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Old 05-18-12, 12:40 PM   #1241
AC_Hacker
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Originally Posted by Mobile Master Tech View Post
Although a hydrocarbon refrigerant system should be safe when designed and serviced properly...
MMT,

There's a lot to ponder here...

There are certainly dangers associated with using hydrocarbon refrigerants, as you have pointed out. The situation you have described was bad, but could have been much worse.

I have read reports of R134a igniting. The conditions required for R134a to burn are not casual, but it can ignite and the heat of combustion is extremely high, and the products of combustion are quite toxic.

As BradC has demonstrated very well, an experimenter or DIY person can take safeguards to minimize the risk when working with organic refrigerants... The greatest danger of all is when a HVAC tech who thinks a system contains synthetic refrigerants, treats the system as such and doesn't take the special precautions that organic refrigerants require. That situation must never occur.

Included with my tank of R-22a were about two dozen stickers to be used on equipment, that clearly spelled out that organic refrigerants were present.

However, stationary refrigeration systems are subject to much less stress and fatigue. Barring an accidental or assault on the system, if an indoor system does develop a leak, it is usually very slow. Slow enough that natural infiltration will carry away leaked refrigerant so that critical build-up is very unlikely.

My greatest quarrel with synthetic refrigerants is the long-term damage they do to the atmosphere. R-22 & R-12 were replaced because they were doing great damage to the ozone layer. An ozone hole opened up over Australia, and cancers and cataracts were increasing at an alarming rate. The US stood by and did nothing... Then the ozone layer developed a hole over Kennebunkport, Maine, which was the town where the vacation home of the Bush family was located. Very shortly after this happened, the US suddenly decided to employ non-ozone degrading refrigerants (& propellants).

The refrigerants currently in use do not degrade the ozone layer, but they do have very serious and very long lasting global warming potential.

I know that some people don't consider themselves to be 'environmentalist', and ignore and reject information and concerns regarding the environment. I find this attitude to be very perplexing... it's as if it would be possible to 'op into' or 'opt out of' the environment.

But as the global warming situation makes it clearer that our options are not unlimited, greater use will be made of hydrocarbon refrigerants.

I'm seeing movement in that direction in Australia and also in Europe.

One of the most reasonable solutions (in use in the UK) is to remove the hydrocarbon containing parts of the equipment to a separate and preferably non-combustible equipment shed, and to use a non-flammable heat conveyor like water to bring the heat energy into the dwelling space.

Regarding multiple refrigerants, I know that work is being done on it and I have seen good documentation on the XtremeSystems Forums site.


They have some very advanced folks doing amazing things there. Their focus is on extreme chilling of CPU cores and they don't have much patience with anybody wanting to heat a house... but there is loads of useful, applicable information to be found.

Best,

-AC

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Old 06-01-12, 01:39 PM   #1242
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While researching refrigerants, I have found LOTS of useful research that has been done through Perdue University. Anyone deciding what refrigerant to run should include Perdue when searching.

AC, I remember somewhere you made a post in this manifesto considering extra pipe surface area in your ground loops by having the pipe make an inverted U at the top, sending the pipe back down the borehole again to a second U at the bottom of the borehole before returning to the top. I don't think that will work well at all-you will never be able to purge all the air out, and even if you did, any future entrained air or gases that come out of solution will form a bubble that will act like a reverse plumbing trap, stopping or severely limiting flow in that loop! This is how bubble circulation pumps (interesting in their own right-see HERE ) work.

After realizing just how versatile PEX is while purposely torture testing then reheating it during my radiant floor installation (details HERE ), I think a better idea is to have a form, such as 2" thinwall PVC, that can be lowered into the borehole. Slip the appropriate return length through the center, heat the pex to make a Ubend at the bottom, then wrap the PEX barberpole style along the outside of the form. Space it out as there is no need to wind it tight-1/2' pex could wrap about 575 times around a 30' length of 2" PVC for a loop length of 480 feet!!! This would be an easy way to avoid pipe welds or connections down the hole while increasing pipe surface area and effective heat transfer due to turbulence in the pipe. Regular 3/4 poly flow is pretty stagnant at the boundary layers because the flow is slower. You can flow almost 1gpm through a 1/2" Pex loop before you get significant head loss if your loops are less than around 300ft.

