PDA

View Full Version : Repairing copper coil in central A/C unit - HVAC question


silk1976
11-25-2008, 11:21 AM
What have I done, and am I in for a world of hurt to fix it?

Without going into all the detail, I made a stupid mistake and ended up nicking a copper tube inside my central A/C unit (in the plenum above the furnace - so the inside heat exchanger portion) with a drill bit. Of course, it was enough of a nick to cause a leak.

Now all the refrigerant is gone, and I have a copper tube in a heat exchanger that needs repair, followed by a recharge of the entire unit.

So I guess my question is whether this is repairable - and how easily can it be repaired. I'm going to leave this to the pro's (I have an appt for someone to come out tomorrow) - I know that I have backed myself into a corner that I cannot get out of without help. I'm just trying to gauge whether it'll be a relatively cheap fix or not. I'm scared that the worst case scenario - total replacement of the entire heat exchanger inside the house - will be necessary. However, I figure that this kind of stuff must happen regularly enough that it seems very likely there would be a less intense (and cheaper) repair option available.

For those who might be HVAC professionals - just to give some more detail: The heat exchanger in the unit is in a pyramid shape, and it looks like the refrigerant tube runs back and forth from top to bottom. The nick is on one of the 180 degree bends. The best I can come up with for a description of the damage is if you were to take a normal sized flathead screwdriver, and hammer it against a copper tube. There is definately some misshapen tube that got bent inwards, and (obviously) a portion has pierced through. It was enough of a leak that all the refrigerant had leaked out within 12 hours. Are those bends something that can simply be cut off, and new tube soldered back on in place? Perhaps it depends on the unit - maybe the copper bends were soldered in in the first place, and they can be easily removed and replaced.
I just dont know what is typical for designs of these things.

Thanks for any words of wisdom and knowledge.

beowulff
11-25-2008, 11:28 AM
What have I done, and am I in for a world of hurt to fix it?

Without going into all the detail, I made a stupid mistake and ended up nicking a copper tube inside my central A/C unit (in the plenum above the furnace - so the inside heat exchanger portion) with a drill bit. Of course, it was enough of a nick to cause a leak.

Now all the refrigerant is gone, and I have a copper tube in a heat exchanger that needs repair, followed by a recharge of the entire unit.

So I guess my question is whether this is repairable - and how easily can it be repaired. I'm going to leave this to the pro's (I have an appt for someone to come out tomorrow) - I know that I have backed myself into a corner that I cannot get out of without help. I'm just trying to gauge whether it'll be a relatively cheap fix or not. I'm scared that the worst case scenario - total replacement of the entire heat exchanger inside the house - will be necessary. However, I figure that this kind of stuff must happen regularly enough that it seems very likely there would be a less intense (and cheaper) repair option available.

For those who might be HVAC professionals - just to give some more detail: The heat exchanger in the unit is in a pyramid shape, and it looks like the refrigerant tube runs back and forth from top to bottom. The nick is on one of the 180 degree bends. The best I can come up with for a description of the damage is if you were to take a normal sized flathead screwdriver, and hammer it against a copper tube. There is definately some misshapen tube that got bent inwards, and (obviously) a portion has pierced through. It was enough of a leak that all the refrigerant had leaked out within 12 hours. Are those bends something that can simply be cut off, and new tube soldered back on in place? Perhaps it depends on the unit - maybe the copper bends were soldered in in the first place, and they can be easily removed and replaced.
I just dont know what is typical for designs of these things.

Thanks for any words of wisdom and knowledge.
It should be an easy fix - the AC guy will just hard solder a patch over the nick, pump it down and recharge. Of course, he'll take this as the perfect opportunity to sell you a new AC...

silk1976
11-25-2008, 11:48 AM
It should be an easy fix - the AC guy will just hard solder a patch over the nick, pump it down and recharge. Of course, he'll take this as the perfect opportunity to sell you a new AC...

That would be AWESOME if the fix can be done that easily.

The unit is only 2 years old, so if he tries to sell me a new one, he'll get a serious :dubious:

Thanks for the encouraging response.

raindog
11-25-2008, 11:58 AM
What have I done, and am I in for a world of hurt to fix it?

Without going into all the detail, I made a stupid mistake and ended up nicking a copper tube inside my central A/C unit (in the plenum above the furnace - so the inside heat exchanger portion) with a drill bit. Of course, it was enough of a nick to cause a leak.

