The Homemade Heat Pump Manifesto

[AC_Hacker]

This is the $35 Refrigeration Recovery machine I bought.



This is a recovery machine a friend of mine bought that I have borrowed.

Originally Posted by Drake

Yes, the refrigerant collector. Can you use it to collect refrig from multiple discarded units to meet needs of new(DIY) system if needed?

If I understand you correctly, you are asking if the refrigerant recovery unit can be used to extract refrigerant from some system and then reuse that same refrigerant in another system... correct?

The answer is yes, if both systems are designed to use he same kind of refrigerant. The refrigerant doesn't wear out. And as far as I know, the lubricant which is mixed in with the refrigerant, is not exposed to air and does not wear out either. However, if the first system failed because the motor or bearings failed, and it overheated and died, there could be problems with re-using the old refrigerant.

There are also compatibility issues that were previously discussed that should be understood.

So, if you plan to re-use refrigerant, make sure you don't mix refrigerants, and make sure that you are using compatible families of refrigerants.

Originally Posted by Drake

On the HX direct to tank, your thoughts on trying a radiator coil at bottom of tank. I know it designed for air xchg but as water is better conductor it should work at least as well I would think and thermo cycling in tank should provide water movement. Coil from AC or maybe dehumdfr?

[* This is a question that comes up repeatedly. I think it springs from a fear of confronting the technology. Once this fear is overcome, a new world of possibilities will be open to you. *]

I think that trying to use a refrigeration-to-air heat exchanger as a refrigerant-to-water heat exchanger might be useful to prove a concept, but beyond that it is a waste of time. It is true that heat will be exchanged, but the aluminum fins will eventually become fouled. Also the galvanic difference between copper and aluminum would invite corrosion. For the price of taking someone out for dinner at a moderate restaurant (not burger king) you can buy a beautifully engineered and perfectly made heat exchanger that will last for many years.

But in-tank heat exchangers are being made and will most certainly work as outlined in Piwoslaw's most excellent thread.

Originally Posted by Drake

If compr and cap tb are matched and sized for heat demand length of refridg line is not also determined(set length) is it? I'm making this assumption from split AC installs where distance between units varies.

I think you are asking me if the length of the 'line set' will have an impact on how the cap tube needs to be configured (sized).

If I have understood your question correctly, the answer is that within normal boundaries, the length of the line set will have a minimum impact on cap tube sizing. The size of the thermal loads, and the operating temperatures, and refrigerant pressure, and the size of the compressor, and the type of refrigerant will have the greatest impact on the cap tube configuration. A long line set can require that more refrigerant be introduced into the system to make up for the extra system volume created by the extra line set length.

In an extreme situation, the line set could be so long that it would itself, become a significant part of the thermal load. Then, the cap tube configuration would be affected.

Best Regards,

-AC_Hacker

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[Drake]

I think you have a point on finely finned HX not being good choice and on serious thought on how actually get one inside a working H2O htr it is probably saner to go pump plate HX route. Same HP can handle line set differing in a few feet over a few inches is what I am inquiring. So many things to consider when not simply able to reverse engineer an exact system that the obvious is often not.

[AC_Hacker]

Originally Posted by Drake

Same HP can handle line set differing in a few feet over a few inches is what I am inquiring...

Yes, for instance, my Sanyo mini-split came with a 15' line set. A 25' line set was also available that didn't require additional refrigerant. Beyond 25' would require aditional refrigerant.

These line set changes don't materially affect the metering device (cap tube).

-AC_Hacker

[Jazzoo]

AC_Hacker,
thank you for taking the time and having the courage to present this inspiring topic to the world at-large.

James

[AC_Hacker]

Originally Posted by Jazzoo

AC_Hacker,
thank you for taking the time and having the courage to present this inspiring topic to the world at-large.

Jazzoo,

Welcome to the discussion, and thank you for the kind words.

But I must say, when I discovered that it was possible to DIY a heat pump with a Coefficient Of Performance of 3 and more (a lot more), I would certainly be a coward if I didn't go Open Source and try to get the word out.

Time is short, do it now.

Best Regards,

-AC_Hacker

[Jazzoo]

AC_Hacker,
After reading this entire thread, I'm really blown-away by your progress.

