Soldering a Steel to Copper Connection – Refrigeration Training

Fred's Appliance Academy
February 26, 2020

Hello everyone. Tim with Fred’s Appliance Academy. Here today showing a video. We’ve had a lot of requests over the last few weeks here. Some technicians out there having some trouble soldering a filter drier, which is steel to copper, or a steel-to-copper fitting on a compressor. Getting a lot of leaks, or they’re getting restrictions because they’re filling it with solder. Today in this video what we’re going to show you here is we’re going to show you joints from steel to copper with the method that we find the easiest. The way we do train here in the academy. It may not be a preferred way for many people. It does work. It works well. But the major focus on this is going to be cleaning. We have our line here that we’re going to be soldering, which will be the steel. I have it in a vise here.

This would be the same thing as if it was in a condenser or right there at the compressor. But you can see that we have a painted line. They paint these from the factory and make everything look good. So we need to clean this line. This steel needs to become bright silver. It cannot be dark. It cannot have any dirt on it whatsoever. This needs to be the cleanest connection that we can find. I found in my methods, my ways in the field there that you use a lot of sandpaper just by trying to take that paint off, and it takes a little bit more time to do. So what I have found is if you warm the line, you’re actually going to burn the paint off. Again, you don’t need a lot of flame for this to happen here. What we’re doing is we’re just melting that paint right off this line here.

Once we get this clean, we’re going to go ahead and let it cool, and we’re going to use sandpaper. We want to get a decent amount here done because the dirt actually travels towards the heat. So if we don’t get enough off of here, what’s going to happen when we go to do our connection, the dirt’s going to travel there, and we’re going to end up with a dirty line. I think we’ve got it pretty well clean right there, and we’re going to go ahead and apply some sand paper after this cools down. All right. Now that we’ve got the line cooled here, what we want to do is we want to go ahead and take a sandpaper Emery cloth, about 120 grit or so, to go ahead and clean this up. I’ve gone ahead and ripped sections off here.

This not only saves you on sand paper, but there’s a little bit of a method that you can do here where you can get all the sides at once here, and it makes life easier just by wrapping it around just like this and using both sides of that sanding paper. So what we’re going to be doing here is getting this nice and clean. You may have to use one or two pieces of sandpaper to do this, but we want to get this bright silver. When you’re sanding, you don’t want to sand in the up and down motion. You want to sand in the circular motion. What that does is, it grooves that piece of steel or copper that you’re going to be soldering and helps the solder flow into that fitting that you’re making. As you can see here, we’re starting to get silver, and we’re going to need another piece of sandpaper here. Good thing I ripped off a couple more pieces here.

But again, cleaning, cleaning, cleaning. Not only is cleaning important, you need to make sure that safety, you have your, as you can see here, my drip tray here. This would be on the customer’s floor. This would be protecting their floor. I have eye protection on. We also want to practice good safety and good techniques in the home to where we’re not damaging the customer’s property. I’m just going to finish up the last little bit here. Just this way here, and you’re going to want to do this to the same thing as copper. Make sure it’s nice and bright shiny. Even though it just comes right out of the package, it’s not clean. If you think it’s clean, they can never be too clean. Always double checking yourself with this. Then go ahead and take a dry rag, and get any debris off that we went ahead and made there just by sanding that down.

Now, we’re going to go ahead and take this piece of copper here. We’re going to replicate maybe putting it into a compressor or a filter drier. What’s going to happen is, this is quarter inch. The steel is three-sixteenths. The inside diameter of this quarter-inch copper is actually three sixteenths depending on how you cut it, what kind of cutting wheel you use. You don’t want to really squish the copper. The copper is soft. It’s not as soft as refrigeration water line copper, but it still is soft so you can squish it. If you end up having a problem where you cannot get this fitting in or together, a Number 10 Torx driver is what you want to use, and you just go ahead and take this inside here, twist and make sure that drive fits all the way in. That’ll make a nice tight connection.

Again, that is one of the things that you want to make sure that you do, is having that nice tight connection. With a very loose connection what’s going to end up happening is, it’s going to be sloppy, good chance that the solder’s going to rush in. So the tighter the connection, the better. Now that I have this clean, my copper’s clean, I’m going to go ahead and apply low heat, and I’m going to use a tinning flux. What I’m going to do first, and we found it worked the best, is if you tin the steel first. Again, if you’re using a propane torch, you don’t need it all the way up like this to where you can hear it. You actually want to use low heat to where you can control it a lot more. So you want to make sure that it’s down low, and under the line.