Now all the refrigerant is gone, and I have a copper tube in a heat exchanger that needs repair, followed by a recharge of the entire unit.

So I guess my question is whether this is repairable - and how easily can it be repaired. I'm going to leave this to the pro's (I have an appt for someone to come out tomorrow) - I know that I have backed myself into a corner that I cannot get out of without help. I'm just trying to gauge whether it'll be a relatively cheap fix or not. I'm scared that the worst case scenario - total replacement of the entire heat exchanger inside the house - will be necessary. However, I figure that this kind of stuff must happen regularly enough that it seems very likely there would be a less intense (and cheaper) repair option available.

For those who might be HVAC professionals - just to give some more detail: The heat exchanger in the unit is in a pyramid shape, and it looks like the refrigerant tube runs back and forth from top to bottom. The nick is on one of the 180 degree bends. The best I can come up with for a description of the damage is if you were to take a normal sized flathead screwdriver, and hammer it against a copper tube. There is definately some misshapen tube that got bent inwards, and (obviously) a portion has pierced through. It was enough of a leak that all the refrigerant had leaked out within 12 hours. Are those bends something that can simply be cut off, and new tube soldered back on in place? Perhaps it depends on the unit - maybe the copper bends were soldered in in the first place, and they can be easily removed and replaced.
I just dont know what is typical for designs of these things.

Thanks for any words of wisdom and knowledge.
That "heat exchanger" is an "evaporator coil." The only thing tricky about this is that the leak is in a "U tube", and the cooper in the U tubes are often paper thin. The tech will not remove the U tube but braze over it; essentially patching it.

From there a qualified tech should pressure test it with dry nitrogen to make sure the patch is good, and there are no other leaks. From there a vacuum pump is put into use to "evacuate" any/all air and moisture. Then it is recharged with new Freon.

In my neck of the woods:
$28 per per pound of Freon. (ranges between $20-35), and there is typically 1.5 to 3 pounds of Freon per ton. Look at your model number outside and there will be some factor of "6" in the model number, as there is 12,000 (12) btus in a ton. For example, if there is a "24" in the model number you have a 2 ton; "30" is 2.5 ton, "36" is 3 tons etc.

So......a 3 ton unit has maybe 4.5 to 9 pounds of Freon in it------at $28/pound. ***Look at your information outside, because many units will list "the factory charge" on the nameplate, that will tell you approximately how much freon this unit holds.*** So, here's my internet bill:

3 ton unit; 3 tons x 2 pounds per ton = 6 pounds x $28/ton = $168 Freon
Brazing rod, gas, nitrogen, etc $20

Travel .5 hrs at $70 $35
1.5 hrs on site @ $70 $105
Vehicle cost $25

Total bill: $356

Now prices vary wildly, so your bill may be higher or lower than this. In fact, my bill might be lower if the repair was simple or the unit takes less freon. But that's my best internet guess.

silk1976
11-25-2008, 01:23 PM
That "heat exchanger" is an "evaporator coil." The only thing tricky about this is that the leak is in a "U tube", and the cooper in the U tubes are often paper thin. The tech will not remove the U tube but braze over it; essentially patching it.

From there a qualified tech should pressure test it with dry nitrogen to make sure the patch is good, and there are no other leaks. From there a vacuum pump is put into use to "evacuate" any/all air and moisture. Then it is recharged with new Freon.

In my neck of the woods:
$28 per per pound of Freon. (ranges between $20-35), and there is typically 1.5 to 3 pounds of Freon per ton. Look at your model number outside and there will be some factor of "6" in the model number, as there is 12,000 (12) btus in a ton. For example, if there is a "24" in the model number you have a 2 ton; "30" is 2.5 ton, "36" is 3 tons etc.

So......a 3 ton unit has maybe 4.5 to 9 pounds of Freon in it------at $28/pound. ***Look at your information outside, because many units will list "the factory charge" on the nameplate, that will tell you approximately how much freon this unit holds.*** So, here's my internet bill:

3 ton unit; 3 tons x 2 pounds per ton = 6 pounds x $28/ton = $168 Freon
Brazing rod, gas, nitrogen, etc $20

Travel .5 hrs at $70 $35
1.5 hrs on site @ $70 $105
Vehicle cost $25

Total bill: $356

Now prices vary wildly, so your bill may be higher or lower than this. In fact, my bill might be lower if the repair was simple or the unit takes less freon. But that's my best internet guess.


