Central AC saga: repair or replace my system
Hello, my name is Peter. My question is simple: should I replace my current Central Air Conditioner, or pay for a repair?
I realize that there are a number of articles about this online, but I’m not sure they accurately apply to me, as the problem itself is rather complex. The simple info is: that I need to repair a cracked condensate pan that is causing leaking into the air handler and mold growth. The repair bill is about $1,900 mostly for labor because the coil must be removed in order for the repair to be made. My system is a Trane XR15, 3.5 ton system, and the house is 2,200 square feet. Estimates for a system replacement (Lennox) range from base model $7,500, to elite $15,000 (all sized 2.5 tons per Comfort Advisor). With the “good” option a 16 seer at about $10,000 without discounts (possibly around $9,000 with discounts). The system is about 10 years old. According to multiple AC Technicians, the rest of the system is in good condition. My one remaining technical problem is that the system short-cycles (6-10min cycles), though part of the above repair would be a fan speed adjustment, which the techs claim will help the short-cycling. I would therefore like some input on what to do.
See the information below which gives more background info on the problem, and the improvements we have made on the house since purchasing it in March of 2018.
I live in Metro-area NY (Climate Zone 5) in a 2,200sqft High Ranch built in 1969 (with very few updates). It is our first house We bought the house in March 2018 for 12% over asking. We overpaid due to a combination of sellers market, bidding war, need to move out of a apartment soon, inexperience, and being guided by an aggressive realtor. The home still needs a lot of updates (new kitchen, new hall bath, new downstairs, etc.). And we have paid for a number of updates already (some we knew we needed, other we found out that we needed later). These include a new 200amp electrical panel, addition of several light fixtures and outlets, additional exterior lights, new garage doors and frames (water damage), rebuild exterior wall between doors with concrete (water damage), refinished wood floors, reinforce staircase, professionally air sealed attic with 12″ blown in cellulose added, insulation added to garage ceiling, and new AC ductwork (see below).
On to the Air Conditioner. We have central AC from the previous owner, installed in the attic (I know it’s not ideal but it’s common around here) with registers in the ceiling. The system is a Trane XR 15 from about 2009 or 2010 (I can’t remember which). I found out this summer that the ductwork was old, in poor condition, lined with interior fiberglass liner, overall under-insulated, and without dampers. The system only effectively cooled some rooms in the upstairs, while the downstairs would get hot & humid, we also found mold spots on a few of the supply registers. The system would also short-cycle (about 7 minute cycles). We were aware of no other problems with the system until a technician opened the access panel to the air handler in June 2019, and discovered that there was mold on the wires and interior insulation. I called in a professional mold inspector who checked the system and said that the mold in the air handler was likely from the condensate line backing up at some point in the past. He recommended doing my best to clean it myself as it was “not that bad” and a pro cleaning would be way too expensive. He did recommend replacing the insulation in the air handler and replacing all of the ductwork, as a duct cleaning would be too expensive and not work well on old ducts.
So after getting some estimates, I decided to replace the ducts and add a duct run downstairs this past September for about $6,000. I cleaned the air handler myself with Mold Control and some towels. The new ducts improved the comfort of the house a lot though it still would short cycle (though not quite as short). feeling satisfied for the time being, we moved on to the next project: professional air sealing and insulating in October 2019 (after energy audit). However, while venturing up into the attic prior to the big air sealing/insulating job, I realized (to my horror) that there was water in the emergency condensate pan underneath the air handler (this was in early October, and the last day I used my unit was in mid September). I opened the air handler and found that the insulation on the bottom of the air handler was wet CRAP!
After the air sealing/insulating was done, I had an HVAC technician check the equipment and confirm that the condensate line was corroded and cracked and was leaking back into the unit….so the mold was not caused by a previous problem (like I had assumed), but by an ongoing problem. The repair bill (as mentioned above) is about $1,900 due to the orientation of the air handler, and the need to remove the coil in order to make the repair.
I spoke to the tech, who said he thought that the air handler would dry out on its own in a few days. I foolishly left it alone, and sealed up my duct supply and return registers (with bubble wrap and tape) for the winter a few days later like I normally do, to keep warm, moist air from migrating up there). Just the other weekend, during a period of unseasonable warmth, I checked on the air handler and found that the insulation was STILL moist and there was some additional mold. I sprayed the area with Mold Control called my mold inspector who suggested leaving the air handler open for a few days to dry out. After 2.5 days, the air handler insulation was STILL moist, but I decided that I had had enough and that I did not want to leave it open anymore and will just deal with it in the spring (when the repair or replacement would take place)
So that is most of the back story of my problem.
Obviously I have made a lot of poor choices that allowed me to miss problems with my Air Conditioner. I do not want to make any more poor choices; therefore, I need some help. As stated above, I am now debating whether or not I should fork over the extra cash and go with a completely new system (which I probably would have done had I known about the REAL problem over the summer), or if I should just pay for the repair, and have faith that the system will last another 5-10 years and that the fan speed adjustment will fix the short-cycling.
Sorry for the long post, but I would be grateful for any advice. Thanks!
