Lineset Sizing

[54regcab]

I just had a rheem 3-ton 13 seer 410a install today that spec. 7/8" @ the condenser but the same 3ton 15 seer only spec 3/4" @ condenser. why is this?

That's what I want to know. What determines minimum line sizing...

[tday99]

What determines minimum lineset sizing is the refrigerant velocity in the pipes, with too large a suction line, the velocity will be too low and therefore will not return the oil to the compressor. Too small a liquid line and you will not have the capacity of liquid at the metering device for the load.
Also when using old linesets there could be numerous problems, such as corrosion, brittleness, pinholes, poor installation, and the list goes on. Any one of these problems coupled with the much higher pressure of r-410 equals callbacks.
If that hasn't convinced you to change them, r-410 uses polyol ester oil and the r-22 unit used mineral, and mixing these oils can form acids, wax and sludge.
Enough said?

[tday99]

http://www.rsl.ca/CAT2012/2012RSLcat.pdf#page924
This might give some more insight.

[Barrettservices]

What determines minimum lineset sizing is the refrigerant velocity in the pipes, with too large a suction line, the velocity will be too low and therefore will not return the oil to the compressor. Too small a liquid line and you will not have the capacity of liquid at the metering device for the load.
Also when using old linesets there could be numerous problems, such as corrosion, brittleness, pinholes, poor installation, and the list goes on. Any one of these problems coupled with the much higher pressure of r-410 equals callbacks.
If that hasn't convinced you to change them, r-410 uses polyol ester oil and the r-22 unit used mineral, and mixing these oils can form acids, wax and sludge.
Enough said?

i understand sizing them correct but i have been changing from 22 to 410 for 8 years now with only purging the existing "right" size lines with nitro, triple evac (never using a lineset flush kit) then vac to 250 microns and i have yet to have a oil, sludge, acid, wax, corrosion or leak issue you speak of. I also don't use fittings and bend all my pipe on site to minimize joints so that may help solve the leak issue. copeland even accepts this method if replacement of the lines is too big of an issue. the minimal residue of mineral with a new filter drier should not affect the system at all.

[tday99]

If the 22year old piping looks good, you feel that there is no dips/sags where oil will be pooled, and you can get a good vac on it I agree with you barrett!

[mark beiser]

r-410 uses polyol ester oil and the r-22 unit used mineral, and mixing these oils can form acids, wax and sludge.

POE and mineral oil are chemically compatible, no acids, wax or sludge will be formed when they mix within the system.

You just don't want to much mineral oil mixed in an R-410a system, because it will tend to collect in the lower refrigerant velocity parts of the system, like the evaporator coil, causing a reduction in cooling capacity.

[beenthere]

i understand sizing them correct but i have been changing from 22 to 410 for 8 years now with only purging the existing "right" size lines with nitro, triple evac (never using a lineset flush kit) then vac to 250 microns and i have yet to have a oil, sludge, acid, wax, corrosion or leak issue you speak of. I also don't use fittings and bend all my pipe on site to minimize joints so that may help solve the leak issue. copeland even accepts this method if replacement of the lines is too big of an issue. the minimal residue of mineral with a new filter drier should not affect the system at all.

Min and POE oil do ok together and won't cause any problems as long as the min oil is kept to a min. Its the fact that the R410A can't carry the min oil is where the problem comes from if too much min oil is left in the system. What your doing is fine to keep the mineral oil amount low enough. Wouldn't even need to pull to 250, but nothing wrong with doing so.

[Barrettservices]

Min and POE oil do ok together and won't cause any problems as long as the min oil is kept to a min. Its the fact that the R410A can't carry the min oil is where the problem comes from if too much min oil is left in the system. What your doing is fine to keep the mineral oil amount low enough. Wouldn't even need to pull to 250, but nothing wrong with doing so.

I used to pull to 1000 and make sure it stayed but ever since i got a nice pump and appions garden hoses i can pump a 60' line down in 20 mins on average so i dont mind going to 250 since it only adds about 5-10 extra mins on the job. Besides i am doing other things while its working so why not...

[beenthere]

As I said, nothing wrong with doing so. only adds a some wear and tear on the vacuum pump at worse.