Yeah I figured there would be a good deal of variance in the price.

My unit is 2.5 ton. I checked the placard this morning and saw that it came charged from the factory. The only number I saw was 1.6 Kg - which at the time seemed unlikely - but now that I think of the conversion factor, I realize that its 2.2 lbs per kilogram, not the other way around.

(As I get older, I forget a little more each and every day. I'm only 32 - I got a lot of forgetting to do!)

Anyhow, I didn't spend a whole lot of time looking (it was raining and I was dressed up for work) - so its possible the 1.6 Kg referred to something else. However, that is is the right ballpark at 3.5 lbs, if a little shy. Your estimates for labor and overhead seem to be in the ballpark for what they will charge me for the service call - so I find your cost estimate to be useful as well. Thank you.

(and ya know - I thought maybe the copper on those tubes was very thin. I've dealt with copper pipe before in sweating connections, and as soon as the damage was done I thought to myself 'damn those tubes must be thin as hell because I didn't hit it nearly hard enough to go through the schedule M pipe I've used in the past!')

So this will be a nice $200+ lesson learned. I hate these kinds of lessons because they usually come down to stupidity on my part and not taking a second to think something through. I'll end up telling myself I'm still ahead of the game because I recently did about $3000 worth of suspension work on my car for the cost of $500 in parts and a weekend of labor.

raindog
11-25-2008, 03:52 PM
Good luck!

Let us know how it turns out.

silk1976
11-26-2008, 12:47 PM
So someone came to look at it.

He basically said that trying to patch over or braze the hole in the copper bend would be a useless effort. He said it would just make the hole bigger, and that even if he could get a patch over it (being on the bend makes it more difficult), the possibility of it leaking would be very high, and then in a year or two I'm back in the same boat.

So he wants to sell me a new coil.

It seems shady to me. I mean - this sort of thing has to happen often enough that the solution cannot be to replace the coil every time.

Also - he was saying it would cost about $90/lb to recharge the system with R-22. That seems a bit high, even for geographical differences (I'm in eastern MA, btw - so who knows).

Dag Otto
11-26-2008, 01:08 PM
So he wants to sell me a new coil.

It seems shady to me. I mean - this sort of thing has to happen often enough that the solution cannot be to replace the coil every time.



He should be willing to provide a warranty with a new coil. Doesn't sound like he would do that with a patch, and a second service call won't make anyone involved happy.

The R-22 sounds high, but does it include the time/steps necessary to charge the system? He may just charge a flat rate per pound on small jobs that include his time.

gotpasswords
11-26-2008, 01:58 PM
As a raw material, $90 per pound for either R22 or R410 is outrageous, but more likely, that includes the labor of pumping down the system, leak testing and re-filling. All of the equipment needed to do this is expensive, so it's part of the price.

As a raw part, a 2.5 ton "uncased" (ie: naked) evaporator coil is in the $200-300 range.

As you've learned, A-coils are supremely fragile things, and repairing them can be iffy, regardless of their age. Have you called anyone else for a second opinion yet?

silk1976
11-26-2008, 02:55 PM
I haven't gotten a second official opinion yet.

The $1500 includes the new coil, and all the service to patch it in and recharge the system.

The price of $90/lb was the response when I asked about just recharging. I didn't confirm, but it sounds likely that the cost includes labor, equipment, etc. In other words, flat rate of about $400 for recharging a system that takes 4 lbs of R-22.

Fortunately its not the cooling season, so I have some time to figure things out a bit more. I'd like to find some old-timer who knows every trick in the book and can fix it in place, but from what I gather, even if it can be fixed it more then likely requires have the whole coil out and on a work bench.

My father in law's coworker does a lot of A/C stuff and has quite a bit of experience (as FIL says - if he can't fix it, noone can). He told us that if we can get the coil to him, he can give it his best shot at fixing it - but until he sees the thing himself, there's no way to be sure. If he can fix it, then we would have to have someone out in the spring to rebraze the in/out connections, and recharge.

I just dont want to make things worse at this point - but I suppose if the coil ends up needing replacement anyway - those in/out connections will be necessary no matter what.

Why are these coils so damn fragile? I mean - its one thing for a DIY'r to screw up and have to pay for their mistake - but I have to believe that even pro's ding those copper U-bends once in a while at job sites for whatever stupid reasons. It just seems to me that its a rather poor design if the best option is replacement.

Dag Otto
11-26-2008, 04:18 PM
Why are these coils so damn fragile?

