I just need some opinions as to what constitutes horizontal boring.

This is what my installer told me was going to be done. When I got to the site it actually looked as if they had just done a grid of vertical drilling. Closed loop installed, everything looks good. As far as pipes sticking out of the ground with slurry drying around it.

Does not horizontal mean at an angle? Or am i out of my mind? I guess I could always ask my father in law. He drills for a coal mine. Exploration is what he does for fun.

Any thoughts would be appreciated.

Maybe it was a typo....?

Horizontal boring to me would be with one of those bore machines they pull lines under a road with.

On an angle, it's called diagonal boring, or angled boring. Vertical is always vertical....

Disclaimer: I'm no expert and have no experience with horizontal boring. This post is relaying info garnered on the subject during IGSPHA installer certification class last month.

The instructor (with 28 years in the business) felt horizontal bore holds much future potential due to being relatively fast with minimal destruction to the site. Machine mentioned during class happened to be manufactured by Ditch Witch (Ditch Witch titles this product line "Directional Drills" on their web site).

During break a loop installer from northern Wisconsin discussed horizontal bore. I got the impression he has installed a significant number of ground loops using this method. He enthusiastically explaining the process and answered questions -- how the drill head is "steered" through the ground, equipment expense, etc. From what I recall ... drilling starts diagonally from behind an excavated hole where loop header will be placed. When drill reaches depth of loop header it is leveled out to drill horizontally. Person with locating device stands ground above drill head to provide visual to the operator during the process. At desired distance drill head is steered upward until reaching surface. Loop pipe with "U" is then pulled through the hole. Whole loop field installed in matter of a few hours. Other advantages include ability to go deeper then traditional trenching and to provide more physical separation between loop pipes by alternating depth of horizontal bore between adjacent pipes.

No grout was used instead relying on hole collapse. The Wisconsin contractor indicated this has never been a problem for him. In his part of the country the hole tends to collapse as soon as the drill is removed. I suspect relying on hole collapse might be a problem in other geographies with different soil type. Perhaps there are ways to address this concern (horizontal grouting?)... or perhaps it is not really a problem. Hopefully someone with actual horizontal boring experience will chime in.

Ray...

rlacasse is right on. I haven't done a horizontally bored system personally, but watched the process done and discussed it at great lengths with some of the first guys to do it in Iowa. When grout is required, during the pulling in of the loop, a tremmie pipe can be pulled in with the loop, and when loop is fully installed, the tremmie is pulled back in the opposite direction and grout fills in the hole similarly to a drilled hole from the bottom up, only with this installation around the loop from one end to another. This installation is just like all other geothermal installations, it depends on soil types and conditions, and the contractors/installers experience with what they are doing.
Dan

Thanks Guys!

You have confirmed my thinking. Horizontal is Horizontal.

This just leaves me wondering if what they have done on my place truly is Horizontal.  Also would there be any difference in longterm efficiency of the system? Horizontal vs Vertical? Four vertical holes at 200' depth seems different then four horizontal at 10' depth. Is it a legitimate difference or simply perception?

I'm doing fairly well in that our ground is almost completely heavy damp clay, with mixed silt layers. Digging down 10' is still solid clay. Heat transfer should be as good as possible. I'm just curious really.

Vertical loops are always more efficient, but seldom our first choice as cost of drilling is much greater than savings vs horizontal excavation.
J

Joe,  you and I are usually in agreement but I have to part ways with you on this one.  I have a horizontal loop that never gets above 70° nor below 40°.

I dare say that most vertical loops would not beat those numbers.

 I am going to go back and add WEL devices to some of the vertical jobs that we have done so I can get good info on how they perform.

It will be interesting to see what  the vertical loops actually do.

I speak of course in generallaties and Geographically. Without a doubt, temperatures just below the frost line in January around here are colder than temps at 75' average depth, but the broader point to be made is the operating cost difference is nominal.
Incidentally, performance charts with Climate Master show open loop as the best method for heating while closed loop achieves the highest cooling eer's. This alone reminds us of seasonal differences that can cancel out performance enhancement/savings with varied depths. My feeling is that vertical loops are for small lots period.
In your back yard, I yield to you Dewayne.

