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Old 08-08-2011, 12:11 PM   #1
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DIY HVAC Progress


Hello,

OK, we're really buying this house with the missing HVAC. Gearing up to DIY:

* I took the EPA tests - passed all four of them. The EPA material was a decent introduction to the subject, but there clearly is more to learn.

* Ordered a copy of "Refrigeration & Air Conditioning Technology" by
Whitman etc. This seems to be the book one might use in a community college course.

* Read through an HVAC course created by the US army:
http://hvacr-resource.com/Army_HVAC_Study_Course.html. A fun read, although a lot of it seemed obsolete or not applicable. Everything from shaded pole motors to design of food storage facilities. Did you know that you can be killed by CO2 gas given off by large quantities of potatoes?

* Ordered a pound of "Sil-Fos 15", so I can practice brazing. Don't envision any problem learning to do this: I already gas weld, TIG weld,
MIG weld, and do electronics soldering. Can brazing be practiced with plumbing pipe, or do I need to get the ACR stuff?

- JerryK
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Old 08-08-2011, 01:19 PM   #2
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if you want to get good at it go to your local metal scrap yard and see if they have a trashed AC condensor. then open it and unweld the compressor and try reinstall it. if you can neatly do that then you may have a decent go at your project. plumbing pipe is too thin and may melt or warp and won't give you a good feel as it will heat up quicker.
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Old 08-08-2011, 02:59 PM   #3
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if you want to get good at it go to your local metal scrap yard and see if they have a trashed AC condensor. then open it and unweld the compressor and try reinstall it. if you can neatly do that then you may have a decent go at your project. plumbing pipe is too thin and may melt or warp and won't give you a good feel as it will heat up quicker.
*** OK, I'll go down to the HVAC store and buy some ACR tubing and fittings.

I wonder if this would be a good excuse to get a Meco torch?

https://www.tinmantech.com/html/meco_midget_torch.php

....Been lusting after one of these for years.

- JerryK
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Old 08-08-2011, 03:28 PM   #4
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I use a full blown oxy acetylene rig and that really is the amount of heat you need sometimes. That little guy or some of the smaller turbotorch tips won't do it. Problem with a small torch or tip is it takes so long to heat the spot that the heat travels down the pipe by conduction too fast. You also need to wrap the service valves with a wet cloth to protect the seals inside and remove the schraeder valve cores. Now you see why an oxy/A is needed. Take too long to weld and excess carbon builds up inside. You are supposed to flow nitrogen thru while welding but LOTS of guys don't and have no problems later but only if you can weld quick.
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Old 08-08-2011, 05:03 PM   #5
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You are supposed to flow nitrogen thru while welding
*** I will *definitely* flow nitrogen. Have to get some anyway to leak check the system. It's one of those cases where patience and preparation can substitute for skill . I'll rent a nitrogen bottle at the welding store for a couple months.

A fun "beginning brazing" project might be to braze an appropriate
connector to a copper union - to flow the nitrogen.

- JerryK
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Old 08-08-2011, 07:01 PM   #6
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If you want to get good at it. make your own tee's from pipe.
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Old 08-08-2011, 08:56 PM   #7
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When you think that you are good with the torch, blow a 1/4" hole in a pipe and try to seal it up with the braze rod only..
If you can do that then you can butt weld two pipes together.
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Old 08-08-2011, 10:37 PM   #8
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When you think that you are good with the torch, blow a 1/4" hole in a pipe and try to seal it up with the braze rod only..
If you can do that then you can butt weld two pipes together.
*** Umm, I'd think the trick is to NOT blow the 1/4" hole in the pipe in the first place .

- JerryK
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Old 08-08-2011, 10:41 PM   #9
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If you want to get good at it. make your own tee's from pipe.
*** As it happens, I have a joint jigger doodad that I got at the flea market - uses a hole saw to make tubing match up to tubing. Should be a piece of cake.

We'll see when the brazing rod comes in. Hopefully, the HVAC store will sell me some short lengths of tubing - things get a little pricey at the 50-foot level.

- JerryK
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Old 08-09-2011, 04:35 AM   #10
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ACR comes in 20 foot lengths. It ain't cheap though.
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Old 08-09-2011, 06:21 AM   #11
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You can go to the box stores and get "L" copper that will do for training purposes. Or get some "K" if you want something thicker but I don't think that's at the local store.
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Old 08-09-2011, 06:37 AM   #12
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go to one of your local hvac contractors and ask them to save a used condensor when they rip one out which should be almost daily. pay them a few $$ for it. then you can chop pieces out of it and recouple them in a more realistic environment. hopefully you have a proper hvacr tube cutter and don't plan to use a hacksaw or a gas ax.
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Last edited by yuri; 08-09-2011 at 06:40 AM.
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Old 08-09-2011, 10:30 AM   #13
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Quote:
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go to one of your local hvac contractors and ask them to save a used condensor when they rip one out which should be almost daily. pay them a few $$ for it. then you can chop pieces out of it and recouple them in a more realistic environment. hopefully you have a proper hvacr tube cutter and don't plan to use a hacksaw or a gas ax.
*** I do have tubing cutters. Are the HVAC ones special? How about this one?
http://cgi.ebay.com/Lenox-21009-Tubi...item1e64c2bbad

*** It needs to be small so it can cut the tubing in the wall. See attached picture. I plan to cut out piece of sheetrock on the other side ( stud to stud ). Luckily, it's in the garage. That will expose a length of not-buggered lineset, and I can cut it off and braze on new tubing.

Also, how does one bend this stuff? The lineset comes out of the house at waist level, and the condenser is on the ground. I need to accomplish a couple of bends for the lines to go down the side of the house, and then on the ground out to the unit. I'm willing to punt by cutting the tubing and brazing in 90-degree elbows.

I have attached a few pix of the situation.

- JerryK







Attached Thumbnails
DIY HVAC Progress-dscn3220-small.jpg   DIY HVAC Progress-dscn3218-small.jpg   DIY HVAC Progress-dscn3226-small.jpg  
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Old 08-09-2011, 11:27 AM   #14
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If you are going to have 90 degree ells I strong suggest you use long radius ells.
Of course the more the brazing points ,the better chance you will have a leak.
So where possible bend the lineset.Use the spring type bender and bend very slowly to avoid kinking.
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Old 08-09-2011, 01:10 PM   #15
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If you are going to have 90 degree ells I strong suggest you use long radius ells.
Of course the more the brazing points ,the better chance you will have a leak.
So where possible bend the lineset.Use the spring type bender and bend very slowly to avoid kinking.
*** What radius bend can you achieve with 3/4" tubing? Can multiple
bends be placed close to each other? Say, within 6 inches of each other?

If I braze in ells, I will probably make it a bit long, cap the end, and leak test it with vacuum and nitrogen. Then cut off the cap and braze the assembly into the system. However, if the bends can be done, I think they'll be superior to a brazed-up system because they'll be smooth on the inside.

- JerryK
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