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Old 06-05-2011, 10:50 PM   #1
Techniker
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Default Auto AC Vacuum Pump Recommendations

I've read a few posts and reviews both here and online, and I'm actually very surprised by the lack of HVAC tutorials out there.

Anyway, I've recently acquired my EPA license and have started working on automotive AC systems. I just bought my first AC manifold gauge set (Robinair) and have used it for diagnostic work. I have an AC system I am set to repair and recharge this week, but in order to confirm the fix (and draw air/water out of the system), I need a vacuum source. I've decided on an electric vacuum pump since I do a fair amount of mobile work on the side. Now my question is, which vacuum pump? I want one that is going to hold up to a little more work than that used by a shadetree mechanic (I plan on using it at least once a week and I want to be able to pull vacuum for an hour without worrying about burning up the motor).

Does a two-stage pump really give that much of an advantage over a single-stage pump for automotive AC work? I am currently looking at the Robinair ROB15150 1.5 CFM two-stage vacuum pump as well as both of the HF pumps (they have a single-stage and a two-stage version).

What concerns me is that, though the HF single-stage pump receives excellent reviews, they say it does loose a lot of oil but they go on to say that this is normal for a single stage pump. Is this true and does this not happen with two-stage pumps? How well do the HF pumps hold up? Would they withstand an hour's usage once a week or would they crap out after a month or two of this?

Your help is greatly appreciated,
Techniker
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Old 06-05-2011, 10:58 PM   #2
bartels_metal_works
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Default Re: Auto AC Vacuum Pump Recommendations

I know nothing about vacuum pumps especially for HVAC but I just ended up with this one. Does it take a special type of pump to do HVAC work?
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Old 06-05-2011, 11:09 PM   #3
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Default Re: Auto AC Vacuum Pump Recommendations

We use a two stage 3CFM unit from Napa at our shop. It works fine for the limited amount of A/C work we do, enough that we don't sublet it, not enough that we have felt the need to buy a standalone machine.

I think it was somewhere around $150, and it's been in use for three or four years now with no problems.
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Old 06-05-2011, 11:15 PM   #4
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Default Re: Auto AC Vacuum Pump Recommendations

Robinair makes a fine vacuum pump. You can earn a living using one. I wouldn't
get an HF pump, its wasted money if it fails. You lose time swapping it out, the
customer waits, nobody wins there. 2 stage pumps are for deep vacuum but a
single stage pump can be faster. Bigger is better (faster).
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Old 06-05-2011, 11:19 PM   #5
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Default Re: Auto AC Vacuum Pump Recommendations

Gast pumps are pretty good and vastly available, some times you can find one for less than 100 on ebay. I heard Yellow Jackets pumps are good, too.

we have few Snap On pumps at school, they are absolutely abused and beaten to death by the numb nuts, they just refuse to quit.
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Old 06-05-2011, 11:57 PM   #6
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Default Re: Auto AC Vacuum Pump Recommendations

FJC and Mastercool also make good vacuum pumps. The FJC is more of an economy brand. I've had my 2.5 cfm FJC for about 6 years and have no complaints. No matter which brand you choose keeping the oil changed and filled is very important. Two stage can pull a higher vacuum but is not really needed. I use a micron gauge and pull down to 500 microns normally. Most single stage pumps are rated at 75 microns at sea level and 2 stage are rated at 25 microns. 1.5 cfm and up should do the job on automotive AC.
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Old 06-06-2011, 05:20 AM   #7
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Default Re: Auto AC Vacuum Pump Recommendations

I would definately get a two stage pump. I personally have a two stage 6cfm Robinair due to working on large systems on trucks and busses. For car use I would get a Mastercool or Robinair, which ever has the better deal and ratings for the size pump you are getting. And remember to change your vacuum pump oil often.
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Old 06-06-2011, 06:08 AM   #8
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Default Re: Auto AC Vacuum Pump Recommendations

Wrong season to buy anything AC related used, and if you are going to be making money with it you can't really skimp on quality. OTOH do you have the budget for EVERYTHING you need to get started? Line wrenches, precision scale, recovery system, leak sniffers, and all the tools needed to replace any part of the AC system?

Are you going to be working for anybody that might be supplying some of these tools?

If money turns out a little tight maybe the HF isn't that bad of an option.
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Old 06-06-2011, 06:53 AM   #9
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Default Re: Auto AC Vacuum Pump Recommendations

The recovery system is your biggest hurdle unless you will only do empty systems or sublet every system that has even slight positive pressure.

Now here is the trick. Get a nitrogen tank (small) with a low side adapter or gauge adapter. A small amount of r22 (4oz or so) and then nitrogen. This makes leak detection a bit easier whther you are bubbling or sniffing. A whole bunch of people are freaking out "whoa whoa whoa, you can't introduce r22 into an automotive system!!!"

