Quote:
Originally Posted by Geo NR Gee
Should I keep looking?
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Well, you didn't mention the price...
Like I said, I got my two-stage pump at HF for about ($140).
I'd use that as a benchmark, if I were you.
All things being equal, the two-stage will pull a deeper vacuum.
The dual voltage thing isn't so important.
Just about all the other items are pretty much standard.
And another thing... the micron gauge I mentioned before is a tool that will allow you to actually test a used pump to see if it is worth buying.
You said your brother is in the HVAC trade, maybe he can loan you a pump and/or a micron gauge.
If I were you and had a bit of time, I would haunt ebay for a modern working micron gauge. The modern ones are pretty small and electronic, there were some older ones that were the size of a school lunch box and looked like they were Heath Kits... don't go there.
I got my micron gauge for $130... I really gulped when I did, but I had no other way of knowing if my vacuum pumps were working correctly. It turned out that they were not working correctly. That micron gauge also told me that the cheapo HF pump, that I took home as a trial, was working much better than the old pumps I had borrowed. Now, the HF vacuum pump will probably not have as long a life as the used American madeb pumps I borrowed, but I'm just not going to build that many heat pumps.
My friend that loaned me the vacuum pumps, bid a micron gauge for $60 on ebay. Petty good deal.
But getting back to the vacuum pump, if it can actually pull a vacuum of 100 microns, that should be good enough. Is it new? Is it used? How much?
If it's new and under $100, it's probably a pretty good deal.
If it's not used much and under $60, it's still a pretty good deal.
But I think that if you're going to use a vacuum pump, you should also have a micron gauge.
You should see what people who are in the trade think about this stuff, check on some off the HVAC blogs, see what they think...
That's what I did before I got my micron gauge.
I can tell you that the HVAC blogs have nothing good to say about HF vacuum pumps, but they use their equipment far harder than you or I ever will.
You might even be able to DIY a couple of refrigerator compressors in series and get some reasonable vacuum (maybe) but you wouldn't know if it's good enough without a micron gauge.
That's what I think.
-AC_Hacker