Flowing nitrogen

[toyotatech]

I will be having a new Trane 2.5 or 3 ton XR12 split ac system installed soon. I feel pretty good about the contractor that will be performing the install, but would like some general recommendations from you guys. I want to know if it is imperative that the installer flow nitrogen when soldering or brazing the lines, or is this just an extra measure that is not really necessary. Also, which is the better or preferred method , soldering or brazing? Approx. how long should a new system be evacuated after the install? Should I request that an inline filter/dryer be installed at the time of installation?

Thanks

[drcustom]

Doubt he needs you to tell him if they're reputable.

[Shophound]

If your installers know their stuff, they will:

a) Flow nitrogen during brazing (not soldering)

b) Pull a 500 micron vacuum with little rise after blank-off

c) Install a liquid line drier

You should not have to request these items be performed if the contractor is reputable and takes pride in their work. I don't see any harm in asking if these procedures are standard practice prior to accepting the bid. If you find a contractor that includes it in writing in the bid, so much the better.

I recently had to select a foundation repair contractor for my house. I chose the one that not only I had a positive prior experience with on another house, but their procedures were clearly outlined on the contract, as part of the contract. The other bidders did not include such detail, and although one was more competitive, I chose the higher bid with the greater detail and good history. The work began yesterday and they so far have done everything called for to do the job right.

[2story]

Shophound-LLdrier on every new install?
respectfully, what is your reasoning?

[Dad]

If nothing else an ounce of prevention is worth a pound of cure.

Every system I have put in from residential to commercial gets a liquid drier. I will spend a few dollars everyday if it prevents a recall with a blocked metering device.

[kerndt]

Shophound, I agree with all you stated including the drier (what’s $10.00).

If it were me, brazing, (with nitrogen) not solder.

Vacuum, 500 microns, and with a good blank off, 1 or 2 hours. I would recommend overnight and a double or triple evacuation process. (Yes I’m extreme)

A simple addition to your system is a TXV valve. I think upgrade costs are relatively low, and the stable and improved performance will pay you back in the future.

An informed customer sure keeps a tech on his toes, and pulling his hair out. I think it is a good thing to be informed, and hold people accountable. But to many times, the home owner goes for the lowest bidder, instead of finding a responsible company.

When its done, post some pictures.

Oh, I almost forgot. Offer the guy a glass of water, sandwich, be nice while you looking over his shoulder

[Edited by kerndt on 04-13-2005 at 02:58 PM]

[2story]

Sorry, brain fart, I read L-L drier but thought suction drier agreed, i like it when the manufacture takes care of it with a good sized drier included

[Shophound]

Originally posted by 2story
Sorry, brain fart, I read L-L drier but thought suction drier agreed, i like it when the manufacture takes care of it with a good sized drier included

2story, no problem. I would also agree that if OEM put in a beefy enough LL drier, adding one on the lineset would seem redundant.

I'd only use a suction line drier for cleanup after a burnout, and then I'd want to watch the pressure drop across the core after a little running time. Ideally it should be pulled after its done its duty...hard to do in the real world, unless you're always on site like I am.

[2story]

shophound, i have a thread in the job discussion area entitled "which way do I go" i would appreciate your advise, if you would not mind.
Sorry to derail this thread.

[berad]

Originally posted by drcustom
Doubt he needs you to tell him if they're reputable.

Trane equipment comes with liquid line filter dryers already insatlled inside the condenser cabinet near the service valves. Adding a second one will drive up the head pressures and strain the compressor. Espeacialy on 410 a. A company I used to work for had an installer adding the redundant drier on 410 systems, the following summer I returned to rplace compressors in about 2/3 of them. It was that fast. Luckily the guy didn't last long with this company. In fact the last time I saw him he was driving a dump truck for a gravel company.

[Shophound]

See my reply to your post in Job Discussions.

[Twilly]

by Dick Shaw
ACCA Technical Education Consultant

As is usually the case, the boss is right! Serious consequences can result down the road with systems that brazing took place without sweeping (purging) nitrogen through the copper tubing during installation or service brazing procedures.

Let’s take a look at the brazing process and why the nitrogen sweep is important. Copper, brass and bronze are non-ferrous metals that can be joined with these as well as other dis-similar metals such as copper coated steel. The pipe/tubing, equipment and fittings when joined in a brazing process of over 800 ° F. can make for a safe, clean and leak free system used in high pressure refrigeration and air conditioning.