Yes you can, and there is no worries of it getting mixed into your other refrigerant since the epa LEGALLY allows you to discharge this small"diagnostic charge" quantity of r22 directly to atmosphere, even with standard vacuum pump.

benefits:
*cheaper than r134 for diagnostic charge
*legal to vent w/o recovery equipment (in specified quantity, and only when drawn more than 4" vacuum)
*breaks up surface tension of residue coating along piping (solvent type action), making detection easier
*easier detected by sniffers




Now you are thinking "how many times would I actually need such a setup" and I will ask "how many times have you dealt with/heard of a leaking ac system? "
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Old 06-06-2011, 07:57 AM   #10
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Default Re: Auto AC Vacuum Pump Recommendations

I am currently leaning toward the Robinair two-stage vacuum pump since I can get it for only about $20 more than the single-stage HF model and actually $3 less than the HF two-stage pump. Thoughts?

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Old 06-06-2011, 02:17 PM   #11
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Default Re: Auto AC Vacuum Pump Recommendations

Just to add my two cents, I have the HF 2 stage and it's a great pump. Very strong, quiet and runs cool. I'm not a pro, however, so I don't know how it would hold up day in and day out.

That being said, if you can get a two-stage Robinair for the same amount of money, get the Robinair.
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Old 06-06-2011, 08:43 PM   #12
Techniker
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Default Re: Auto AC Vacuum Pump Recommendations

Tragic news everyone- Advance Auto had the best price on the pump...and the factory doesn't have any in stock! So much for that- I'm trying to keep my absolute max price at $120 right now, so I am considering a Mastercool Single-Stage Pump. Thoughts on Mastercool? I know they make good AC manifold gauges.

Thanks again,
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Old 06-06-2011, 09:02 PM   #13
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Default Re: Auto AC Vacuum Pump Recommendations

my buddy bought his own acr2000 a few years back , 2 grand
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Old 06-06-2011, 09:07 PM   #14
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Default Re: Auto AC Vacuum Pump Recommendations

Whatever pump you end up using, make sure to change the oil regularly.
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Old 06-06-2011, 10:18 PM   #15
83diesel
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Default Re: Auto AC Vacuum Pump Recommendations

Now here is the trick. Get a nitrogen tank (small) with a low side adapter or gauge adapter. A small amount of r22 (4oz or so) and then nitrogen. This makes leak detection a bit easier whther you are bubbling or sniffing. A whole bunch of people are freaking out "whoa whoa whoa, you can't introduce r22 into an automotive system!!!"

Yes you can, and there is no worries of it getting mixed into your other refrigerant since the epa LEGALLY allows you to discharge this small"diagnostic charge" quantity of r22 directly to atmosphere, even with standard vacuum pump.

benefits:
*cheaper than r134 for diagnostic charge
*legal to vent w/o recovery equipment (in specified quantity, and only when drawn more than 4" vacuum)
*breaks up surface tension of residue coating along piping (solvent type action), making detection easier
*easier detected by sniffers

How is R22 cheaper than R134a? Have you priced them lately? It does detect leaks easier
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Old 06-07-2011, 01:47 AM   #16
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Default Re: Auto AC Vacuum Pump Recommendations

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How is R22 cheaper than R134a? Have you priced them lately?
Sure have! R22 is $226 locally, r134 is $240. Other places the price different may be even greater. Hear some places get more than $300 for 134a.
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Old 06-07-2011, 08:19 AM   #17
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Default Re: Auto AC Vacuum Pump Recommendations

Around where I am at, I can get R22 and R134a for about the same price (give or take a couple of dollars)... $200 for 30lb.
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Old 06-07-2011, 08:27 AM   #18
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Default Re: Auto AC Vacuum Pump Recommendations

Maybe I should jump on that then. Here, R12 is about $240/30 lbs. I can get R134a for $140-$160/30 lbs.

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Old 06-07-2011, 11:12 AM   #19
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Default Re: Auto AC Vacuum Pump Recommendations

regardless of r22s actual price, it serves as a diagnostic aide when mixed with nitrogen. You don't have a recovery machine, so if I bring an empty system to you in need of charge, you would have to charge it up with 134a, hope to find leak before it leaked out, and then if some is still left, deliver my car to a shop to be evacuated, and then you recharge again. If you are lucky and fixed all the leaks the first try, that is it. If it is still leaking, you get to take it back to the shop and pay to get it evacuated again.

Of course, it is physically possible to just vent the full system charge to the atmosphere, but we are talking about professionals here.

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