ESPCO May / June 2013 Newsletter
To drill or to trench?…that is the question
In my ‘Introduction to Geothermal Heating & Cooling’ class I speak to the many options for the ‘Ground Heat Exchanger’, GHEX, and I wanted to take the conversation one step further.
In my class, I use a portion of a tutorial for the Comfort-Aire LoopLogix geothermal design software narrated by the great Bob Sykes, retired Director of Sales at Heat Controller, Inc. Bob uses an example of a three ton system and he demonstrates how the LoopLogix software allows the designer to go back and forth from any number of GHEX applications, and in doing so, shows how each application changes the amount of tubing required for the GHEX…in some cases, dramatically changes the amount!I always point out these dramatic changes to the class attendees and I emphasize that one must balance the additional tubing required for ‘trench’ applications with the cost of vertical borehole drilling to truly see which is the more cost effective…that is the ‘next step’ I want to take here.
We need to obviously set a scenario here…not every job allows us the luxury of choosing between trenching or vertical application but for this example we are going to assume we have the land to do whatever we find to be the best, most cost effective approach.
I just spent a couple weeks in the mid-west, (Iowa & Nebraska), and traveling through that very beautiful, (and very flat), part of our great country inspired me to do this exercise. My new friends in the mid-west often have many application options with geothermal as they have plenty of land, (farms), often with ponds and / or small lakes on them. The choice often comes down to cost of tubing and trenching versus cost of vertical drilling.
Let’s use the example Bob Sykes uses in the LoopLogix tutorial. The result of our ACCA Manual J heat gain / loss calculation requires a three ton heat pump. Now, let’s not only see how much tubing, drilling or trenching will be required for this job buts let’s put some real numbers to the example and see where we are at the end…is trenching more economical over drilling or are they a wash?
Ok, let’s start with a vertical GHEX…LoopLogix tells us that based on the design criteria we have entered, a vertical application will require the following:
- Three vertical boreholes of 200’ depth
- 1200’ of ¾” HDPE tubing
Let’s try and put some real costs to this…I’m going to use costs associated with my neck of the woods here in New York & New Jersey and they might be different from where you are so you can make adjustments where needed.
- Three vertical boreholes of 200’ depth
- $18.00 / foot drilling, pipe insertion & grouting
- $10,800.00
- Three ¾” U-bend coils of 230’ length
- $167.00 / coil
- Three coils = $501.00
- Total cost for vertical GHEX = $11,301.00
Next, let’s look at the same job but now plug it into a two pipe backhoe application. LoopLogix shows us, among many other things, that our annual ‘operating costs’ changes by a whopping $11.00…obviously insignificant. It also shows us the following is required:
- Three trenches 2’ wide X 5’ deep X 577’ length
- 3461’ of ¾” HDPE
- 1154’ of ¾” HDPE per trench
On the surface, (excuse the pun), this might seem like a ‘no brainer’ based on the amount of tubing required alone…the trench application requires almost three times more pipe!
We need to look closer however, to see if indeed this is as simple as it appears.
Like we did with the vertical application, lets apply some real costs associated with the trench application:
- Three trenches of 2’ wide X 5’ deep X 577’ length
- Two day rental for a Case #580M backhoe = $630.00
- Five coils of ¾” HDPE tubing X 700’
- $194.00 / coil
- $970.00 tubing cost
- 2 men labor / two days = $3,680.00
- Total cost for horizontal GHEX = $5,280.00
Pretty dramatic results!
Let’s now take a look at the same job using a slinky GHEX:
- Three trenches 3’ wide X 5’ deep X 200’ long
- 4826’ of ¾” HDPE tubing
- 1609’ of ¾” HDPE per trench
Our tubing requirement has gone up yet again, (by another 1325’), and we also need a wider trench to accommodate the slinky loop diameters of approximately 36”. Although the trench is wider, it is also considerably shorter so I believe two days for trenching is still a reasonable estimation for this application.
- Three trenches 3’ wide X 5’ depth X 200’ long
- Two day rental for a Case #580M backhoe = $630.00
- 4826’ of ¾” HDPE tubing
- Seven coils of ¾” X 700’
- $194.00 / coil
- $1,358.00 tubing cost
- 2 men labor / two days = $3,680.00
- Total cost for horizontal slinky GHEX = $5,668.00
So there we have it…where we can trench, the numbers show it to be the economical choice by far.
You can download the Comfort-Aire LoopLogix geothermal design software for FREE here.
Next time, I want to look at two other popular applications…’pond slinky’ and ‘directional drilling’ and see where they fall in this scenario.
You can now download the notes from any ESPCO class!
Click on the tab ‘Downloads’ on the menu bar and choose the class you attended:
You will need to enter a password in order to download the notes…passwords will be given at each class and each class has its own unique password. Those students who attended a class in the past and still want to download the notes can email me directly at:
You will need to provide me with the date, location and subject of the class you attended and I will forward you the password.
Kerr Controls of Canada
I have added some pictures of the classes I conducted for the Kerr brand of mini splits distributed in Canada by Kerr Controls. You can see the pictures here.
I was privileged to visit Kerr locations in Ontario, New Brunswick, Nova Scotia and Newfoundland last month and at each location they had a huge crowd for me to address…in fact, in Truro, Nova Scotia we had the biggest crowd in 2013 so far! So big that we had to change venues and conduct the class in a local hotel’s ballroom…it was like playing Vegas!
The following is from Kerr’s company bio:
‘In business since 1949, Kerr’s business has grown over the years from a humble beginning with the founder (and current chairman David Kerr Wilson) selling and servicing out of a milk truck. This start to Kerr Controls took place with the founder identifying suppliers around New York and selling throughout New Hampshire and surrounding areas along the route. When the business started taking off Dave established a presence closer to his home in Truro, Nova Scotia and expanded throughout Atlantic Canada from there’.
One of the pictures in the ‘gallery’ on my website shows David Kerr Wilson in his red ‘milk truck’ …this picture, along with the company’s mission statement, is displayed at every Kerr location.
My time in the Atlantic north of Canada was made especially productive and fun because of Serge Cormier of Kerr Controls. Serge is the Sales Manager at Kerr and was with me at each location…he was a wonderful asset to me while there and for Kerr and Kerr customers, he is an invaluable asset year round!
In the group of pictures from the Kerr classes are two pictures of an ‘eatery’ in St Johns, Newfoundland called ‘Long Dicks Sausage Emporium’. I want to stress that this establishment has nothing to do with Kerr but I just couldn’t resist taking a picture…I could resist eating there, as I thought submitting a receipt for expense reimbursement from ‘Long Dick’s’ might not be in my best interest!
The best way to contact Gerry
Just want to remind everyone that the best way to contact me is via email. I’m either driving or flying most the time, and when I’m not, I’m conducting classes, so the best way to contact me is via my email…I tend to answer emails when I’m in my hotel room at night so you have a much better chance of getting the quickest reply through email.
That said, I also need to remind everyone that if your question is related to a Comfort-Aire or Century mini split in the United States you must call ‘Technical Services’ in Jackson. MI at 517-787-2100 first and they will involve me if necessary.
If you are calling about a Comfort-Aire, Century or Kerr mini split in Canada please call Aiton’s Equipment at 888-744-2911.
I am glad to assist when I can but because of my schedule I often cannot reply promptly and I don’t want to disappoint anyone so it is best to call the above numbers.
See you all soon!