The melting point of copper is 1,981° F. and the brazing process requires temperatures above 800° F. The actual melting point of the solder depends on the alloys it contains and the percentage of silver contained. At these high temperatures, installations, such as refrigeration/air conditioning, medical gas, high-purity piped systems that must result in a clean interior, the use of an inert gas such as nitrogen purged during the brazing process is required. The purge gas displaces oxygen from the interior of the system while it is being subjected to the high temperatures of brazing and therefore eliminates the possibility of copper oxide formation on the interior tube surface .

A good example is the black scale (copper oxide) that we see accumulated on the outside of a pipe when it is brazed. The inside of the pipe looks the same as the outside where the black scale accumulates. The oxygen (on the inside and outside of the pipe) causes this black scale. And, by displacing the oxygen with dry nitrogen we prevent black scale formation and end up with a clean system interior.

When a refrigeration or air conditioning system is manufactured and field installed it results in numerous connections, the scale can amount to a considerable quantity if dry nitrogen sweep/purge is not incorporated. When a refrigeration/air conditioning system is started the scale begins to move with the refrigerant and oil. The scale is either trapped in the oil, the filter drier(s), or the metering device, whichever it reaches first. Just like noncondensables and other contaminants, we don’t want scale in a refrigeration/air conditioning system to be the cause of system failure. So, let’s keep listening to the boss.

[hackmaster]

Yep that black scale is the one and only reason to use nitro when brazing. Just one little itty bitty piece can screw up a metering device and cause you big time headaches. Sadly enough there are many techs who were never taught this even in todays classes. Its a pain in the buttox to carry them heavy nitro cylinders to the unit but in the end it saves mucho headaches.

[toyotatech]

twilli3967 thanks for the thorough explanation, now I know why. Thanks for everyone's input, except for drcustom's

Drcustom, I am not sure what you are trying to communicate to me by the statement "Doubt he needs you to tell him if they're reputable." Please clarify. It does not make any sense.

Thanks

[drcustom]

Originally posted by toyotatech
twilli3967 thanks for the thorough explanation, now I know why. Thanks for everyone's input, except for drcustom's

Drcustom, I am not sure what you are trying to communicate to me by the statement "Doubt he needs you to tell him if they're reputable." Please clarify. It does not make any sense.

Thanks

What happened was I started answering, backspaced through it all and said screw it. Try the search mechanism next time before asking. Brazing with oxy/acet, air/acet. should never be done without flowing nitro through the lines. But you knew that already, either from working on cars a/c or from reading the thousands of posts regarding it's necessity. This is such a basic concept that ANY company worth it's sand will do this when installing lines. In 16 years, I have never seen it done without it. Is there really a geographical island left within the US where it's impossible to find a reputable company? Usually it's a question of going with a low bid and then standing over a cheap hack's shoulder telling him his shortcomings--trying to make up for his low-cost-low-knowledge approach--with your supplemented rudimentary factoids like the one posed by your initial question. Go with a reputable company and you can sit on your couch sipping a beer as cool dry air wafts throughout your house. Nitro pfftt. That's why you hired someone. When I have a mechanic work on my clutch, I don't need to know how tight the nuts on a bell housing should be. I go with a past-history, referred mechanic and have never been sorry. Of course...it's never the cheapest. So go ahead and post now how you've tons of bids, carefully selected the mid-cost one and that this response it totally outrageous. Should've let this one die....

[casturbo]

If a line set were silver soldered instead of brazed, would that preclude the nitrogen purge all together? We have silver-soldered many lines throughout the years and never one problem to date.

[Dad]

Originally posted by casturbo
If a line set were silver soldered instead of brazed, would that preclude the nitrogen purge all together? We have silver-soldered many lines throughout the years and never one problem to date.

The way I understand it is anytime you put heat of over 500 degrees you will cause carbon flakes inside of copper unless you flow nitrogen.

People that don't use it would be smart to install a filter just before the metering device.

[dash]

Without the nitrogen for brazing or any high temp solder,you will likely have problems,though you may not SEE them.

[oilman52]

Question....isn't todays solder strong enough to use on AC system? I can see brazing 2 different type metals but is it necessary to braze copper tubing? Not being a smart a@@,just want to hear your opinion.

[drcustom]

I have a buddy at another outfit who swears by #8 silver bearing solder with which he uses a regular small propane or MAPP tank with. That is, he only brazes in new compressors and the like, using the solder for refrigerant runs on residential splits. Claims he never ever had a leak nor a complaint from a disgruntled homeowner seeking recompense for a leak repair. For me the manufacturers' specs spell it out perfectly clear in every I & O I've read: braze with nitro flow.