REusing Copper piping from split type air conditioners

[piashaw]

Due to a new incentive in Greece for people to change their AC units to new inverter styles, I'm often removing old systems and installing new ones.

generally removing systems with R22 or R407C and occasionally R410A.

Can one reuse the pipes rather than tossing out the old ones. Is there likely to be much contamination inside the pipes?

Distances are normally between 3 and 6m but some of the jobs I've done have had horrendous routes so that's why I'm seeing if I can reuse them.

New systems are either R407C or R410A. Units vary between 9000Btu to 24000Btu.

So can I reuse them and if so what caveats? eg R410A may need thicker copper, need to flush tubes etc.

Finally if I can reuse them eg if the Gas is the same, can I reuse different size tubes eg old system had 1/4" and 1/2" and new system requires 1/4" and 3/8", can I just reduce the 1/2" to 3/8" and add some extra ***** to allow for the larger pipe? If so anybody got any good tables for me to calcualte the additional ***** required?

Thanks

[fridgemandan]

well i would always say take out original runs and re pipe as there is no problems further down the line, if u use mitsubishi systems they do have replacement technology, always triple evacuate if u have to but becareful as it isnt ideal

[ozairman]

Can one reuse the pipes rather than tossing out the old ones. Is there likely to be much contamination inside the pipes?

Distances are normally between 3 and 6m but some of the jobs I've done have had horrendous routes so that's why I'm seeing if I can reuse them.

New systems are either R407C or R410A. Units vary between 9000Btu to 24000Btu.

So can I reuse them and if so what caveats? eg R410A may need thicker copper, need to flush tubes etc.

Finally if I can reuse them eg if the Gas is the same, can I reuse different size tubes eg old system had 1/4" and 1/2" and new system requires 1/4" and 3/8", can I just reduce the 1/2" to 3/8" and add some extra ***** to allow for the larger pipe? If so anybody got any good tables for me to calcualte the additional ***** required?

Thanks
On the whole if you can replace the piping then it would be quicker and cheaper to re-pipe.

Asking how much contamination there could be is a bit like asking how long is a piece of string, you as the man on site are the best person to determine that. If you must try and re-use existing pipe then it's up to you to ensure it is adequate wall thickness/pressure rating for the new refrigerant, clean and free of any old residual oil and contamination. There is debate on what is an acceptable procedure to use and what solvent as well as how much residual oil or solvent is acceptable. In the eyes of the manufacturer/supplier the answer will be NONE.
As for changing line sizes it is not recommended, most split system units have the refrigerant control/expansion device in the outdoor unit. The "liquid line" is in reality a long capillary between the expansion device and the distributor on the indoor coil. Changing pipe sizes here can mess up the system balance especially on a reverse cycle system. Also suction line pipe sizes are selected to maintain high gas velocities for correct oil return within specified limits.
Ultimately it all comes down to you and what risks you want to take. As deviation from the manufacturers/suppliers requirements gives them good grounds to deny/refuse a warranty claim if it all goes pear shaped and you will be left carrying the can;)

[piashaw]

Thanks for all of that. I never knew that the pipes were also sized for gas velocity etc. One learns something new everyday!!!:D

[Steve J C]

Re your pipework query: Generally copper pipework up to 1/2 inch will be OK for 410a gas, 5/8 on requires thicker wall. Problems start with residual oil in pipework. The two different oils do not mix and I believe will cause "lumps". A good purge of Nitrogen will generally clear them if you are absolutely stuck, but generally not good practice. Further, the refrigerant charge in Inverter type units is critical. The only way to re-gas them for optimum performance is by weighing the refrigerant in. Therefore oversized pipework or purging the system will generally upset and reduce their performance, and viod any warrentee.
I am also looking to make contact with aircon people/companies in Greece with a view to moving there. Any-one in the area please contact me
Regards

[Sridhar1312]

It is advisable to go for new pipes as if it is R410 A working pressures are more and higher thickness is required.
Further even if you have to use the existing pipe you need to clean with solvent to remove all old oil wax scaling in the pipes.
The cost of cleaning for reuse may be more and still not fail safe than using a new pipe.Hence it is better to use new pipe so that the life is longer.

[Thermatech]

The Mitsubishi Electric Mr Slim power inverter systems have ' replace technology'
The system runs in a test mode when you first power up & flush the refrigerant through the system & traps any contamination in a special filter which is then isolated from the system so for normal operation the system is cleaned from any contamination.
but
There are some restrictions with pipe sizes & pipe lenght that need to consider as R410a generally have smaller pipe size than R22 / R407c.

So you need to consider the pipe sizes & pipe lenght to see if the existing refrigeration pipe installation will fit into the Mr Slim replace specifications.

For most domestic applications with short pipe lenght I suspect this may not be the cheapest option.

[udarrell]

One of my concerns is the wall thickness for the higher pressure refrigerants.

What are the minimum USA wall thicknesses for R410A in the different OD sizes?

I would re-pipe for R-410A. - udarrell