The neglected refrigerant for air conditioning systems. R 134a.

[mr r134a]

I just have to compliment the people that maintain this board, for keeping a nice place going here.
I have loitered around here, as a non-registered reader, for a long time.

This is my first post, and it will probably be my last post. I prefer to stay on the side. I just thought that I would make one post regarding a subject that has perplexed me for a long time. That is the lack of R12, and modern R134a central air, and other air conditioning systems out on the market. Nothing seems inherently wrong with using R134a in central air units, and in some ways, R12/R134a seems better suited for central air conditioning systems. So, why are they almost non existent?

I will go over my basses for my opinion below.
Feel free to set me straight, and point out the error in my ways.

I have done a moderate amount of thinking in regard R134A in central air conditioners.
R134a is my juice of choice. (Hence my nickname)
It’s temperament is to my liking.
No major problems with heat of compression. (Don’t really like R22)
No wacko PSI levels. (I am no fan of CO2)

There is a small penalty with regard to line size, and increased refrigerant flow rate, but that is not enough to rule out the use of R134a in air conditioning. When you consider the higher heat tolerance levels resulting from lower heat of compression, then R134a also has a few benefits too. With the relatively uncontrolled condensation temps that central AC’s are subject to, R134a should be far more tolerant. Especially on situation where the evaporator freezes up, to the point that a R22 system would burn it’s valves and carbonize it’s oil from the high pressure lift.

Even using certain existing pieces of R22 equipment, you should be able to produce a air conditioning system that is far more durable, and heat tolerant.

My ideas are aimed at discharge cooled compressors.
Rotaries, some recips, and select scrolls.

Now down to the math.

For an existing R22 system, converted over to R134A with just an oil change, and TXV.
Existing size of compressor…….. Lets say 10KBtu in a standard environment..

Standard environment (for this comparison) will be evap temp of 35F and condensing temp of 100F.

R22 heat of vaporization is 87.65Btu per pound at 35F
107.9-20.25 = 87.65
R134a heat of vaporization is 84.93Btu per pound at 35F.
108.2-23.27 = 84.93

R22 enthalpy drop from 100F to 35F is 19.25 Btu per pound
39.5-20.25 = 19.25
R134a enthalpy drop from 100F to 35F is 21.88Btu per pound
45.15-23.27 = 21.88

Net cooling effect for R22 is 68.4Btu per pound
87.65-19.25 = 68.4
Net cooling effect for R134a is around 63Btu but per pound.
84.93-21.88 = 63.05

Density of R22 at 35F is 1.396 Lb per f^3
Density of R134a at 35F is 0.9544 Lb per f^3

Compressor displacement of a 10KBtu AC is 1.75cfm
(10,000/(68.4*1.396))/60 = 1.7454.…..

Btu of a 1.75cfm compressor on R134a
63.05*0.9544*1.75*60 = 6318Btu.

Compressor pressure lift.
R22 will have a 134.4PSI lift.
210.6-76.2 = 134.4
R134A will have a 93.8PSI lift.
138.9-45.1 = 93.8

Compression ratio of R134a is a bit higher than R22.
Motor load will be about 62% of R22
Motor efficiency will not be as high with reduced load.
So power consumption will be a bit more than 63% to 64% of R22
But the boosted real world COP, from boosted evap and condenser efficiency, from the reduced capacity will make that difference up plus some.

Reduced Delta T of the evap and condenser will increase suction, and decrease discharge pressures, so the net EER effect will be a positive one.

Heat of compression is far lower with R134a, so discharge temperatures will be way lower. So no major burn out problems from poor air flow over condensers.

With a discharged cooled compressor, the compressor will think it’s driving a condensing temp of about 70F to 85F instead of 100F

Compressor discharge temps/pressures, and the temperature/pressure of the refrigerant in the compressor will be about the same as it would be on a 70F or lower day.

Vapor density around the compressor components, vapor temperature, and compressor load would be the same as if it was running R22 on a cool mid summer day, instead of 100F+. Compressor cooling will not be a problem.

You will have made just a slight improvement in efficiency, increased operating margins for the compressor, and increased reliability by reducing strain on the system.

If it is in a hot climate, where the compressor normally operates overloaded from extreme discharge pressures, then you may actually improve the efficiency of the compressor, including everything else.

And if the contractor put in a system that is twice as big as the house needed (don‘t they always?), then you will now have one that is almost right on the mark.

Suction cooled compressors may not work very well though.
With the 45PSI suction, the compressor will think it’s pulling a 5F to 10F evaporator. It would not be within it’s designed parameters. Refrigeration density around the motor may be low enough that overheating of the windings may be a problem, Even at reduced load.

