Home » Public Forums » GMCnet » AC pressure switch R12/134a ?
| AC pressure switch R12/134a ? [message #311433] |
Sat, 10 December 2016 16:19  |
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Loffen
Messages: 1087
Registered: August 2013
Location: Norway
Karma: 1
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I am going from R12 to 134a in my AC system, would it be an idea to change the pressure switch and if so what on off values should it have ?
1973 23' # 1848 Sky Blue Glacier called Baby Blue and a 1973 26'-3 # 1460 Parrot green Seqouia Known as the Big Green,
And sold my 1973 26'-2 # 581 White Canyon lands under the name Dobbelt trøbbel
in Norway
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| Re: AC pressure switch R12/134a ? [message #311440 is a reply to message #311434] |
Sat, 10 December 2016 19:38  |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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R134 in older R-12 system==poor solution most of the time. Higher pressure required, more heat generated to atmosphere, more noise from compressor, more time required for change of state to gas, less lubrication quality for compressor parts, and less cooling performance at low compressor RPMs. Use the Duracool or other hydrocarbon refrigerant if you can.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: AC pressure switch R12/134a ? [message #311449 is a reply to message #311433] |
Sun, 11 December 2016 09:50 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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134a is $3,99 here on sale. Don't be penny wise, dollar foolish. (( or converted to your money system!) If you don't like the HC you can simply vent it off. If you go 134a you need to flush and change all O rings to green, use correct oil and use only 80% of the R12 recommended amount.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: AC pressure switch R12/134a ? [message #311456 is a reply to message #311449] |
Sun, 11 December 2016 15:40 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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JohnL455 wrote on Sun, 11 December 2016 10:50134a is $3,99 here on sale. Don't be penny wise, dollar foolish. (( or converted to your money system!) If you don't like the HC you can simply vent it off. If you go 134a you need to flush and change all O rings to green, use correct oil and use only 80% of the R12 recommended amount.
John,
One of parts of this equation is that R134a is being phased out. It turns out to have potential to be an agent of anthopogenic climate change (and, the patent is run out so others can make it cheap). The new guy in line is HFO1234yf. It is currently kind of expensive, flammable and toxic, but other than that, it looks good.
I am liking HC-12 more all the time. The only reason my coach still has 134 in it is because it hasn't leaked out yet.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: AC pressure switch R12/134a ? [message #311458 is a reply to message #311456] |
Sun, 11 December 2016 16:39 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Matt Colie wrote on Sun, 11 December 2016 15:40John,
One of parts of this equation is that R134a is being phased out. It turns out to have potential to be an agent of anthopogenic climate change (and, the patent is run out so others can make it cheap). The new guy in line is HFO1234yf. It is currently kind of expensive, flammable and toxic, but other than that, it looks good.
I am liking HC-12 more all the time. The only reason my coach still has 134 in it is because it hasn't leaked out yet.
Matt IIRC, HC-based refrigerants are legal in commercial chillers but not residential. In some states, HC-based refrigerants are illegal in automobile air conditioners. No real reason other than the FUD being fed to lawmakers to keep the artificially produced chemicals in service. Otherwise, any given manufactured refrigerant has an HC-based analog that will cost less up front, in maintenance, and energy costs to run. Not to mention being less damaging to the environment. For some reason, it is ok to have a 500 gallon propane or butane tank in the back yard and a pipe into the house for winter heating, but a few ounces of propane/butane mix in the heat pump is so many orders of magnitude more dangerous that it is illegal.
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| Re: AC pressure switch R12/134a ? [message #311463 is a reply to message #311433] |
Mon, 12 December 2016 12:06 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I agree on the low pressure switch. On later models (77-78) with cycling clutch the cycling is controlled by the evaporator temp switch. So clutch should engage until temp is cold enough. The only caveat is enough pressure static to close the low press switch. There is less volume of 134a with correctly charged, but vapor pressure is higher (???) so usually this is not a problem. So glad I still have R12 in mine.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: AC pressure switch R12/134a ? [message #311477 is a reply to message #311446] |
Tue, 13 December 2016 09:21 |
TR 1
Messages: 348
Registered: August 2015
Location: DFW
Karma: -7
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Ken Burton wrote on Sat, 10 December 2016 21:19R-134, Duracool, antifreeze, oil, gasoline, and propane that are in your coach are all flammable.