This is interesting, and not what I would have expected.

I always thought, for the residential market, that horizontal loops were the most cost effective.  Slightly less performance than a vertical loop, but much less cost to install.  Those of us with borehole fields are (usually) because we didn't have the space to spread out horizontally.

Taking a few moments to put some analysis to this paragraph, to see if it can be quantitatively supported:

I looked up the 'down deep' temp for Salt Lake City.  It's 53°F.  Assuming for the moment a borehole field, add to this about 9° for continuous earth heating to get to the hottest point of the summer.  That's bring the earth temp up to 62°.  Then add a 'swing' of about 8° for a 24 hour day, during the hottest part of the summer, to reflect heat rejection in excess of the the borehole field's steady state absorption capacity, and you've got a high of about 70°.

So, using a 'ball park' analysis method, it looks like indeed, with a vertical loop, the upper end EWT for a properly sized borehole field is about 70°.

Now, turning to horizontal loops, looking up the annual soil swing for Salt Lake City, it's 24°.  So I would think that the earth temp surrounding horizontal loop pipes would be about 65° at the hottest part of the summer (53° + 12°).

I'll guess that continuous earth heating for a horizontal loop is half that of a vertical loop, because the horizontal loop is much more exposed to rain and other conditions making heat transfer twice as fast.  So that's 65° + 4° = 69°.  Now add an 8° 'swing' for a 24 hour day that probably occurs during the hottest part of the summer, and that brings the horizontal loop EWT up to about a high of 77°.

Again, a 'ball park' analsysis.  Using it, for the horizontal field, it looks like the upper end EWT for a properly sized loop is about 77°.

This too matches what I would have expected.  The vertical loop, at a much greater expense, having a little better EWT high (70°) versus the horizontal loop, at a much lower cost, with a little higher EWT high (77°).

My guess is that the EER performance difference for something like my WaterFurnace Envision units, for EWT of 70° versus 77°, is marginal.  And hence the readings I've done that have said that the performance difference between vertical vs. horizontal does not offset the cost difference.

I look forward to learning from the experts on this.

Best regards,

Bill

Interesting analysis Bill.

I am not seeing an 8° swing  in EWT during the daily cooling cycle.  If you look here,  you will see that my EWT stays almost constant during the day while I am cooling.

The EWT is about 68° in the morning and still below 70° in the evening.  Part of the reason for this IMO is I have 6000' of 1" pipe in the ground.  Had this been a vertical system,  I would probably only had 1000' of pipe in the ground.  

The extra mile of pipe gives the loop fluid a much longer "residence" time in the ground plus at lot more ground in contact with the pipe.  Which means that more heat can be rejected and keep EWT's down.

I will soon be inserting sensors down to the level of my loop to get a reading on soil temps.  I love my WEL unit!!!

Surface area is a major factor when comaparing vertical to horizontal. When we are contracted for a job, we tend not to oversize as much (as we do at our homes) as we are trying to put folks into geo for the lowest sensible cost (maybe a little padding but not an extra thousand feet). To pad a vertical field is obviously much more costly due to the drill and grout. It may be that a contractors common practice of "a little more never hurt" is skewing these numbers.
One thing is for sure, the EWT in January in MI for a horizontal field will not stay above freezing. A Vertical field with enough loops could, but there's the diminishing return conversation again.
Bill; still would love to see a description of your mechanical room, on it's own thread to see if we can help you solve your HWG issue.
Joe

Thanks for the note, Dewayne.

If you instead add just a 1° swing to my 'ball-park' estimate of your current earth temp (69° - see above), then that puts your EWT high at about 70°, which generally matches what you're seeing with your horizontal loop.

Thus, the question, is your 6000' of horizontal pipe, translated to feet/ton, at a 1" pipe size, typical for a residential installation, in your geographical area?

