the Easiest System for Self Installers!
it in the ditch and cover with dirt!
Pre insulated Pex Pipe
for outdoors - underground
What's nice is
that you have 4 Pex lines for heating your domestic hot
water tank too.
This also gives you a fill or supply
line for your outdoor furnace. The 4 Pex pipes are
surrounded by insulation - FOUR WRAPS of insulation with a
black pipe around that.
That is 33% more insulation
than triple wrap pipe!
Heat loss is only 1 degree
F per 100 foot run!
Choosing the Right Underground Insulated
for Your Outdoor Wood Furnace
There are lots of options available when it comes to
installing the underground pipe for your outdoor wood
furnace. Sectional or seamless, foam or foil wrapped, the
right underground piping can make a huge difference in how
effective your outdoor wood furnace operates.
It wasn't too long ago that insulating underground pipe
was timely and very expensive. To save on cost most
homeowners turned to 10 foot sections of insulated 4 inch
PVC pipe that had already been available on the market for
other specialty plumbing needs. The outside of each pipe
was insulated and wrapped with a plastic bag material.
Long pieces of Pex or Pex vs. Pex-Al pipe were fed through
these sections of 4 inch pipes. After threading each
section the pipes would be glued and sealed using tape.
The job was awkward, difficult and labor-intense. Sealing
each section proved to be nearly impossible and the pipe
would fill with water, causing major heat losses and
ruining any advantage of an outdoor wood furnace.
Other sectional pipes have also come onto the market but
they all have the same basic flaw, seams underground. The
flexible foam variety not only lack adequate insulation
value but are susceptible to water penetration through
each and every joint underground.
Modern underground pipe lines for outdoor wood furnaces
have many advantages; namely, there are no seams buried
under the ground. Even within this seamless category there
are advantages and disadvantages.
Most manufacturers wisely use Pex pipe in their
construction. Foam filled varieties seem to be the
best alternative but a deeper investigation proves that
foam isn't always the answer.
The insulation itself should
also be considered. Piping used for supplying heat
from a hot water source, such as an outdoor wood furnace,
lose heat in 3 ways: Convection, Radiation and Conduction.
Convection is air moving
across a surface similar to a radiator or
heat-sink. Convection doesn't apply when outside air is
sealed off, such as in insulated Pex pipe. R-value,
a measure of convection, means little when convection is
is heat moving from hot to cold, like we all learned about
in high school physics. Conduction, related to
convection and radiation has to do with how heat moves
through materials like air, foam or plastic.
Click on image for a larger image.
Radiant heat loss is the
most relevant when speaking of underground insulated pipe.
We'll return to this shortly.
Conduction, heat transferred away by the materials
surrounding it, is best controlled by wisely choosing the
proper materials for insulation.
Click on image
for a larger image.
underground pipe use urethane-based foams that limit heat
loss based strictly on R-value, trying to limit how much
heat is lost to convection. Foams only limit radiant
heat loss by absorbing heat in a slightly limited way and
is subject to cracking when rolled up for shipping and
then un-rolled at the installation site - because it is so
thick and rigid.
choice for underground lines is a pipe incorporates foil
wrapped insulation. The foil wrapping retains
over 97% of the radiant energy back into the pipe,
virtually eliminating heat loss.
Foil wrap must be contained. Strong, flexible
corrugated pipe provides a shell of protection for the
foil wrap and also creates a space of dead air that serves
as a conductive break. Having the correct corrugated
pipe is important, too stiff and it will crack when bent
or compressed, too thin and it may be pierced by rocks or
other sharp objects in the ground. After
installation this type of underground pipe, expanding foam
should be used on each end to seal the air space,
eliminating heat loss by convection.
Use the blue colored
can foam. When everything is installed and in it's final
resting place, tape a cut piece of cardboard securely to
both ends of the outer corrugated pipe. Make a hole the
size of the
spray nozzle and add foam into each end. Do
not add too much. Remember that some expansion will occur.
Allow at least 5 hrs. dry time before removing cardboard.
Insulated Pex pipe installed and ready to
cover up with dirt!
This looks like good dirt here;
with no big rocks in it. Avoid dropping rocks on the pipe,
so that do not damage it. holes in the outer casing will
result in water in the pipe, which dramatically increases
Recommended Dimensions for Concrete Pad
need to put the pipe at exact 45 degree angle,
are making your own insulated Pex and using PVC pipe -
OR you get cab pre-made insulated Pex from us!