sweating copper

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Hello,
I have some 1/2 inch type M copper pipe and 4 90* elbows that I'm sweating together for practice. I've cut some 8 inch pieces and yesterday was able to solder one end of each ell to 2 tubes. It took a few extra tries but I was able to draw the solder into the joint pretty well. There was alot of smoke created, white and brown. I'm using yellow canister (Map gas?), cleaning the joints with emery cloth, flux and using lead free solder.
Today I can't seem to get the solder to draw in. I've prepared the joints as before and am attempting to create a square with the tubes so this time the ell is connected to 2x 8 inch pieces. I also notice that even though the solder is eventually melting it is not drawing in the joint, and when it hardens it has a yellow color to it.
Is the yellow color significant and does it indicate a problem with my technique? Can there be a noticable difference between yesterday and today as relates to how quickly the joint heats up, as today I have 2x the amount of tube to heat?
TIA,
Teabird
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teabird wrote:

The solder should melt the second you touch the heated metal with it, leading me to think that you are not heating the joint hot enough. Put more heat on a freshly cleaned and fluxed joint and see if that helps.
Jon
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Are you also using a MAPP torch? You won't get a proper flame if you try to use a bottle of MAPP gas with a propane torch.

Where are you applying the heat? A common mistake is to heat the joint between the pipe and the fitting. Always heat the fitting only: the pipe will get plenty hot enough anyway.
Also, make sure to clean and flux both the fitting and the pipe.
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On Tue, 7 Feb 2012 14:41:58 +0000 (UTC), Doug Miller

You always heat the biggest heat sink first - which in this case is the PIPE. The fitting is smaller and thinner and heats faster. I always heat the pipe where the fitting ends, then move the torch to the fitting just as I touch the solder to the joint.

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snipped-for-privacy@snyder.on.ca wrote in

Garbage.
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On Wed, 8 Feb 2012 04:03:45 +0000 (UTC), Doug Miller

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snipped-for-privacy@snyder.on.ca wrote in

And therefore, that must be the right way to do it. No possibility that some other way might work better.
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snipped-for-privacy@snyder.on.ca wrote in

Garbage. Heat the fitting, never the pipe: this loosens the fit and allows solder to flow in easily.
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On Wed, 8 Feb 2012 04:05:55 +0000 (UTC), Doug Miller

heat - so you heat it first, then when it is just about at the right temp to melt the solder you move to the fitting, the whole assembly reaches melt temp at about the same time, and the solder draws into the joint neet as you please, with no grapes or bubble-gum hanging from the joint and no leaks. No overheated fittings and burned flux either.
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On Wed, 08 Feb 2012 16:54:57 -0500, snipped-for-privacy@snyder.on.ca wrote:

If it works for you continue. In reality, you don't heat the pipe directly. I used to work in a department that made heat transfer coils. The guys used to solder or braze thousands of joints per day. Never did they heat the tubing first. Always the fitting.
What they did though, was custom make torch tips with two flames at 45 to 60 degrees heating the joint, flame facing up. While soldering one joint, it was pre-heating the next.
Some coils were automated for soldering. Tubes had a slight flare and the elbow sat inside with a ring of solder. They too heated the joint, not the tube.
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Tubing and copper pipe are 2 totally different situations. Tubing is thin like the fitting. Even Type M, which is the cheap light crap with the red stripe is heavier than most fittings, while the blue L and green K type are a LOT thicker. In a lot of heat exchanger units the manifolds/fittings are significantly thicker/heavier than the tubes.
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snipped-for-privacy@snyder.on.ca wrote in

You should stick to subjects you know something about; this isn't one of them.
I just miked a piece of 1/2" copper pipe and a 1/2" coupling: the pipe wall measured 0.023" and the wall of the fitting 0.040". So tell me, which is the larger heat sink, the pipe or the fitting which is almost seventy-five percent thicker than the pipe?
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On Thu, 9 Feb 2012 02:45:34 +0000 (UTC), Doug Miller

cheap-asses Type M tubing (and poorly at that - it's .028" wall thickness) - while L is 040 and L is .049. (assuming half inch - anything bigger is thicker)
A straight coupling ( 1/2") measures .028", and an LB is thinner because it STARTS at .028 and is stretched to fit over the pipe, as well as being stretched on the outer radius. At least a LOT of them are. I have a 3/4" street elbow in my hand, and it is as thin as .025 and as thick as .035" 3/4" K is .065", L is .045", and M is .032"
So how 'bout YOU stick to what YOU know.
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snipped-for-privacy@snyder.on.ca wrote in

Whether it's 0.023 or 0.028, the 0.040 fitting is still thicker. So much for your harebrained notion that the pipe is thicker than the fitting.
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On Thu, 9 Feb 2012 14:57:47 +0000 (UTC), Doug Miller

Were you measuring a BRASS fitting by chance? I gave you the measurements for 2 copper ones. They are accurate. They are lighter than all but the cheap-assed type M, which I NEVER use.
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snipped-for-privacy@snyder.on.ca wrote in

No, I was measuring copper. The obvious conclusion is you don't know what you're talking about.
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On Fri, 10 Feb 2012 02:06:00 +0000 (UTC), Doug Miller

No, the OBVIOUS conclusion is we are either measuring different fittings or YOU can';t measure. - and you are a cheapass who uses inferior M copper. I never use M - and for me, with the fittings we get here, my method works - and works extremely well. I'm not saying you have to do it my way - Unlike you, I don't say anyone who dissagrees with the way I do things (or don't but think others should) is wrong, or stupid, or inferior. Different strokes for different folks - but if someone is having a problem doing things the way they are doing them, and asks for information, finding out what works for others can be valuable. The OP can try the way I recommmend and see if it works for them. If it does, good. If it doesn't, no big loss and no skin off my teeth, or yours.
You don't want to try it? Too bad, so sad - doesn't bother me at all. You already know it all so you will never learn anything off this group anyway - so you may as well crawl into your hole under a bridge somewhere and congratulate yourself on knowing all there is to know and being perfect.
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snipped-for-privacy@snyder.on.ca wrote in

Wrong again. The obvious conclusion is that you are -- wrong again.

Oddly enough, you *did* say that the way to do it is to heat the pipe first -- IOW, that that's the "right" way to do it.
And that simply isn't true.
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If you have the copper run a marathon, it'll sweat.
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On Wed, 08 Feb 2012 21:00:03 -0500, snipped-for-privacy@snyder.on.ca wrote:

Quite right, but I never said anything about copper pipe did I? I'm talking tubing. The same .022 and .025 tubing used in most refrigeration, unit heater and transfer coils in water and steam systems. Return bends were made from similar tubing.
We made aluminum finned coils from 6" x 6" x 1" up to 48" x 180" x 24". About 90% was copper, but we did some brass and cupro-nickel for high pressure in ships.
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