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What
type of loop should be installed? (Horizontal, Vertical, Pond) |
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Should
a thermal conductivity test be performed for vertical loops? |
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How
is borehole depth determined? |
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How
many bore holes should be used? |
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What
size of pipe should be used? |
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What
type of grout should be used? |
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Where
should the loop be located? |
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When
should a distribution vault be used? |
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How
deep are horizontal lines placed?
|
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Q. |
What
type of loop should be installed? (Horizontal, Vertical, Pond) |
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A.
|
The
type of loop has a lot to do with the land the project is sitting
on. Horizontal loops use a large mass of land and if the building
loads are large it will increase the amount of land required. Horizontal
loops fall in the price range between vertical loops and pond loops,
unless the trench is required to be compacted. If the trench requires
compaction it often drives the cost of installation high. Vertical
loops are very popular in commercial installations. They can be placed
in many different areas around the building. Pond loops are the most
economical loop to install. You must have a pond or lake of considerable
size to facilitate the loads of the building. This body of water needs
to be a minimum of 8 to 10 feet in depth. |
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Q. |
Should
a thermal conductivity test be performed for vertical loops? |
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A.
|
Yes,
a thermal conductivity test can provide many valuable results. A thermal
conductivity test is done by first drilling a vertical hole to the
depth that you want to obtain. This will provide the geological formations
that will be drilled through. If we don’t have this information
the driller has to guess what they will be drilling through, and is
typically reflected in the bid amount. The test also provides us with
what the thermal conductivity is of the ground. It could show us that
the ground has a high thermal conductivity – resulting in less
bore hole footage needed, or it may have a low thermal conductivity
– resulting in more bore hole footage. Once the thermal conductivity
number has been obtained it can be entered into software that calculates
the total bore footage for a job based on the loads of the building. |
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Q. |
How
is borehole depth determined? |
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A.
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This
depends on a couple of things. The amount of area is available for
the loop field, and the type of geological formation being drilled
through. |
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Q. |
How many
bore holes should be used? |
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A. |
There
are several variables, including the load on the building, the depth
of borehole and the amount of area available. When we design we look
at the total bore footage needed, then try and design the loop with
the minimum head loss. We typically stay with a borehole that is no
more than 300 ft. |
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Q. |
What
size of pipe should be used? |
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A. |
In
the borehole the pipe size should be between 1" and 1.25"
depending on depth. One-inch can be used on bore holes up to 300 ft.
in depth, and 1.25" on bore holes deeper. Common pipe sizes for
polyethylene are ", 1", 1.25" 2", 3" 4",
6", 8", 10", 12" 14", 16". |
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Q. |
What
type of grout should be used? |
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A. |
There
are different types of grouts on the market today, from Benseal (clay)
to thermally enhanced grouts (thermally enhanced compound & silica
sand) that provide higher thermal conductivities. On the smaller jobs
(60 holes or less) thermally enhanced grouts usually are not practical
due to cost. On larger projects the thermally enhanced grouts can
save money on the overall project by reducing the total bore footage
significantly enough to offset the cost of the grout. |
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Q. |
Where
should the loop be located? |
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A. |
Loops
can be located anywhere. Sporting fields are usually good places because
it’s a wide-open area. Parking lots are another good area for
the same reason. One thing to remember is the farther away the loop
is from the building, the more cost incurred for supply and return
piping. |
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Q. |
When
should a distribution vault be used? |
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A. |
If
the well field is a long distance from the building it is usually
cheaper to run two larger pipes from the building out into a vault,
and place a distribution header inside of the vault. Vaults can also
be used to move a large manifold out of a mechanical room freeing
up more area inside of the building. |
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Q. |
How
deep are horizontal lines placed? |
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A.
|
We
like to see the headers and supply and return lines buried at the
four-foot level. It helps keep the cost of excavation down, and provides
an OSHA safe trench to work in. |
