A/C Charging with Easy Cheap Safe Alternative Refrigerant
09-23-11, 03:38 PM
#51
And those that understand refrigeration cycles know that humidity is half the battle. A standard (no evaporative aids such as is the case with all automotive A/C) A/C system operating in AZ at 120 deg dry bulb (a common summer high temp) will often NOT have its capacity taxed as much as those in sub 100 temps with high dry bulbs....turns out pulling water out of air takes a lot of energy...
In any case not trying to be a jerk, just pointing out that people who hang their hats on dry bulb temps as the primary factor in the sizing and capacities of A/C systems are going to find out they never have enough cooling...thus A/C systems are taxed by far more than straight air temps...
A lot of factors go into it, but with very basic and antiquated systems like automotive A/C the above holds true more often than not.
I will agree that we dont find ourselves maxing out A/C capacities for as MANY days as in the south...not even close...
In any case not trying to be a jerk, just pointing out that people who hang their hats on dry bulb temps as the primary factor in the sizing and capacities of A/C systems are going to find out they never have enough cooling...thus A/C systems are taxed by far more than straight air temps...
A lot of factors go into it, but with very basic and antiquated systems like automotive A/C the above holds true more often than not.
I will agree that we dont find ourselves maxing out A/C capacities for as MANY days as in the south...not even close...
I also agree that it doesn't get hot here as often but I don't really think that's the point. Then again we had a record heat wave this year...
09-23-11, 04:41 PM
#52
obviously it's not the same feeling but it often takes less a/c cooling to help in more humid climates simply to dry the air. i don't exactly agree also that it takes alot of effort to dry the air with the a/c system.
basically 89* in key west felt like a 110* day here in the desert, where the car takes almost 10 minutes to pull down the ambient temperature inside the car to be semi comfortable, in the south it takes much less time and less heat generated for the engine in return to do the same job.
basically 89* in key west felt like a 110* day here in the desert, where the car takes almost 10 minutes to pull down the ambient temperature inside the car to be semi comfortable, in the south it takes much less time and less heat generated for the engine in return to do the same job.
09-23-11, 08:16 PM
#53
Sensible vs. latent heat
You guys brush up a little on your physics, specifically the field of psychrometrics.
You are guys are arguing sensible vs. latent heat. This is an argument of the ignorant, no offense. Sensible heat is the 'dry-bulb' temperature, basically the heat capacity of dry air. Latent heat is related to the 'wet-bulb' or dew-point. Both contribute to the load that must be removed from the interior air and rejected by the condenser in front of the radiator. The calculation of sensible heat load vs. latent heat load is call the SHR or Sensible Heat Ratio. In a car, the SHR can be changed by adjusting the speed of the fan. Lower the fan speed, the SHR becomes lower; turn the fan up, the SHR becomes higher.
Why does this matter? Well, if you are in a 'humid' but not hot area, your drip should be nearly a stream. In the desert, there may be less drip, but there should always be drip unless the area has a dew point lower than 40*f. How do you know the dew point? check your weather ap on the iPhone
or look at your night temps. Unless you are in an urban heat island, the night temps will approach dew point. Dew point does not vary much from night to day.
The argument becomes irrelevant within a few minutes after the car is started. Why? Because you should set the air on recirculate, at least during initial cool down. Now you are dealing with the actual load, solar gain, heat from the mechanics of the car, ambient heat conducted through the body, heat radiated up from that hot roadway etc. These loads are all independent of latent load (humidity) and are directly related to the sensible (ambient temp) load. These loads are by far the majority of the heat that our auto A/C must remove. The humidity removal is almost a by-product of this process.
Just in case your car leaks massive amounts of air (thus letting additional amounts of humid air into the interior) FIX YOUR CAR!
Now, when you Yankee's finish whining about how hot it gets in Minnisota (Mmmiiiniiiisohhhtah) or Canada (Eh?) keep in mind that I live 12 miles from D/FW airport. I will pick you up and buy the beer if you ever get the urge to experience 105+ degrees with dew points well over 80*. We will take in a late August Texas Rangers night baseball game when the on field temps are in excess of 100* and dew points are over 80* during the 7th inning stretch. You will leave for home a different person!
That is a valid offer,
only if you are legal to drink!
