Old A/C with New Furnace??

[climatecontrol]

Tell me if you see a problem with this...

I live in Nebraska, we have a lot of furnace only installs. If the A/C and Furnace are the same age lets say 25 years and the heat exchanger has a crack in it, most of our customers do not want to replace their A/C if it is running fine.

Evertime I go on a call and see this, I ask the homeowner a lot of questions about thier existing A/C to see if there is a problem. If I dont see that there is a problem and everything is running okay on the A/C side I just tell the homeowner, "well there might not be a problem with it now, but once they reach a certain age we dont know if they are going to go out tomorrow or 5 years from now its hard to say."

But the point I am trying to say is, do we hurt the system by replacing the furnace only and leaving the old A/C, Coil, and lineset?

[nashobasales]

My opinion on this is of course it is best to do the whole system together, but if the coil isn't leaking into the furnace and isn't clogged up than I don't see it as a huge problem. A service tech may say differently. We have done numerous furnace only changeouts and left the a/c to be changed at a later time. We haven't had any problems with it so far. Just my 2 cents.

[drhvacr]

you should at least replace evaporator coil with a furnace install, as most manufacturers will void warranty if it is not done. the reason they do this is if you have a old coil, with an old drain pan and it leaks water on the heatexchanger and it causes it to rust = voided warranty. seen it happen. therefore always change coil with a furnace.

[Traneguy]

Replacing the coil in the furnace if it has a plastic pan mutes the point above although valid for metal pans which a lot of manufactures still use....the reasons for coil replacement would be the aluminum fins tend to degredate and turn literally to white dust therefore lack of transfer hence eff... is affected and in this day and age energy management, cost savings and overall performance are determining factors. Those nasty quick connect kits should be and have to be eliminated so if a coil has those on it poof gonzo. also some coils will restrict air flow in the case where they are blocked partially or more........ just some thoughts. :cool:

[BaldLoonie]

Void the warranty if an old evap is left above a new furnace? Where in blazes did you get this?????

The evap is matched to the outdoor unit. If it is OK, leave well enough alone. If you change it just to change it, you are severely limiting the customer for a future A/C. He'd have to find an outdoor unit that matches what you put in and with R22 units getting less plentiful, could be an issue. If the old A/C fries and fills the new evap with acidic sludge, they either have to replace it again or risk some contamination in their new system. If the current system is oversized, which so many are, putting in a new coil could limit downsizing to correct size in the future.

[drhvacr]

Baldloonie....talk to the manufacturer of the equipment they will tell you the same! all of the other things you listed are reasons why it is better to replace the whole system. a good salesmen could turn any customer from just a furnace to a whole system, by allowing the customer to understand the benefits of changing the whole system. then there is no worrys at all.

[gevans]

Omaha? I could see leaving the old system in place. Plenty cold that far north, and not a major trajedy if it fails.
Here in the deep south, people don't play around with their a/c. It's a sure bet you will need it!
Changing out a working a/c would be a hard sale, even if it was 25 years old. It won't cost that much more to replace it in 1, 5, or 10 years when it fails. And if you only run it 30 days a year, you will never recoup your investment in energy savings.

[BaldLoonie]

No vendor around here even wants the old heat exchanger back. They sure don't ask if the coil has been changed!

Sure it is wise to yank a 25 year old A/C but there are cases, especially in cool climates, where budget doesn't allow.