Because copper is expensive. Profitability of AC manufacturers took a big hit when the cost of raw materials like steel and copper went up a few years ago. Plus, they are usually protected from drill bits by the air handler housing.

beowulff
11-26-2008, 04:21 PM
If it were me, I'd call around until I found an A/C guy willing to try a patch. Explain to him upfront (maybe send some digital photos) where the hole is.
It's probably going to require some skill, but it shouldn't be impossible to do. Besides, it's already broken - what do you have to lose by trying to patch it?

Melkor28
11-26-2008, 06:08 PM
The guy is being a bit of a prick. I install ductwork for a living. LU 28 NYC Sheet Metal Worker. I install the A/C units "50/50" with the Steamfitters, LU 638.( 2 Sheet Metal Workers, 2 Steamfitters). The steamfitters hook up the copper, I hook up the duct work. My father told me "Your not a real "Tinknocker" untill you hit a coil!" I put a tex-screw into a coil a few times; and the fitter simple solders the hole closed. This has happend on small A/C units, feeding like 2 rooms; so the coil would be about the same thickness as yours. He is just trying to get more money out of you for an easy job.

The worst was actually my partner, all 8 screws from the duct connection hit the coil. We had to go back and reinstall the duct they took down to repair the unit. I say it was a bad design to have the coil about 1/16 of an inch from the discharge of the unit.

Snnipe 70E
11-26-2008, 07:54 PM
He should be willing to provide a warranty with a new coil. Doesn't sound like he would do that with a patch, and a second service call won't make anyone involved happy.

The R-22 sounds high, but does it include the time/steps necessary to charge the system? He may just charge a flat rate per pound on small jobs that include his time.


If I was in the field I would not give any warranty for a hack job. The A coil is fragle for several reasons. Origonal cost. Thinner copper will have a better heat transfer rate among the most common.

Depending on the size of hole, location, and construction of the A coil will determine if it can be repaired.

From earlier posts I was thinking you were in for an expensive repair.

raindog
11-27-2008, 09:56 AM
Don't talk to this guy again. gotpasswords (who I think is in the business) was right; the wholesale cost of a new coil is $250-300. With markup, labor, misc materials we would sell this (in SW Ohio) for $7-800 and that includes new Freon. $1500 seems outrageous no matter where you are.

The U tubes on coils have been paper thin forever. Soldering them is trickier that a leak on the "lineset" because the copper on them is much thicker.

To solder a hole in a U tube requires a filler metal other than [soft] solder. (products like "Stay Bright 8", or "50-50.") Soft solder has a very low melting point and so propane or mapp gas can be used. But not in this case.

When it's a hole, most often you have to use "brazing rod" as a filler metal. That requires acetylene or oxy/acetylene, not propane. The filler metal will not "liquify" until it hits around 1400F. (and propane doesn't burn that hot)

The problem is, the melting point of your brazing rod is close to the point you'd melt the [paper thin] U tube. It's certainly not impossible (I've done it many times) but it requires a guy with a little experience in brazing. It's the same process as fixing any other leak, just a little trickier because of the wall thickness on the U tube.

Keep calling to you get someone who will talk some sense.

I also see no reason to remove the coil unless access is difficult. This will only increase costs. Fix it in place unless there is no other option.

Snnipe 70E
11-27-2008, 11:39 AM
You do not use soft sodder on a AC system unless you want it to come apart.

beowulff
11-27-2008, 11:48 AM
You do not use soft sodder on a AC system unless you want it to come apart.

I wouldn't use sodder on anything.

Q.E.D.
11-27-2008, 11:50 AM
That requires acetylene or oxy/acetylene, not propane. The filler metal will not "liquify" until it hits around 1400F. (and propane doesn't burn that hot).

I use oxy-MAPP for brazing. The stuff is much easier and safer to handle or store, plus it burns nearly as hot as oxy-acet. On the downside, unburnt MAPP stinks.

Goblinboy
11-27-2008, 01:20 PM
I wouldn't use sodder on anything.

Doesn't stop people from using it who should know better.

A word of warning. If you get any weld work done on the system, check to make sure you've got a filter downstream before you get to your compressor. If any metal shavings or solder gets to the compressor it can destroy the valves and require a complete replacement.

raindog
11-27-2008, 01:49 PM
You do not use soft sodder on a AC system unless you want it to come apart.
I used to believe this, however I went to a brazing class given by the JW Harris Company, the people who make "Dynaflow", and "Sta-Bright 8", two of the most common products in brazing/soldering.