Now that we have done a basic conversion, and not lost any of the EER rating, now we can do something to boost the EER even more. something that I almost never see on R22 systems, because it would put them past the edge of operability.

That is, a heat exchanger on the liquid/gas lines. Like you see on R12/R134a refrigerators. Where the suction line is soldered to the liquid line going to the evaporator. It makes a highly efficient linear heat exchanger. How many times have you seen the suction and liquid line soldered together going to the inside evaporator coil on a central air unit? Even though it would boost the EER/SEER by several points. The reason you don’t, is because the extreme superheat, combined with the heat of compression of R22, would kill the compressor quickly.

So, lets strap the liquid and condensate line together, and see what we would get with R134a.

Lets say that the superheat of the refrigerant leaving the evaporator is 10F. Or a total temp of 45F
Nix that….. The heat that it would of lost from the 10F gain after it all changed to liquid would equal the amount that it would provide to the liquid stream. So lets just say zero super heat for the comparison.
35F vapor refrigerant going from evaporator to the compressor. 100F liquid refrigerant going from the condenser to the evaporator.

Lets say that the vapor temp reaching the compressor is about 95F, which would be achievable on a moderate length line set. So lets see how many Btu the 50F shift in vapor temp will give the liquid.

You will have a Btu gain of 6.2Btu per pound
115.7-109.5 = 6.2Btu

That is 6.2Btu that isn’t lost by the temp drop from the high side to low side conversation at the TXV
So, net R134a cooling capacity per pound is now 69.25Btu.
63.05+6.2 =69.25

Btu of a 1.75cfm compressor on R134a with heat exchanger is now
69.25*0.9544*1.75*60 = 6940Btu.

That is close to 70% of the cooling power, with only about 60 to 63% of the power draw.
That should boost a 14 SEER system to about 15.5 to 16 SEER.
Compressor discharge temps on discharge cooled compressors will still be within the range that you would see on a normal R22 system. So compressor damage should not occur.

As far as real world testing.
I have operated a few R22 rotary and scroll discharge cooled compressors on R134A with a oil change, in a controlled environment, and I have found that it extends the operating range greatly before destructive temperatures are reached..

Condensing temperatures can be pushed up a good deal ~140F to 150F and the compressor case (windings) temp will be running at the same point as A R22 filled compressor running at a condensing temp of 100F to 120F.

If you are in a mild climate, then changing the compressor out with a purpose built R134A unit may be advisable. A refer compressor would do a great job of pulling the outside coil down to sub freezing temps on a heat pump heating cycle.

Now I know some would call me a hack, for thinking about that type of stuff. Ow well….
I am just sharing my ideas. Do with them as you please.
I am just doing my best to think outside the box.

Normal disclaimer.
Things listed in the above article are only my opinion.
Procedures listed above, will void any equipment warranties.
Any damage you incur, while implementing any ideas stated, is your own problem.

[mattm]

How long did it take you to type all that?

[bigbird]

I got such a headache after reading all that i had to go take my chickens for their evening walk.

[Diceman]

I read the first few lines and the disclaimer.....wat up wit dat disclaimer???

But I agree, why not use 134 for A/C, anything has to be better than that 410 junk they are pushing on us.
I ain't an engineer though, matter of fact, I only been on a train once.

[bigbird]

Was that the freedom train on mlk day?

[Freezeking2000]

I think that would be a great idea. I have a few R-500 units running on an r-12 replacement gas (mp-66) and i have never had a problem after the conversion and the units are very old. (1965 carrier) I would like to know how big of a suction line would you need for a 5 ton split? 1 3/8in? for a 75 ft run.

[oroy54]

The lower the dishcharge pressure and condencer exit temp the better. I don't know. I think that R-22 is more forgiving in freeze up. 134a will freeze quick at low pressures.

[mr r134a]

Originally posted by Freezeking2000
I would like to know how big of a suction line would you need for a 5 ton split? 1 3/8in? for a 75 ft run.

That is pretty close to the mark

Cross section/volume goes up with the square of the size.
There is 5/3’rds the refrigerant flow of r22
Square root of 5/3 is 1.29
You multiply what you would expect to see on a R22 system
by 1.29 to get the size for R134a for the same gas
velocity in the suction line.

Originally posted by Diceman
I read the first few lines and the disclaimer.....wat up wit dat disclaimer???

It’s kind of a joke targeted at the “sue everyone” mentality these days.

[Freezeking2000]

I have a hard time with 7/8 in soft, imagine the cost to repipe a 1 3/8 in line. Thats one reason Mfg wont go 134A

[mr r134a]

Originally posted by Freezeking2000
I have a hard time with 7/8 in soft, imagine the cost to repipe a 1 3/8 in line. Thats one reason Mfg wont go 134A

I was basing the 1 3/8 off of the fact that I see installation charts for 5 ton systems that quote 1 1/8 suction line for that type of run.

