New Trane XV20i and ducts sweating

[SmashedIxnay]

I wanted to upgrade AC and wanted a variable speed, so I went with a Trane XV20i back in April. The owners son was the salesman, came out, very likeable guy, and we made the deal. I made sure to ask him about my duct work since the house is from 1987 and I don't know how old it is. He inspected it and said it would have no issues.

Fast forward to about September and they had to replace my thermostat. Last week we noticed water marks on a few of our vents. I called Friday morning and they had some come that afternoon. The tech said all of our ducts are sweating, which has never happened in the 9 years we owned the house (8.5 years with 17 year Goodman). The weekend goes by and I call today to get an update on what is happening. I get the owners son who came out to sell me the Trane XV20i and one of his guys this afternoon. They verify the ducts are sweating.

They come back to me saying he had good intentions when he sold me the system to say my ducts were good, but didn't realize they would not work right with this unit X months later. He said it's kinda like selling you a used car, only for it to stop working on you a few months later.

Now I'm trying to figure out if he's telling me the truth about why our ducts are sweating 5 months later. He said this year is a record year for the dew points and because the unit is on almost all day, more colder air is staying in the ducts longer. Since my ducts are probably original from 1987, where metal was used and then a small 4.5 insulation rating, now it's not drying out as fast as before. With my old unit it'd turn on, cool down, shut off. With this one being on 19-22 hours of the day it's just not drying out as fast.

I had someone mention to me that I could turn my fan speed up and that may fix the issue, since it'd push the air out quicker, but it's not a guarantee fix. I had another buddy tell me since my old unit was 3.5 ton and this is now a 4 ton, that it's pushing more air and keeping it colder than before. He said technically since it's variable speed, they should have gave you a 3 ton, and with it being a variable speed it's conpensate being a smaller tonnage and work with your duct size better than the 4 ton.

The company that sold me the unit said the only guaranteed fix would be to change out every bit of duct work from the handler on. They basically want $ after their $ discount, or it'd basically be about $ to fix it. He said he feels bad and wants to help me, so he's willing to change all boots, insulate the ones they can't remove, new flex ducts (12) and new "trunk line." I'm pretty sure he said they would balance everything out so all rooms are blowing the same temperature. I asked my buddy about the price and he said $ is about average and the guy won't be losing or making any money.

Does the company sound right, or did they screw up by not changing my duct work? Also, do you think something as simple as changing my fan speed to a faster one may fix my issue?


I'll take any and all advice. My buddy said to check the temperatures from the areas where the returns are to the vents to get the temperature difference, but I don't have anything to do that. I'll try to find something to do that.

[Restaurant Mech]

I don't have experience with this particular system. However I HAVE somewhat solved these problems by adjusting fan speed in oversized systems.
It's certainly worth a shot before spending even more money

[beenthere]

I would try increasing fan speed first.

[dan sw fl]

What is the thermostat setpoint ?

What is the Relative Humidity in the house?

Where are the ducts located?

ZIP _ _ _ _ _ ?

[pecmsg]

1st T E S P MUST be tested to find out exactly how many CFM's the existing ducts can handle.

With that information decisions can be made.

Personally id make them change the outdoor unit to a 3-Ton at there expense.

Another major concern is how much of the fiberglass duct insulation has gotten water logged?

[Mr Bill]

I had another buddy tell me since my old unit was 3.5 ton and this is now a 4 ton, that it's pushing more air and keeping it colder than before. He said technically since it's variable speed, they should have gave you a 3 ton, and with it being a variable speed it's compensate being a smaller tonnage and work with your duct size better than the 4 ton.

I don't believe this at all, I would be willing to bet you, that your old Goodman condenser had a larger or at least the same size compressor as your new condenser. If you have the model number from your old Goodman, you can check for yourself the size of the old Goodman compressor. Also, if your buddy told pushing "More Air" is colder, I disagree with him, if this was so, why increase your airflow? here's why, because increasing your air flow, will raise the air temp a bit.

