[malysh]

Alright, so the 8+ old year R22 evaporator coil leaked right on schedule, R22 appears to be too risky for only a new coil (in terms of benefits/cost). The house has 2 units, so can mitigate 1 unit failure for a few days (but the full comfort is not there ...).

20+ year old Copeland scroll compressor in the Carrier is probably fine (hard start kit seemed to be doing a fine job!), but not sure it'd last another coil lifetime (~8-9 years), plus R22 costs (even if the cheapest tank from internet).

Location: southeast TX, so the AC is pretty much on all the time May-Oct, mostly off Nov-Apr. Gas furnace and AC coil are totally separate sub-systems, can swap either whenever. Electricity costs are ~9.5 cents if in bulk (~2000 kWh).

Current thinking - replace compressor/evaporator coil to get it to R410A (most simple hardware config, to ensure longevity), keep the furnace while it runs. Mostly likely the next repair would still be the R410a evaporator coil (not the furnace). R410a pressure is higher, so the leak will occur sooner.

I am crunching the numbers here, don't see a more sensible path forward. R410a is a necessary evil at this point, but the gas furnace gets too limited use, so let it be while it lasts. The blower motor is dumb (simple), if it fails, just swap it.

Other thoughts?

 

[ss120396]

Your thinking seems right... I wouldn't want to pour a lot of money into a 20+ year old system. Time to replace if you can afford it.

To clarify though... the higher pressure of R410A does not mean that a leak will occur sooner. Leaks are not caused by refrigerant pressure. It just means that when a leak does happen, it will leak out a bit faster than with the lower pressure of R22. The increased frequency of leaks in recent years is not because of R410A, rather it's because of thinner, rifled tubing in the new coils that they use in order to get higher efficiency ratings. Anything corrosive in your house's air will eat through this thinner copper tubing in no time. These changes happened around the same time with most manufacturers though, which is why people confuse the two sometimes. Luckily the manufacturers have switched to all-aluminum coils now, which seem to be holding up a lot better than the copper ones.

Nothing wrong with just replacing the condensing unit (I assume this is what you mean, rather than just replacing the compressor) and coil, saving furnace replacement for another day. The only caveat to this is that if you buy a higher efficiency unit, you will need to upgrade to a furnace with a variable speed blower to actually get that efficiency rating.

 

[malysh]

...

To clarify though... the higher pressure of R410A does not mean that a leak will occur sooner. Leaks are not caused by refrigerant pressure ... Luckily the manufacturers have switched to all-aluminum coils now, which seem to be holding up a lot better than the copper ones.

This is interesting. What's the expected leak time for an all aluminum evaporator coil and R410a? It's clear they would leak - but when?

 

[ss120396]

This is interesting. What's the expected leak time for an all aluminum evaporator coil and R410a? It's clear they would leak - but when?

The big leak problem with copper coils was formicary corrosion... Basically pinhole leaks caused by organic acids in the home's air. You can't really predict how long it will take to leak in a particular home as there are so many variables: how often the AC is used (and the coil exposed to corrosive condensate), the thickness of the copper tubing, concentration of organic acids in that home's air, etc. Some people were seeing failures in under 5 years... other people it took longer. This Carrier research paper has more info about the phenomenon:

https://aplusair.ca/wp-content/uploads/Carrier-Evaporator-Coil-Formicary-Corrosion-Report.pdf

Aluminum coils are completely immune to formicary corrosion, which is why the manufacturers switched to them. Leaks in aluminum coils are nearly always due to manufacturing defects with that particular unit, rather than simply being exposed to the home's air over time.

 

[ammoniadog]

I had an aluminum evaporator in my home that was pushing 40 years old with zero leaks when I finally replaced it. The only reason I replaced it was because I was installing a new, higher efficiency furnace and I wanted a new cased coil to go with it. The new evaporator is also aluminum. It came with a R410A expansion valve that I switched out to a R22 valve to make it compatible with the 40 year old, all aluminum condenser that's still trucking along with it's original refrigerant.

When you think about how the old standard type of evaporators are made with copper tubing going through aluminum fins and steel frames/tube-sheets, and they are in constant contact with water when they are operating, you can see how accelerated corrosion can become a problem. Combine that with what ss120396 said about the copper being thinner and of lower quality that it used to be, and its a wonder that they last as long as they do.

 

[Bazooka Joe]

Shouldn’t automatically assume your next system the Contractors will be bidding aluminum indoor coils, you certainly can ask for bids with aluminum cased or uncased coils to hook to your existing older functioning furnace.