We took a 1 1/8" piece of ACR hard copper about 10" long and brazed (with Dynaflow & oxy/acetylene) a cap on one end and soft soldered (with Sta-Bright 8 and propane) a male adapter on the other end.

We took the finished pipe and put in a hydraulic chamber with clear plexiglass and pumped it until it burst. In every single test the pipe burst near the brazed cap. Every Single Time.

The burst pressure was around 3000psi. (this was either "L" or "K" thickness) I brazed two of them back together and they burst again around 1800 psi. (the hole was around the size of a dime; a tear)

The engineer explained to us that the heat of the oxy/acetylene weakens the copper sufficiently that it will always burst there.

On top of that, I asked the engineer about oxidation. When you braze the pipe oxidizes and there is flaking and discoloring etc. the exact same thing is happening inside the pipe and that oxidation is potentially harmful to the A/C system.

I also took a test to be certified in brazing/soldering some years ago. The tensile strength------the strength to pull apart a soldered joint was around 30,000 psi if I remember correctly.

So I continued to quiz the engineer:

"It seems to me that soft soldering produces:

1) Superior bursting strength
2) Superior tensile strength, and most importantly,
3) No polluting of the inside of the refrigeration system

Doesn't that mean that overall soft soldering with propane is a superior connection?"

He said, in his view, definitely yes.

Now I've asked this question dozens of times in the years that have passed, and I've heard nothing that disputes it. My experience is that for patching, or large holes, or for older, particularly sloppy fittings brazing is the way to go.

But a new system with new lineset and fittings? IMO Sta-Bright 8 with propane is a superior connection.

Snnipe 70E
11-27-2008, 02:13 PM
IOn top of that, I asked the engineer about oxidation. When you braze the pipe oxidizes and there is flaking and discoloring etc. the exact same thing is happening inside the pipe and that oxidation is potentially harmful to the A/C system.

I.

That is why when brasing you should be using nitrogen gas to purge the lines. If you do not you could end up withmajor problems.

A numer of years ago I had to repair a lot of lines on a system that had soft sodder used on them. The building was a grocery store that went out of business. A department store purchased the building and was using it as a clearance store. Additional AC was added to the building. Someone came up with the bright idea of using the old condencers for the cold storage units. They were R12. The AC units that were put in were R22. Temperatures and pressures on R22 are higher than R12. On a really hot day the soft soddered joints began to leak and come loose. So al low temperatures soft sodder may be stronger but I would question anyone who would use it on a AC system.

raindog
11-27-2008, 02:44 PM
That is why when brasing you should be using nitrogen gas to purge the lines. If you do not you could end up withmajor problems.

A numer of years ago I had to repair a lot of lines on a system that had soft sodder used on them. The building was a grocery store that went out of business. A department store purchased the building and was using it as a clearance store. Additional AC was added to the building. Someone came up with the bright idea of using the old condencers for the cold storage units. They were R12. The AC units that were put in were R22. Temperatures and pressures on R22 are higher than R12. On a really hot day the soft soddered joints began to leak and come loose. So al low temperatures soft sodder may be stronger but I would question anyone who would use it on a AC system.
Soft solder melts at temperatures around 350F or higher, iirc.

An R22 system will run maybe 300psi on a very hot day. That corresponds to 130F. (and, in fact, pretty inefficiently at that. Most R22 systems will run 250-300 psi on hot days)

At 350 psi it will be at 145F.

At 500 psi--------which no R22 compressor will run at for more than a couple seconds------it will be at around 210F.

Have you ever seen a R22 with a liquid line temp anywhere near 350F?

I haven't. I haven't even seen it in a heat pump where the suction line becomes the discharge line!

raindog
11-27-2008, 02:53 PM
I think you highlight the only risk associated with soft soldering vis a vis brazing:

Lower melting point.

But in my experience A/C systems don't see temperatures anywhere near the melting point. Ever.

In my experience, the benefits ------for new systems with clean, new, fittings------far outpace the near impossible risk of melting the solder.

Snnipe 70E
11-27-2008, 05:06 PM
Soft solder melts at temperatures around 350F or higher, iirc.

An R22 system will run maybe 300psi on a very hot day. That corresponds to 130F. (and, in fact, pretty inefficiently at that. Most R22 systems will run 250-300 psi on hot days)

At 350 psi it will be at 145F.