On subject that keeps coming around is data-logging; ore more to the point instrumentation. Being a scrounger myself, I was wondering if you had considered using automotive type sensors as they are plentiful, cheap, robust, made for a very demanding environment. Specifically, most Automotive AC systems contain a pressure sensor on both the Hi-side and the Lo-side. The sensor range is from 100-3400 kPa (14.5 - 493.13 psia) +/- 1% @ 25 deg C with an output voltage of +/-0.01% of Vcc (generally either 5 or 8 VDC).

James

[AC_Hacker]

Originally Posted by Jazzoo

On subject that keeps coming around is data-logging; ore more to the point instrumentation. Being a scrounger myself, I was wondering if you had considered using automotive type sensors as they are plentiful, cheap, robust, made for a very demanding environment. Specifically, most Automotive AC systems contain a pressure sensor on both the Hi-side and the Lo-side. The sensor range is from 100-3400 kPa (14.5 - 493.13 psia) +/- 1% @ 25 deg C with an output voltage of +/-0.01% of Vcc (generally either 5 or 8 VDC).

I'm very glad for your input. I had thought of auto sensors, but I didn't know anything about their range or outputs.

For my next build I did buy a new automobile oil pressure sensor which has a full scale range of about 150 psi, which will give me a half scale reading that is about where the low-side R-290 seems to fall. So it is a good match.

I also bought a new Honeywell sensor that has a full scale range of about 450, and the half scale again is about where high-side R-290 seems to operate. Again, a good match.

The oil pressure sensor is pretty big and heavy and the screw threads are much bigger than the Honeywell, so I'm still looking for a replacement... I was thinking on haunting ebay until a Low-Side range Honeywell popped up, but I hadn't even thought of looking in the wrecking yards.

I also picked up 20 1-wire temp sensors and 20 LM335 analog sensors. Since I've gotten into this stuff, I want to be able to data-log the behavior. I have reams of hand-written data, and I have learned quite a bit by doing it but I'm ready for a machine to do the note taking.

Do you have any experience with Arduino, or Machine Control, or Data Logging? I could use some help in these areas.

By the way, I don't know if you found it, but strider3700 has a very excellent thread on his experiences in designing and building a home power data logger... not to be missed.

Ultimately I want to be able to automatically log:

1. Evaporator HX water-in temp
2. Evaporator HX water-out temp
3. Evaporator HX refrigerant-in temp
4. Evaporator HX refrigerant-out temp
5. Condenser HX water-in temp
6. Condenser HX water-out temp
7. Condenser HX refrigerant-in temp
8. Condenser HX refrigerant-out temp
9. Low-Side Pressure
10. High-Side Pressure
11. Outdoor air temp
12. Indoor air temp
13. Compressor case temp
14. Relative Humidity indoor
15. Relative Humidity outdoor
16. Buffer Tank temp

That's pretty much what it would take to get the full picture.

Best Regards,

-AC_Hacker

[Drake]

Would not elec power consumptn be of interest as well to record against all other variables? Or is that just a given.

[Jazzoo]

I'm very glad for your input. I had thought of auto sensors, but I didn't know anything about their range or outputs.

My suggestion for using Automotive sensors is they are designed to work on a low system voltage in a very harsh environment. This works to our advantage two fold. One, they will likely interact with Micros’ such as the Atmel processor in your Arduino. Two, they should function reliably over the 20-25yr system life expectancy.

An area of concern, repurposing devices, are the chemical interactions at the physical contacts. I.E. Will the membrane in the Oil-Sensor react with the Refrigerant? This may not be the case, I don’t know. I’d be willing to wager that the Hi and Lo sensors from the AC would be a good match for the Evaporator, Condenser, and Compressor.

Do you have any experience with Arduino, or Machine Control, or Data Logging? I could use some help in these areas. I'd be happy to share what little knowledge I have.

Arduino, no and yes. I have worked with the Atmel Micros and like them very much; very handy. I have not put hands on the Arduino platform (just its core). Machine Control, yes. Data Logging, yes.