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Replies
What is your heat source? Is your AC a heat pump or is there a gas furnace?
Why would there be water in the condensate pan in January? It should be dry even if you have a heat pump the pan should only get a few drops in the defrost mode and that should be less than 3% of the time.
If the diagnosis is a leaky pan I say prove it. Cap the drain and fill the pan for 12 hours. If the level drops it is a leak, if not it is a misdiagnosis.
My wild guess is the moisture you are seeing in January is condensation on the walls of the air handler. The air handler is in a cold vented attic, so the case of the air handler gets cold often below the dew point of the air in the house so it sweats and stuff gets wet and moldy.
If you are stuck with ducts in your attic, you are stuck with poor options. My opinion is a conditioned attic is a poor choice and is likely to be the least bad option you have.
Is your short cycle problem is because the equipment installed is to large and in it changes the temp of your house more than 1° in 10 minutes or that the thermostat is located in the wrong location so it changes faster than the rest of the house?
Walta
I TOTALLY agree with Walta that you may be seeing condensation in cold ductwork. I’ve seen this before in equipment with ducts tough through unconditioned spaces. It’s really common to see in certain types of greenhouse heaters too.
Condensate drains should be plastic, usually PVC air vinyl tubing. Condensate is nasty corrosive stuff, plastic pipe is the only thing that really lasts in this application. Note that if you have issues that prevent the condensate drain from sloping away enough, you can get little tank/pump assemblies made to handle condensate that needs to be pumped up to a drain. These little units aren’t terribly expensive, they’re not very big (maybe the size of two half gallon milk cartons or so), and they are pretty easy to install.
Your quotes sound really high to me too. Maybe you have an extra tricky job, or maybe it’s the market you’re in, but you might want to bid the work out. I know residential HVAC guys have pretty high markups, which I discovered when one of my commercial HVAC contractors did a side job to help me out on my house. He gave me a deal since I work with him all the time, but he told me a lot how he was “in the wrong business” because he found out the residential guys make things up a LOT more than the commerical guys do. If have any contacts in the trades they might be able to help you here, otherwise take bids for the work from at least three vendors to make sure you’re not getting gouged by someone.
Bill
Hi. Thank you for replying.
More background: My house is heated by baseboard pipes via a gas boiler. The AC condenser is located outside and the refrigerant is run via a long line up to the attic and across to the air handler, which is located up in the attic, near the middle of the house. This is a common practice in my area (though I agree that it is not efficient). I think it is done because there is virtually no room to fit ductwork and an air handler inside these houses that are not heated by a furnace. I honestly wish the house had no AC system to begin with, so we could have payed less for the house and installed a system the exact way that we wanted (probably ductless).
Regarding Thermostat Location: The thermostat is located in hall, near the ac return (there are no supply registers in the hall) so I don't think thermostat location itself is the problem. With the old ductwork, the master bedroom, which has two supply registers (overkill, IMO) and is relatively close to the thermostat, got VERY cold and clammy very fast. I think this contributed to the problem before. With the NEW ductwork, the house is more balanced and the short cycling is slightly better (but still less than 10min) and the whole house is more comfortable.
Regarding the size of the equipment: to me this seems to be the most logical explanation for the short cycling, especially because 9 supply registers were upstairs ans two small, weak flowing registers were downstairs. So basically the 3.5 ton system was cooling 1500 square feet, not 2,200 square feet. The new duct run and newly balances system has remarkably improved airflow downstairs, so the system now is cooling the whole house, BUT, I still wonder (especially considering all the air sealing and extra insulation we added to the attic this October) if the house & ducts are now so efficient that a smaller system would be more appropriate. ALL the companies who came by said a 3.5 ton system "should" be the right size for the house...but I still wonder. (This is def. something I would like some input on)
Regarding the choice to install new ductwork: When I was initially considering options for new ductwork, I thought about scrapping the whole central AC system in favor of ductless AC units. But that was VERY expensive as my house would need at least 4 units, and they run about $5,000 each. Plus I would still need to remove all the old ductwork and patch the ceiling holes left by the removed registers. So I decided that I should stick with my least worst option, which was to get new, properly insulated and sealed ductwork, followed by the newly air sealed, insulated, and vented attic (I added some soffit ventilation myself).
Regarding condensation as a cause of water in the unit: I have attached two photos. One shows the now obviously cracked condensate connection (made of metal), and a view of the inside of air handler. The section of the insulation closest to the edge is what has remained wet for the longest time. I'm not sure why, but it may be because there is a small lip there where the water may collect, and not enough air an get to it, so it does not dry. It is possible that air inside the handler is condensing on the walls of unit and running down the edges to the bottom insulation and making it wet. Whereas I have very limited access to the interior of the air handler
Regarding other causes of the water backup: I have been suspicious that the cracked condensate connection is not the only reason for the water backup. The condensate line is a gravity feed to my front gutter. Both the emergency condensate pan and the interior condensate pan connect to the same line (which I don't like, but I am not sure what other option there is considering the layout of my attic). I wonder if the line ALSO drains too slowly, which also contributes to water backing up into the machine.