You are guys are arguing sensible vs. latent heat. This is an argument of the ignorant, no offense. Sensible heat is the 'dry-bulb' temperature, basically the heat capacity of dry air. Latent heat is related to the 'wet-bulb' or dew-point. Both contribute to the load that must be removed from the interior air and rejected by the condenser in front of the radiator. The calculation of sensible heat load vs. latent heat load is call the SHR or Sensible Heat Ratio. In a car, the SHR can be changed by adjusting the speed of the fan. Lower the fan speed, the SHR becomes lower; turn the fan up, the SHR becomes higher.
Why does this matter? Well, if you are in a 'humid' but not hot area, your drip should be nearly a stream. In the desert, there may be less drip, but there should always be drip unless the area has a dew point lower than 40*f. How do you know the dew point? check your weather ap on the iPhone
or look at your night temps. Unless you are in an urban heat island, the night temps will approach dew point. Dew point does not vary much from night to day.The argument becomes irrelevant within a few minutes after the car is started. Why? Because you should set the air on recirculate, at least during initial cool down. Now you are dealing with the actual load, solar gain, heat from the mechanics of the car, ambient heat conducted through the body, heat radiated up from that hot roadway etc. These loads are all independent of latent load (humidity) and are directly related to the sensible (ambient temp) load. These loads are by far the majority of the heat that our auto A/C must remove. The humidity removal is almost a by-product of this process.
Just in case your car leaks massive amounts of air (thus letting additional amounts of humid air into the interior) FIX YOUR CAR!
Now, when you Yankee's finish whining about how hot it gets in Minnisota (Mmmiiiniiiisohhhtah) or Canada (Eh?) keep in mind that I live 12 miles from D/FW airport. I will pick you up and buy the beer if you ever get the urge to experience 105+ degrees with dew points well over 80*. We will take in a late August Texas Rangers night baseball game when the on field temps are in excess of 100* and dew points are over 80* during the 7th inning stretch. You will leave for home a different person!
That is a valid offer,
only if you are legal to drink!
09-23-11, 08:22 PM
#54
Why Psychrometrics Matter?
The dew point in Minnesota that day was 72.13727953741228*f
The Dew point in Argyle that day was 72.56600593310179*f
This means the Actual Moisture (Latent load) content of the air was almost EXACTLY the same.
What was different between these locations? Sensible load!
Thank you. Thank you very much.
09-24-11, 09:28 AM
#55
Except the problem is your initial assumption of design conditions. Which do not match what i am submitting.
Fairly certain my understanding of psychrometrics, is...lets just say plenty. I have a BME, and have designed HVAC for 13 years. I have corrected many service techs whos assumptions are often based in voodoo...
Dont mean to get into a whos brain is bigger fight, but just took slight offense to saying that nobody in MN understand refrigeration and psychrometrics...
Fairly certain my understanding of psychrometrics, is...lets just say plenty. I have a BME, and have designed HVAC for 13 years. I have corrected many service techs whos assumptions are often based in voodoo...
Dont mean to get into a whos brain is bigger fight, but just took slight offense to saying that nobody in MN understand refrigeration and psychrometrics...
09-24-11, 04:32 PM
#56
and beating a horse, as still even R134a can do the job if the system is working properly and you service it properly. not as well as R12 or even your alternative however. the fact that people are claiming that you can't get it cold in some areas tells me that they don't know as much as they claim.
who really blows out the evaporator core or even thinks to in automobiles? it can be a problem and many times it is the core problem, yet sight unseen left alone. how many people actually blow out all the leaves in front of the condenser core? the space between the oil cooler and core is almost always packed with garbage and can reduce efficiency a bit as it covers the core by about 33%. also i have had better luck with the earlier compressors, pre '88, the later model ones usually cannot handle the higher load or compress the charge as well.
who really blows out the evaporator core or even thinks to in automobiles? it can be a problem and many times it is the core problem, yet sight unseen left alone. how many people actually blow out all the leaves in front of the condenser core? the space between the oil cooler and core is almost always packed with garbage and can reduce efficiency a bit as it covers the core by about 33%. also i have had better luck with the earlier compressors, pre '88, the later model ones usually cannot handle the higher load or compress the charge as well.
09-25-11, 06:07 PM
#58
Except the problem is your initial assumption of design conditions. Which do not match what i am submitting.
Fairly certain my understanding of psychrometrics, is...lets just say plenty. I have a BME, and have designed HVAC for 13 years. I have corrected many service techs whos assumptions are often based in voodoo...
Dont mean to get into a whos brain is bigger fight, but just took slight offense to saying that nobody in MN understand refrigeration and psychrometrics...
