Rusty? This ain't no love shack!
May 18, 2010 8:29 AM Subscribe
HVAC Advice. I have a six year old house with a Goodman AC system.
Three years ago the evaporator coils rusted like crazy and leaked out -- replaced under warranty. Three years later, low and behold, the coils have started to rust up like crazy. Techs and I are stumped -- "This shouldn't happen." Any ideas?
Approxmately three years ago, the evaporator coil started leaking R-22, and upon examination the coils were all rusted to heck and the coil was replaced under warranty. I had the coolant line freeze up yesterday, which suggested low refridgerant to me, so I had it checked out -- most of the lower half of the coils I can see are covered in rust.
The tech was dumbfounded -- "Didn't we just replace these coils?" -- air filter upkeep is fine, the filter looked fine, there are no drainage issues, the unit seemed to cool fine.
For what its' worth, the air filters I use are MERV 8 replaced every 3 months like clockwork. I asked if maybe the MERV 8 was too much resistance and he just looked at me incredulously and said it's a 3 ton unit -- should not be a problem.
The only angle we have right now is these Goodman coils were "uncoated", and that I now have the opportunity to purchase a "coated" coil which purportedly will reduce the chance of corrosion for 150% the cost of the uncoated coals.
I've talked to two other HVAC guys and they're like .. yeah.. rust is gonna happen eventually, it's dark and wet in there, but... er.. 3 years?
Any ideas?
Approxmately three years ago, the evaporator coil started leaking R-22, and upon examination the coils were all rusted to heck and the coil was replaced under warranty. I had the coolant line freeze up yesterday, which suggested low refridgerant to me, so I had it checked out -- most of the lower half of the coils I can see are covered in rust.
The tech was dumbfounded -- "Didn't we just replace these coils?" -- air filter upkeep is fine, the filter looked fine, there are no drainage issues, the unit seemed to cool fine.
For what its' worth, the air filters I use are MERV 8 replaced every 3 months like clockwork. I asked if maybe the MERV 8 was too much resistance and he just looked at me incredulously and said it's a 3 ton unit -- should not be a problem.
The only angle we have right now is these Goodman coils were "uncoated", and that I now have the opportunity to purchase a "coated" coil which purportedly will reduce the chance of corrosion for 150% the cost of the uncoated coals.
I've talked to two other HVAC guys and they're like .. yeah.. rust is gonna happen eventually, it's dark and wet in there, but... er.. 3 years?
Any ideas?
To support MsKim, check out an earlier answer I gave regarding electronic rustproofing, which may give some insight into what's happening here...
Do you know what material the coils are made from? To be honest, I'm surprised they would consider using an unfinished (what I'm assuming they meant by uncoated) metal of any kind on evaporator coils, since they're going to be heat cycling, wet, and mostly undisturbed. Do you know what kind of finish/coating they'd be applying to the coils?
posted by This Guy at 8:46 AM on May 18, 2010
Do you know what material the coils are made from? To be honest, I'm surprised they would consider using an unfinished (what I'm assuming they meant by uncoated) metal of any kind on evaporator coils, since they're going to be heat cycling, wet, and mostly undisturbed. Do you know what kind of finish/coating they'd be applying to the coils?
posted by This Guy at 8:46 AM on May 18, 2010
Are you getting actual brownish rust? Or is it copper or aluminum corrosion? Because generally A/C coils aren't iron/steel and they shouldn't rust.
Either way I'd check for the presence of high sulphur drywall sourced from China.
posted by Mitheral at 8:47 AM on May 18, 2010
Either way I'd check for the presence of high sulphur drywall sourced from China.
posted by Mitheral at 8:47 AM on May 18, 2010
Why is my air conditioner rusting so fast?
"Install Corrosion Grenades"
"Electrolysis: Whenever different metals are placed in a conductive liquid you create a battery. If you connect pieces of metal together, current will flow. The current will be removing metal from one of the metal pieces= electrolysis.
Galvanic Scale: (Metals at beginning will corrode faster than metals at the end of the scale)
Zinc
Aluminum
Galvanized Steel
Cadmium
Mild Steel, Wrought Iron
Cast Iron
Lead- Tin Solder
Lead
Brass, Bronze
Copper
Stainless Steel that has been chemically cleaned
Avoid contact between metals that are farther apart on the scale. All refrigerant lines are made of copper, when you have an aluminum coil you have dissimilar metals contacting each other. One reason why I prefer Copper coils to Aluminum.