I feel this will work for depths up to 50 feet before handling the pipe gets unwieldy. Looks like most of us doing boreholes without a professional well driller won't be going deeper than that. Now the only limiting heat transfer issue is the borehole field itself.

I'll also post this in the borehole/well thread, but I referenced it here since the loop idea is in here somewhere!
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Old 06-01-12, 03:53 PM   #1243
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...you made a post in this manifesto considering extra pipe surface area in your ground loops by having the pipe make an inverted U at the top, sending the pipe back down the borehole again to a second U at the bottom of the borehole before returning to the top. I don't think that will work well at all-you will never be able to purge all the air out, and even if you did, any future entrained air or gases that come out of solution will form a bubble that will act like a reverse plumbing trap, stopping or severely limiting flow in that loop!
The IGSHPA manual actually had a section on the advantage of an extra loop in the hole. They said that the advantage was small, on the order of 5% advantage. With regards to purging, I don't think that would be an issue once purging velocity was reached. If my memory serves me right, the velocity was about 3 ft/sec... at that point, bubbles don't stand a chance. But your other point is a correct one. There are air separators that are used in hydronic floor installations, you probably have one in yours, that do a good job of getting rid of micro-bubbles before they become bigger bubbles. There would be another way this could be done, and that would be to have a mini-manifold in each hole, so there was no bubble trap. It's all a lot of work for 5%. But I was struck by the wetness of my soil (in mid-August), starting at about 8' down... and I know that wet soil is a much better conveyor of heat than dry soil.

Quote:
Originally Posted by Mobile Master Tech View Post
After realizing just how versatile PEX is while purposely torture testing then reheating it during my radiant floor installation (details HERE ), I think a better idea is to have a form, such as 2" thinwall PVC, that can be lowered into the borehole. Slip the appropriate return length through the center, heat the pex to make a Ubend at the bottom, then wrap the PEX barberpole style along the outside of the form. Space it out as there is no need to wind it tight-1/2' pex could wrap about 575 times around a 30' length of 2" PVC for a loop length of 480 feet!!! This would be an easy way to avoid pipe welds or connections down the hole while increasing pipe surface area and effective heat transfer due to turbulence in the pipe. Regular 3/4 poly flow is pretty stagnant at the boundary layers because the flow is slower. You can flow almost 1gpm through a 1/2" Pex loop before you get significant head loss if your loops are less than around 300ft.
You may be on to something... or, you may also be over-thinking a simple problem. If you're convinced that your idea is a good one, make two test holes and do an A-B test, find out for sure.

But one of the big lessons I learned is how slowly heat travels through the ground. It's flow is not like water, it's much more like "molasses in January". It may be that you have created a much more effective HX, but if the heat will not move fast enough for your system to realize that advantage, then you're just not very far from where you started.

But don't take my word for it. I think you already said you had a post hole digger... dig some holes and do some small tests, that's what I did. If they look promising, carry on, if not try something different.

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I feel this will work for depths up to 50 feet before handling the pipe gets unwieldy.
If your heat transfer is significantly better, unwieldy won't be such a problem, because gravity will be on your side.


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Looks like most of us doing boreholes without a professional well driller won't be going deeper than that.
I have heard of amazing holes being dug with the gas engine type drilling rig, in the sandy southern states. You would want a frame for your rig and a power winch because the drill string + power head will get pretty heavy. Don't be too quick to limit your thinking to a 50 foot hole at your location. You just may be a lot more fortunate than those of us in other areas. Have you talked to well drillers yet? They can be a great source of info, especially after lunch.

Good luck,

-AC
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Old 06-02-12, 04:13 PM   #1244
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-AC
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Old 06-19-12, 12:03 AM   #1245
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Default CO2 as a refrigerant?

Has anyone considered using carbon dioxide as a refrigerant in their systems?

"
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The use of CO2 in conventional refrigeration systems presents several interesting properties that must be addressed. The pressure/temperature relationship of this refrigerant is one of the primary concerns.

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Old 06-19-12, 03:40 AM   #1246
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Although CO2 is in some situations are much more efficient than the alternatives, the very high pressure it demands seem to be a reason for people not using it much. 4400 psi is quite a lot, and both difficult to work with and demands much more expensive components.

Chapter 9: Carbon Dioxide (R744) The New Refrigerant (updated 5/7/09)
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Old 06-19-12, 03:45 AM   #1247
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Has anyone considered using carbon dioxide as a refrigerant in their systems?