Fairly certain my understanding of psychrometrics, is...lets just say plenty. I have a BME, and have designed HVAC for 13 years. I have corrected many service techs whos assumptions are often based in voodoo...
Dont mean to get into a whos brain is bigger fight, but just took slight offense to saying that nobody in MN understand refrigeration and psychrometrics...
I didn't say no one up 'North' understood MVAC, obviously you do. I have stated and stand by the reality that you guys don't live in the same world, design conditions, that we do in say, Dallas. You have to live it.
Latent heat removal may be half the battle, but it is the SECOND half the battle. Here the battle starts with 150-160* heat-soaked interiors, 105* ambient and then also includes dew points in the mid-80's.Somewhere I have a picture of my IR gun reading 158* on the Shift **** of my 90Vert.
One remarkable feature of the Texas heat event this year is that it was dry heat. That is unusual. We often had dew points in the low 70's and upper 60's. Typically our humidity and heat come together during July and August, then leave together in early Sept. This year was different.
You guys had a few of days of truly monstrous heat/humidity this summer. I track the weather in MN, MI, CO and OH on a daily basis during the summer, part of my job. We ship several million $ worth of 'horticultural products' which are specifically grown in Minnesota, Michigan and Colorado because of the summer climate. Specifically for the cool night temps that are attainable due to the low WB. Adiabatic cooling is used quite effectively during the day due to a.) the relatively cool DB temps and b.) the relatively low WB conditions. We can attain +/- 80% of the delta. We grow 'stuff' all over the world. We pick the climactic conditions for specific crops. Central America, South America, Africa, Canary Islands, specific altitudes, specific latitudes etc.
Still offering to buy that Beer, but the Ranger's games are pretty pleasant this time of year, so you need to wait till August to truly suffer.
09-27-11, 09:48 AM
#62
your aim should be as close to freezing point as possible without actually freezing the evap core. generally around 36-38f, which is nearly impossible with 134a in hotter climates. see the previous page, same conditions as you, 39.6*F temp at the vents.
09-27-11, 02:51 PM
#63
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You can do way better. Im curious, did you clean out all the lines with some sort of fast solovant and blow them out with air including the evaporator and condenser? Also, did you bench flush the compressor as well as install a fresh new reciever dryer? Did you use the correct oil and ammount of oil and disperse it throuout the system?
Given your results Im guessing no to most of the above. Just an FYI, anytime your switching refrigerants and the oil for the old one is not compatable with the new one you MUST PURGE THE SYSTEM OF ALL THE OLD OIL!! or you will have very crappy results.
Im not some refrigeration expert, just have some real world experince doing these conversions. The shop I was at did loads of these, we were all trained on it and had a very good record.
One thing I will add, expect to add a pusher fan when doing a 134 conversion. Youd be supprised how many cars come from the factory already wired to do this, Including the FC which came with actual pusher fans on the condenser.
Freez 12 is hands down a better refrigerant, I will be giving it a go on my next conversion, but, unless you get out all the old oil and add proper o-rings, new reciever dryer ect... Just like with 134 your going to have crappy results.
Given your results Im guessing no to most of the above. Just an FYI, anytime your switching refrigerants and the oil for the old one is not compatable with the new one you MUST PURGE THE SYSTEM OF ALL THE OLD OIL!! or you will have very crappy results.
Im not some refrigeration expert, just have some real world experince doing these conversions. The shop I was at did loads of these, we were all trained on it and had a very good record.
One thing I will add, expect to add a pusher fan when doing a 134 conversion. Youd be supprised how many cars come from the factory already wired to do this, Including the FC which came with actual pusher fans on the condenser.
Freez 12 is hands down a better refrigerant, I will be giving it a go on my next conversion, but, unless you get out all the old oil and add proper o-rings, new reciever dryer ect... Just like with 134 your going to have crappy results.
