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Discussion Starter · #1 ·
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Is this a fixed orifice or is something with with a little piston inside or are those also fixed orifices?

Let me take it from the top. This goes back to about 1983. Residential R22 2.5 ton. In 1994 the compressor failed and the condensing machine was replaced due to a failed compressor. I don’t think any other changes were made.

Flash forward to present day. It still runs, still cools, but weekly. Enough to produce condensate but typically just a 12-15° drop. Pressure has been checked. It’s a Copeland recip. Prob just very worn out.

I know I should replace the whole caboodle for max efficiency but I just got a great deal on a 3 ton R22 brand new old stock (2009) condenser.

The plan was to get a tech to recover, hook it up, pull a vacuum, open her up, and top off as needed. I have a filter/dryer for them to add. It’s a Carrier with a Copeland scroll. But it says not to use it with cap tube or fix orifice. If that’s what I have, would it damage my new toy? Should I have a TXV added? If so I’d kinda like to get it myself so they only need to braze it in. What’s the crucial factor? R22 & 2.5 or 3 ton? Not sure of the evap model but it’s so old I doubt it appears in any table. Yes, I know this might be a kluge at best.
 

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If there's nothing else after that, inside the plenum, then it would be a piston.

Either way, you really should be changing the inside coil when it's that old. It's only a matter of time before it leaks. You can use a piston on a scroll as long as it's the right size, although you get better performance with a TXV.

Cheers!
 

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Potential leakage is not the only concern - a 13 seer will not hit full efficiency or capacity on a coil designed for 10 seer.
Change the coil.

It's stupid to use an r22 unit at this point, the refrigerant isn't made any more.
Why not sell the r22 unit and buy a 410a matching set?
 

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Discussion Starter · #4 ·
Potential leakage is not the only concern - a 13 seer will not hit full efficiency or capacity on a coil designed for 10 seer.
Change the coil.

It's stupid to use an r22 unit at this point, the refrigerant isn't made any more.
Why not sell the r22 unit and buy a 410a matching set?
 

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Discussion Starter · #5 ·
Lol that would make too much sense. It’s a downflow which means pulling the furnace. Which should be replaced too. Just dragging my feet. This will help me drag it out more.

Just to be clear, a piston dealy is not a fixed orifice?

Any advice on choosing a TXV if I go that route?
 

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A piston is a fixed orifice, same thing.

2.5 ton coil designed for 10 seer will be horribly undersized for a 3 ton 13+ seer.
A r22/407c txv would help the outdoor unit work better with an old coil, but still at a reduced capacity.

If the existing coil is uncased, it may be possible to change it without removing furnace, if there's enough space.

Doing what you propose will come back to bite you.
Better to just use window units until you can afford to get this done properly.
 

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Discussion Starter · #7 ·
A piston is a fixed orifice, same thing.

2.5 ton coil designed for 10 seer will be horribly undersized for a 3 ton 13+ seer.
A r22/407c txv would help the outdoor unit work better with an old coil, but still at a reduced capacity.

If the existing coil is uncased, it may be possible to change it without removing furnace, if there's enough space.

Doing what you propose will come back to bite you.
Better to just use window units until you can afford to get this done properly.
 

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Discussion Starter · #8 ·
Oh, I can afford it; I just enjoy going a different route. I don’t need 3 ton capacity. 2.5 was enough for decades. Efficiency is bound to increase from what I’ve had the last few years. I just don’t want the new unit to hurt itself. (Or me.) If all is well when I get the furnace replaced that be a good time to replace the evap. Maybe the lineset too. Then I will achieve 2009 efficiency! Woo!
 

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Oh, I can afford it; I just enjoy going a different route. I don’t need 3 ton capacity. 2.5 was enough for decades. Efficiency is bound to increase from what I’ve had the last few years. I just don’t want the new unit to hurt itself. (Or me.) If all is well when I get the furnace replaced that be a good time to replace the evap. Maybe the lineset too. Then I will achieve 2009 efficiency! Woo!
To get a real efficiency increase, the indoor coil has to be appropriate for the outdoor unit.
A 3 ton/13 seer on a 2.5 ton/10 seer coil could use the same amount of electricity or more than what you have now -> a gross mismatch. Not just a question of getting full capacity.