"
You need everything special to work with it. For DIY person it is too expensive. Propane is much more friendly.....
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Old 06-19-12, 01:14 PM   #1248
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Has anyone considered using carbon dioxide as a refrigerant in their systems?
This thread is aimed at DIY folks and experimenters, and we like to encourage experimentation.

We have discovered that it is possible to use readily-available tools to modify existing, readily-available de-humidifiers, air conditioners and heat pumps into efficient, useful heat pumps at a tiny fraction of the price of commercial units.

As the previous posters have commented, CO2 is more efficient, but operates at considerably higher pressures than R298 (propane), R22, R134a and R410a. These refrigerants are listed as they are commonly used and are listed in ascending levels of pressure.

Commercial manufacture and sales of CO2 units has taken quite a while because of problems that were required to be solved due to the high pressures involved. Several Japanese companies have invested the time and money in the development of these units and CO2 units are now entering the market.

Also, the tools (manifold gauges, etc.) that are able to withstand the pressures of CO2 are not commonly available, and simply do not exist on the used market at this time.

So, it looks like the problems you will face if you want to push ahead with hacking CO2 units are:
  • Locating donor units
  • Locating tools that can withstand the higher pressures that CO2 requires

But we are always looking for more efficient solutions.

If your work with CO2 proves promising, please let us know.

Don't let yourself be discouraged by anything anybody says. Inform yourself and act.

A month ago, if someone told me that you could weld metal with vodka instead of inert gas, I would wonder if they were hallucinating... but I saw it with my own eyes.

Trust yourself, don't get discouraged.

Best of luck!

-AC_Hacker
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Old 06-21-12, 11:42 AM   #1249
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Default Hi; not sure what I am doing here.

Hi; I just charged a Klimeair 12K minisplit with R290. ((Long story how I got to this point)) I ran the first test cycle yesterday with about 2/3rds of the volume by weight installed. The results are nuts. 10 degree change on the compressor and the air handler air flow. Gas line temp 60 psi 72 degrees. liquid line 60 psi 32 degrees. frosting heavily where exposed. I shut it down yesterday and thinking that I screwed something up and so I pumped the system down, pulled another vacuum, leak check and restarted this am. Same results. anyone got any ideas. thanks Owen
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Old 06-21-12, 06:32 PM   #1250
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Hi; I just charged a Klimeair 12K minisplit with R290. ((Long story how I got to this point)) I ran the first test cycle yesterday with about 2/3rds of the volume by weight installed. The results are nuts. 10 degree change on the compressor and the air handler air flow. Gas line temp 60 psi 72 degrees. liquid line 60 psi 32 degrees. frosting heavily where exposed. I shut it down yesterday and thinking that I screwed something up and so I pumped the system down, pulled another vacuum, leak check and restarted this am. Same results. anyone got any ideas. thanks Owen
Theprof,

It is just possible that you have gone where no man has ever gone before.

I don't know much about Klimeair mini-splits.

What kind of refrigerant is your unit suppose to use?

Is it an inverter type?

Is it A/C only?

Is it A/C & heat pump?

There is a dim possibility that you have too much refrigerant.

There is also the possibility that your unit is just gonna be bonkers until it gets the right refrigerant.

Going from R22 to R290 is a pretty safe change, because the two refrigerants have fairly compatible characteristics.

I haven't seen any indication that R410a and R290 have compatible characteristics.

I'm not even sure if R290 is compatible with the lubricant that R410a would use.

I have heard someone say that he heard someone say (now there's a pretty worthless credibility chain...) that the switch would work just great.

I can think of more reasons that it will not work very well, if at all. Then again, I have not tried it.

Be advised that R290 is an excellent refrigerant. It is also very dangerous to work with and may be illegal, depending on the country you live in. There is the possibility that you might destroy your mini split. You might also set your house on fire. You might also seriously injure yourself and others around you. In short, you'd have to be a fool or idiot to continue working with it.

If you are determined to give it a try, I would suggest to keep testing it with reduced charge levels, down to a low-side pressure of maybe 25 psi, and monitoring and recording performance at every level of charge.

Let us know what you discover. There is a possibility that you are really on to something here. I really don't know of anyone that has tried what you have tried.

Keep detailed records and let us know what you find out.

May the god of flammable gases be with you...

-AC



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