I've always done a/c work with a robinair machine which took a lot of the work out of fixing a/c. I'm now looking at buying a vacuum pump and gauges for the service truck. Is a 4 cfm 1/3hp pump big enough? also do you guys use a scale and a tank of r-134a or just the 12 oz cans? any recommendations on equipment? I've seen gauges from $39.95 to 300. don't mind spending the dough I just don't want to waste it. thanks and yes I know its February, not july
im no expert but i when i use a vacuum pump i check to see if it could make enough vacuum to boil water at room temp. not sure if it that big of deal but the way i see it if it boils water at room temp them it should be able to pull the moisture out of the system more efficiently my guages are from napa they were like 100 and i have no complaints thus far
I do a lot of a/c work 4 cfm will be plenty and I use a tank and scales its to much trouble to haul a bunch of cans
I got lucky and found a vacuum pump at auction for $5. I don't have a scale just guess for now but I should get one. I think I got my Gage's from napa about $100. A lazer tem gun helps for trouble shooting.
I have Napa gauges as well. The ends that it comes with are not the best, but the gauges are fine. I use a $15 Harbor Freight air-powered vacuum pump. Pulls 28 in. just fine. For someone that is going to work on A/C everyday, you should have a good scale. I just have the equipment to be able to fix a leak, or add a can if needed.
Buy a keg or 2 of juice. I get a 30lb for $75 this time of year. Summer they are over $100. A nitrogen cyl. to find leaks is also mandatory. I suppose you could use the clean dry air from a torch set also. Plug er in and spin the regulator till something pops or you hit 300psi!
NO! Do NOT use oxygen from a torch set! Good way to kill yourself or someone nearby when the pure oxygen causes a flammable lubricant to explode inside the AC system! Just my $.02, better safe than sorry. Nitrogen is CHEAP, used to run air wrenches off tanks of Nitrogen in the local circle track pits.
I know about using nitrogen and I have 3-4 years experience on a/c, I've just always had a machine to use. I'm more interested in getting set up to do a/c with a pump and gauges.
From my basic welding class in college, I remember the instructor telling us just one drop of oil into the cylinder side of a regulator could be a deadly mistake. DO NOT use pure oxygen from a torch tank. I think they almost give cylinders of nitrogen away.
any set of gauges will work!!! a GOOD QUALITY scale is a must have, that's why the mfg puts the tag on it that says how much is in the system.. 4 CFM is plenty on the pump. the big difference on gauge sets is the 2 or 4 handle set, & the quality of the hoses.. I have 4 sets 2 on the truck & 2 at the shop.. I like the longer hoses ( 5') so it will reach the pump or cyl of Freon ( I use the 25# cyl of Freon).. I will also add use nitrogen with a regulator to pressure the system!! NEVER USE OXYGEN TO PRESSURE TEST ANYTHING UNLESS YOU WANT TO KILL YOUR FOOL SELF!!! another nice addition is a vacuum gauge that way you can be sure the moisture is out of the system. im not talking bout a compound gauge that comes on the manifold either!! separate electronic that ties into the top of the vacuum pump..
What chemical reaction takes place between the oil and O? I play with large amounts NH3 all the time. I know about do and do nots at the proper time in the reaction. Its only dangerous if you dont know what will happen.
Statements like that is what gets people killed and injured. Take a look at this video. https://www.youtube.com/watch?v=9lw_fhNAIQc There hundreds of documented examples of the perils of oxygen and oil accidents that had disastrous results.
That was just plain stupidity to loosen a fitting on a pressured up vessel. No oil involved. Also lack of training. Back to the oil and a/c To get a reaction you would need a ignition source first. Second the flash point of oil is pretty high unless atomized (will happen when a line breaks) I understand that straight gas O is a oxidizer times 3 I also understand that most people can not differentiate between a educated controlled risk and shaking hands with danger. It's safer just to put it all in the danger category.
An educated controlled risk in my book is working on live wiring, or cutting an oil tank, or working on a running engine. If you're "educated" there are ways to control the risk. Pressure testing with Oxygen OR Acetylene is always just plain stupid. "ignition source" and "flash point" at normal atmosphere are irrelevant when using pure pressurized oxygen. Lots of other gasses available if you don't want to carry a nitrogen cylinder.