10-02-11, 07:19 PM
#65
well i tried this **** today and i'll say i'm rather impressed with the results...
ambient temp in the shade of the shop= 85F, 92F ambient outside in the sun, only 18% humidity today though.
temp at the vents in the 85F shade = 32.6F(given the ambient conditions this is about as good as you could ever expect before you're compressor begins cycling to dethaw your ice brick of an evap core).
that was with only a partial charge of 10 oz(well technically only about 8 ounces, i was having trouble with the shitty side can tap...), compared to the 16 ounces i normally have to charge to get worse results from R134a. also only had it on recirc for about 2 minutes before checking with the gauge. i had to turn down the fan speed because it was too cold inside.
now i just need to diagnose why the powerfc isn't turning on the compressor clutch(had to hard wire it because the powerFC is known to have issues in the FD).
ambient temp in the shade of the shop= 85F, 92F ambient outside in the sun, only 18% humidity today though.
temp at the vents in the 85F shade = 32.6F(given the ambient conditions this is about as good as you could ever expect before you're compressor begins cycling to dethaw your ice brick of an evap core).
that was with only a partial charge of 10 oz(well technically only about 8 ounces, i was having trouble with the shitty side can tap...), compared to the 16 ounces i normally have to charge to get worse results from R134a. also only had it on recirc for about 2 minutes before checking with the gauge. i had to turn down the fan speed because it was too cold inside.
now i just need to diagnose why the powerfc isn't turning on the compressor clutch(had to hard wire it because the powerFC is known to have issues in the FD).
10-02-11, 11:08 PM
#67
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All the information you need is above, read.
10-03-11, 12:03 PM
#68
i generally just pull it into a vacuum and let it sit for 5 minutes to see if the vacuum drops any. if not i add about 1oz of dye and recharge the system if it has already been converted(most have already been drained and ester oil added).
the stop leak stuff you usually see rarely does anything and i can imagine it actually hurts a/c performance. best to add dye so if there is a leak you can easily pinpoint it. ideally in a shop environment you would do the above then go over the car with a dye light after about 15 minutes to find any leaks, recover the refrigerant, repair the leak and then recharge it again. but with R134a and now R152a it isn't enough of an impact if you do not have the tools to recover it from the system and cheap enough to simply replace each charge as needed.
the stop leak stuff you usually see rarely does anything and i can imagine it actually hurts a/c performance. best to add dye so if there is a leak you can easily pinpoint it. ideally in a shop environment you would do the above then go over the car with a dye light after about 15 minutes to find any leaks, recover the refrigerant, repair the leak and then recharge it again. but with R134a and now R152a it isn't enough of an impact if you do not have the tools to recover it from the system and cheap enough to simply replace each charge as needed.
10-08-11, 11:18 AM
#69
i generally just pull it into a vacuum and let it sit for 5 minutes to see if the vacuum drops any. if not i add about 1oz of dye and recharge the system if it has already been converted(most have already been drained and ester oil added).
the stop leak stuff you usually see rarely does anything and i can imagine it actually hurts a/c performance. best to add dye so if there is a leak you can easily pinpoint it. ideally in a shop environment you would do the above then go over the car with a dye light after about 15 minutes to find any leaks, recover the refrigerant, repair the leak and then recharge it again. but with R134a and now R152a it isn't enough of an impact if you do not have the tools to recover it from the system and cheap enough to simply replace each charge as needed.
the stop leak stuff you usually see rarely does anything and i can imagine it actually hurts a/c performance. best to add dye so if there is a leak you can easily pinpoint it. ideally in a shop environment you would do the above then go over the car with a dye light after about 15 minutes to find any leaks, recover the refrigerant, repair the leak and then recharge it again. but with R134a and now R152a it isn't enough of an impact if you do not have the tools to recover it from the system and cheap enough to simply replace each charge as needed.
Does everyone normally change to ester oil when they do the converion? I bought the car with the conversion done and didn't do 152a because I'm not sure what kind of oil is in it.
Anyway, here is what my car with a freash 134a charge did with about 85F outside and 80% humidity and a low ffan setting.
10-09-11, 08:11 AM
#71
He has the remote probe for 'outside' stuck in the center vent, thus 'outside'=vent temp.
Likely the conversion didn't include any oil at all, most don't. If they had used PAG, the system would have already been completely gummed up. If they were SO professional that they completely cleaned, chemically flushed the chlorine and mineral oil from all components so they COULD use PAG, they would have also documented that supremely professional conversion with the EPA-mandated conversion sticker. It would have specified the oil.
So the likelihood is that they either didn't add oil, or they added some Ester.
You need to measure that vent temp at high fan, recirc on. If you are not moving, the engine speed needs to be 2000rpm +/-. You should use a shop fan to assure the condenser gets ambient air and is not recirculating the air from the back of the condenser/rad back to the front.
Keep in mind that 152a and 134a are chemically compatible. In regards to the selection of oils: They tolerate some mineral oil in the system but the system cannot be totally mineral oil; they are compatible with both PAG and Ester. For example, I have a 2002 626 that developed a leak. I fixed it and charged back with 152a. It works better than with 134a it was designed for.
