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Old 06-07-15, 08:53 PM   #111
MEMPHIS91
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Yes that is what I am finding in my research as well. I have been looking through a handful of devises that are 1/2-1/3 sized compressors and I can find none that have a tiny a cap tube as I have on the rig now. I will continue making this one shorter though to start with. So more data to come.

I know someone said a while back about a coated copper tube. That might be the way to go if you are really worried about it. 210 feet is some crazy depth and should provide extremely stable temps. Not that you would need to go that deep though.
I did do some research on the tricone bore bit. It would cost way more than my simple setup but might be worth looking into.

Thanks this has been a fun project.

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Old 06-07-15, 08:59 PM   #112
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Originally Posted by MEMPHIS91 View Post
Ah ok so no TXV. Looking at my numbers I still think I can go shorter on the cap tube. When first starting running test the cap tube would "squirt" and visibly shake at about 14 psi. That shaking doesn't start til 27psi now.
I am wondering if a larger diameter and longer cap tube might not work better for this.
The initial rumble is from your condenser reaching its critical point. At startup, as much of the liquid that will condense will be in the coldest section. This will be your borehole, or in winter, the outdoor plumbing. When the compressor starts, this liquid quickly boils off to pressurize the condenser. Until you develop subcooling, the liquid will not stay that way in the cap tube.

Don't worry about your cap tube being too short until it is less than a foot long. Most vehicles without txv metered evaporator cores have a cap tube about 4 inches long in them. This is why they start putting out cold air quickly after you start the car.
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Old 06-07-15, 09:13 PM   #113
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The initial rumble is from your condenser reaching its critical point. At startup, as much of the liquid that will condense will be in the coldest section.
What if this rumbling goes the entire time after 27psi? It has not stopped at any point. What you said about start up makes sense though. And I will keep making it shorter.
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Old 06-07-15, 10:55 PM   #114
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The rumbling or whoosh sounds come from liquid and oil passing through. It's a good thing. When you hear nothing or hissing sounds, it means there is only gas passing through. Not good except at startup.
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Old 06-08-15, 04:18 PM   #115
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MEMPHIS91,

I'm just thrashing around here, thinking of possible problems & approaches...

Whatever happened to the original cap tube? Was it damaged when you dismantled the machine? There is a possibility that you might be able to get things going with it... if it's still intact.

BTW, when you were brazing, did you use some kind of purging gas, so the tiny black flakes did not form? Because if you didn't, just one flake could be a problem.

Also, most of the attention is being paid to the compressor balance issue, when the problem might be elsewhere.

* * *

So, I was considering this thing from a 'black box' point of view. You have three black boxes: BOX #1: ground loop box, BOX #2: compressor box, and BOX #3:water heater box.

Unfortunately we don't have any way to determine if the mass flow is what it should be for this system... right?

BOX #3
The water heater box has been proven to be a viable concept, and several EcoRenovators have use this configuration, first time out. So the concept is sound, but do you know for sure that your implementation is good. The only problem I can think of would be a kinked tube that you did not notice. If all else fails, you could test this by disconnecting it from your system and blowing compresses air through it to see if a reasonable flow is happening. This is really the least likely failure, but as a last resort, you might test this.

BOX #1
Another 'black box' is the ground loop. Here, you are in new territory, since there haven't been any EcoRenovators, or any other DIY hacker to try this (with the exception of the very first heat pump ever made, and your general configuration, of burying tubes in the ground, was what he did). So we do have second-hand confirmation that this can be a viable configuration. Then the question is of implementation. There could be a possibility of a kink. There could also be a possibility of an oil-flooded tube, that is impacting your performance. If you need to, you could test this in the same way that you could test the tubing in your water tank... disconnect from the compressor and blow air through it, and assess if it has reasonable flow.

There is another possibility of the ground loop, and that would be that your ground loop is not extracting heat from the ground fast enough to supply to the tank (via the compressor). I know that the ground gives up its heat slowly, and that is why a 200 foot deep hole is required to extract 12,000 BTU/hr (in Oregon, where the temp is 52F). As I recall, you have a 5000 BTU compressor. So if the Oregon hole requirements work for MS (not the best assumption, MS should be better yield), then your hole should be:

Depth = 200ft * (5000 / 12000) = around 83 ft deep.

It is possible that the depth, or number of holes is insufficient. I have made some really flakey assumptions here, but I think that I'm generally headed in the right direction.