At 500 psi--------which no R22 compressor will run at for more than a couple seconds------it will be at around 210F.

Have you ever seen a R22 with a liquid line temp anywhere near 350F?

I haven't. I haven't even seen it in a heat pump where the suction line becomes the discharge line!


I am not going to dig out my PT chatrs but 145 degres at 350 sounds about right for saturated temperature. But the discharge from a compressor is superheated. Last time I shot the heads of a compressor with a rey teck the temp on the compressors with an water cooled tower was in the 190 to 230 degree range.

Rick
11-27-2008, 05:42 PM
I would like to note that the OP has a hole in the evaporator, which is on the low side of the system, and while in operation probably will never see the high side of 100PSI.

silk1976
11-27-2008, 08:50 PM
Don't talk to this guy again. gotpasswords (who I think is in the business) was right; the wholesale cost of a new coil is $250-300. With markup, labor, misc materials we would sell this (in SW Ohio) for $7-800 and that includes new Freon. $1500 seems outrageous no matter where you are.

The U tubes on coils have been paper thin forever. Soldering them is trickier that a leak on the "lineset" because the copper on them is much thicker.

To solder a hole in a U tube requires a filler metal other than [soft] solder. (products like "Stay Bright 8", or "50-50.") Soft solder has a very low melting point and so propane or mapp gas can be used. But not in this case.

When it's a hole, most often you have to use "brazing rod" as a filler metal. That requires acetylene or oxy/acetylene, not propane. The filler metal will not "liquify" until it hits around 1400F. (and propane doesn't burn that hot)

The problem is, the melting point of your brazing rod is close to the point you'd melt the [paper thin] U tube. It's certainly not impossible (I've done it many times) but it requires a guy with a little experience in brazing. It's the same process as fixing any other leak, just a little trickier because of the wall thickness on the U tube.

Keep calling to you get someone who will talk some sense.

I also see no reason to remove the coil unless access is difficult. This will only increase costs. Fix it in place unless there is no other option.

Ok, so here is an update. My father in law works with an A/C guy - they live in W Mass - about 60 miles from me.

He is going to take a look at it to see if he can fix it. I dont know the guy personally, but as I mentioned in a previous post, apparently this guy knows a thing or two about fixing this kind of thing (according to FIL).

Having him take a look at it required that he be able to have the unit on his bench - which meant removal and disconnection of the A coil from the refrigerant supply and return lines. So last night I disconnected everything, figuring that if he can't fix it - it'll need replacement anyway, so no harm done. Today when we were visiting the in laws, I dropped the A coil off, and FIL is going to bring it in to work tomorrow. I"ll have an idea as to the repairability by EOD tomorrow.

If it can be repaired, he'll do so, and at some point I'll pick the unit up and put it back in. Then in the spring this guy can come out, braze the supply and return connections, and recharge.

This appeared to be the best option on the table at the moment. Even though I dont know the guy, going on the word of my FIL is better than randomly shooting darts at names in the yellow pages. It might be a little more effort having to remove the unit as opposed to an in place fix, but again - seemed to be the best and most known-quantity option on the table.

If it works out, I can use the coil I already have, and be down the cost of supplies and whatever payment this guy will accept (he recharged my wifes vehicle A/C in the past for a batch of home made cookies - so there is the chance he'll ask for very little, if anything). If it doesn't work - then its likely the coil would need replacement anyway.

In my opinion - the original guy saw an ancient furnace, and an A/C unit that uses R-22 which has a bit of an EOL to it (since R22 cannot be obtained after 2020) - and tried to take the opportunity to suggest replacement of the coil at a minimum, and heavily suggesting to replace the entire A/C unit.

I think that personally, because he's not an independant guy (works for a larger corp), that their mode of operation is to replace with a warrantable unit, rather then patch.

silk1976
11-28-2008, 07:42 AM
Another update - FIL coworker was able to patch the hole pretty easily. It was put on his desk @ 7:05 in the morning and by 7:45, it was patched, the in/out tubes plugged and the unit filled w/nitrogen to protect it until it can be installed in the spring.

The guy asked 'what the hell was the other guy thinking, saying that it couldn't be fixed?'

Snnipe 70E
11-28-2008, 09:04 AM
Another update - FIL coworker was able to patch the hole pretty easily. It was put on his desk @ 7:05 in the morning and by 7:45, it was patched, the in/out tubes plugged and the unit filled w/nitrogen to protect it until it can be installed in the spring.