Regarding the cost of the installation: I can contact other vendors about this. The prices above are from the company that installed the new ductwork. I got a lot of quotes for that, and they had the most reasonable prices and were the most committed to the job (so I was most comfortable with them). It may just be my area. I live in Rockland County, NY and it seems that everything around here is priced up.
Thank you so much for replying. I really appreciate your input. I am willing to answer any questions and can send more photos if needed.
-Peter
At this point the only thing you can do is get the fan on the AC running this should keep the ductwork and air handler above the dew point and end the moisture problem at the cost if wasted electricity extra heat loss and cold drafts.
Maybe someone could build a system to control the AC fan. Put a sensor in the spot showing the most condensation. When the sensor gets close to the dew point the fan runs for 10 minutes.
Do the research on conditioned attics as it sounds like the least bad option available. Be sure to connect the attic to the house with air vents and monitor the attic temp keeping it well above the dew point.
Walta
"Regarding the choice to install new ductwork: When I was initially considering options for new ductwork, I thought about scrapping the whole central AC system in favor of ductless AC units. But that was VERY expensive as my house would need at least 4 units, and they run about $5,000 each. Plus I would still need to remove all the old ductwork and patch the ceiling holes left by the removed registers. So I decided that I should stick with my least worst option, which was to get new, properly insulated and sealed ductwork, followed by the newly air sealed, insulated, and vented attic (I added some soffit ventilation myself)."
I see this as a bait and switch scam!
You ask for mini splits they give you a bid for a grossly over sized system with a head in every room. When you are shocked at the very high price tag they conveniently have a much more reasonably priced conventional system to offer you.
Sadly it is a common practice
Walta
Hi:
I will admit that I haven't researched conditioned attics much. It seems too late now, that I've added all the insulation, done the air sealing and increased the ventilation in the attic.
The cost of the ductless systems was pretty consistent with other companies. Another company thought I should give up trying to cool the downstairs with the current central AC system, and just add a ductless system downstairs instead. That would've been 1 unit for $4-5K. So I don't think they were trying to scam me.
On the last day of using the AC system (in September, before I knew about the leak) I ran the fan on the unit for about 11 hours, just to get rid of any leftover condensation (on the advice of another HVAC contractor). Obviously that wasn't enough, and I probably would need to run it for several days. I am reluctant to do this not only for wasted energy and drafts, but that it will blow the moist air throughout the ducts in the process, plus any dust that got in the unit from it being open to the attic over the weekend. I could be wrong, but since every thing I have tried to do seems to make things worse, I figured I should just leave the unit as is and wait until Spring to try and clean it and unseal my duct supply/return registers. Around that time is when I will have to decide if I want to simply repair the unit or get a whole new one, which is the initial reason for my post.
The other option is to repair the unit and sell the house (at a loss) and just get a condo. A thought that has crossed my mind a few times.
Your issue is warm, moist air rising from your house into the system and condensing on the ducts and other things. How can I be so sure? Look at the screws on the terminal strip in your middle pic — see how they’re all corroded? This is because the humid air is condensing on them too, and everything else (the access panel in the last pic, for example).
You could rig up a system to run the blower as Walta describes. Get a “snap thermostat”, which is just an all-mechanical heating-only thermostat. Mount it on the ductwork somewhere that you think is the coldest spot, and wire it into the fan connection on the 24v thermostat connection panel. Set the snap thermostat to something a bit above the expected dew point. What will now happen is that thermostat will close the contacts and activate the blower whenever it gets below the temperature you set, and turn the blower off when things warm up enough. It’s not very efficient, but it will probably work.
If that condensate line is routed in a way that it vibrates, that could explain any cracks. A piece of flexible vinyl a foot long or longer tubing between the rigid line and the unit will work as a flexible coupling and should solve that issue.
Check that the main thermostat isn’t mounted on a wall with a duct behind it. I’ve seen that before. The duct in the wall heats or cools the drywall the thermostat is mounted on and confuses the thermostat. Your issue with airflow was probably balancing. It’s common to run more airflow to the upper levels in the summer when air conditioning and then reverse that for the winter heating season. The reason is that hot air rises, and your goal is to keep a relatively consistent temperature throughout all levels of the house.
Bill
Hi:
I think that some of the white residue you see in the pictures is from the Mold Control that I have sprayed on the inside of the unit. According to the label, mold control is supposed to be allowed to dry in surfaces to kill the mold and resist further mold growth. The black on those screws (and the wires) is mold that I could not get off.
This is only our second winter in the house, but both times, I have sealed the return and supply registers with bubble wrap and tape before winter to prevent air from migrating up there and condensing. So air might've gotten up there in the past, but it is unlikely that it is happening now.
There is not duct in the wall behind the thermostat.
Again. Thank you for the responses.
My 1700 sq' 70's home had a over sized 4 ton AC. I installed a 3 ton and it runs alot and keeps the house cool and dry.. On the hottest days, it runs non stop. My entire system, furnace and all cost less than 5k for the equipment, but my old boss would have charged 9k after it took me 1 1/2 days to install.