BOX #2
Box #2 is the compressor box. I have been following the analysis of the compressor's role in the problems you are having, and I would have to say that I am truly impressed by the help that has been flowing into this thread, to try to assist you in achieving success. It is really shows the very best of our community, when we come together to solve a problem.

And I have to admit that the caliber of expertise is well over my head, and I have nothing to add that could be helpful.

Best,

-AC
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Old 06-08-15, 04:57 PM   #116
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Default Hole Depth...

I came across this very interesting document just now:


Table 1 is called:

Table 1. Recommended Lengths of Trench or Bore Per Ton For GCHPs

It adjusts for ground temperature, soil conditions, the whole thing.

I need to get some work done, but in a few hours, I can parse the relevant information.

In our favor:
  • MS has nice warm, wet dirt.
  • DX heat extraction is around 15% more efficient
  • No HXs to 'pay tax' to.

Against us: Physics

Back in a few hours...

Sincerely,

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Old 06-08-15, 05:17 PM   #117
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If I recall, Memphis stated that he has water to within 8 feet of the ground surface. If this is indeed true, then about 22 feet of the total 30 feet of copper 1/4 inch ground loop ("box 1") in full water contact.

I am wondering if there are too many of the "loopty - loos" (oil traps) in the ground loop.

AC bring up an excellent point of brazing caused "crud" in the line. This would certainly block a capillary tube or cause significant restriction that might be a variable.

Memphis. What is the water height in the bore hole and did you use an inert gas when brazing?

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Old 06-08-15, 10:04 PM   #118
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Jeff, that's really good to know. Cause I really thought something was wrong. Makes sense now though

Ac, all you say is very well thought out. And some things I have thought about. I did purge the lines, but I'm now seeing maybe not the right way. Basically I flowed high pressure propane through it several times. But should I have done this after every time I brazed on a shorter cap tube? The cap tube I started with was the original. And I have been trimming it down as I went. When I break the system open again I will run some air through the borehole to see what kind of flow I get. When the borehole was finished my water table was at 5 feet. But we have been having crazy amounts of rain lately.
I will purge the system again before this start up. Any better methods?

Everyone of you have been so very helpful. Thanks for the time and effort you have put into helping me.

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Old 06-09-15, 02:19 AM   #119
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...I have thought about. I did purge the lines, but I'm now seeing maybe not the right way. Basically I flowed high pressure propane through it several times. But should I have done this after every time I brazed on a shorter cap tube? ... I will purge the system again before this start up.
When you braze, you want to keep oxygen away during the brazing process because it will form copper oxide flakes inside the heated copper. These flakes can plug up a cap tube.

Most technicians, and also sane people, use dry nitrogen for this purpose, and they use it by making sure that a very slow amount of nitrogen is flowing through the tubing, thereby displacing any oxygen, while they braze.

If you dig back through the Manifesto, you will see that I did the same thing using propane. First I let enough propane flow through to flush out any oxygen. Then I hooked up some tubing and put the end in a dish of water, and adjusted the gas flow way, way down, so I could tell by the bubbles that very slowly came out, that there was slow but positive gas flow... it also kept the propane that was coming out, well away from my torch.

When I brazed, there was a very tiny flame at the braze joint, which soon went out when the joint was 100% brazed.

I only use propane because it was too late to go out and buy more equipment. I wouldn't recommend that anybody use propane... it is insane.

Some people use argon or CO2, most use nitrogen.

But the tube in the dish idea worked really well as a visual indicator of a very slow but steady flow.

So the trick is to keep a very slow flow of gas going, while you braze, to keep the oxygen away.

Don't be discouraged, you are more than half way home.

Best,

-AC

P.S.: If you hack another one, use or keep the original cap tube, because it is at least matched to your compressor.
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Old 06-09-15, 06:20 AM   #120
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Ac, I see what your saying. You are meaning purge as I braze not after. I did not do this. Its strange because i've not seen any of the local HVAC techs do that. It does sound much cleaner and safer way of doing things. Good news is that there has always been left over propane in the system as I was brazing on the shorter cap tubes so at least those were done right.
I would have keep the original intact but it was the only cap tube I had that size. But I did measure it very well so I should be able to duplicate it if it is needed.
I use to do some pretty serious paintballing so I still have access to CO2 and HPA. Both I think would purge very very well.
Work has been crazy busy and some family in the hospital. I'll get another test run done soon and post the data.

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