We already have what, 17 gallons of propane on board in the motorhome? What's another few ounces...
I agree with what is said above... 134a should stain in 134a based systems. Keep R12 systems charged with R12 or some form of HC. Too many drawbacks to converting to 134a, but the most important drawback is the reduction in efficiency. If 134a improved cooling over R12, all those other drawbacks would be worth it, IMO... But to spend all that effort and $$ to convert an already taxed system to something that works worse?
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
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| Re: AC pressure switch R12/134a ? [message #311485 is a reply to message #311477] |
Wed, 14 December 2016 02:40 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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I have a large tank (30 pound?) of R-134 here. I use it in R-134 vehicles and appliances. I also have a stock of Duracool. It goes in all R-12 applications.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: AC pressure switch R12/134a ? [message #311491 is a reply to message #311485] |
Thu, 15 December 2016 08:32 |
TR 1
Messages: 348
Registered: August 2015
Location: DFW
Karma: -7
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Ken Burton wrote on Wed, 14 December 2016 02:40I have a large tank (30 pound?) of R-134 here. I use it in R-134 vehicles and appliances. I also have a stock of Duracool. It goes in all R-12 applications.
+1 on the 30 pounder... Sam's Club usually has a great price on the 30s. Think it ended up costing 1/3 what you pay for the smaller cans when I bought one 5 years ago... And I believe I paid $200 for a 30 pounder of R12 like 15 years ago... Paid about the same for an R22 30 as well 5 years ago. So far, the price of refridgerant only goes up as it is discontinued... R12 is going for somewhere between $700 and $1000 for a full 30 pounder now. R22s starting to go up too, and I assume 134a will once they stop making it...
Use it as long as you need it... Then sell it when you no longer have any ACs that use it. Not a bad ROI...
Speaking of which, I've never used any sort of HC12 in an AC, but I do understand the benefits of doing so over charging with 134a or even R12... However, what is the benefit of using a product like Duracool, vs just charging with straight propane?
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
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| Re: AC pressure switch R12/134a ? [message #311493 is a reply to message #311491] |
Thu, 15 December 2016 16:17 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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TR 1 wrote on Thu, 15 December 2016 09:32<Snip>
Speaking of which, I've never used any sort of HC12 in an AC, but I do understand the benefits of doing so over charging with 134a or even R12... However, what is the benefit of using a product like Duracool, vs just charging with straight propane?
Mark,
Years ago, an acquaintance accidentally did just that. As far as we could tell, it did no damage. It was real anemic as A/C goes, but I'm sure it was better or worse than it worked when it was charged with R-12. I do no that both C3H8 and R-12 had very similar P/T curves at room and somewhat higher temperatures.
Then there is the fact that my old halogen detector died. I do still have hope of recovering it, but I also have a mystery leak in my propane tank. I stumbled across a combustible gas leak detector at an advantageous price. After I find where the propane tank is leaking, I am going to charge my wife's car's A/C with propane and hope to find where that is leaking. So, I will let you know when I know more.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: AC pressure switch R12/134a ? [message #311494 is a reply to message #311491] |
Thu, 15 December 2016 17:05 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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TR 1 wrote on Thu, 15 December 2016 08:32...However, what is the benefit of using a product like Duracool, vs just charging with straight propane? The 35% butane in Duracool changes the P/T curve vs straight propane. Makes it more efficient in the design range of the R-12 compressor/condenser/evaporator system.
If you don't want to spend a lot, get some camp stove fuel and combine it with the propane. Mix 19.56 oz. of propane with the contents of one 16 oz can of 80/20 campstove fuel to produce 35.56 ounces of HC refrigerant for an R-12 system.
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