For years all manufacturers have been plagued with the expensive problem of condensing coils corroding. When this happens it results in unsightly and ineffective coils and resulting in higher electric bills. Generally condensing coils are cleaned twice a year. Corrosion is a continuous process and will degrade them between cleanings. Cleaning the coils more often shortens the life of the fins and results in the need of replacement. Coil Coatings have been used but often require recoating during the life of the equipment. The condensing unit is made of Copper, Steel and Aluminum. Salt acts as an Electrolyte. Therefore the Electrolysis (Galvanic Corrosion) begins damaging your system as soon as you turn it on. The Electrolysis will only damage one metal and that is the softest or weakest metal on the system.
The Corrosion Grenade is 100% Zinc and protects all metals on your air conditioning system because it is the softest or weakest metal on the Galvanic Scale and protects the metals acting as a sacrificial anode. As soon as you have attached the Corrosion Grenade you have introduced a softer metal than any other on the Galvanic Scale. This increases the life of your system and helps maintain the efficiency. Water heaters have used sacrificial anodes for years as well as boat engines used in saltwater.
Here in Florida we started using Corrosion Grenades in 2006 on direct beach front properties and after two years of results we starting including them on every system change out no matter the location of the unit. The results have been nothing short of remarkable. We have not had to start changing the grenades out so far but will update when it happens. You can add these to your existing air conditioner and the sooner the better. So ask your service provider to add a Corrosion Grenade to the Suction line of compressor where it usually remains wet. It is secured using stainless steel Allen bolts."
posted by Floydd at 8:53 AM on May 18, 2010
"Install Corrosion Grenades"
"Electrolysis: Whenever different metals are placed in a conductive liquid you create a battery. If you connect pieces of metal together, current will flow. The current will be removing metal from one of the metal pieces= electrolysis.
Galvanic Scale: (Metals at beginning will corrode faster than metals at the end of the scale)
Zinc
Aluminum
Galvanized Steel
Cadmium
Mild Steel, Wrought Iron
Cast Iron
Lead- Tin Solder
Lead
Brass, Bronze
Copper
Stainless Steel that has been chemically cleaned
Avoid contact between metals that are farther apart on the scale. All refrigerant lines are made of copper, when you have an aluminum coil you have dissimilar metals contacting each other. One reason why I prefer Copper coils to Aluminum.
For years all manufacturers have been plagued with the expensive problem of condensing coils corroding. When this happens it results in unsightly and ineffective coils and resulting in higher electric bills. Generally condensing coils are cleaned twice a year. Corrosion is a continuous process and will degrade them between cleanings. Cleaning the coils more often shortens the life of the fins and results in the need of replacement. Coil Coatings have been used but often require recoating during the life of the equipment. The condensing unit is made of Copper, Steel and Aluminum. Salt acts as an Electrolyte. Therefore the Electrolysis (Galvanic Corrosion) begins damaging your system as soon as you turn it on. The Electrolysis will only damage one metal and that is the softest or weakest metal on the system.
The Corrosion Grenade is 100% Zinc and protects all metals on your air conditioning system because it is the softest or weakest metal on the Galvanic Scale and protects the metals acting as a sacrificial anode. As soon as you have attached the Corrosion Grenade you have introduced a softer metal than any other on the Galvanic Scale. This increases the life of your system and helps maintain the efficiency. Water heaters have used sacrificial anodes for years as well as boat engines used in saltwater.
Here in Florida we started using Corrosion Grenades in 2006 on direct beach front properties and after two years of results we starting including them on every system change out no matter the location of the unit. The results have been nothing short of remarkable. We have not had to start changing the grenades out so far but will update when it happens. You can add these to your existing air conditioner and the sooner the better. So ask your service provider to add a Corrosion Grenade to the Suction line of compressor where it usually remains wet. It is secured using stainless steel Allen bolts."
posted by Floydd at 8:53 AM on May 18, 2010
I came in to say what Mitheral did. The most obvious result of the bad drywall from China is premature corrosion on metal parts in the house. Something to check for at least...
posted by Babblesort at 8:54 AM on May 18, 2010
posted by Babblesort at 8:54 AM on May 18, 2010
I'm not understanding the "Corrosion Grenade" thing they're advertising. It looks to be, literally, a big chunk of zinc that's placed somewhere along the line to alleviate corrosion throughout the coil pipes. That would work for the area of metal directly in contact with the zinc, but there's no real way to "throw" corrosion resistance any distance away from where the zinc actually is without using some kind of potential-shifting voltage I mentioned in the electronic rustproofing answer. Coating the base metal in zinc would actually deliver on their promise of a sacrificial anode. It's a solid theory that's being applied incorrectly here, if I'm reading this piece right.
