soldering vs brazing of ac unit

george_42

should central ac units be brazed or soldered and if soldered does that violate the warranty on the unit. My unit was soldered 7 years ago and solder joint now leaks.

ChrisJ

As far as I know, all joints should be silver soldered while flowing dry nitrogen which some refer to as brazing.

You say the joints were soldered, do you mean soft soldered?
Are the joints silver in color? Silver colored joints suggest soft solder. Brazed / silver soldered joints will be copper colored.

ChrisJ

Here's some pictures.

First, is a proper joint.









This picture shows soft solder used for plumbing.

Paul S_3

As ChrisJ said must be brazed with nitrogen flowed through to prevent flaking ....the pic below are brazed refrigeration connections...some guys use stabrite 8 which i believe is silver solder....i use 15% brazing rods

ChrisJ

Paul S said:

As ChrisJ said must be brazed with nitrogen flowed through to prevent flaking ....the pic below are brazed refrigeration connections...some guys use stabrite 8 which i believe is silver solder....i use 15% brazing rods

I thought I remembered something like Staybrite 8.
I remember one of our monitor top guys using something like it.

So far, I'm a stay-silv 15 guy which I believe is a 15% silphos rod.
80% copper, 5% silver, 15% phosphor I think?

Paul S_3

80 cu
5 phosphorus
15 silver

ChrisJ

I was close.
Ok, not really.

george_42

Thanks. mine are silver in color indicating soft solder

ChrisJ

george said:

Thanks. mine are silver in color indicating soft solder

Can you post some good quality pictures of the joints?

RJ_4

In the past Staybrite 8 and some other soft solders were allowed to be used to solder suction lines, liquid lines, driers, and txv,s. . Any thing on the discharge side of system, hot gas line , oil separators and service valves required sil-floss (stay silv 15 ) or a high rated silver solder, partly due to the excessive vibration on the discharge side, Staybrite 8 has a shear strength of 11,000 lbs. With the new refrigerants like 410a which operate at higher pressures, solder requirements have changed These all depend on the equip you are working on, type of refrig. and local plumbing/mechanical codes. You can also check with Harris solder Co. This is of course what I learned over the years, others may have different insights.

Big Ed_4

The reason for brazing and nitrogen is to keep the inside of the AC system clean and free from acidic . Flux is an acid base and the nitrogen displaces the oxygen out of the system so it would not burn with the torch and leave carbon ... Which I understand turns acidic as well .. Rod you don't need flux and with the higher pressures 15% rod should be used .

Techman

In general, most mfrg's say to Braze(Hard Solder) in R410A systems.Some places like NYC require the systems be brazed( I was told). If using a silphos 15 braze rod (SILver PHOSphous- w/ 15% Silver) the phos is a flux. .In ChrisJ photo all of that darker colored copper is where "oxidation" took place, the oxidation was all of that "powdery,flaky stuff" . You can blow lots of it away, or wipe it away. So ,where it is on the outside of the pipe it is also on the inside of the pipe, so a Nitrogen sweep is used to prevent that contamination from happening.
On service I Soft Solder( StayBrite#8 w/6% Silver) most all LL&SL stuff, and braze all Discharge Line and Cond unit coil stuff.

Dave0176

Staybright 8 supposedly creates a stronger joint, but doesnt handle vibration very well. I braze all my refer joints.