Quote:
Originally Posted by AC_Hacker
Why don't you edit in relevant, appropriate graphs? They are much easier to understand, if your purpose in posting is for a new, unsophisticated reader to understand you and solve their problem. Graphs are much better than word count.
In your post I count at least 8 unexplained concepts and relationships.
Is your purpose to actually help someone or is it to put your concepts on display?
-AC
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Graphs and images are worthwhile but sometimes get lost, including some from the earliest pages of this manifesto and my "Don't Waste That Heat" thread. Text doesn't get deleted. I'm not a genius at creating new graphs, but where a graph or an image tells the story better, I will add them and include a brief text summary just in case.
As you asked, I am trying to not re-explain topics that I or others have already detailed. Please post which ones you would like me to document further.
My purpose is to help everyone, including myself, find the best way to economically have a comfortable, energy sustainable lifestyle. I hope good concepts from all contributors get "airtime" without bias and the best rise to the top, no matter whom they are from.
I hope my experiences and research help others. If anything I present turns out to be wrong or not a good practice, I want to know. I will be the first to acknowledge it and edit accordingly.
If someone wants to see the amount of BTU's a specific compressor can move at a specific set of temperatures with a specific refrigerant and how much power it will take to do it, I will help them find the chart. The general principles I described remain, though. I have seen charts of a Tecumseh compressor I was considering that showed it would move almost 50% more BTU's at my proposed conditions than the ASHRAE conditions used to establish it's nameplate capacity.
Don: AC and Jeff just gave some great discussion about equipment and refrigerant choices. I recently commented on why the flammability of a refrigerant isn't as big a concern as we thought.
There probably would never be a material compatibility problem with the kinds of refrigerants we might use. Ammonia can't be used with components containing copper, for instance, but I doubt anyone will be hacking an ammonia system together.
We can't greatly exceed the mechanical limits of the equipment. You can fudge a bit, but
THIS LINK shows the pressure/temperature curves of many common refrigerants. R410a's pressure is too much higher than R22 equipment was designed for, so we need one that will work in our temperature ranges at similar pressures or less while cooling the compressor enough (or be helped along enough by blowing a fan on the compressor body, for instance). R134a's pressure is low and easy to work with, but you do need more flow to move a given amount of BTU's. R290 and several other "drop-in" refrigerants, such as R424a, have similar pressures and BTU moving capability as R22 equipment was designed for, so there are many good choices.
The refrigerant needs to be compatible with the oil in the system. However, this also isn't as big a deal as first thought, and compressors can also work fine if drained and changed to a different oil.
Originally, it was thought and recommended when retrofitting a car's R12 AC to R134a that in addition to changing the labeling, fittings, expansion valve (to meter the 134a properly), and the dryer/accumulator (because earlier desiccants weren't compatible with R134a) you had to do the following:
Replace all hoses/seals with newer "barrier" type (since R134a is a smaller molecule that can escape easier), flush all the mineral oil out of the remaining components, remove and drain the compressor (because R134a requires a PAG/PolyAlkyleneGlycol or POE/PolyOlEster oil), and add booster fans for the condenser (since R134a moves fewer BTUs for a given amount of gas flow and operates at a higher pressure).
Now we know that none of those things are required. A retrofit in practice is easy. R134a works fine with the existing mineral oil, you can mix mineral with POE oil as you top up, hoses/seals made since the late 80's had enough "barrier" properties anyway, and in practice the flow/pressure differences only meant that performance was slightly worse at idle speed and slightly better when the car is moving. Only one R12 compressor model, the FS10/FX10, ever got any reputation for failing more frequently because of the higher load(and it already failed very frequently on R12)-all the others did fine. I've personally retrofitted several cars without these extras and they are going strong.
Your refrigerant should be easy to obtain, inexpensive, easy on the environment and easy to comply with requirements.
The US since April 2015 is allowing flammable refrigerants in many types of equipment and removed the requirement for R290 and R600 to be recovered as described
HERE. Other refrigerants would require recovery/recycling equipment, more stuff a hacker doesn't need if using R290.
The reason other refrigerants require recovery/recycling equipment is the potiential environmental damage. Most refrigerants have a Global Warming Potential of more than 3,000. This is the
EPA's SNAP APPROVED REFRIGERANT LIST for HVAC. Notice the GWP. R424a's is 2,440. R134a's is 1,430. R290's is "3"!
Many refrigerants would work well with components designed for other refrigerants, but R290 can be had from your barbecue grill or a bottle from the grocery store, plus the flammability is less of an issue than previously thought. R134a is inexpensive and can be had without a license from any auto parts store. Other good possible refrigerants (such as R134a blends, R424a, etc etc) have extra requirements, require a license, are expensive, or harder to get. I'm going to be using R290, myself.