Propane (R-290) for heat pumps?

[randallkc]

Well if your afraid of blowing yourself up you had better not use any R22 replacements.
410a high pressure. R290 600 much better refrigerants

[Xringer]

I'm not too afraid, if I can keep my fresh-air & anti-radon system running..
The air intake is about 8" off the floor slab.. What does worry me is the X-10 relays I'm using now..
But, they are about 4-5 feet up from the floor...
Since it's a 800 sq feet, the propane level on the floor might not be more than a foot deep..?.
I guess the X10 boxs could be sealed up a bit..

[AC_Hacker]

Originally Posted by randallkc

About 10 years ago I was in Belize... The most efficient heat pumps over seas already use it!

Thanks or sharing this very valuable information.

I suspected that propane was in far wider use than we realize.

I appreciate your very useful post.

BTW there is a global committee that is grappling with the problem that we are destroying our planet, in part, through the use of environmentally disastrous refrigerants.

I am waiting for them to discover propane. HA!

Best,

-AC_Hacker

[AC_Hacker]

randallkc,

It is also good to note that NONE of the previous posters, who advise not to use propane, have ever used propane.

In other words, they don't really know what they are talking about... and you do.

Thanks again.

Best,

-AC

[stevehull]

AC,

You state that posters have not used propane.

But I have; in my old Nissan truck! But not in my basement . . . .


Best regards,


Steve

[randallkc]

The biggest thing with R290 is the orifice difference. You can use a TXV built for R22 if you adjust it. That is what I do.

I tried to put in R290 to a capillary system without resizing the tubes. Total disaster! Very low super heat and sub cooling unless over charged. And even then was not right.

With pistons. I have not played with them much. But go smaller and play with it. I believe the orifice needs to be about 1/3 smaller than R22. R290 just is more liquid and flows easier.

As far as Oil, I don't want to risk going to synthetic oils that can wax up. I am happy with the old r22 oil. R290 does do a little better with synthetic but it also works fine with good old mineral oil. I don't want to rock the boat there.

I have only retro-fitted R22 systems. I took some ancient R22 systems from the 1980's that used capillary tubes. Dropped in new A coils and TXV valves. simply amazing! I have these two ton compressors almost 40 years old doing a great job! I have noticed a serious reduction in power consumption as well. Lower bills for units that I pay the utilities on. Most of that is the TXV but propane is slightly more efficient than R22.

Nothing like playing with a 40 year old AC system with nothing to loose. That is how I started to learn to hack R290. Love the stuff. I keep my old R22 systems alive off reclaiming R22 from systems I convert. If it has a A coil leak I replace with new A coil, TXV and R290. No way I will pay $600 a bottle for R22 or start replacing systems!

[jeff5may]

^^ OBVIOUSLY EXPERIENCED (with R-290)^^

I have dropped bbq bottle propane into multiple (smallish capacity) cap tube systems without having to change any plumbing at all. They did great. The main thing to remember is that propane has a little less vapor pressure at the same temperature vs r-22. So at any given pressure, your saturation temp is slightly higher. Fwiw, With a cap tube I set the system charge in a hot tin shed on the hottest day of the year.

At low pressures, this difference is pretty trivial. For example, at 60 psig, r-22 has a saturation temp of 34 degF, and r-290 is at 37 degF. This difference widens as temperature increases. At 300 psig, this difference has grown to 10 degF.

In cooling mode, a stock cap tube will do just fine as long as you don't overcharge the unit with propane. For practical purposes, the gauge scale for R-22 can be used to set saturation point and superheat. I have found that if you charge by weight, about 1/3 of the nameplate value for R-22 charge is a good starting point. This will give you a little extra superheat vs R-22, but that's ok. We don't want to flood the compressor. Oil is more soluble in propane as well, so the extra superheat helps cut down on foaming effect. Fwiw, I set the system charge on the hottest day of the year in early afternoon. HOWEVER, I set the txv superheat during sub-zero outdoor temperatures. Warmer it gets outside equals more dT outdoors and more heat gathered per minute of runtime.

