Replacing the whole house HVAC

[Hohn]

Nothing can stop a Trane? Well, a design flaw like copper tubes touching galvanized headers on the evaporator sure seems to. That said, nearly 20 years isn't a bad run. But it's aggravating to have replace the system in the peak of summer for a preventable failure.

Anyway, this Trane setup from 2005 is an XB10 air conditioner and an XB90 furnace (presumable 90k BTU?).

I've never liked this system from the day we moved in and I noticed the furnace filter (a wimpy 14x20x1) was installed in a way that the airflow was LIFTING IT OFF THE SEAL. A truly dim apprentice laid this out. I had to call the number on the sticker to get them to install another filter anchor so the instead of entirely going around the filter it would have less leakage.

The air mover velocity-- even with a fresh filter and clean ducts-- is pitiful. You can barely tell any air at all is coming out when it's running.
The furnace seems "ok" but has needed a couple small parts replaced over the years. It's gas, not much to go wrong.

The basic ductwork in the house doesn't seem too bad-- the main trunk seems quite generous (about 2ft wide and maybe a foot tall). It runs through the floor of our full-basement ranch house, and is now enclosed when the basement was finished.

This is going to be expensive but hopefully I'll end up with something better when all is said and done.

Local dealer of good repute carries Lennox primarily. I'm so jaded I just assume everything is garbage now, but apparently they have an all-aluminum evaporator that appeals to me.

I wouldn't have thought to buy Lennox necessarily but I'm inclined to think that since almost everything can be junk, I'd shop local dealers and installers primarily and just buy whatever they sell and support.

 

[mike93lx]

Hopefully they (or you) are doing a sizing Calc. Good luck with the redo

 

[mm08822]

Did you get a price to replace/upgrade the evaporator coil, pressure test, evacuate and recharge? (I know everyone wants to sell complete new systems.)

 

[Hohn]

Did you get a price to replace/upgrade the evaporator coil, pressure test, evacuate and recharge? (I know everyone wants to sell complete new systems.)

Can’t get a coil replacement— they no longer support this system.

 

[Firebrick43]

I am putting in three separate 1 ton mini splits so when the junk fails hopefully its just one at a time and can be swapped out with the other two still functioning.

 

[Overboost44]

I replaced two Trane units (xl 14 and xl 16) that were from 2005. I had my share of problems with them though. In 2023, I put in two Carrier units (2.5 and 3 ton). Spent between $16-17k. So far, so good. They are middle of the line units.

 

[danski0224]

Nothing can stop a Trane? Well, a design flaw like copper tubes touching galvanized headers on the evaporator sure seems to.

Almost all residential evaporator coils are made like that, unless it is an all-aluminum coil. Go back far enough, and the tubes looked like 1/2" copper tubing and I believe the end sheets were also copper.

The copper tubing on anything made within the last 25 years or so is *super* thin. The end sheets rust, swell, and eventually make little pinholes in the copper.

That said, nearly 20 years isn't a bad run. But it's aggravating to have replace the system in the peak of summer for a preventable failure.

That's what happens when one runs it until it breaks... it won't break in January.

The only way to prevent the rusting end sheet failure is to choose an all aluminum evaporator coil, they aren't necessarily a new thing.

Anyway, this Trane setup from 2005 is an XB10 air conditioner and an XB90 furnace (presumable 90k BTU?).

I've never liked this system from the day we moved in and I noticed the furnace filter (a wimpy 14x20x1) was installed in a way that the airflow was LIFTING IT OFF THE SEAL. A truly dim apprentice laid this out. I had to call the number on the sticker to get them to install another filter anchor so the instead of entirely going around the filter it would have less leakage.

It's all about time and money. Residential replacement places *buy* their duct, they make very little. And they will use as little as possible, and just slap the new one in.

The air mover velocity-- even with a fresh filter and clean ducts-- is pitiful. You can barely tell any air at all is coming out when it's running.
The furnace seems "ok" but has needed a couple small parts replaced over the years. It's gas, not much to go wrong.

The basic ductwork in the house doesn't seem too bad-- the main trunk seems quite generous (about 2ft wide and maybe a foot tall). It runs through the floor of our full-basement ranch house, and is now enclosed when the basement was finished.

There are things that can be done to improve airflow.

This is going to be expensive

Yup.

but hopefully I'll end up with something better when all is said and done.

Probably not, as far a function is concerned. New equipment will not fix the existing ductwork.

