A Question for the HVAC Experts

[MrSurly]

I'm going to have to replace the cased coil on the central unit and I need some direction on selecting the specific replacement.
The unit is under ten years old and the A-coil has sprung another leak. A couple of years ago it popped a pinhole in the center of the coil (pic3) and I re-routed the coil piping to bypass the offending segment, (pic4) knowing that I was just buying a little time. The unit's been doing fine but now my borrowed time is up...at the height of the summer heat, of course.
The pics show the tag, and part of the dilemma about selection.
The installation is quite cramped as seen in the pics, (pic2) so I'd like to replace this with a shorter unit for clearance, but that's not of major importance.

I mainly want to replace this with one that is tin-coated so that maybe the coil could at least outlast a fan motor or two.
I'm hoping you guys can decipher the info from this one and possibly provide the number of the appropriate replacement.
Maybe an N-coil? Sheet metal/plenum alteration is no problem.
R22 Unit CAC/BDP CD5AXA048021ABAA

Thanks for your help.

[YankeeBob]

I didn't do any coil replacements in my career, so I'm not going to be much help with choosing one. My a/c experience is limited to installs and compressor changes, as I started doing a/c work only later in my career. But, your statement "sprung another leak" draws concern. Acidic refrigerant comes to mind. I would be looking at the whole system very carefully, not just swapping out coils.

[Infidel!]

This is NOT the best time for your AC to go out. It was 109 yesterday! You may want to call KenR

[J.A.F.O.]

Get a Goodman cased coil...

looks like you need a 4 ton.
They have a couple of different widths, so measure the width of your furnace and match it to that.
The new one will probably come with an expansion valve, so your SEER will go up a bit.

[J.A.F.O.]

Oh and it's, a Carrier coil well, actually Carriers builder line, Stay away from it, they suck, 4 tons, built in 2004.
Are you using R-22 or 410a?

[MrSurly]

Yeah, they used the cheapest thing on the market. I've been reading a bunch about the troubles everyone has been having with these p.o.s. Carrier coils.
What do you think about going to a TXV? I'm thinking it's a plus all around, except that they CAN get sticky sometimes.
Does the model number provide enough info to be able to determine the number for the replacement?
The unit is R22. The case is 21 X 21 X 25.5 high.
Have you seen a lot more failed coils these days, compared to a decade ago?
My reading seems to indicate that it's an epidemic lately. (and it's on the interwebs so it MUST be accurate)
What do you think about the tin-coated coils? Recommended?
Thanks for your help.

[J.A.F.O.]

Originally Posted by MrSurly

Yeah, they used the cheapest thing on the market. I've been reading a bunch about the troubles everyone has been having with these p.o.s. Carrier coils.
What do you think about going to a TXV? I'm thinking it's a plus all around, except that they CAN get sticky sometimes.
Does the model number provide enough info to be able to determine the number for the replacement?
The unit is R22. The case is 21 X 21 X 25.5 high.
Have you seen a lot more failed coils these days, compared to a decade ago?
My reading seems to indicate that it's an epidemic lately. (and it's on the interwebs so it MUST be accurate)
What do you think about the tin-coated coils? Recommended?
Thanks for your help.

Go with a TXV, the only TXVs I've had a problem with are ones that American-Standard put out a few years ago. Other wise...I've been dealing with them for about 30 years, especially when I did refrigeration and they work great,.
I haven't seen nor heard of any excessive evap coil issues.
To be honest, I don't pay attention to what these things are made of. If I started to have issues with the Goodman coils then I might be interested. But as of now, they've all been fine.
As far as I know, they are copper tubes with aluminum fins.

Don't over think this.
get a 4 ton cases coil that will fit your air handler. Goodman would be fine, if they aren't available in your area, let me know what is and I'll suggest the best one for you. BTW, Amana and Maytag are Goodman.
Get one with a TXV and off you go.

[MrSurly]

Pepe, I got by the local Baker outfit late today and found that he had the cased coil in a Heil but no (r22) TXV for it; None local...
Of course, the system's down and it's 104 today and I hafta do something but I was way outta time. I got from him the only 'fix' he had on hand, which was a Mortex A-coil uncased, piston type. As I was leaving at 4:59 he said he found a TXV for the Heil, there's one about two hour's drive away.
I'm stuck right now, not wild about the Mortex (never heard of 'em) and thinking that in the morning I'll go get the TXV and the Heil coil. Your thoughts?