Heating mode is a different story. With any cap-tube metered system, capacity is always traded for low-temperature stability. If the unit is going to be operating in freezing (or sub-zero) outdoor temperatures, the cap-tube will have to be a lot longer than a cooling-only unit. Thus, the check valve and extra length of cap-tube is installed to limit suction saturation temperature in heating mode. This extra length of cap-tube also reduces mass flow and (maybe) heat flow from outdoors in. Depending on many factors, this safety cushion eats at heating efficiency.

For DIY ecorenovators, a choice has to be made between ultimate simplicity and ultimate efficiency. The old-school, cap-tube metered a/c and heat pump units are very reliable because they have very few moving parts. They just go and go like the energizer bunny, sometimes for a human generation or lfetime. If something fails, it is usually a capacitor or switching device. Much later in life, corrosion, friction, and fatigue take their toll as the unit approaches retirement age.

OTOH, the newer TXV or computer-controlled units cost less to operate because they push the efficiency envelope. They have many more moving and/or electronic parts, all of which increase the risk of failure. If something does fail, it is not as easy to identity what went wrong without gauges, thermometers, and other test equipment. While they operate, the energy savings is pretty substantial, but chances are the unit will not live as long. Sensors and transistors generally don't live as long as a piece of pipe.

With modern technology changing the way people use (and feel the need to be constantly upgrading) equipment, the manufacturers have followed this trend. Stuff just isn't built to live as log as it used to be. Whether or not you justify these changes makes a big difference in system design and operating parameters.

[randallkc]

I have four R22 cap systems from the late 80's The performance on those was awful. The super heat and sub cooling was awful. I could not get to beer can cold without over charging and even then it was not right. Suck and reload with 22 and wow! works perfectly. It's all about the orifice system.

I swapped out a crap old leaking A coil to a newer one and installed a TXV and bamm! Now we are cooking with gas so to speak. The TXV did require some adjustment but worked very very well. I took a old old system and cut power consumption by a easy 40%. It is on a unit I pay the utilities for so I can tell!

R290 is more fluid and requires more of a restriction than R22. It also requires less of a charge form my experiences. That's just the way it is. Maybe performance is different from system to system but a old cap system running R22 from the 80's needs a upgrade anyway.

TXV's allow for adjustment that cap tube system's don't. Pistons can be changed. cap's can't easily. If you want to play with R290 avoid cap systems.

[Xringer]

A guy used Propane with an R410A split system, without any mods. Think he used 20% less charge weight.?.
But, he said the cooling was really good and the power use was way down..
I think his YouTube video of the hack is gone now..

[jeff5may]

I have had good luck using TXV's in older units as well. They are a little more picky than cap tubes, as in they don't like to see any gas in the liquid line. Placing the sensor bulb in the right place and orientation is also critical for reliable behavior. For units smaller than about 10k btu, the potential savings is not really substantial compared to a decent captube setup. But for units rated over a ton of capacity, expansion valves are the bees knees. The extra efficiency can be seen on the utility bill.

With heat pumps and a/c units especially, it is important to use a TXV with MOP charge. The MOP charge keeps the evaporator from running too warm and cooking your compressor. Many of the surplus valves are for commercial freezers and cryogenic coolers and have a different type of charge in the bulb. A little research goes a long way toward picking the right valve for the job.

Some older systems are just begging for an upgrading. The old captube and "flowrator" piston indoor coils on whole-home units are terribly inefficient. Besides the obvious metering device deficiencies, many of the heat exchange surfaces are not optimized for energy savings. A new indoor coil with a txv most likely has been designed on a mainframe or supercomputer, and optimized for much better heat transfer. Like randall said, mucho dinero can be left in your pocket come bill-paying time. A few hundred dollars for an indoor heat exchanger with txv metering could pay for itself in a year or three.