If your planning on keeping your furnace for many years, and are into matched AHRI systems, you may want to get a outdoor unit at around 14 SEER and save a few bucks, as chances you will not get 16 SEER rating ( on paper not real world numbers ) with a more expensive upfront cost of a 16 SEER outdoor unit. Homeowners tend to think you only go by the rating of the outdoor unit to get your SEER and EER, but it’s a combination of matching the indoor selection to the outdoor unit that gives you the certificate of ratings.

Here’s a couple manufacturers that make pretty much just coils, that can be AHRI matches for pretty much any outdoor unit brand. Looks to still make copper and aluminum coils. Looks to be dated 2020 and 2021 so their current lineup.

May want to get model numbers in writing on the bids, as Contractors are having a hard time getting equipment.

Make sure to register each piece as manufacturers warranty decreases if system is never registered.

https://www.google.com/url?sa=t&rct...D&url=https://www.adpnow.com/evaporator-coils/&usg=AOvVaw3irxmNw8BgHLhPihjph2Y-

ADP is owned by Lennox


https://www.google.com/url?sa=t&rct...DsEQFjAAegQIDRAD&url=https://www.aspenmfg.com/&usg=AOvVaw2gyI6NjmcrvjrWr9jgVEAl

 

[ss120396]

Shouldn’t automatically assume your next system the Contractors will be bidding aluminum indoor coils, you certainly can ask for bids with aluminum cased or uncased coils to hook to your existing older functioning furnace.

I didn't realize there were still brands selling copper coils. For the brands I'm familiar with, Carrier, Trane, and Rheem, the only thing I can get at my local distributors is aluminum. If that's the case, definitely a good idea to make sure you're being a quoted an aluminum coil as advised.

 

[Bazooka Joe]

I didn't realize there were still brands selling copper coils. For the brands I'm familiar with, Carrier, Trane, and Rheem, the only thing I can get at my local distributors is aluminum. If that's the case, definitely a good idea to make sure you're being a quoted an aluminum coil as advised.

I have couple no frill 12 SEER 16 year old Heat Pump systems ( Goodman brands ) with copper indoor coils, so far so good with it not leaking, ( one Air Handler in attic other in basement ) and even the outdoor copper coil, the coil diameter isn’t as thick as something from the 70’s/80’s but guessing a tad more thicker than for the most part modern paper thin copper coils?

 

[ss120396]

I have couple no frill 12 SEER 16 year old Heat Pump systems ( Goodman brands ) with copper indoor coils, so far so good with it not leaking, ( one Air Handler in attic other in basement ) and even the outdoor copper coil, the coil diameter isn’t as thick as something from the 70’s/80’s but guessing a tad more thicker than for the most part modern paper thin copper coils?

12 SEER yes, coils from those days held up decently with most manufacturers. It was the minimum-13 SEER era (2006) that things started to get really bad. Although the manufacturers who were playing around a lot with very high efficiency coils before then (mainly, Carrier and Trane) had earlier issues. This is why they were the first to introduce alternative indoor coils (tin-plated and aluminum respectively, although Carrier later switched to aluminum like everyone else).

 

[Bazooka Joe]

12 SEER yes, coils from those days held up decently with most manufacturers. It was the minimum-13 SEER era (2006) that things started to get really bad. Although the manufacturers who were playing around a lot with very high efficiency coils before then (mainly, Carrier and Trane) had earlier issues. This is why they were the first to introduce alternative indoor coils (tin-plated and aluminum respectively, although Carrier later switched to aluminum like everyone else).

Yes 13 SEER minimum took effect Jan. 2006, I bought the outdoor units ( rated at 12 SEER ) shortly before that time as distributors where selling 10/12 SEER units cheaper to make room for the minimum standard 13 SEER outdoor units. Thinking the Air Handlers where rated at up to 13 SEER thou. So yes it was around when the minimum 13 SEER standards took effect. Even thou it was a 12 SEER rated, all companies warranties where 5/5 back then and even Goodman had those standard warranties of 5/5 at that time, that particular model came with a 10/10 as it was a higher SEER rated than their 10 SEER units out there.

I’ll probably change them out in a few years, as a PM before my body doesn’t work anymore, I don’t want to leave that decision to my wife to deal with, paying the big bucks and who knows the quality of install, it’s not like I’m a spry young guy.

 

[malysh]

Good material in here!

I had no idea that the evaporator coils could ever avoid leaking. Will ask for the new type!

Indeed, I will grab the cheapest SEER 14 unit, to go with the old furnace. Our AC does not need to be fancy - just need to work a lot in the summer.

 

[BBeerme]

My evap is probably 40 years old. I'm guessing standard copper tubing. I installed it ~20 years ago, evap robbed from a then old package unit, maybe 20 years old.

 

[joemach]

Make sure to register your new equipment so you get the 10 year equipment warrantee.