You should use 70% of the factory 134a charge (by weight).
We just fixed a leak on my car (f-ing shreader valve for the conversion) and I refilled with 134a.
Does everyone normally change to ester oil when they do the converion? I bought the car with the conversion done and didn't do 152a because I'm not sure what kind of oil is in it.
Anyway, here is what my car with a freash 134a charge did with about 85F outside and 80% humidity and a low ffan setting.
Does everyone normally change to ester oil when they do the converion? I bought the car with the conversion done and didn't do 152a because I'm not sure what kind of oil is in it.
Anyway, here is what my car with a freash 134a charge did with about 85F outside and 80% humidity and a low ffan setting.
So the likelihood is that they either didn't add oil, or they added some Ester.
You need to measure that vent temp at high fan, recirc on. If you are not moving, the engine speed needs to be 2000rpm +/-. You should use a shop fan to assure the condenser gets ambient air and is not recirculating the air from the back of the condenser/rad back to the front.
You should use 70% of the factory 134a charge (by weight).
10-11-11, 12:29 AM
#75
Rotary Enthusiast
Thought I'd chime in. I recently sold my 1978 Corvette that I converted to R134a using a new parallel flow condenser. This thing was wonderful and gave me 36 degree air on 105 degree days (granted, it was a much larger condenser than could possibly fit under an FC's hood)
With a (brand new) horrible GM R4 compressor this setup maintained a 235PSI high side even on a disgustingly hot Phoenix day which I was very impressed with.
When I get my next FC, I'm going to go the same route now that I'm MUCH less intimidated by the process.
The condensers are available in a huge range of sizes and only cost less than $100 shipped to your door. They all come with #8 and #6 Male O-Ring fittings and are reversible and don't care which position you orient them in.
The stock TURBO RX7 condenser has a #8 MOR fitting and a #5 MOR fitting. This means you should be able to reuse the line from the compressor. You will have to get the high pressure line custom made since it is a #5 MOR fitting and aftermarket condensers use a #6.
The stock NON-TURBO condenser uses the same #8 MOR and #6 MOR fittings that aftermarket condensers use. You will still have a custom hose made as the non-turbo condenser has an outlet on each side of the condenser where aftermarket models have inlet/outlet on the same side of the condeser so the stock pressure line won't fit.
Again, this is not as intimidating as it seems. I found a local AC shop by the name of RMACC here in Phoenix that asked me what fittings I needed and made me the hose for a grand total of $45 .
All and all it's a very worthwhile venture considering how well parallel flow condensers cool coupled with the low cost and high availability and serviceability of R134a. Don't be afraid of the process it's not nearly as complicated as you might think.
You should also, if possible of course, consider the safety of replacing the low pressure cut out with a binary high/low switch.
I'd be happy to help guide anyone along with this process with vendor names and addresses if needed. Don't hesistate to ask!
With a (brand new) horrible GM R4 compressor this setup maintained a 235PSI high side even on a disgustingly hot Phoenix day which I was very impressed with.
When I get my next FC, I'm going to go the same route now that I'm MUCH less intimidated by the process.
The condensers are available in a huge range of sizes and only cost less than $100 shipped to your door. They all come with #8 and #6 Male O-Ring fittings and are reversible and don't care which position you orient them in.
The stock TURBO RX7 condenser has a #8 MOR fitting and a #5 MOR fitting. This means you should be able to reuse the line from the compressor. You will have to get the high pressure line custom made since it is a #5 MOR fitting and aftermarket condensers use a #6.
The stock NON-TURBO condenser uses the same #8 MOR and #6 MOR fittings that aftermarket condensers use. You will still have a custom hose made as the non-turbo condenser has an outlet on each side of the condenser where aftermarket models have inlet/outlet on the same side of the condeser so the stock pressure line won't fit.
Again, this is not as intimidating as it seems. I found a local AC shop by the name of RMACC here in Phoenix that asked me what fittings I needed and made me the hose for a grand total of $45 .
All and all it's a very worthwhile venture considering how well parallel flow condensers cool coupled with the low cost and high availability and serviceability of R134a. Don't be afraid of the process it's not nearly as complicated as you might think.
You should also, if possible of course, consider the safety of replacing the low pressure cut out with a binary high/low switch.
I'd be happy to help guide anyone along with this process with vendor names and addresses if needed. Don't hesistate to ask!