 

[PoorUB]

Can’t get a coil replacement— they no longer support this system.

Twenty year old system so it is probably due, but can't get a replacement coil is BS. You might not be able to get a OEM, but aftermarket coils are readily available.

 

[Hohn]

I am putting in three separate 1 ton mini splits so when the junk fails hopefully its just one at a time and can be swapped out with the other two still functioning.

I was tempted to do that also. Maybe next time. I think the idea makes a lot of sense

 

[mm08822]

I am putting in three separate 1 ton mini splits so when the junk fails hopefully its just one at a time and can be swapped out with the other two still functioning.

It's nice to have 1 even 2 backups. Obviously they won't make up for missing capacity but the house remains very livable.

Certainly better than 1 or none!

 

[aggie113]

Just replaced my RUUD 3 ton unit this spring. Unit was still working so it was on my timetable. Installed 2009, so about average run for unit in south Texas. Replaced it and the gas heating with a Mitsubishi hyperheat heatpump unit. I know it's probably overkill for the hyperheat, but honestly the installer gave me such a good deal compared to the other two quotes I got that the additional 2k for the equipment was lower than other quotes with regular heatpumps.
Installer also adjusted the intake baffles box to open up another side it could pull from to improve airflow (and additional filter area to keep pressure issues to a minimum).

 

[Hohn]

The new condenser is much larger than the old one.





So far, so good. The basic hardware seems well-made. I'm seeing good heat sinking and proper wire securing and generally good design and workmanship on the Lennox product.

The installers are doing well.

 

[pima67]

What was the SEER rating of your old system and what is the rating for your new system? And did they reuse the existing line set?
Two springs ago I had the original installer of our 2006 Rheem systems check them out. He found problems with the fans, contractors and capacitors. Didn't do anything about them and they have worked OK since (hope I didn't jinx them just now!). Anyway they recommended replacing them with Lennox (their new brand) which included replacing perfectly good air handlers (furnaces). I know this stuff won't get any cheaper in the future, but I declined. Can't recall the SEER increase.

 

[Hohn]

What was the SEER rating of your old system and what is the rating for your new system? And did they reuse the existing line set?
Two springs ago I had the original installer of our 2006 Rheem systems check them out. He found problems with the fans, contractors and capacitors. Didn't do anything about them and they have worked OK since (hope I didn't jinx them just now!). Anyway they recommended replacing them with Lennox (their new brand) which included replacing perfectly good air handlers (furnaces). I know this stuff won't get any cheaper in the future, but I declined. Can't recall the SEER increase.

The old system was SEER of 10 I believe.

This system is "up to" 18 SEER.
Everything is new. Lineset is all new, wiring is all new (added surge protection for the sensitive variable electronics). The only old stuff reused is the ducting and some drain lines.





I had them entirely remove that stupid whole-house humidifier that I disabled after the first winter in this home (2008) when I noticed it was causing mold on the cold OSB rim/band joists.

 

[Hohn]

New System as installed: The old system had 3” PVC for the flue discharge which is not necessary, so the connected the 2” to the old 3” PVC. There’s also a cleanout now on the condensate drains.

 

[danski0224]

Square throat elbow on the return? Ugh.

 

[mike93lx]

Square throat elbow on the return? Ugh.

What would be the better way to do it? Is there a different style elbow that fits in that space or would the return have to be brought out to the right so it has more space to turn in? Something else?

 

[Firebrick43]

Square throat elbow on the return? Ugh.

Still has to flow better than where it joins the horizontal plenum above with absolutely no radius

 

[danski0224]

No turning vanes.

That 90 degree corner in the throat is roughly equivalent to 120 lineal feet of ductwork when it's at the fan.

The radius heel does absolutely zero for airflow.

What it does do is save a little material because it's shorter overall than a 90 degree heel like the throat.

But, that's what's for sale in the "drop kit" at the supply house.

Properly installed turning vanes would result in an equivalent length of 20 feet.

 

[danski0224]

Still has to flow better than where it joins the horizontal plenum above with absolutely no radius

Nope, it's the same. Heel does nothing for airflow on that elbow.

 

[danski0224]

There's pictures in the Manual D book for anyone that wants to look it up.

 

[mm08822]

There's pictures in the Manual D book for anyone that wants to look it up.

In the abridged or full version?

 

[danski0224]

In the abridged or full version?

