| ||
| AgTalk Home | ||
| ||
 R/D sight glass for R134AJump to page : 1 Now viewing page 1 [50 messages per page] | View previous thread :: View next thread |
| Forums List -> Machinery Talk | Message format |
shaun3480 |
| ||
Phillips Co NW Kansas | Is the sight glass serve any purpose other than seeing if Freon is flowing through the R/D? I was taught or at least thought I was that if you didn't know the systems capacity that you filled until the bubbles were gone in the sight glass. I was told today that that is wrong and with R134A you will always have bubbles. Which is correct? Thanks for all replies and help. | ||
| |||
| dave7745 |
| ||
| Depends on vapor pressure and or saturation temp....With A/C there is no liquid receiver as in refrigeration so one will see bubbles or clear at times...Always charge to specs with a scale......R 134a is zeotropic so gas can be added or topped off.. Some of these azeotropic witches brews or drop in replacements have to much glide to not pull it all out and recharge Edited by dave7745 7/16/2013 16:37 | |||
| |||
| Jon Hagen |
| ||
 Hagen Brothers farms,Goodrich ND | The sight glass in a converted system ?? What I got from a couple of AC retrofit sites that were heavily into so many conversions, said this. They said that synthetic ester oil in R134a, never blends with the refrigerant, it moves through the system as globs of clear oil, looking exactly like bubbles, so you will never have a clear sight glass with that oil and refrigerant combo. They said to ignore the sight glass, as you can be seriously overcharged and still have what appears to be bubbles. In reality it is globs of oil that is rushing past the sight glass. My best luck recharging either a top up or full fill of R134a, is to charge by vent temp. Add enough to get it working, then add a few oz at a time untill adding a bit more does not drop the vent temp. Converted my last R12 machine doing that last week. Old 92 chevy BB one ton. Has 34 degree vent temp on an 85 degree day, so I was not going to change to the blue orfice tube like was so popular back a few years ago. Edited by Jon Hagen 7/16/2013 17:37 | ||
| |||
| dave7745 |
| ||
| The chlorine in the R 12 made the mineral oil move...POE only moves with refrigerant velocity....Over charging and slugging will move it...When the chlorine was removed, we encountered stuck solenoid valves and push rods from lack of lube....If U put 134a in a refrigeration system and don't change the oil to POE..U can hear the 134a popping out of solution Edited by dave7745 7/16/2013 17:07 | |||
| |||
| olf20 |
| ||
NW ILLINOIS | I was taught that the gauges, sight glass and sweating of the return / low pressure line were all needed if you did not know the exact amount to put in. Also the hotter the day the better. olf20 / Bob | ||
| |||
| scott nelsen |
| ||
Leeds, North Dakota | Shaun agree with other posters, never looked at sight gauge, I use a scale if using 30 lb kegs, if your converting if I remember correctly 80 percent for r-134, versus R-12, correct me if I am wrong, Scott. | ||
| |||
| dave7745 |
| ||
| Sight glasses are the compressor manuf. best friend...Oh and Wal-Mart...The after market mechanic in a can ....It allows everyone to try their hand at it...If some is good. .then more has to be a lot better...Remember when all gas was called Freon...a trademark of DuPont. I've been doing it for 41 years and still am amazed at how many people are clueless as to what they are doing or why they are doing it...Some can even tell the actual pressure without gauges and diagnose the system with calibrated fingers.......Ask em to calibrate their gauges w/a refrigerant cylin....They are in total confusion Edited by dave7745 7/16/2013 19:04 | |||
| |||
| Jon Hagen |
| ||
Hagen Brothers farms,Goodrich ND | scottnelsen - 7/17/2013 17:07 Shaun agree with other posters, never looked at sight gauge, I use a scale if using 30 lb kegs, if your converting if I remember correctly 80 percent for r-134, versus R-12, correct me if I am wrong, Scott. Scott, a couple of online AC repair / retrofit sites I used to visit a lot, determined that 80% was good for automotive use, but often left off road AG or construction stuff slightly overcharged and running too much high side pressure if they had a little trash plugging of the condenser or radiator. They determined that 70-75% was about right for off road and ag stuff. This was 10-15 years ago when the epa banned new R12 manufacture and R12 was very expensive or impossible to get. At this time there were millions of old slightly leaky older R12 systems out there that the owners wanted working with this new R134a stuff. I always did my own AC work on the dozen or so rigs around the farm with AC, so I also needed badly to learn what I had to do to keep my AC units working without spending half the value of the machine on a retrofit.. I had a good set of basic AC tools and a good basic "fix your AC" book for operating theory and oil capacity specs, plus a used vacuum pump I horse traded out of another fellow. I found a couple of totally priceless AC repair sites with a friendly format much like NAT, that were operated by people in the AC repair business. As usual, 2 or 3 really knew what they were doing and were more than willing to share