If you are going with 7/8 for r22 then 7/8 by 1.29 is about 1.1 inch. That is close to 1 1/8

[Diceman]

You're up to 3 posts, pretty soon ya have to start paying for advice in here.

[gruntly]

Everything, EVERYTHING, everything...is about cost EXCEPT the boss' wife's bathroom.

[ozone drone]

Pretty passionate over 134a...Hey you ain't the naked guy I had arrested for trying to get it on with my Chiller #2 are ya? (Each of the 3 chillers has 750# r134A)

[mr r134a]

Originally posted by ozone drone
Pretty passionate over 134a...Hey you ain't the naked guy I had arrested for trying to get it on with my Chiller #2 are ya? (Each of the 3 chillers has 750# r134A)

Dag namit….. How did you know it was me????????
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

It’s a long story of convoluted logic and strange correlations.

To me, the government regulations on the refrigeration/air conditioning industry resemble the regulations on the alcohol industry so closely that it’s uncanny. I abide by the rules, but I don’t like them.

To me, it almost appears like the government is trying to insert control over who has the “privilege” to bestow the luxury of COOL.

If I ever get up enough gumption to type it out, I will post it as a new thread.

It will be titled…….The quest for illegal COOL.

The story of G men, Revenuers, COOL runners, and illegal cool.

[oroy54]

You build it and we will come. I shot some R-12 in my house unit a year ago. Every thing seems cool to cold around here @ 95 degrees outside. Roy

[condenseddave]

R12 was a very common refrigerant many years ago, for light commercial and residential cooling.

Have you ever actually seen the size of a 5 ton air handler and condensing unit that uses 12???????

[jacob perkins]

Although most of your post went way over my head,I am glad to see your question.I hope to see some an answer,too.

Carrier did make 134a air condition systems.Here is a condensing unit model number: 38TNO48320.

I tried to get a link to the service manual and associated literature ,but didnt have any luck.

I assume this model pre-dates the advent of 410a.Why it was discontinued,I do not know.

Maybe it used too much gas.

[mattm]

I can see the headlines now. Long time HVAC-Talk member R12 in a vicious battle with new member R134A. They both want their favorite refrigerant made into the norm. R12 just got fired again so he's on a bus to Washington to become a lobbier for the return of R12......

Somebody else finish the story I have to go.

[mr r134a]

Originally posted by condenseddave
R12 was a very common refrigerant many years ago, for light commercial and residential cooling.

Have you ever actually seen the size of a 5 ton air handler and condensing unit that uses 12???????

If you are referring to the size of some of the old ones with huge pipes and everything? As in, they look like they should be in the middle of a Texaco oil refinery, instead of in the equipment room in the back of the building………

Back then, they built the things to last!
That customer was paying top dollar for cooling back in those days.
When he bought a 5 ton AC, gosh darn it, That sucker better weigh 5 ton!!!!!

The size of some of that stuff resulted from over designing. A modern 5 ton evaporator/condenser would be a small bit larger than their R22 counterparts, if you wanted to keep the same temperature drops and everything.

Originally posted by jacob perkins
Carrier did make 134a air condition systems.Here is a condensing unit model number: 38TNO48320.

I tried to get a link to the service manual and associated literature ,but didnt have any luck.

I assume this model pre-dates the advent of 410a.Why it was discontinued,I do not know.

I know.
I cried the day that I heard it was being discontinued.

(Conspiracy mode on)
They probably started production of it, thinking that the government was going to restrict the sale of HFC refrigerants, like R134a. Which would of forced people to call a tech, every time they needed a top up on refrigerant, or other maintenance. That would of allowed the techs to constantly push the customers to upgrade. Or even allow the techs to flatly refuse to recharge a slightly leaky system, which would basically force the customers to upgrade to new equipment.

But, when they found out that they wasn’t going to restrict HFC sales, they had to come up with a custom refrigerant so that they could price it to the point that it would allow them to keep defacto control over their supply stream. And the price is to the point that it makes it uneconomical to recharge a slightly leaky system. So you end up with the same result. You can force custimers to replace equipment that is reaching the end of it’s life cycle.

How can you control the life cycle of your product in the field, if you can’t control the stuff that keeps them running?

It all means more money for the manufactures.
(conspiracy mode off)

[hvacpope]

All jokes aside, you are 100% right, the corporations and their government servants manipulate the public into believing such fallacies like refrigerants are bad for the environment and the ozone layer etc.
its all about expired patents and profits. The joke is on us the people, I can only imagine the masters behind the lies and manipulations laughing out loud in a fancy meeting room somewhere, they feed us crap, we eat it and ask for more.