That's the point, Oxygen is an oxidizer, and the higher the pressure, the faster oxidation occurs, to the point where anything flammable, especially liquids, will self ignite from the heat of the oxidation. Oxygen creates it's own ignition source, violently. It's not a controlled risk, it's more like Russian Roulette.
Yes, lantraxco is absolutely correct, oxidization creates its own heat. Heat is a byproduct of all oxidization processes. Rusting is an oxidization process that is used in hand warmer packets using an oxidizer with a very fine iron powder. Given an oxygen rich environment effectively lowers a combustibles flash point.
I would also bet that the person in the video and the people in most all the other accidents that happened thought they knew what they were doing.
leak if you have a leak you need to bring down to complete vac to make sure no moisture in system before topping up other wise your doing it wrong
anybody ever try one of these? http://www.mile-x.com/mastercool-69110-automotive-a-c-recovery-system/
Looks good, I'd sure like to try one!
Well said, Lantraxco. As a fire fighter, we learned right away the fire triangle. Fuel, air, heat. From the other posts, we know about pure O² properties as an oxidizer. My other point, I have never seen an oxygen regulator that doesn't have the words USE NO OIL somewhere on it, or the gauges.
Yes Mike, I have one of these, it works very well, it replaced my Robinair unit that I had for 14 years
right now I've got the Robinair 34788 on my truck. does it work the same way? hook it up and let it go? I tried to find a video on youtube but didn't have any luck.
no I don't think it has a built in scale
mike I do a lot of AC work on equipment.. most of the recovery machines work on the same idea, hook up it pumps liquid Freon out first then the vapor into the recovery cylinder, down to a vacuum.. when the first recovery machines came out they were BIG & expensive, now days they r still expensive but have gotten a lot smaller & more powerful. I have a buddy that bought that unit last fall & has had very good luck out of it so far.. if you have any questions ill b happy to ask him,
I have the Robinair one. It is simple enough to use and had it for ten years. Even with the bricks I work with, it still is very dependable. The one you listed Mike looks good, also had he recovery tank.
A quick question. What pressure does everyone go up to when looking for leaks. I had trouble with a few machines lately where I show and the there is little no gas in the system. When I pressurise and try to find the leak I can't find anything. I have only been going up to 110 psi or there about as I don't know if it was good to put to much pressure in the low side. So what does everyone else do. Cheers
He's what happens when there is a drop of oil in a oxygen regulator. I replaced the high pressure gauge with one I had in the drawer. Obviously I must have used it to check hydraulic pressure before. I turned on the tank and it hit me right in the eye. Luckily for me not in the center of my eye and only bruised it. It almost blew it out of the threads. I've read just a piece of dirt can cause this. The best advice is to look away from the gauges EVERY time you turn them on. Every one stares at them when turning on.
I usually don't pressurize higher than 50 lbs and then use a lot of soapy water. I also unhook my nitrogen tank and check the shrader valve on the coupler for leaks. I had one leak there but had hell finding it cause I had the tank hooked up.
I go to 300 psi on the nitrogen charge. My tech teacher said it was fine. Ive seen high sides at 400 psi so why not. The pressure it what will find it quick. Had a hose leaking slightly on the low side that took a while to find. Nitrogen found it real quick.
X2... it wont hurt anything at that pressure!!
In the rough and tumble world of field work an air powered vac. works well,I know they're noisy but they're durable and won't leak oil if overturned. I have never used a scale only charged them to good gauge readings. Most of the beaters I worked on had no tag or were a Red Dot shop install so a scale was never on my radar. My old Mac gauges are 15 years old and still going, just don't use em much in my new job.
Yep, guy that used to do all my work had a scale and used it if the spec was handy, but all my stuff he did by the gauges and a pocket thermometer stuck in the outlet air flow. Never had any complaints
It's better if you have a thermocouple to measure superheat/subcool but use pressure alone if you have to...however if charge weight info is available and you have reason to suspect it is correct, then use it I say. I have seen some strange things happen when trying to charge by gauges alone, and then you have to be concerned about compressor floodback.
I always test with Nitrogen to 250Psi
I had one of those compressed air vac setups and it went to hell on me for some reason?? So I bought a 3.5 or 4 cfm Matco vac pump.....way better. Faster and pulls more vacuum. I've just got an old set of Matco gauges, a pail of hot water, a 30lb keg and a 60lb feed scale. Haven't had any complaints. Though hearing more about this nitrogen for leak tests makes me think I should at least try it...