The Homemade Heat Pump Manifesto

[AC_Hacker]

Originally Posted by pick1e

Maybe I'm reinventing the wheel here but wouldn't a system be better off with the loops arranged in parallel rather than in series? When I see that diagram my first gut reaction is that the first loop will be doing the most work while the remaining loops will be doing far less work, logarithmically, as the delta T decreases along the line. By the time your water gets to the final loop, that loop is probably not doing much of anything, so there may be heat in the ground waiting to be picked up but that's just sitting there because there is no delta T to transfer it.

I think you have not yet fully realized how slowly heat travels through earth, nor how very large are the huge "earthen cylinders" at play here.

Originally Posted by pick1e

If the first loop has transferred all the heat it can, and the surrounding ground approaches Twater, then the deltaT of the second loop is higher and that one starts doing the heavy lifting...

Slowly, slowly... The first loop releases its heat very, very slowly. It will not give up all the heat that it can, not in a whole year.

These are not small aluminum chunks. these are huge earthen cylinders weighing many, many tons each.

You do the math. How much does an earthen cylinder weigh that has a diameter of 15 feet and is 50 feet deep? [...average density of dirt is 120 lbs per cubic foot...]

Regards,

-AC_Hacker

[Vlad]

Most things that were said were theory but reality is simple
HDPE wins over PEX and Copper because:

1. It is cheapest compere to PEX and copper.
2. It does not corrode like copper and PEX fittings
3 It is proven (all formulas and calculations are based on its properties)

HVAC equipment MUST work 20-25 years (radiant floor part- 50 years) and not 5 or 10. You have no way to test reliability of copper and pex.
Many houses were built using copper tubing inside concrete slabs for heating. Most of them leaked 10-15 years later. Copper fails even indoors you want to use it outdoors???

If you want to reinvent the wheel I would rather use your energy on something more useful.

[Vlad]

Originally Posted by pachai

BTW,
I found a site that answers some of my
more naive questions - for example
why the trench should be dug after the
boreholes.
keram - faq

(note, that reason is one that could be solved:
Trench, plywood platform for boring machine,
then bore. But then again I never did this :-)

or, whether you can bend the pipe in a U shape?
(no, you can't)

Seth

I tried to dig trench before drilling. Do not do it this way. I had to fill trenches back and started over again. You drill first put loop in grout it. Then you dig trench. last 10-15 inches dig by hand and you will not hit the loop.

[AC_Hacker]

Originally Posted by Vlad

I tried to dig trench before drilling. Do not do it this way. I had to fill trenches back and started over again. You drill first put loop in grout it. Then you dig trench. last 10-15 inches dig by hand and you will not hit the loop.

This is how I did it.

Only, if you set your holes slightly off of the trench line, you can trench very close to the holes, so you only have a very few inches to dig by hand.

Sixteen holes and no pipes hit!

Regards,

-AC_Hacker

[AC_Hacker]

Originally Posted by pachai

BTW,
I found a site that answers some of my
more naive questions... keram - faq

Seth

Seth,

This is a really good resource.

Although the FAQ is metric and is really brief, most of the important considerations are there.

The Chinese are doing some really interesting things in the field of GSHP.

-AC_Hacker

[pick1e]

Originally Posted by AC_Hacker

but there comes a point where you gotta put your shoulder to the wheel.

No doubt! I have my air conditioner working now and have some copper tubing. Just need some thermocouples that I don't mind burying

Originally Posted by AC_Hacker

you do know one person, me.

Fair enough! It's just strange I've never heard of it. Here in Michigan it's not uncommon to live or work in a building erected more than a century ago, and still be using original plumbing.

Originally Posted by AC_Hacker

You might also consider that in the case of radiant floors, running heated fluid in metal pipes increases the chemical reaction rate, so that a 40 to 50 year life can be drastically shortened.

Additionally, you might want to consider what is actually involved in replacing pipes in a 3 or 4 inch thick concrete slab, especially if it is to be done every 20 to 30 years.

For sure. I am definitely not questioning the logic for indoor, radiant floor use. I am only talking about the outdoor portion. Another things to consider is that concrete has a VERY high pH. Not to mention that in concrete you need something with matching thermal expansion or you will get great stresses with temperature fluctuation, busting everything up. In soil, though, you don't have that problem.

Originally Posted by AC_Hacker

Check out the slinky method. Also the previously mentioned GSHP manual gets into these issues.

I'm familiar with that, I just have never seen anything regarding a hybrid of the two, or a vertical slinky, and I find that very curious.

Originally Posted by AC_Hacker

You may have found your purpose in life.

Nope! I already have that. But my second purpose is to question conventional wisdom and think outside the box. I have found my purpose in this thread, however.

I just know that a lot of conventional wisdom is boooooogus. I work in the IT industry and know that much of what is though to be written in stone is bogus. Someone wrote an article or book or someone did a study funded by a corporation looking to make money, and the results are passed around like truth without question.

[pick1e]

Originally Posted by Vlad

Most things that were said were theory but reality is simple
HDPE wins over PEX and Copper because:

1. It is cheapest compere to PEX and copper.
2. It does not corrode like copper and PEX fittings
3 It is proven (all formulas and calculations are based on its properties)

HVAC equipment MUST work 20-25 years (radiant floor part- 50 years) and not 5 or 10. You have no way to test reliability of copper and pex.
Many houses were built using copper tubing inside concrete slabs for heating. Most of them leaked 10-15 years later. Copper fails even indoors you want to use it outdoors???