[shellkamp]

XV20 has a variable capacity compressor.

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[dan sw fl]

I wanted to upgrade AC and wanted a variable speed, so I went with a Trane XV20i back in April. The owners son was the salesman, came out, very likeable guy, and we made the deal. I made sure to ask him about my duct work since the house is from 1987 and I don't know how old it is. He inspected it and said it would have no issues.

Fast forward to about September and they had to replace my thermostat. Last week we noticed water marks on a few of our vents. I called Friday morning and they had some come that afternoon. The tech said all of our ducts are sweating, which has never happened in the 9 years we owned the house (8.5 years with 17 year Goodman). The weekend goes by and I call today to get an update on what is happening. I get the owners son who came out to sell me the Trane XV20i and one of his guys this afternoon. They verify the ducts are sweating.

They come back to me saying he had good intentions when he sold me the system to say my ducts were good, but didn't realize they would not work right with this unit X months later. He said it's kinda like selling you a used car, only for it to stop working on you a few months later.

Now I'm trying to figure out if he's telling me the truth about why our ducts are sweating 5 months later. He said this year is a record year for the dew points and because the unit is on almost all day, more colder air is staying in the ducts longer. Since my ducts are probably original from 1987, where metal was used and then a small 4.5 insulation rating, now it's not drying out as fast as before. With my old unit it'd turn on, cool down, shut off.

With this one being on 19-22 hours of the day it's just not drying out as fast.

Does the company sound right, or did they screw up by not changing my duct work?

Also, do you think something as simple as changing my fan speed to a faster one may fix my issue?

I'll take any and all advice.

My buddy said to check the temperatures from the areas where the returns are to the vents to get the temperature difference, but I don't have anything to do that.

I'll try to find something to do that.

Supply Air is to DIFFUSERS
____________ RETURN AIR is from Grilles

How can the air handler provide ANY more dehumidification
if is ALREADY operating 22 hours every day.?

In other words, essentially it Never turns off.!

HYGROMETER - ACURITE 1083M Pro
https://www.acurite.com/shop-all/wea...y-monitor.html

[Mr Bill]

XV20 has a variable capacity compressor.

I understand that, but when talking btu's it's all the same. I still don't believe his new condenser, the compressor will still produce the same btu's as his old Goodman.

Edit: If his unit is running around 20 hrs a day, and the ducts are wet, my guess is the ducts are to small, are it's overcharged, are the home is leaking like a screen door on a submarine.

[shellkamp]

I understand that, but when talking btu's it's all the same. I still don't believe his new condenser, the compressor will still produce the same btu's as his old Goodman.

Edit: If his unit is running around 20 hrs a day, and the ducts are wet, my guess is the ducts are to small, are it's overcharged, are the home is leaking like a screen door on a submarine.

The issue I see with those is the extended run time will cause the ducts to sweat due to inadequate duct insulation and especially if the ducts do not have an air gap around them to maintain a high enough surface temperature.

I've actually seen water pool in flex ducts when it's got a dip in the run and it's touching the ceiling insulation.

For that unit too have a "duct too small" issue it would generally only manifesting at 100 percent capacity.

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[Mr Bill]

I wanted to upgrade AC and wanted a variable speed, so I went with a Trane XV20i back in April. The owners son was the salesman, came out, very likeable guy, and we made the deal. I made sure to ask him about my duct work since the house is from 1987 and I don't know how old it is. He inspected it and said it would have no issues.

The issue I see with those is the extended run time will cause the ducts to sweat due to inadequate duct insulation and especially if the ducts do not have an air gap around them to maintain a high enough surface temperature.

If this is the case, the owners son was a true salesman, if he couldn't see this.

[BNME8EZ]

Starting at point 1, did the guy do a load calculation (Man J) or did he just size it based on your old equipment. Based on your old system being 3.5 ton my guess is that he sized the new 4 ton based on the 3.5 you had before.

