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CAN I BRACE A HVACR LINE WITH R410a / R407c INSIDE

02/27/2013 3:16 PM

I have a 15 TR chiller with refrigerant 407c. It has valves in the liquid line before and after dryer. Can I do brazing between these valves after closing it, when refrigerant is inside line at about 8 bar pressure. I red that R 407c and R 410a are non flamable.

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#1

Re: CAN I BRACE A HVACR LINE WITH R410a / R407c INSIDE

02/27/2013 4:29 PM

No; first you need to "pump out" that portion of the line.

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#2

Re: CAN I BRACE A HVACR LINE WITH R410a / R407c INSIDE

02/27/2013 4:41 PM

Is there a bleed port (schrader valve or non US equivalent) so when the braze starts to chill it does not make a pin hole?

Why would you have service valves, and then want to braze in a new dryer?? Couldn't wait to buy the right one with flare fittings?

Proper practice is to purge with nitrogen, the only people who don't do this are refer boys that want to come back for future maintenance, or maybe the dryer is also a filter for oxidized crud, to remove bad installation procedure (make expansion valve leak). If this system has a receiver, then close the king valve, and do a pump down. The dryer should be down stream of the receiver if system was installed by competent refer-person. As you want it in the coldest liquid. If the king valve does not leak, and the compressor valves are good, very little refrigerant will leak back to the suction access fitting, which needs to be open.

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#3

Re: CAN I BRAZE A HVACR LINE WITH R410a / R407c INSIDE

02/27/2013 6:47 PM

No. Period! End of story. No.

Maybe, just maybe, you could do it, if you have ever done it before and KNOW WHAT YOU ARE DOING, AND KNOW WHAT YOU NEED TO DO.

Do you have a vacuum pump? If yes, see #1

Keep the pump, you'll need it later, too.

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#4

Re: CAN I BRACE A HVACR LINE WITH R410a / R407c INSIDE

02/28/2013 2:29 AM

Definitely NO?

If there's an isolating valve - make sure that particular parts are totally isolated and recover the remaining refrigerant.

Next repair the leaking portion of the pipe, pressurize the line/leak test and vacuum.

If dehydration is ok, open the line and run test. add the recovered refrigerant.

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#5

Re: CAN I BRACE A HVACR LINE WITH R410a / R407c INSIDE

02/28/2013 3:15 AM

Hot-tapping would be an easier, and safer, way of adding branches to the pipework. However, if the pipework is old and leaking, a patch overlay repair kit may be the way to go pending a shutdown and piecemeal replacement.

Brazing onto a closed live line? Not on anyone's nelly!

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#6

Re: CAN I BRACE A HVACR LINE WITH R410a / R407c INSIDE

02/28/2013 6:45 AM

Absolutely NO under any circumstances.

1. It is unlawful in the United States to vent refrigerant to atmosphere, even blends such as 407c which are not considered to be ozone depleting. It is punishable by severe fines and revocation of your 608 license.
We could debate whether "about 8 bar pressure" is "de minimus" or not, or whether you would "get caught" or not - but instead just pump it down, and be safe legally.

2. You should have a 608 license to be handling refrigerants. If you do not, if it unlawful for you to be working on charged equipment.

Again see point above.

3. 407c will burn when brazing, most assuredly.

UNUSUAL FIRE AND EXPLOSION HAZARDS:

R-407C is not flammable at ambient temperatures and atmospheric pressure. However, this material will become combustible when mixed with air under pressure and exposed to strong ignition sources.

Contact with certain reactive metals may result in formation of explosive or exothermic reactions under specific conditions (e.g. very high temperatures and/or appropriate pressure.

Like others before me, I recommend pumping the section down to a steady vacuum prior to beginning brazing. With the already low pressure, it should not take very long to accomplish the procedure. I mean: you will likely not be saving tons of time by trying to skip the pump down and go straight to torching.

Be safe - pump down, don't get yourself in a double hazard - personal safety and legal liability.

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#7
In reply to #6

Re: CAN I BRACE A HVACR LINE WITH R410a / R407c INSIDE

02/28/2013 7:53 AM

OP's in Nigeria.

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#8
In reply to #7

Re: CAN I BRACE A HVACR LINE WITH R410a / R407c INSIDE

02/28/2013 8:04 AM

Oops. I got so excited about torching refrigerant that I didn't notice.

I don't know what their laws are. I would like them to not vent refrigerant anyway.
Plus, it's still not a good idea.

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#9

Re: CAN I BRACE A HVACR LINE WITH R410a / R407c INSIDE

02/28/2013 5:10 PM

I am very concerned with the pressure in the line between two closed valves. First, as the line is heated the pressure will rise, possibly to the point of causing an explosion just from pressure, not flammability. Second, you will not get a good joint with pressure on the line. All of this is not even worrying about creating sludge out of the traces of oil in the line.

The system should be pumped down to a vacuum, vacuum broken with nitrogen and a slight flow of nitrogen through the section of pipe being worked on to keep the inside of the pipe clean. -- JHF

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