[YankeeBob]

A TXV will increase your system efficiency because it will meter the correct amount of refrigerant to the coil in any given (variable) load. However, it may put a larger demand on an older compressor due to the fact that between cycles, the TXV shuts off the flow of refrigerant to the low side. This can make the compressor start harder than it would with a fixed orifice. If your compressor isn't too old, I wouldn't worry about it.

[J.A.F.O.]

Originally Posted by YankeeBob

A TXV will increase your system efficiency because it will meter the correct amount of refrigerant to the coil in any given (variable) load. However, it may put a larger demand on an older compressor due to the fact that between cycles, the TXV shuts off the flow of refrigerant to the low side. This can make the compressor start harder than it would with a fixed orifice. If your compressor isn't too old, I wouldn't worry about it.

Actually, it shouldn't matter...When the system shuts down, the TXV will throttle open due to a warm suction line. The TXV thinks it needs to open to supply more refrigerant.
In any case once the system shuts down, the pressures will equalize whether its a cap tube, piston or TXV.


If possible;e go with the TXV, in the long run it'll help with your efficiency.

[MrSurly]

I did the running this morning, got the Heil coil (don't know their rep either) its a cased 410a txv N coil setup. I'll hafta swap the TXV and mod the plenum, but I think I'll get 'er done.

Someday I'll share the rant about the original install guy's work.

[YankeeBob]

Originally Posted by J.A.F.O.

Actually, it shouldn't matter...When the system shuts down, the TXV will throttle open due to a warm suction line. The TXV thinks it needs to open to supply more refrigerant.
In any case once the system shuts down, the pressures will equalize whether its a cap tube, piston or TXV.


If possible;e go with the TXV, in the long run it'll help with your efficiency.

Makes perfect sense.
I trust the words of a man who has "been around the block a few times". You can always learn something.

Thanks!

[y2kflhr]

Originally Posted by YankeeBob

Makes perfect sense.
I trust the words of a man who has "been around the block a few times". You can always learn something.

Thanks!

he was around the block in a low rida......

[Ken R]

I think all replacement coils from Carrier come with a TXV now. I see from your pictures that your system uses R410a TXV. All carrier coils come with a compatible TXV.

The nomenclature for a "tinned" coil is that the part number has "ATA" as the last three characters. But one of my former employees told me that there is something even better now. I don't know what it is, but the distributor will know.

All coil manufacturers were having pinhole leak problems starting about 12 to 15 years ago. When the federal government insisted on higher efficiency, one of the ways to comply was with thinner copper evaporator coil tubing that was "rifled" inside to swirl the refrigerant. Within a couple of years, the problems with pinhole leaks surfaced. Rheem/Ruud, Lennox, Goodman, et al . . . . they all developed leaks; some sooner than others. At first they thought it was impurities in the copper. Then they blamed it on household products like hair spray, cleaning sprays, etc. Finally, they tried different things to stop the leaks. The "tinned" coils was their best answer at the time. Carrier was the first to come out with it and they led the industry in leak-free evaporator coils with their tinned coils. They really were the best.

All the Carrier coils nowadays are warranted for 10 years. (labor extra). You can get a labor warranty . . .I have labor warranty on my home systems. (I'm tired of working on AC systems . . . . especially my own).

Freon dynamic pressures are way lower than the new Puron pressures. All new coils are designed and built to hold Puron (R410a) refrigerant.

Ken

[MrSurly]

It is done, but there is more to sort out...
I pumped down the unit and installed a 4ton Heil coil with txv designed for r410a. My system is r22, the perforated A coil was a piston set up. I changed the txv in the new coil to the proper r22 txv. Pulled a vacuum, no leaks. Opened the service valves and fired it up. I didnt add gas to it as the suction pressure seemed to slowly creep upward.
All seemed great but I'm not thrilled yet.
It's 101 and the system is not keeping up. Note that it never kept up well in these temps before but did better than just now. Previously it would get to about 78-79 but today it's 88 (!) in the house.
I have suspicion as to cause but lemme give you the particulars and see what y'all think.