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Old 10-11-09, 02:58 PM   #31
AC_Hacker
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Default Vacuum Unit...

Quote:
Originally Posted by Xringer View Post
Found a place locally that sells this 2-stage pump..

Robinair 15150 Vacuum Pump, 1.5 CFM, Two Stage, 110V

Robinair 15150, 15300, and 15500 1.5, 3, and 5 CFM VacuMaster Vacuum Pump - on Sale at the Test Equipment Depot

They have a pretty good price, even with the taxes..
I think this should be a pretty good unit. If you were working at HVAC for a living, you'd want to get a paying job done as fast as possible, so bigger would definitely be better, especially so if you were working on large systems. But as it is, a smaller unit should be just fine.

The 'vacuuming times' page you cited gives times "as a guide". Since your pump will be on the smaller side, your pump-down times sould be longer, by what factor, I'm not quite sure.

...and as food for thought, I have heard that HVAC techs may, in the middle of a pump-down, close the appropriate valves, change oil, turn on the pump and re-open the appropriate valves and continue on to finish.

A manifold gauge set would give you the valves to do this.

* * * *
Should you need to make up some special fittings, just to save you some grief, I'll share a lesson from a previous experiment. I needed a very small valve to manually control refrigerant flow, so I went to my local big-box retailer and got a needle valve that had compresson ring fittings. I hooked it up, torqued it appropriately, went on with my work, only to watch the compression ring fittings leak like like crazy. My guess is that they were meant for non-refrigerant use, like water or something, and when the rapidly expanding refrigerant hit them and chilled them to some ungodly low temperature, the copper shrank away from the compression ring. I mean I really had a mess on my hands!

Only use brazed fittings (although they refer to these as 'sweat fittings' in the trade, don't be fooled into thinking that you can sweat solder them), or flare fittings.
* * * *

Best Regards,

-AC_Hacker

%%%%%%%%%%%%%%%%%%%%%%%%%%%%


Last edited by AC_Hacker; 10-11-09 at 03:18 PM..
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Old 10-11-09, 04:11 PM   #32
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"...and as food for thought, I have heard that HVAC techs may, in the middle of a pump-down, close the appropriate valves, change oil, turn on the pump and re-open the appropriate valves and continue on to finish."

I was doing some reading on the topic too. Read about people doing 3 pump downs.
Go full vac, fill up with dry air or Nitrogen and repeat three times,
ending with a vacuum.