Also, it looks like from your WEL charts, at this point in the season, you don't run your GSHP unit(s) during much more than a 6 hour period of the day, giving your soil plenty of time to recover from the small daily 'swing' EWT temp you have.

And, it looks like your actual run time is not much, meaning you're not removing a lot of heat from your residence / dumping a lot of heat into your 6000' of 1" pipe, giving the 69° estimated earth temp plenty of opportunity to quickly absorb the heat without impact to your EWT.

Overall, my guess is there's 'roll reversal' when Winter season arrives, compared to what I need from my vertical loop in a Dallas Winter.  You probably need every bit of your 6000' of pipe for heating purposes.  My guess is your earth temp surrounding your pipes gets down to 41°, before you further take into account the EWT 'swing' performance of your horizontal loop across a 24 hour day.  My guess is you have antifreeze in your loop water!

Best regards,

Bill

 

Joe, I looked up the soil temps for Detroit, MI: 50° 'down deep', 25° horizontal loop swing.  Battle Creek is similar.  And it must be really cold near Sau St. Marie, with 'down deep' at 42° and a horizontal swing at 26°.

Taking the 'milder' Detroit example, for a horizontal loop, I estimate ('ball park') 38° soil temp surrounding the horizontal pipes, in early Feb., before you even start trying to extract any heat from the soil.  Subtract about 4° for long term cooling due to season long heat extraction, and you're down to about 34° soil temp immediately surrounding the pipes.  And if up to an 8° swing is associated with typical horizontal loop installs due to intensity of heat extraction during certain parts of the day (probably night time), you're looking at 26° soil temp immediately surrounding the pipes at night time.

For a vertical loop, my guess is 50° soil temp surrounding the pipes, before starting to extract any heat from the soil.  Subtract again about 4° for long term soil cooling out to early Feb., and you're down to about 46°.  Subtract another 8°, assuming a typical 'cost effective' borehole field, and you're down to 38°.

So, again if the estimates are 'in the ball park,' it's a horizontal loop at around 26° EWT versus a vertical loop at around 38°.

In this (Detroit) example, it looks to me that there may be some possible (reasonable) payback on a vertical versus horizontal loop, if there's enough significant difference in COP at 38° EWT versus 26° EWT, for a long enough season-long run time.  If not, then again, it looks like it's the "diminishing return conversation" affirmed.

Best regards,

Bill

 

 

I'll start the thread.

Best regards,

Bill

Bill,  just a few thoughts.

I didn't design my system,  the design was done by a local distributor.   At the time I knew nothing about geothermal.

My system has 1250' of pipe per ton.  We now design for 1000' of pipe per ton.  We might cut this back based on the data we get back from several WEL units we are going to install.

We are definitely heating dominate here.  The estimated run time for cooling is 590 hours and 3150 hours for heating.

It will be interesting to see how the 6000' of pipe does during heating season.  I have had thermometers on my system in the past and spot checks have shown EWTs in the low 40s.  The WEL  will give us a better picture.

Dewayne, the data will be interesting for Winter months.

Thanks for the note.

Looks like WEL units will give you information that will allow you to quantitatively affirm just where exactly the optimum design versus cost point is for your accounts, that may then allow you to reduce your material costs / charge a lower price while comfortably knowing the installations will perform well.  Sounds like a key competitive strategy!  Good luck.

Best regards,

Bill

Bill,
The cost difference between vertical and horizontal tons in this area is about $1,250 (what I pay the diggers/charge my customers), add to that the time you pointed out would have the most significant benefit, is when we are relying most heavily on the auxillary heaters (as closed loop systems are almost always undersized here) do to diminished returns.
I think the more interesting thought (especially given Dewayne's observations on his field temps) would be the ROI of longer horizontal loops. It might be a happy median between lower COP of horizontal in Feb vs extra cost of drilling. No question that larger surface area maintains higher surrounding soil temps.
Dewayne, do you have lowest EWT temps for some of the shorter fields you are now installing?
J

Bill,  the only loop I have EWTs on is my loop.  I going to buy some more WELs so I can monitor others.