Steel to Copper Braze on Chiller Barrel

[kevink1955]

I have a chiller (2, 5 ton circuits) that has a leak at a steel to copper braze. Was originaly done with SilPhos 15% 12 years ago, I now know this was the wrong alloy for this application. It's a 1 3/8 suction line.

I am going to take the thing completly apart (both circuits) the one that is leaking is the back one anyway so the front one needs to come out for access anyway.


As luck would have it this comes at a good time of the year, it's 16 degrees outside and it's runing on the dry cooler so I can recover the R22 and open it up for as long as I have to. Cools a Server room and a Dispatch center for a F.D. and runs 24-7-365 a year.

It's a built up system with a Standard (MFG) 15 ton 2 circuit chiller barrel, 2 roof top condensers with 5 hp copelamatc compressors with headmasters, pump down system. The chiller barrel is oversized due to the Glycol in the system.

With all the original installation removed and the steel cleaned up the question of the day is what alloy and flux would you use on the rebuild. I do not want to do this one twice.

[onetime]

45% silver solder and silv-alloy flux should do the trick. Remember the steel will heat really fast so heat the copper first and then move to the steel, even then keep most of the heat on the copper. If you don't do this much a couple of dry runs on a 3/8 black nipple to 3/8 copper is a good practice run.

[frozensolid]

45% is the way to go but I would use the harris sticks with the blue flux on it. Seals easier and less chance of a leak.

[MikeySq]

i use those blue sticks, man the fumes from them are killer haha, i still use a bit of additional flux when i use those coated sticks

[freezerfixer]

i normally use 45% with stay-silv flux.

[kevink1955]

Looks like 45% it is. It looks like I can cut the steel back and start over with a clean steel end.

Does 45 flow like Silfoss 15%

I will do a practice run on a section of steel pipe with a section of copper tube, only want to do this job once.

Thanks for your help, will let you know how it turns out

[TGoodrich]

45% Silver is more fluid than sil-phos. It flows more like 60/40 plumbing solder. Like the others said, you must keep the heat mostly on the copper and avoid overheating the joint or it will not "take" to the steel. Be careful not to add too much solder to the joint also. It can turn into system debris. 45% silver does not have the bridging capacity to fill gaps the sil-phos does either. Make sure the joint is clean and properly fitted. Sil-phos should only be used on copper-copper joints. Use 45% on copper to steel, stainless or brass.

[jaysongoff]

After finishing with the 45%, I like to build a shoulder with 15% silfos to add strength to the joint and it joins to the 45% well. I don't feel like I have to use so much of the expensive alloy to build up the joint.

[yotaman16]

huh thats a good idea jay.. I will try that next time i have to use 45%

[MikeySq]

i use those harris flux coated sticks to build, does a good job!..... besides it's only money, customers got lots of it

[kevink1955]

Did the copper to steel today, took me 2 hrs with a Dremel tool to grind to old SolPhos 15% off the steel stub on the chiller. The Braze went real well I now have a 7" long 1 5/8" copper stub on both circuits. Could not come up with the reducing coupliing I needed to finish it today (holiday, everyone closed)

Will finish it in the morning, pressure test with nitro at 125. Looks good, hope it's good. Will let you know.

Your right, that 45% does not build like 15% SilPhos but it did flow into the fitting real nice so I think I am good to go. I only had SilPhos so I did not build it up with that but I did manage to get a nice build with 45% and controlled heat.