Changing refrigerants

[Brain Freeze]

I'm replacing the furnace in my home. By replacing the furnace, I am also replacing the evaporator coil for my air conditioner. The current condenser (10 SEER) is about 10 years old, appears to be working fine and I don't want to replace it if I don't need to. One contractor told me that I should replace the condenser because when the system is purged of refrigerant, any residual referigerant will likely be incompatable with new one so he recommended that I replace the condenser to make sure it is all gone. "Oh, I see....that makes sense."

However, I've been thinking about it. I'm a chemistry teacher so I understand that when two liquids are mixed together in solution that it changes their boiling points. On the other hand, if the refrigerant is a gas, shouldn't it be easy to completely evacuate it from the system? Would trace amounts of residual refrigerant cause a problem? Or should I be concerned about something else?

A second contractor suggested using my existing condenser. He said that it had more than enough capacity and they are easy enough to change that if it wasn't working properly, it could be switched without costing more than the additional cost of doing it with the furnace replacement.

I could upgrade to a 13 SEER or higher, but I live in Chicago and I only use the air conditioning for a few of months out of the year and the annual return on investment (5%) would not warrant the additional capital.

Should I be concerned about refrigerant compatability?

Thanks

[Brian_UK]

Hi and welcome to the forum.

An open statement - "It all depends on the type of refrigerant"

I would assume that your unit is presently running on R22 which is probably still available.

Your contractor is perhaps looking to the future when the gas is no longer available or very, very expensive so don't hit him too hard :)

There are various 'drop-in' refrigerants that can be used in place of R22 and can be changed without major works.

Changing to a different refrigerant altogether can be a mind bending experience. The existing oil may not be consistent with the new gas and will have to be changed, this can take many oil changes to irradicate the old oil.

So I would suggest that you ask your contractor about 'drop-in' refrigerants to minimise costs.

[The MG Pony]

Personaly? I would stick with the old unit, the other guy is correct, swapping to a new one if needed is the same either way. The first guy as brian said may have been looking ahead but the way he worded sounds like he us being dishonest or dosn't quite under stand what he's doing, you pick.

[BigJon3475]

http://www.refron.com/InfoCenter/TechData/DuPont_Replacement_Guide.pdf

[lana]

Hi there,

As Brian mentioned, oil is the problem not the refrigerant. When system is evacuated then there will be no "old refrigerant" there.

If the system worked with mineral oils, and new refrigerant needs synthetic one then there is a major concern. Mineral oil must be completely drained from the system otherwise, when mixed with synthetic one will cause contamination and huge problems.

Cheers