Insulation of underground pipe [RE-wrenches]

Thu Aug 23 14:14:54 PDT 2001

Naked foam in the dirt will not last the 20 years that an SDHW system 
should. Water perks both down and up. There was an industrial buried pipe 
system available for a long time (Gilsilate) that was made with power, 
poured into a form around the pipes, and covered with plastic. They almost 
all failed in less than 10 years. The powder migrated into the soil, the 
water went everywhere, and the pipes became effectively uninsulated.

Pipes move underground due to thermal forces in the pipes and in the 
ground. As they move, the ground and the pipes will tear the foam apart. 
Dirt and rocks will migrate into the foam, although at a slower rate than 
into the powder.

Field fabbed underground piping just does not keep stuff water tight over 
the long term. Any idea you can think of has been tried in the field (I've 
had sales folks try to sell many of them to me...) The only ones that work 
have a heavy non-metallic outer jacket with either o-ring or plastic fused 
seals, with solid insulation foamed inside. They are pricey, and even they 
must be put in just right. Anchor blocks, expansion loops, guides, etc. 
It's a good design exercise.

For the sizes we're seeing in our jobs, it's a lot easier, cheaper, and 
less risky to not rely on the jacket as waterproof. If that cannot be done, 
then don't scrimp, go for a good solid pre-engineered product.

Jeff

----------
From: 	Dana Orzel[SMTP:slrwrk at ocinet.net]
Reply To: 	RE-wrenches at topica.com
Sent: 	Wednesday, August 22, 2001 8:21 PM
To: 	RE-wrenches at topica.com
Subject: 	Insulation of underground pipe [RE-wrenches]

Wirsbo PEX comes with an insulated cover if desired up to 1 1/2" I think.
Not cheap but deffinitely areal fine system. I have also run 185 foot each
way and set the pipe on blocks and had a spray foam company come and cover
the pipes and then covered it with plactic to reduce diredt water
percolation downward.
Energetically - Dana
Great Solar Works
.
----- Original Message -----
From: jay peltz <jay at asis.com>
To: <RE-wrenches at topica.com>
Sent: Wednesday, August 22, 2001 11:58 AM
Subject: Re: solar thermal pumps [RE-wrenches]

> Hi Jeffrey,
>
> In regards to insulating the pipe.  I have used a pipe in a pipe system 
in
the
> past.
>
> If you are using say PEX pipe, then install the insulation around the
pipe,
> then install a second ( usually PVC) pipe around this, glue up then
install in
> the ground.  The biggest heat loss is due to moisture pulling the heat
away.
>
> If you have other ideas I'd like to hear them,
>
> jay
>
> Peltz power
>
> "Jeffrey Wolfe, Global Resources" wrote:
>
> > Our experience with glycol (we've standardized on DowFrost / DowTherm 
at
> > 60%) is that is DOES slush, but that the March pumps we've been using
will
> > pump it when the day warms up. The hardest part to get moving can be 
the
> > underground piping (no sunshine on it), but the underground in our
systems
> > has always received heat from the house basement, so the worst pipes 
are
in
> > the spaces behind the collectors.
> >
> > I believe that pushing this cold slush does wear the brushes faster,
> > resulting in more maintenance.
> >
> > If a DC pump must be used, seriously look at Windy's. If you must go
> > brushless (and I understand...) then you really must go AC.
> >
> > The advantage of PV direct seems to fad on the larger systems. As the
size
> > increases, having one controller doesn't seem like a big added
complexity.
> >
> > Pipe all the collectors in parallel as Smitty says. They'll give you
more
> > BTU. Otherwise you're heating progressively hotter water in each
collector,
> > cutting efficiency in each one.
> >
> > Provide some means to balance the system. Parallel piping loops can
create
> > sections that get no flow. Arrange the collectors in say two banks of 3
> > collectors, with globe valves on the return from each section. Set 
these
> > return valves so that you get equal temperatures from each collector 
set
> > (therefore equal flow).
> >
> > The piping should be minimum 1". The 3/4" would be good up to MAYBE 3
> > gallons per minute, but that's high with glycol. The bigger pipe does
have
> > the disadvantage of more fluid, longer travel time, etc., but that can
be
> > overcome with a little extra insulation. (Insulation is cheap,
collectors
> > are expensive.) So run 1" out to the panel location, then feed each 
bank
of
> > 3 collectors with 3/4".
> >
> > Bury the pipes in an oversized smooth wall drain pipe. Pitch this pipe
back
> > to an open drain. Buried piping either costs about $200 PER FOOT, or it
> > gets water in it. Since ours always costs less than $200 per foot, we
give
> > the water some place to go, rather than sitting in the pipe and
insulation.
> >
> > Good luck.
> >
> > Jeff
> > ----------
> > From:   Smitty[SMTP:smitty at aaasolar.com]
> > Reply To:       RE-wrenches at topica.com
> > Sent:   Tuesday, August 21, 2001 11:38 AM
> > To:     RE-wrenches at topica.com
> > Subject:        Re: solar thermal pumps [RE-wrenches]
> >
> > Kurt, for what it's worth, Richard Lane and I have conducted some tests
> > of various pumps moving glycol and water at the large Packerland system
> > (R.I.P.) in Green Bay. I am assuming this system is going to be in
> > northern Wisconsin. What we found is that in the dead of winter, with
> > very low temps, the glycol will start slushing and even become a
> > semisolid ice plug, but not enough to pop anything. At daylight the
> > panels tend to thaw out, but the glycol in the insulated above ground
> > plumbing remains semi frozen or very thick. The DC pumps we tested had 
a
> > very tough time with this. Sorry Dan, but the El Cid just didn't cut it
> > with semi frozen glycol. The Hartell did a bit better but in the final
> > analysis I would use an AC pump and a differential controller if
> > possible. A few days of the year, we would even have problems with the
> > Packerland system, and that was with 6"-14" pipes and many 10 hp pumps
> > (5000 collectors). If you go DC, I would oversize the PV panel to
> > accommodate morning incident angle, so it at least it has chance of
> > getting the glycol moving.
> >
> > The panels should be plumbed in parallel.
> >
> > The smaller a pipe is, the more frictional wall loss there is. 3/4" is
> > the smallest I would use. Hope this helps. Smitty.
> >
> > Kurt Nelson wrote:
> >
> > > Greetings all (and Smitty?), I'm doing a solar thermal system/in-slab
> > > hydronics, and though I have done a number of SDHW systems, I'm new 
to
> > > moving fluid through larger arrays. The collector is 5  (possibly
> > > six), 4x8 Solar Kings ground mounted about forty feet from the house.
> > > I would like to run the pump(s) PV direct and it would seem that 
there
> > > is a shortage of pumps to choose from here.  I was thinking two 
Hartel
> > > HEH-10's (did I get the model numer right) and would welcome other
> > > suggestions.  Also, .... 1 - Is it best to plumb (pipes) them in
> > > series, or parallel?2- Is it best to wire them each to individual
> > > 18-22 watt panels (my guess) or both to a single 38 to 44 watt 
panel.3
> > > - The burried and insulated piping from the array to the house.... 
 go
> > > with 3/4 inch pipe (or even larger) to accomidate flow, or 1/2 inch 
to
> > > reduce heat loss from piping surface area AND the increased time the
> > > heat transfer fluid spends in the pipe? Thanks in advance for 
thoughts
> > > and suggestions.Kurt NelsonSOLutions
> > >
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