Some of your purchases and reference to Strider3700’s thread seem to be going in two different directions. Strider3700’s thread and your purchase of “one-wire” temperature sensors (DS18 series?) indicate a desire to use “digital” sensors. However, your purchase of LM355s would indicate you would like to head in the analog direction (?as well?). Combining multiple approaches tends to complicate the design...not at all un-do-able just more complex (read time consuming).

Using a Micro to read the sensor value “directly” will require an ADC (Analog to Digital Converter) and possibly an instrumentation operational amplifier (IOP) to clean–up and amplify the signal. ADC no problem, as your Micro has at least 8 of these; however, the IOP is another matter.

Personally I like to experiment but; I’d rather stand on the shoulders of giants so long as I can still clearly see the ground.

“1-wire” was designed to be a LAN based approach to gathering data. There are lots of Open-Source and Sharware programs for accessing a “1-Wire” bus directly from a PC Parallel or serial port (with some discrete components) and USB to “1-Wire” adaptor(s). I like simple as in (KISS). Eliminate as much of the system as you can and remain working at the desire level of performance.

If it were my time and money I would get a PC to dedicate to the project. An older model with a serial port (DB9 or DB25). Can be had for free or nearly free.

Build or Buy a 1-Wire interface
• DS9490R USB to 1-Wire
• RS232 to 1Wire [ www(dot)lookass(dot)ch/content_files/dthowto(dot)txt ]

Temperature
• DS18 series 1-wire

Pressure Sensor
• Misterhouse(dot)wikispaces(dot)com/1-Wire+Pressure+Gauge

Relative Humidity
• owfs(dot) org/uploads/File/humsensor(dot)pdf

Power
• Still Working on this one...but I know I have a link somewhere.

• Postpone Arduino Implementation for the time being. The PC web/cloud/etc interface to the data will be the same regardless of the source (micro data-logger or PC). One possible aside here would be using the Micro as the control system/board. My Water-Furnace uses a PIC based micro. I'm assuming when you "finish" this thing you are going to want to "set the Temp and forget it." Yes, I know "Master-pieces are NEVER really finished," But the wife may want to make use of the furnace while you out fishing.

NOTE : The suggested routes for gathering Pressure, Relative Humidity, and Power all employ the DS2438 (Battery Monitor). This is a really flexible piece of kit that has an on-chip ADC that makes it a great work-horse for sensor development.

I'll scrounge around and see if I can't cobble some of this together and share what I find out.

Thanks again for sharing your hard work,

James

[AC_Hacker]

In previous attempts to log data and calculate COP of my mini-split and also collecting data from electric resistance heaters to use for a baseline, I was puzzled as to why, on days when the temperature was exactly the same and the wind conditions were also the same, did I get very different data.

The reason I have finally come to understand, is differing relative humidity. Thermometers don't see it but energy used by heating devices is different because of RH (relative humidity).

I have several devices, some of them digital, that purport to show RH but I have gotten such wide variation that I didn't feel I could trust any of them.

So when I came across a nicely made sling psychrometer in a junk shop, I bought it immediately.

It has two identical mercury thermometers, with a small 'water wick' on one of them. It also has a chain and a handle for slinging the thermometer assembly around in the air.

If the RH is high, water will evaporate in the wick slowly and the wet thermometer will not cool so much.

When the RH is low, water will evaporate in the wick quickly and the wet thermometer will cool much more.

After slinging the assembly about for a few minutes, a reading is taken of both the Wet Bulb thermometer (WB) and the Dry Bulb thermometer (DB). Then it is required to consult a Psychrometric chart to find the RH.

Fortunately, calculators can be found online like this one that will do the math for you.

I think it would be pretty easy to DIY a sling psychrometer, with two identical cheap thermometers, and a piece of a cotton shoe lace tied with thread to the WB thermometer.

After I did the test, I found out that the RH in my living room is 36%. My analog RH said it was 52% the digital RH indicator that is built into my light switch cover said it was 37% and the digital RH indicator that is built into my multimeter said RH = 48%.

I was able to reach in back of the analog unit and turn the assembly until it agreed with the sling psychrometer. The digital unit that read 48% is built into my multimeter and it can't be changed.

Now I trust the RH on the light switch cover.

Regards,

-AC_Hacker

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