If you want to reinvent the wheel I would rather use your energy on something more useful.

But, we are on a DIY thread, not a mass production thread. So there are far more variables that can be considered, not the least of which are soil conditions and resulting installation types and resulting labor. And you're equating copper embedded in concrete with copper in soil, which is totally different. Concrete is extremely alkaline which will corrode most things including your skin

I'm not concerned with the longevity of the system, I don't plan to live here more than a a few more years. So advising me to not TRY copper tubing for my project based on the premise of longevity isn't a reasonable argument.

I guess my point is saying "there are some points to consider before choosing a ground loop material" is far different from "copper won't work."

[pachai]

There was a discussion on another forum
that might be useful to some on this one.

Someone with the handle FBBP
speculated on what would happen if we could
find a way to directionally drill two wells some
distance apart to meet at X and than fish the
loop down one and up the other

My reply was...

I have been thinking about this...and I may do one
(pair) of these even if I end up having a commercial
driller do the first 2 wells.

My thoughts are 2 ways:
1. drill two boreholes 6" diam, 18' down, just 12-14" apart...that's about 18" on center.
(Note, I only had time to go 18" down, one hole
so far, so I cannot speak from experience.
Maybe Sunday I'll do the second hole :-)

My drill is based on a 6" diam. drain pipe,
so that's my diameter.
I am using a 3/4" black pipe for a drill shaft.
There is a female hose coupler at the top.
Basically hoping to pressure wash my way to China.
Or at least 18' down. I just got the coupler,
so this part is not yet tested.
Need to add a valve...

The drill shaft is up to 20' of 3/4" black pipe.
Put an elbow at the end, it will go to the bottom
of the bore, and turn it on. (Mark the
pipe so you know which way it is "drilling")

Use shop vac to collect water and mud.
(see caution about shopvac in next post)

Repeat from the other hole. 6 + 6 = 12.
Watch for the water in the original hole.
A 20' 2x4 may be needed to oppose the
equal and opposite forces....

Again, not speaking from experience, but
Aluminum adaptor plates for electric cars
have been cut with a water laser...so dirt
ought to be easy enough.

2. Other approach. As the original poster said.
Dig 2 bore holes...start 5' - 10' apart,
do some math, and
angle them toward each other the right amount.
This is hard, only for Math Majors.
sine, cosine, or arctangent or all of the above.

If you do it right, you will make a Vee and not
need the elbow mentioned above for breaking through.

It would be imporant to soften the inside of the V
so it doesn't hurt the pipe.
Left as as exercise for the creative people who try this.

Next post for benefits...!

[pachai]

I mentioned a hose and shop vac....
I saw a Youtube on drilling with two hoses
and 2"x20' pvc and shop vac.

One small piece of Wisdom gained from experience...

When using a shop vac,
it's good to use a Collection bin of some sort,
so the Vacuum can pull, but it can't pull the mess
into the motor.
I may use the old shopvac for this.
(guess how it became the "old one"?)

That's the advice I got from google
how to protect my new shopvac
(thanks for the shopvac Craigslist!).

Also, unplug tool before emptying tub,
lest the top flip over and turn on and
suck mud into the motor.

(enjoy :-)

[pachai]

As a follow-up to the idea of using two bore holes
near each other with an underground link.

(At this time, I am not evaluating whether
proximity reduces efficiency.)

(note, I worked for a few years in Rockefeller Center,
a complex of 19 commercial buildings that are
connected by an underground mall :-)


Now, being an IT guy and a DIY home renovator,
and with 15 years of experience "fishing" wires
with the wrong tools and the right tools, the next
part is easy.
Fish a pull string from one hole to the other
and pull it up. Tennis ball may help.
Or, put an elbow on the 2"pvc shopvac extension.
As in Perl, there is more than one way to do it.

Attach an end to a pipe and pull ( gently).
(Lubricate - with water?) Actually, push the
pipe down while guiding it with the pull string.

The Advantage to this is, I can have a vertical bore
with no weld. I hate to harp on this, but I TRIED to learn to weld to make battery racks, until my friend
described the metallurgic drawbacks of welding. Drilling and bolting makes fewer stress points.
And requires fewer skills.


Another thought...
We originally thought to have a U tube in the hole.
Now we have an "l" in the tube.
Maybe we could have an || ?

Two parallel loops in passing through
the same PAIR of bore holes.
The question is, should water in the pipe
flow the same direction in both,
or perhaps they should be in opposite directions - one will
be transferring the most heat in the top of the hole
and the other in the bottom? (or, in my design,
one is doing more in hole A and the other in hole B)

My reasoning with two loops passing through each
pair of boreholes is to not forfeit the linear footage.

The above question of flow direction highlights the
thought I had that each pipe should be labelled
on each end that will emerge into the basement..
but even labelled IN and OUT so that you know.

Also label your diagram to match, so that if a
leak is detected at the manifold, you can
refer to the diagram to see just what to dig up.

Hope this help spark more thought on this...
Seth