And, just about everyone says to change the oil before each use..

~~~

Also read about using a micron gauge. One guy had three of them and they all gave different readings.
Another fellow said they were a luxury that you really didn't need,
and spend your money on a good manifold and a good pump and keep it good shape.

I guess that pump is the one. Now I need to look for a good R410A manifold.
Are the fittings going to be compatible?? Or will I need an Adapter?
R410a Adapter KIT Sanyo, Panasonic, Mitsubishi, Fujitsu - eBay (item 400033059094 end time Oct-20-09 17:27:17 PDT)
1/4" Male flare with Schrader valve x 5/16" also known as 1/2"-20 UNF Female.

Thanks!
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Old 10-11-09, 05:23 PM   #33
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Default Robinair 15150 is on the way!

Robinair 15150 Vacuum Pump, 1.5 CFM, Two Stage, 110V $141.89
Subtotal $141.89
Shipping & Handling $0.00
Tax $8.87
Grand Total $150.76

I was kinda surprised to see the 15150 in a local e-store for this price.
I looked at about a dozen other sites and most were $50+ higher.

Now, I need to find a local AC supplier where I can buy some pump oil..
Oil Capacity: 7.5 oz. (220ml)!

Edit:
That was fast! Ordered on Sunday and I just got a shipping notice today (Monday).
It should be here tomorrow.

Last edited by Xringer; 10-12-09 at 05:45 PM.. Reason: Update
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Old 10-13-09, 02:13 PM   #34
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R410A Refrigerant Gauges W/ Hoses & Manifold - eBay (item 290357569109 end time Oct-13-09 11:05:24 PDT)

R410A Refrigerant Gauges W/ Hoses & Manifold
R-410a air conditioning gauges !!!W/ SHUT OFF HOSES!!!

Are on their way.. (I hope)!

Edit:
The pump came this afternoon, and it looks pretty good.

Last edited by Xringer; 10-13-09 at 04:33 PM.. Reason: adding pic
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Old 10-13-09, 06:37 PM   #35
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Default cute pump!

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Originally Posted by Xringer View Post
The pump came this afternoon, and it looks pretty good.
Wow! Cute pump...

As I recall, I bought one R-410a adapter from my local HVAC supply house. That was all I needed to be able to use my exusting tools.

So you're just about ready to go.

Regards,

-AC_Hacker
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Old 10-13-09, 08:47 PM   #36
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Yeah, the pump matches my Ford Escape..
I'm almost ready, but have no way to really know if the vacuum really low enough. Still looking into that problem.


Was that R-410A adapter one of these?
R410a Adapter KIT Sanyo, Panasonic, Mitsubishi, Fujitsu - eBay (item 400033059094 end time Oct-20-09 17:27:17 PDT)


Thanks,
Rich
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Old 10-13-09, 09:35 PM   #37
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Quote:
Originally Posted by Xringer View Post
Was that R-410A adapter one of these?
Yeah, it was, but it was just the adapter, and not the whole kit thingie. However, I paid the same amount.

BTW, you mentioned that the local supplier wouldn't sell to you, have you tried other HVAC outlets in your area? I found that here, some would sell to a non-pro, others would not, and others had a work-around that if you paid at a particular store, they'd give it to you when you brought proof of purchase.

Regarding the local supplier that was the most helpful, I found that they did not 'suffer fools lightly', and that they'd answer a few questions per visit, but didn't see themselves in the public education business. So I researched as much of the info as I possibly could on my own and only prevailed upon them for the really tough stuff. They came to understand the scope of my project and were guardedly amazed at what I was trying to do. I also think they even got a kick out of seeing how fast I was absorbing such a broad area of trade-lore.

Good luck,

-AC_Hacker
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Old 10-13-09, 10:30 PM   #38
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Okay thanks for the info! I also just got the word on my new R410A hoses.
They are regular 1/4", so the adapter converts it to 1/2" ACME Male-20UN on the Sanyo.
I just 'won' one on Ebay. Be here in a few days.


Questions? I've got a million of them and very little time before the snow
starts coming down!
I know about asking some of these guys too many questions.
Now when I go in to buy parts for my heating system, I know exactly
what I need, and they don't ask me where I work.


Installing this Sanyo doesn't look near as difficult as adjusting the
valve clearances on a 1999 CRV for the first time ever..

I'm not too worried about problems. I have a couple of guys on-call if I get in too deep..
I just don't want to have to make that call.


Edit:
I just found something at Sears.. It looks just like what I needed.. for a few bucks less.
http://www.sears.com/shc/s/p_10153_1...ord=Mastercool

Last edited by Xringer; 10-15-09 at 04:36 PM.. Reason: Sears
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Old 10-14-09, 11:47 AM   #39
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Quote:
Originally Posted by Xringer View Post
Questions? I've got a million of them and very little time before the snow
starts coming down!
I think you're gonna do just fine. You've crossed every 'T' and dotted every 'i' that I know of...

Something you might do though, since you have so many new pieces of equipment, you probably already have a coil of copper tube left over from some previous project. You might want to fold and braze (or solder in this case) one end and put a 1/4" flare on the other, or better yet, if you can find one local, a 1/4" Schrader valve (standard refrigeration part), and do a couple practice pump downs on it, just to get the feel of the process.

I had already kludged together my first heat pump before I installed my Sanyo, so my confidence was fortified just a little.

If you decide to do this with a Schrader valve, the valve core is identical to a car tire valve, and has rubber seals. Make sure to remove the valve core before you solder or braze and do not re-install it until everything is cool to the touch.

* * *

I've been mulling over in my mind what you said previously:

Quote:
Also read about using a micron gauge. One guy had three of them and they all gave different readings.
Not quite sure what he meant by "they all gave different readings", but almost all of the micron gauges today have numerical digital readouts, but they have analog sensors, and there's going to be some variation there. Also, modern micron gauges have a glass bead sensor that can become fouled, but is easily cleaned.

I think that digital outputs can lead people to expect a level of absolute accuracy that may not be warranted. Digital gauges are popular because they have become cheaper to manufacture than analog in some cases, and they are usually easier to read.

One weakness of a numerical digital gauge is being able to convey the nature of variation of the system under measurement. Is there a rythmic swing in voltage, current or pressure? This could be important. If the settling time of the gauge is long, you might never get a sense of the nature of the variation.

Regarding micron gauges, this variation isn't so important, so a numerical readout is appropriate.

But if the person in you cite had three gauges and one read 300 microns, another read 335 microns and another read 400 microns, they're essentially telling him the same thing. If the spread was 70, 115 and 1500, that's a whole different story.

Quote:
Another fellow said they were a luxury that you really didn't need...
I'll never forget the time I was in New Orleans, talking to a local Cajun guy who had just cooked up a great Etuffe. I asked him how he made it, and he said, "Well, you make you some roux, and fry you up some chicken and vegetables to your likin', and flavor it up 'til it tastes right." If I had grown up in Louisiana, and had eaten Cajun food all my life, that would have been enough information for me to make Etuffe. But since I hadn't, "...flavor it up 'til it tastes right", had no meaning to me.

So there's the possibility that after 20 years in the trade, you really don't need that luxury.

There's also the possiblity that his installations lasted past warrantee, but not much more.

* * *

The manifold gauge set is primarily designed to give you information when about what's going on when you are charging a system. It will simultaniously read the pressure of the high side of the system and the low side of the system, and show you if there is abnormal variation happening. Their best accuracy is at mid-scale and they are designed so that the proper levels of charge pressure occur at mid scale.

But the manifold gauge set will not tell you if you've vacuumed low enough to allow for the removal of water. The accuracy is simply not there.

If you have a new pump, with fresh oil, you're probably ok. If your gauge, whether it is a single gauge or a manifold gauge set, is new and with good seals, you're probably ok. If your hoses don't leak, you're probably ok. If you've screwed your fittings down properly, you're probably ok.

But even with twenty years experience, unless you measure your vacuum with a gauge that is designed to measure deep vacuum, you really won't know for sure.

I installed my Sanyo without a micron gauge, I'm probably ok. But in fact, I'm not completely sure.

If I were doing it again, would I leave my micron gauge sitting in my tool box while I was installing a brand new mini-split heat pump?

I think you know the answer.

Quote:
...spend your money on a good manifold and a good pump and keep it good shape.
My advice to you would be to get a good micron gauge, and a cheap (or used) manifold gauge, make a test setup and measure the gauge set to see just how good it is.

...but then, "I'm not an HVAC tecnician, in fact, I'm just barely a hacker."

Best regards,

-AC_Hacker

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Old 10-15-09, 10:55 AM   #40
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Dang! The Sanyo is still on backorder! ETA unknown!

The manifold set and adapter should all be here this week.
Perhaps I can do some testing on the hoses and make sure they are tight.

I've been wondering about making a bell-vacuum jar experiment.

I would build a little tube made of heavy clear plastic with caps and a 1/4" fitting.

Put a drop of water in the tube, pump out the air and watch the drop.
If it quickly vaporizes, not leaving a trace, the vacuum is pretty good.?..

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