The guy asked 'what the hell was the other guy thinking, saying that it couldn't be fixed?'


Congrads I am glad it was repairable. It is also good to see that a N2 charge was used. The rest of the system needs to be protected from moisture.

ZenBeam
11-28-2008, 10:11 AM
Congrads I am glad it was repairable. It is also good to see that a N2 charge was used. The rest of the system needs to be protected from moisture.Should silk1976 consider having the coil reinstalled now, rather than waiting until Spring?

raindog
11-29-2008, 04:21 PM
Should silk1976 consider having the coil reinstalled now, rather than waiting until Spring?
Doesn't matter, as long as he tapes up the lines that were cut. You don't want dust, spiders, moisture etc to get into the system.

Tape up the lines and next year they'll pressure test and then pull a vacuum on the system.

I generally would prefer installing now, but it's not absolutely necessary.

raindog
11-29-2008, 04:27 PM
I am not going to dig out my PT chatrs but 145 degres at 350 sounds about right for saturated temperature. But the discharge from a compressor is superheated. Last time I shot the heads of a compressor with a rey teck the temp on the compressors with an water cooled tower was in the 190 to 230 degree range.
It it was the discharge line I would always braze. (even though it would still be unlikely to melt, though certainly not impossible) However the discharge is a foot long and only from the compressor and condenser coil.

But he's got an A/C system and Rick points out that this patch is in the evaporator will likely never ever see even 100 psi---- a P/T relationship much less than 130F.

Still, the patch must be done with brazing. But the system itself, in my view, can be soldered. (and if it's already brazed, theres nothing wrong with rebrazing.)

Snnipe 70E
11-30-2008, 01:26 AM
Should silk1976 consider having the coil reinstalled now, rather than waiting until Spring?

He would be better off. Just tappiing up the lines will not keep out moisture. Moisture and most refer oil = acid=a lot of problems. The moisture can be removed in the spring time but is extra work and expense.

silk1976
11-30-2008, 01:40 PM
He would be better off. Just tappiing up the lines will not keep out moisture. Moisture and most refer oil = acid=a lot of problems. The moisture can be removed in the spring time but is extra work and expense.

I am going to have the same guy who patched it also rebraze the connections and recharge the unit. At this point, I think that going with someone who I know to be capable is the best option.

The only issue is that due to a new baby in his household, he wont be able to make it until around spring. Plus, from what I gather, that is the best time to recharge a unit with refrigerant. This is based on what the original repair guy said, so I take it with a grain of salt. I dont quite understand why it would make that much of a difference - seems to me an experienced person would be able to look at the original charge in the condensor, take into account line length from the condensor and evaporator, and get the proper amount of refrigerant in there.
OTOH, the guy who repaired it originally said himself that someone would have to fill it in the spring. So perhaps there is something going on there that I'm not aware of.

So a long winded way of asking - since its not going to be reconnected until spring - what would be the best option for preserving the two open lines now coming from the condensor? Right now I just have tape to keep some dust, etc out - but moisture can still get in. Is there anything else I should do to maximize protection, short to a full reconnection?

Snnipe 70E
11-30-2008, 04:28 PM
I am going to have the same guy who patched it also rebraze the connections and recharge the unit. At this point, I think that going with someone who I know to be capable is the best option.

The only issue is that due to a new baby in his household, he wont be able to make it until around spring. Plus, from what I gather, that is the best time to recharge a unit with refrigerant. This is based on what the original repair guy said, so I take it with a grain of salt. I dont quite understand why it would make that much of a difference - seems to me an experienced person would be able to look at the original charge in the condensor, take into account line length from the condensor and evaporator, and get the proper amount of refrigerant in there.
OTOH, the guy who repaired it originally said himself that someone would have to fill it in the spring. So perhaps there is something going on there that I'm not aware of.

So a long winded way of asking - since its not going to be reconnected until spring - what would be the best option for preserving the two open lines now coming from the condensor? Right now I just have tape to keep some dust, etc out - but moisture can still get in. Is there anything else I should do to maximize protection, short to a full reconnection?


Close off the valves on the condencing unit. There should be a valve on the return line and another valve on the liquid feed line. I would talk to the man that repaired the coil he will have suggestions.

The propere way to lay up the unit would to be to cap the lines, evacuate, and put on a N2 charge. Some what like what was done with the coil.