved with the Earthlink DX? How is that pipe installed? Does it require drilling or can it be installed horizontal?

Thanks

It can be vertical, diagonal, or horizontal. When horizontal, the lines need to be +/- 6" to level. So from the highest point of the loop to the lowest, it can range 12". It also needs to be fairly close to the house. By that, I mean that the manifolds that tie the loops together---from the manifolds to the air handler/blower, can't exceed a line length of 125'. Also, if the soil is rocky, naturally you'd want to bed the loop in sand/clean soil/crushed limestone...

Typically, a water based loop system needs double or more of the piping in the ground, thus requiring at least double the excavation and footprint of the loop.

> THERE IS ABSOLUTELY NO PROBLEM WITH COPPER GROUND LOOPS!!!!!!
> COPPER COMES FROM THE GROUND. IT'S A NATURAL ELEMENT!!!
> IF IT NATURALLY CORRODES, WHERE DOES IT COME FROM?!
>
> Sorry, but I'm sick of this concern. There is absolutely nothing to be concerned with using copper
> ground loops. They're more efficient systems (EarthLinked DX) and always require less footprint
> for the ground loop. It saves money on installation, and saves money on operation.

Sorry, but copper is NOT mined from the top 20 feet of Baltimore County, Maryland, where I live. And every copper pipe I have seen in the ground on my property has developed leaks from being corroded to paper thinness.

What kind of copper line is it? Does it have an inert gas/liquid flowing through it (like refrigerant)? Or does it have water? If it has water, there can be electrolysis, and that's why it's corroding. What's the pH of the soil? Is it lower than 6.0? If not, then the copper is not corroding from the ground. Instead, it is corroding from the water passing through it. Talk to a chemist. It's fact that copper won't naturally corrode in conditions with pH above 6.0.

Ships in the sea use copper in the paint as a protective barrier against the harmful effects of the salt water. That's because oxidized copper is actually a protective barrier.

You're right. A copper water line will corrode. But that's from the inside out, not the outside in. Copper propane lines could corrode from contaminants in the propane gas. Once again, that's from the inside, not outside. When you circulate refrigerant in copper, you don't have electrolysis. You don't have corrosion from the inside.

If the pH of the soil is below 6.0, that means the soil is acidic. What's happening to the copper then? The acid is stealing electrons from the copper element--a noble metal. What needs to happen if acid is taking those electrons? It needs to have a cathodic protection. The best kind of cathodic protection is an impressed current cathode/anode setup, not a sacrificial anode rod. EarthLinked has developed an impressed current cathodic protection system that constantly bombards the copper with electrons to replace the ones being taken by the acid. It's also FOOL-PROOF.

One more point I want to make...to reiterate what I've said...

If I use pine 2x4 lumber for an exterior deck, and don't treat it, should I expect it not to warp/rot? Would it last? Nope. So, since my house (which had it existing) has a deck with rotting, untreated wood, I shouldn't use untreated pine lumber for inside work on my house, right? Wrong. It would be a completely different use of that lumber, right?

That's the same as it being a different use for copper with water vs. refrigerant in it.

Well, I reached out to 2 contractors in my area. One responded, but suggested to do the open loop system with my current well to save costs. I really don't want to do the open loop, problem is where to dump the water, I have wet property as it is. I also use an irrigation system on the well, so I don't want to beat up the pump anymore than I do already. I emailed him back telling him that, but also that I am open to discuss. I have not heard back again.

I did however have an excavation contractor that I know out to look. He suggested that if 2000' of tubing is needed instead of a 10' * 200' trench just do a 50'*40' "cellar hole" in the lower area and bring the yard up to the grade of the house. If I need 3000' then go 50'*60*. Then I would add to the yard and only have to dig down 2-4 feet. Money would be saved on digging time, also less disturbance for the rest of the yard, less trees cut and stumps removed, etc. He has piles of clean fill he can sell me cheap to raise up to grade after burying the pipes nice and snug. I can raise the grade up to match the rest of the area around the house and make the pipe depth 6 feet.

My problem though is getting someone out here to evaluate and design a system.

Clark, I am really looking hard at the Earthlink DX. I can see the benefits of that system. If I could ask you though, and let me preface this by saying I understand if you don't want to just throw numbers out there withough knowing anything first hand about my situation. Is it possible to give me a ball park idea of how much smaller the loop footprint would be with a DX system compared to HDPE tubing? If iI am able to tell you that I have an average house with average soil type and temps and need 2500 feet of tubing for a 3 to 3.5 ton system, what could I reasonably think that the footprint would be with a DX copper coil? 2/3? 1/2? 1/3?

Also, since I am up here in central MA, it does get cold in the winter. Would I benefit much by going 7 feet down instead of 6 feet?

I'm headed back to the earthlink site to look for a local dealer out here, but I just wanted to throw these two questions out there for some other opinions.

Thanks,
Dane

Sometimes we accidentally submit the same posting twice.  Be aware that each poster has the ability to edit their own post after it has been submitted.  The duplicate post could be edited down to blank space or better still, ask the moderator to delete the duplicate.

You could go 20' deep if you really wanted, but it won't improve the operation of the heat pump system.

A 3 ton EarthLinked horizontal pit is 35' x 49', +/- 6" to level. It's recommended to be put at least 18" below frost line. I like to go 6' deep in our cold area. 7' will work. 5' will work.

A 3.5 ton EarthLinked horizontal pit is 39' x 48.5', +/- 6" to level.

Oh yeah, I should have mentioned. I have 2 zones so I would need 2 units. Both units could be 1.5 tons each, or the first floor could be 2 tons.
About what size fields would those require?

Sorry for all the questions, I just want to see if this will work with my property.

Thanks,
Dane