using oxygen free nitrogen

[refcon32]

When brazing out or in a fitting, e.g. expansion valve or four way valve on a vrf air conditioning system. How do we put OFN through the system to protect against effects of brazing. Is it simply a case of putting system into recovery mode to open all valves and connecting OFN line to HP valve on unit, taking schrader out of LP valve to allow flow and putting OFN through system at slow flow. Or should we be doing something else.
Yet again, I am trying to get out of bad taught methods, without using OFN.

Nev

[james10]

exactly as you say put it in at one side and let out at the furthest point from there you only need a few psi

[monkey spanners]

On small stuff that only has one access point i would pull a vacuum and break it with nitrogen, i might be tempted to do this with a big system too as it would be a job to know when the nitrogen had displaced all the refrigerant at the point you are working. This is based more on monkey logic than any formal training :D

[JoeAT50A]

When brazing out or in a fitting, e.g. expansion valve or four way valve on a vrf air conditioning system. How do we put OFN through the system to protect against effects of brazing. Is it simply a case of putting system into recovery mode to open all valves and connecting OFN line to HP valve on unit, taking schrader out of LP valve to allow flow and putting OFN through system at slow flow. Or should we be doing something else.
Yet again, I am trying to get out of bad taught methods, without using OFN.

Nev

When you do brazing for components from outdoor units such as LP/HP valve/switches, LEVs, 4Way valve and as well as compressor, using OFN method is impossible to apply. Do apply some brazing points between indoor and outdoor units. Also could able to apply on replacement of indoor expeansion valve.
Idea of OFN brazing is to replace Oxygen and not to form any oxide scale during the brazing process.
Just run through OFN (est: 10psi to 15psi depends on piping length) just to replace the Oxygen with OFN from copper tube. Not expensive solution so that we should do it as a good installation practice of pro.
Those scales are hard to remove, try to clean your A/C system as much possible as you can to achieve optimum performances and also life span of components like LEVs and compressure will increase as well.

[Peter_1]

JoeAT50A, unless there's a build-in NRV in the compressor - most compressors don't have any - , you can have a OFN flow through the compressor while brazing. Brazing a TEV and a 4 way-valve with an OFN flow is also possible.
But it isn't always that easy in real world situation.

[JoeAT50A]

VRF VRF compressors do not come with non return valve, in fact no manual valves at all, and on top of that some normally close or open such as Solenoid valves, and program controlled linear expansion valves (LEV) and many more.
Possible but difficult to do so. If you can apply OFN, that's the best for your system in theorectically.