Now add to that your old duct system was sized for 3.5 ton, not 4 ton and is most likely undersized for 3.5 ton. If the duct is even marginal for 3.5 ton it is too small for 4 ton.

Next we have the new thermostat which most likely has the dehumidification setting set up on it to help remove more moisture slowing the blower down, making the air colder and lowering duct temperature causing excessive sweating. Then if the old duct has inadequate insulation the issue is just compounded.

This is what happens when salesmen don't understand all the ramifications of the equipment they sell and why the load calc (Man J) is so important. Looking at the duct is important but they need to be tested using the old system to see if they can handle the amount of air needed by the new system. Part of the problem is manufactures have been saying since the first VS blower system came out (in the 90's) that they can compensate for bad duct situations. It sounds like you fell into that perfect storm of many things being just a bit off that together create a major issue.

I would say the first thing would be to get a proper Man J done to see what size you need. If the 4 ton runs most of the day my guess is you will not be able to get by with anything less than 3.5 T. If that is the case your only option is to get the ducts fixed. It is likely that they have been a problem since day one, it was just not noticeable until they got pushed to the limit. That being the case they needed upgraded anyway, this just pushed the issue. I don't know you and am not saying this in a bad way towards you but the reality is probably if he would have said you needed new ducts you would have went with the guy that said they were fine for the new system and went that way as it would have been less expensive and you would have no knowledge that would have told you why they needed changed. Now you know. Talk to the installer and see what deal you can make.

[pecmsg]

That 4-Ton can run most of the day if the ducts are in fact too small for 3.5-Tons and the 4-Ton is overcharged to compensate.

With no #’s we can only guess

[shellkamp]

Gentleman, you all are not understanding what kind of unit the OP has.

It's variable capacity and can ramp down to 30 percent of it's rating. It's not as simple as "ducts are too small for 4 tons of air" - because it will rarely run at full speed.

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[pecmsg]

Again a lot of Assuming Then.
If running at minimum speed it will not dehumidify al lot if at all. I’m basing that on minis that are oversized and the outlet gains sweat

[BNME8EZ]

Gentleman, you all are not understanding what kind of unit the OP has.

It's variable capacity and can ramp down to 30 percent of it's rating. It's not as simple as "ducts are too small for 4 tons of air" - because it will rarely run at full speed.

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Except for not knowing if the inside unit is a TAM 9 or VS furnace I know exactly what kind of unit that is and have installed some myself. Sure the duct is only going to be too small when running above 75% Based on most duct is about a 1/2 ton too small or more are what I see anyway. I also know that even when they ramp down the air is cooler than most A/C's so it still does not change that the old duct is probably not insulated well enough for the new system. Add to that the Dehum. feature on the stat and that air is going to be cold going through those ducts.

[mgenius33]

I would say the first thing would be to get a proper Man J done to see what size you need. If the 4 ton runs most of the day my guess is you will not be able to get by with anything less than 3.5 T. If that is the case your only option is to get the ducts fixed. It is likely that they have been a problem since day one, it was just not noticeable until they got pushed to the limit. That being the case they needed upgraded anyway, this just pushed the issue. I don't know you and am not saying this in a bad way towards you but the reality is probably if he would have said you needed new ducts you would have went with the guy that said they were fine for the new system and went that way as it would have been less expensive and you would have no knowledge that would have told you why they needed changed. Now you know. Talk to the installer and see what deal you can make.

I agree!
At least you’re getting a deal on new ducting.
Replace the ducts, it will benefit in cleanliness, efficiency, and fixes the sweating issue.
Also, like Shellkamp said, make sure the ducts are strapped up so air flows around them.

[catmanacman]

need to increase the minimum air flow at the outdoor unit cda . also might need to raise the humity level at the thermostat . the xv18 and xv20 will run a very cold coil if the airflow is set to low and also if the humidity level is set to low the blower slows to dehumidify also causing a very cold coil and i turn causes ducts to condensate