what they knew. One thing that smacked these guys hard, who did AC repair to pay the rent, was the cost of a retrofit. Doing it the way they were told it must be done. Early on in the R12 to R134a retrofit business, the "experts" had told these guys that to have any chance of making a R12 system retrofitted to R134a work. The "experts" assured these guys that you had to replace the compressor, as the shaft seals, O rings and internal parts would not tolerate R134a, All hoses, seals, O rings must be replaced as they would leak R134a like a seive. The dryer, no matter how new or clean, had to be replaced as it would explode internally and fill the system with garbage the instant R134a touched it. The expansion valve or orfice had to be replaced as they would not work at all with R134a. Many even thought the condensers and evaporators had to be replaced. Also had to flush, flush, flush, as the system was doomed if one drop of mineral oil remained. The result was that when some Joe walked in off the street, wanting to know what it would cost to convert the AC in the older rig, most of these guys would turn tail and walk out the door. Either deciding to live without AC or heading on down to Walmart for a $30 Interdynamics retrofit kit and a rental vacuum pump and try to do their own conversion. These guys were seeing 75% of the retrofit business walk away and it was hurting the bottom line big time. These guys quickly decided to experiment a bit to see if they could do a retrofit cheaper and still have it reliable with minimum comeback First thing they learned was that 90.9% of old compressors worked just fine with the new refrigerant. They also quickly learned that a well used R12 hose in good condition leaked very little of the new refrigerant. years of having mineral oil flow through them, had all the pores in the rubber filled with mineral oil, when R134a hit this mineral oil coating, it turned it into a tire slime like jelly that effectivly sealed the R134a leaks . If you had to replace a leaking hose, it had to be the new barrier type to prevent leaks. They also found that most all R12 type dryers and the R12 type expansion valves / OT's worked fine with R134a. These guys also found that as long as you retrofitted using ester oil that was compatable with mineral oil, you were better off not flushing, as it removed that natural mineral oil stopleak. Many did not even remove the remaining mineral oil unless the system was full of failed compressor trash, or if the Fords showed signs of "black death" or the GM's had the OT screen full of plastic from a failing compressor, or the system was naturally very marginal cooling for the application, which needed every bit of condenser / evaporator for refrigerant , and could not afford that space taken up by oil.. They found they could do a reliable retrofit for a fraction of the original estimate , so their business came back. They saved me a lot of money doing it red green style (never ever do this-----------, unless it works ;). I have done a lot of cheap but reliable AC work for myself and others, following those fellows advice. They saved me a ton of money. The last one I converted last week, was our old 92 chev 1 ton trailer puller with 454. It's tired junk, but brother needs it to pull his antique tractor toys to shows / parades. Those trucks are super tight under the hood with a 454 and tended to run hot from new. Mainly I suspect because they have a little 3 core radiator with junk like AC condenser, trans cooler , fuel cooler, engine oil cooler stacked 6 inches deep infront of the radiator. Thing often sees 240 degrees pulling a trailer in summer. We pulled the grill, aux fan, 2 oil coolers, hood latch support and tried to clean 20 years of crap from the radiator. Found no way to clean the radiator without either removing the radiator or AC condenser. Decided removing the condenser was the lesser evil. I advised brother to leave the condenser out in hope of getting enough extra air flow to keep the thing cooler, roll down the blasted windows, but brother would have none of that. My vision is so bad that I need my "owl eyes" reading glasses to read a gauge set or do any even slightly detailed work. I told brother This retrofit was going to be down and dirty, as I have no patience for stuff I have such a hard time seeing. No way was I going to take that cluttered mess apart to drain the old mineral oil. I pulled a vacuum on the system and checked for leaks. Used a can of Wallmart / Interdynamics "oil charge" that puts in 8 oz of POE oil, pushed by 2 oz of R134a, added more R134a untill the vent temp stabilized at 34 degrees on an 85 degree day. Ran the electronic sniffer over the system and found no leaks. Cools the cab like a meat locker. Now if the good cleaning only gives us a little more cooling for trailer pulling. Edited by Jon Hagen 7/17/2013 09:31 | ||
| |||
| scott nelsen |
| ||
Leeds, North Dakota | Yes played that game, I thought it was a crock myself, did as you have described, was just 80 percent as a rule of thumb, I watch gauge pressures and monitor interior temp, Scott. | ||
| |||
| Jump to page : 1 Now viewing page 1 [50 messages per page] |
| Search this forum Printer friendly version E-mail a link to this thread |
| (Delete cookies) | |