And unless there is contact between two dissimilar metals throughout the coils, the galvanic scale isn't completely applicable here, except where the coils are mated up to the feeder pipes.
posted by This Guy at 9:18 AM on May 18, 2010
And unless there is contact between two dissimilar metals throughout the coils, the galvanic scale isn't completely applicable here, except where the coils are mated up to the feeder pipes.
posted by This Guy at 9:18 AM on May 18, 2010
They're assuming that moisture will bring all the metal into electrical contact. I saw an episode of "Dirty Jobs" in which zinc ingots were used in a lock (the kind ships go through) for a similar purpose. The dirty job was replacing the anodes inside the locks. This worked because the locks were submerged in seawater.
posted by kindall at 9:33 AM on May 18, 2010
posted by kindall at 9:33 AM on May 18, 2010
The zinc has to be in direct contact with the metal it is protecting. The blocks on the locks are bolted directly to the iron of the locks (same thing is done with iron ships BTW). It looks like the zinc bomb are bolted around copper pipes, this would make a difference by forcing the galvanic corrosion to degrade the zinc before the aluminum or copper in the system.
posted by Mitheral at 9:53 AM on May 18, 2010
posted by Mitheral at 9:53 AM on May 18, 2010
People use zinc sacrificial anodes all the time on boats in contact with seawater. Everything is electrically bonded together, and the cheap zinc corrodes first, instead of the expensive engine parts. Looks like this product is trying to do the same thing.
Can you check your drain lines and make sure that your condenser isn't sitting in a pool of water? Seems like the wetter the environment, the quicker the corrosion. A dehumidifier might help as well, depending on whether it's a split unite.
posted by jenkinsEar at 10:33 AM on May 18, 2010
Can you check your drain lines and make sure that your condenser isn't sitting in a pool of water? Seems like the wetter the environment, the quicker the corrosion. A dehumidifier might help as well, depending on whether it's a split unite.
posted by jenkinsEar at 10:33 AM on May 18, 2010
Response by poster: Hi there,
Mith -- thank you, I imagine you are correct and it may be corrosion? I'll take a picture of it when we replace it tomorrow.
That zinc grenade looks funny -- I'm hoping the "coating" will help with this, but I don't have any better description of it yet as a "treatment to prevent corroding of the coil."
Thanks for the thoughts so far! I, too, wondered about the whole chinese drywall thing -- but nothing else in the house is affected? And it's not a tract home, and no egg smell.. ? Whew.
posted by cavalier at 4:53 PM on May 18, 2010
Mith -- thank you, I imagine you are correct and it may be corrosion? I'll take a picture of it when we replace it tomorrow.
That zinc grenade looks funny -- I'm hoping the "coating" will help with this, but I don't have any better description of it yet as a "treatment to prevent corroding of the coil."
Thanks for the thoughts so far! I, too, wondered about the whole chinese drywall thing -- but nothing else in the house is affected? And it's not a tract home, and no egg smell.. ? Whew.
posted by cavalier at 4:53 PM on May 18, 2010
Response by poster: Replacement coils have failed 4 months in. Either Goodman makes really great coils, or there is something else constricted on the unit. Hrmn. Pix soon!
posted by cavalier at 4:20 PM on September 23, 2010
posted by cavalier at 4:20 PM on September 23, 2010
This is a tough problem cavalier. Do you have access to a voltmeter? You might want to see if there's any stray voltage/current running through the coils? That, along with moisture, would create an ideal corrosive environment which would help explain a lot.
posted by This Guy at 10:06 AM on September 27, 2010
posted by This Guy at 10:06 AM on September 27, 2010
Response by poster: A thousand apologies This Guy, I managed to miss your response to this thread.
I was wrong; the coils were fine, it was an installation error that led to a leak, not coil failure.
Here's to X more years!
posted by cavalier at 4:03 PM on April 2, 2011
I was wrong; the coils were fine, it was an installation error that led to a leak, not coil failure.
Here's to X more years!
posted by cavalier at 4:03 PM on April 2, 2011
This thread is closed to new comments.
posted by MsKim at 8:38 AM on May 18, 2010