HVAC Vacuum pump question
 

I purchased a vacuum pump to use when installing a new mini-split.

http://ecorenovator.org/forum/projec...project-4.html


And tonight I'm looking at different vacuum gauges when I find this:

FAQ - Vacuum Gauges

"When I hook up the VG64 to a new vacuum pump and isolate the pump, I get an initial reading of 440 microns and then a quick rise to 1200 microns? Always use vacuum hoses not charging hoses as they permeate and leak. Also new hoses have gas in them, so they must be gassed out. If this procedure is not followed, the gases in the hoses will cause a rise in vacuum readings once the vacuum pump is shut off."


My hoses are clearly marked as charging hoses, but have cut-off valves.

http://ecorenovator.org/forum/projec...project-5.html

~~~

So, this is my plan.. Once the pump has done it's work, and we have
what we hope to be a good vacuum,(29.9"?) I should be able to shut off the
hose, right at the service port (isolating the line-set) and let vacuum do it's thing inside the line-set tubes.


After waiting for a while, I'll turn the pump back on and wait until it shows
29.9" again, then open the hose valve. (The hose and line-set pressure matches?).

IF, the line-set was still holding a good vacuum, the gauge needle should not drop at all.
If it does, due to out-gassing, I'll keep repeating the process until there is no drop..

That's the best plan I can come up with.. Any of you guys have any suggestions?

Thanks,
Rich

Found this http://www.thermalengineeringcompany...appliances.pdf

and after looking at the chart on the second page, I think maybe I'm on the right track. They did 5 pump downs in about an hour. The last one was great.

Great Info...
 

Xringer,

This is great info. It went straight into my library.

You know, for an old man, you're pretty relentless...


Best Regards,

-AC_Hacker

Haha!
I've been bidding on Ebay gauges, but no luck so far.
Even the old ones go for pretty big bucks.
Vak-Check 4501 Thermal Engineering Vacuum Gauge - eBay (item 180420368808 end time Oct-22-09 19:08:15 PDT)

http://img.auctiva.com/imgdata/1/0/8...97155928_o.jpg

I've read a few good reports on this old model. And it's still being made,
I think..

This looks like an early micron gauge. You may want to check around some of the blogs to see if any info about this model gauge pops up. It looks like you go through some kind of manual calibration before you use it. Not such a bad thing but the digital ones do this automatically.

As I recall, I got my micron gauge new, from a local supplier for $130. I'm not seeing any on ebay that cheap.

When I was shopping on ebay for a mini split, they were more expensive than from an online dealer.

It pays to shop around.

Regards,

-AC_Hacker

Supco VG60 Portable Hand-Held Vacuum Indicator Gauge
 

I did check it out on the web and found some good reports.
That used 4501 went for $95.30 last night.

I'm reluctant to spent that much, since these;
http://www.kaeltetechnik-shop.at/bil...oss/5934_6.jpg
are available New for $114, and one of these might be suitable for my needs.

What model did you buy?

Oh yeah, yesterday I picked up some fittings that I can use to make
a micro Bell-Jar experiment. I'll mess with that today, since my
3 quarts of RobinAir vacuum pump oil is coming in today.

Yeah, I saw these, I like the simplicity. It should work just fine, for a long time.

Here's the one I got:


It works fine for me. I came across some blog-opinions that were less than glowing, but I'm still satisfied.

So, what are you using for the micro bell jar?

I met a very interesting inventor/designer/wood worker/machinist the other day who made a small (vol = 1 ft cube) vacuum/pressure chamber for various projects. I'm not exactly sure how he's using it but it intrigued me.

Regards,

-AC_Hacker

I just used a couple of brass fittings to allow me to drop in a couple drops of water and pull a vacuum on it.

It works great! It sure looks like this pump is going the job.. To some extent.

http://ecorenovator.org/forum/projec....html#post4519

It was neat to feel the end cap getting cold as the vacuum vaporized the water.
It happens pretty dang fast, I was surprised.
I'm pretty pleased with the results. I can tell by the sound of the pump motor
when it's getting down to the last little bit of air inside the hoses, manifold etc.

I sure wish that I had a good gauge to see just how low it's getting.
But, right now I'm pretty sure this pump is suitable for this job,
even if I don't get the fancy gauge..

Since the Sanyo is going to be here Monday, I don't have a lot of time left
to be ordering stuff. Maybe I can find something local like you did..

I have had the hoses manifold under vacuum for the last couple of hours
and the compound gauge is sitting right there at 30 and not dropping.
And when I start the pump and open the cut-off, I can hear the pump
run fast for a few seconds and then go into labor as it hits the Hard work again.

I'm watching a VG200 on Ebay..
CPS VG200 DIGITAL VACUUM GAUGE,VACROMETER,HVAC,A/C - eBay (item 280413650762 end time Oct-29-09 12:18:40 PDT)
But, that thing is going to be on there for a week!
Have to check the local AC suppliers, if I can convince myself that I really have to own one of these things..

My problem is, I love gizmos.. :p

Edit:
Fieldpiece SVG2 Standalone Vacuum Gauge: FIEL18 Climate Doctors
This one looks like a more reasonable price.. I've got some local distributors to call this Monday.

I am using Robinair 15500 2-stage 5CFM VacuMaster Economy HVAC Vacuum Pump. This pump is perfect for HVAC technicians. We can easily maintain it.