The heat actually rises, and it will actually help heat this steel up a little bit quicker. We’re not looking for brazing to where it’s going to get cherry red, but we are looking that this flux will actually melt down your sizzle. Now, here’s the important part. When we go ahead and fit our line together, we want to make sure that we’re making a good connection here, and again, you may have to twist that on or so. What we want to watch here is, we want to watch to make sure that this steel line does not turn black. If this steel line turns black, just stop. At that point. You need to pull your connection off. You need to go ahead, re-clean your steel line, because the solder will not adhere. It will not set to the copper and the steel. So we’re going to apply very low heat to our steel and our copper.

We’re going to heat the steel first. We don’t need to heat that much, and we’re going to come over to the copper. We want to go ahead then, use the flux again. I’m going to come over to the copper this time. Now, you can see that this turns it like a silver so it already looks like we’ve already put some solder on there. This is the method that, reason, why we say, works the best, you can actually see the change in this. What we’re looking for here is the change in this silver. When it gets to a bright shiny silver, you’re ready. That tells me right there that you didn’t use too much heat, and we’re not going to use too much solder. We have a color change there. We’re going to go ahead and melt the solder right on, and we’re going to bring it in for capillary action. Let it sit.

You want to let it sit for a few seconds or so, and if you take a damp cloth and go ahead and cool that section down then. Now you’re getting the flux off there, which is very corrosive. So make sure you’re carrying your flux in a different bag than all your shield system tools together. But you want to get that flux off there. Not only can it become an oily residue, it can also eventually damage that line or that connection. Now, if we take a look at our connection here, the solder went all the way around because we have already tinned it with the flux that we used, and you want to make sure that you’re not using too much. We actually recommend sometimes to make a little bit of a hook inside your solder there, so that way there, if you’re using this much of a hook, you’ve used way too much solder. You can use that practice there.

When all is said and done, you want to be careful, especially with the filter drier. You may not have a lot of steel there. When all is said and done, if we take this line, take it out of our vise here, and if I bend here, if I can twist this apart, it would actually resemble over time with vibration that we may have a leak. Right now I’m twisting, and this is not coming apart, so we want to make sure that we have the solder all the way around the joint. You can see that the steel itself did not darken, become black again. We have a nice silver. We have a nice silver color around the copper as well that shows that the cleanliness of that joint was done well. We’ll go ahead and do … I’ll show you what we have happened when you actually use too much heat on steel.

We can still see, I’m going to do it right on this section right here, put this back in the vise. You could still see that what’s going to end up happening is, if it turns black, and how quickly it turns black, you’ve used too much heat. So if you have your heat up too high, what’s going to happen is, you’re not paying attention or so, and you’re heating this up, and just watch. Just watch how that carbon built up on there, and it’s now starting to discolor and turn black. If you’ve gone to that point there, like I said, what you’ll want to do is go ahead, cool it down, start fresh again, because when we wipe this off here, you can now see that it’s black.

Take a piece of sandpaper again, and go ahead and clean this up to where it’s nice bright shiny silver again, and then go ahead and make your connection. So cleaning, tinning first, cleaning the copper, warming it, tinning the copper, adding flux with that little hook there. This should save you a lot of time, a lot of trouble in the field because again, your leak is likely going to be from your steel-to-copper joint, and that’s what we see out in the field there.

I hope this video here was helpful to you. If you wish to subscribe to our page, or Like this, please do. Please share it because we want everyone out there to be able to do this job. Refrigeration is not the easiest. It’s an art. It does take some time. If you want to practice, feel free to go ahead, go to Home Depot, Lowe’s, your local hardware store. Pick up some copper. Go to the auto parts store. Get some galvanized steel line, brake line, that they have there, three sixteenths that’s coated, and practice, practice, practice. It comes with time. Be patient with yourself.

Don’t get frustrated, and you’ll eventually get that feel. We have a lot students that come in here, never have done this project before in their life. They turn out real well their first time around. It may be a little luck. Then we have some guys that have done it in the field for years, and they still have a lot of trouble with it. So you could be the best technician out there, but this is still going to be your weakest joint. Again, thanks for joining us, and watching the video, and we’ll see you the next time.


Leave a Reply