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Old 08-13-2011, 08:31 AM   #1
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Test Equipment on a Shoestring


To do this job right, will have to measure a few things. I figure I need the following

* A thermometer
I do have
- a "Traceable" ( that's the brand name ) digital thermometer that displays Celsius or Fahrenheit to 5 digits of precision.
That's probably 2 or 3 more digits than needed. It has a four-inch long stainless steel probe.

- a cheap Chinese DMM with a type K thermocouple consisting of
a pair of wires terminating in the bare junction
- an assortment of food thermometers, both analog and digital.
- a cheap IR "point and shoot" thermometer, coming from Amazon in a few days.

I hope to measure wet bulb temp by slipping a shoelace over the Traceable and sticking it in the blast from a muffin fan.

Will I need a clamp-on thermocouple, or can I fake it by taping the bare thermocouple to the tubing with a bit of velcro tape?

* A micron gauge
This is harder to fake. The cheapest one seems to be the Fieldpiece AVG2, which is an accessory head for their stick DMM. Anybody know if this unit is easy to adapt to another DMM? I have a collection of DMMs, including a perfectly good Fluke 77, and see no reason to buy another one.

A ebay search for "vacuum sensor" turned up a motley array of items. There seem to be a lot of sensors that have octal tube sockets. I think they're standard for super-high-vacuum stuff, like for semiconductor manufacturing. Which uses far tighter vacuum than anything you'll see in HVAC. I did some work on systems like this back in the late 70's ( I was a test instrument repair tech ). First, they would use a roughing pump to get most of the air out, then complete the job with a cryopump ( liquid nitrogen or helium cooled head - the molecules hit it and just fall down ) or an oil-diffusion pump ( spray a mist of oil through a chamber, the molecules stick to it and fall down ). The vacuums were so tight that if you left a fingerprint in a bell jar, it would prevent you getting a vacuum until the fingerprint outgassed.

- JerryK

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Old 08-13-2011, 10:57 AM   #2
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Test Equipment on a Shoestring


Here's one.

http://cgi.ebay.com/Yellow-jacket-69...item3a69207975

Any particular reason you're not hiring this job out? It may end up costing more to do it yourself and there will be no warranty (on anything).

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Old 08-13-2011, 10:58 AM   #3
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Test Equipment on a Shoestring


Your 4" probe won't make good enough contact on pipe.
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Old 08-13-2011, 11:20 AM   #4
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Your 4" probe won't make good enough contact on pipe.
*** How about the type K bead thermocouple?

- Jerry
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Old 08-13-2011, 11:23 AM   #5
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They are ok.
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Old 08-13-2011, 11:42 AM   #6
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*** Yeah, I saw that one. Bar graphs don't really do it for me.

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Any particular reason you're not hiring this job out?
*** It's just Who I Am. I like to read. I like to learn about new technologies. I like to create things and fix things. I am much better with stuff than with people. People tasks like - finding good contractors.
After I put this together, I'll get a little thrill every time it comes on, because I'll know I did it myself. Brazing, measuring, repairing and building - MUCH more fun than writing big checks. This stuff tends to start out small - reading a few web articles. Then I buy a book, then a few tools - and it just mushrooms .

Many years ago, I taught myself to fix cars, because I couldn't afford one to just buy and drive. Wound up working as an auto mechanic for a year. Got interested in computers, taught myself to program - and worked as a software engineer for 20 years.

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It may end up costing more to do it yourself
*** Could be, but I doubt it. This is the SF Bay area. The cost of living is very high. Labor here is very high. Want to get your car fixed at the dealership? $210/hour. Independent shop? $150/hour. Need a plumber? $100/hour. Just last week after hours I paid a plumber $340 to pull a toilet, replace the wax ring, and reseat it. A contractor would also put a markup on the equipment itself.

[
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] and there will be no warranty (on anything
*** It will have the Jerry warranty. That is, I'll have the knowledge and tools to recover, evacuate, replace the stuff myself if it dies. Searching the web, I've seen many instances of:

* I bought air conditioner XXXXX
* The compressor died after time YYYYY
* The factory gave me a new compressor worth $X, but my HVAC contractor charged me $Y to R&R it. $Y > $X.

And there might be ways around the warranty issue. Perhaps I can pay a local contractor to come out and inspect it and sign off - with the understanding that he would have no actual repair responsibility.

- JerryK
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Old 08-13-2011, 02:32 PM   #7
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Test Equipment on a Shoestring


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*** Yeah, I saw that one. Bar graphs don't really do it for me.
Jerry, I wish you all the best in your project.