The coil should be an approved match for the outdoor and it is not a good idea to replace a a/c system in bits and pieces at different points and be stuck with r22.

Get everything done right the first time.
 

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Oh, I can afford it; I just enjoy going a different route. I don’t need 3 ton capacity. 2.5 was enough for decades. Efficiency is bound to increase from what I’ve had the last few years. I just don’t want the new unit to hurt itself. (Or me.) If all is well when I get the furnace replaced that be a good time to replace the evap. Maybe the lineset too. Then I will achieve 2009 efficiency! Woo!
You could possibly make the unit less efficient then what you currently have by going this route. With a gross mismatch.
 

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Discussion Starter · #11 ·
You both are missing the point. When I say more efficient than what I have now I am not referring to the old gear as installed or over much of its life but as it is today, very worn out, with very long cycles just to drop the temp a couple of degrees. It’s not difficult to beat that.
 

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You can do what you please, but I’d advise against it. Sometimes sweet deals leave a bad long lasting aftertaste.
You'll be changing the metering device to a TXV.
 

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Discussion Starter · #15 ·
I think for the time being I’m going to do nothing and see how the old girl fares. If something comes along that is more of a direct swap maybe I’ll do that or look into the present one in greater detail. For now I’ve built a crate to keep keep it pristine in the garage.
 

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If you really insist on it, then it'll work. It won't be ideal, but it'll work. I'd still recommend replacing the evap though, at least at some point. Sooner the better. Make sure the new one is rated for 410A in case that new-old unit doesn't last nearly as long as you'd hoped. Technically you don't need factory certified matching parts if you know how to match specs. I usually get better performance then the factory spec sheets, by a significant margin. It's still highly recommended that you get matching components as you really need to know what you're doing otherwise. R22 is NOT cheap, so it'll become a worse option as the years pass. My customers really don't like it when I quote them my prices, and options. Drop in replacements are just as bad price wise. Good luck, you'll need it.

Cheers!
 

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Good chance your current indoor/evap coil needs cleaned.

Putting a 3 ton condenser on that 2.5 ton coil without increasing air flow can cause a lot of problems. Such as the indoor coil freezing up. Water over flowing the drain pan and running into the duct work and causing mold.
 
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Discussion Starter · #18 ·
As it’s at floor level, there is really nothing to clog as the drain comes right out and water flows to a floor drain. It’s difficult to see the whole coil but from what I can see it’s not particularly dirty. I had thought enough dirt had gotten past the filters over the many years to make the coil in serious need of cleaning but no, I’m not seeing it.

This was my late folks’ house and I have vague recollections of it being installed and raising two questions either then or some subsequent service call. One was a sharp bend in the suction. I was assured there was an elbow but I had my doubts as it would seem difficult to pull the insulation over it. Finally, after all these years I razor bladed the insulation (putting it back an aluminum taping it in place). Yes there really is an elbow there.

The other question was about the furnace (a downflow) sitting on what appeared to be a tin box of thin ductwork metal cut and brake-press folded. They said there is a frame carrying the weight. Well, so far I cannot see any frame. But there must be, right? If I can’t see anything then safety obligates me to assume there is nothing but the box and that limits my disassembling it. Guess I could rig supports to take the furnace weight. I already rigged a sort of indicator to show any vertical movement. Gas line is rigid black pipe so I don’t want any movement beyond maybe a mm or two.
 

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Discussion Starter · #19 ·
If you really insist on it, then it'll work. It won't be ideal, but it'll work.
Thank you. Long story but I’ve got a jug of R22 (primarily as a backup for a package system at my business. Landlord takes care of that but better safe than sorry. Old building engineer had an EPA card. Not sure about now.) Anyway, I think I’m okay sticking with it for now.

If I do press on with this, any help in selecting a TXV? Just choose one for R22, 2.5 ton?
 

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The TXV must be for the size of he outdoor unit.

And you will need to increase air flow, or the indoor coil will freeze over
 
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