I don't particularly care for the "bar-graph" vacuum gauges either, just thought I'd throw that out there for ya because it's about the least expensive option that will get the job done.
To be honest, there are a lot of AC systems installed without the use of a vacuum gauge that work fine for years and even decades.
A vacuum gauge isn't something that will take the place of proper installation procedures, it's just a tool that helps ensure that the system has no leaks and no non- condensibles. For you it would mean "peace of mind" that the system is at least not going to lose the charge due to a leak.

Here is a picture of some of the tools I use at home on my own systems and on family and friends systems.



On the left is a Welch Duo-Seal, Model 1400 vacuum pump, to the right of that pump is a Victor Oxy/Acetalyne torch kit.
To the right of the torch is a J/B DV-85N 3CFM vacuum pump. Hooked on the handle of that vacuum pump is my J/B DV-22N digital vacuum gauge. In front of the torch is a UEi DT200 dual K-type temp probe (not top of the line, but accurate and rugged).
In the foreground is my Thermal,. model 14571 analog thermistor vacuum gauge.
Directly in front of the Welch pump is my nitrogen regulator for purging linesets. The gauges I have pictured are a set of J/B R-410A and Y/J R502/R22/R12 analog gauges.
I propped a tube of 15% silver solder up against the torch kit. That is what I use most for brazing linesets. I also keep a couple sticks of the orange flux coated rod for making copper to brass connections.

These are just some of the tools I keep at home. Most of the good stuff is at the shop.
Some of these tools were Ebay purchases and were very, very good values.

Again, good luck and let me know if you have any questions.
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Last edited by fabrk8r; 08-13-2011 at 02:35 PM. Reason: Can't speel or punctuate!
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Old 08-13-2011, 02:50 PM   #8
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For your pipe clamp thermocouple. Put the thermocouple on the pipe and use double sided velcro to hold it to the pipe. For vacuum gauge supco makes one with led's. I would rather have new permiated hoses, and seals, if I had to skimp on a few things. And I have.
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Old 08-13-2011, 02:52 PM   #9
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Don't forget to check the pawn shops. Lots of goodies in those places. Try a local shop, the chain pawn shops don't have anything but tv's and electronics.
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Old 08-13-2011, 04:25 PM   #10
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Not sure if a muffin fan has enough velocity to give you a good WB reading. I hook my thermometer onto a room fan and crank it up.
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Old 08-14-2011, 12:03 PM   #11
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Jerry, I wish you all the best in your project.
*** Thank you. I am itching to get started. We are scheduled to close later this month. I cannot in good sense spend large amounts of money on this until my name is on the deed. When that happens, I will drop
the hammer on a lot of stuff. I will order a 2.5 ton condenser, a bottle of R22, a short lineset, etc etc, plus whatever tools I need to restore the upstairs AC. The downstairs system will wait a bit... not a shortage of $$$ but rather of time. There are only 24 hours in a day. I will pull a permit as an owner/builder for the HVAC.
Somewhere I have a brand new Robinair charging manifold that I bought at a garage sale. Damned if I can find it though. If not, I'll look forward to buying one of those too. The manifold that I use for cars is just crap, and I'm not going to risk this project on it.


Quote:
Originally Posted by fabrk8r View Post
I don't particularly care for the "bar-graph" vacuum gauges either, just thought I'd throw that out there [...]

To be honest, there are a lot of AC systems installed without the use of a vacuum gauge that work fine for years and even decades.
*** Installed by persons who are confident in their work. As a one-time
project, I prefer to have every assurance. It's worth the $80 for a micron gauge. At this time, I am leaning toward the Fieldpiece AVG2. Doesn't have any display at all, just a 0-2V output to an existing voltmeter.

Quote:
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Here is a picture of some of the tools I use at home on my own systems and on family and friends systems.
Nice. I especially like the old-style vacuum pump at the left. I used one like that for doing an R134A conversion on an old Mercedes It had come to me with an engine swap and half of the AC hoses missing.

Thank you very much for your help.

- JerryK
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Old 08-15-2011, 09:28 AM   #12
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OK,

This morning I ordered a Fieldpiece AVG2 micron gauge head. Also a
Mastercool ratcheting tubing bender. So will be ready to put this system together with minimum joints, and evacuate/test it properly when it's done.

- JerryK
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Old 08-15-2011, 09:44 AM   #13
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Great! Let us know how it goes.
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Old 08-15-2011, 09:46 AM   #14
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I have probably passed the point where I "save money" by doing it myself. The cure for that is simple: I will avoid adding it up .

- JerryK
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Old 08-15-2011, 10:18 AM   #15
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wait till you get our bill for the advice. LOL

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