Probably the full version. Do not know about an abridged version. I bought mine a long time ago.

 

[mm08822]

Probably the full version. Do not know about an abridged version. I bought mine a long time ago.

Full is ~2x price of abridged. 8th edition from 2016. I held off and winged a Manual J calc using explanations from ACCA vids.

 

[Hohn]

Square throat elbow on the return? Ugh.

It was baked into the pie unfortunately and fixing it would have involved redoing the entire return trunk into the utility area.

#sudivisionbuildquality

 

[Hohn]

Still has to flow better than where it joins the horizontal plenum above with absolutely no radius

I doubt it's much better at all. The problem isn't the lack of radius at the outside of the bend, it's sharp corner at the INSIDE.

 

[danski0224]

I don't remember what I paid, I also got a discount. It's about 3/4" thick.

 

[danski0224]

It was baked into the pie unfortunately and fixing it would have involved redoing the entire return trunk into the utility area.

#sudivisionbuildquality

They could have fixed the drop and left the horizontal duct alone.

This assumes that they can fabricate their own ductwork.

 

[Hohn]

No turning vanes.

That 90 degree corner in the throat is roughly equivalent to 120 lineal feet of ductwork when it's at the fan.

The radius heel does absolutely zero for airflow.

What it does do is save a little material because it's shorter overall than a 90 degree heel like the throat.

But, that's what's for sale in the "drop kit" at the supply house.

Properly installed turning vanes would result in an equivalent length of 20 feet.

I hear you, but if I fixed every corner cut in the building of this house, I'd have $50k in remodeling or more for a house whose basic floorplan I don't really like.

I'd rather move than remodel this house. Other defects noted in the nearly 20 years of occupancy here:
-- Blown attic insulation is incredibly uneven and mostly piled up near the access point because hey why should i have to actually enter the attic to install properly.
-- Master tub plumbed backward (hot/cold)
-- No blocking/crossbracing on shower piping in the wall (ask me how I learned this)
-- Multiple wiring defects. Can lights on the front porch that have never worked. Lights over tubs that flicker. Part of me is stunned this house hasn't burned down. I took a ceiling light fixture down once to find NO BOX just taped bare hot wires from romex sticking out through a tiny hole.

This is in a 2005 built home, not a 1975 one. Codes weren't THAT lax back then.

 

[Hohn]

They could have fixed the drop and left the horizontal duct alone.

This assumes that they can fabricate their own ductwork.

They fabbed the adapter from the top of the A/C unit so presumably they have basic sheetmetal skills.

I'm not sure how useful or helpful you think your post-hoc criticisms of the freshly installed system are, but I assure you I'm not calling them back to "fix" something because an internet HVACR said they did it wrong.

 

[MovingAlong]

And how's the new system at cooling your home now?

 

[Hohn]

And how's the new system at cooling your home now?

Brilliantly. It's not just cool, but the air feels cleaner too. SOmehow the new filtration system is really killing it too.

It feels relaxing in a way the old system never was. I'm very happy with it.

 

[mm08822]

Keep tabs on the filter. Buy a spare element now while you have plenty of time to shop.

 

[danski0224]

I'm not sure how useful or helpful you think your post-hoc criticisms of the freshly installed system are,

May not help you, but it may help the next person.

This is another problem that happens with the run it until it breaks crowd, because the extra time needed to make changes may not be available, which is wholly separate issue.

 

[Hohn]

May not help you, but it may help the next person.

This is another problem that happens with the run it until it breaks crowd, because the extra time needed to make changes may not be available, which is wholly separate issue.

I guess I'm in that run-it-till it breaks crowd for HVAC. Are you in the habit of replacing functional parts before they break? Just swap a coil every 5 years or so?

Why would someone replace a capacitor in advance when it's such a simple repair?

What's the alternative?

I've run--until it breaks-- two microwaves, two dishwashers, a washer/dryer set, two televisions. I did no maintenance on any of them.

I'm very diligent with maintenance in general. So if I'm dropping the ball in changing my compressor oil or something, I'd like to know how my neglect is contributing to the system demise.

And what exact maintenance would have prevented the known galvanic corrosion of the copper coil tube ends that is a known issue with this design?

 

[niget2002]

The previous owners of my house had new AC put in at some point. They chose trane. At the time, trane handlers were being built using plastic covers on everything instead of metal. The heat/cold cycle in the attic in a North Texas home causes said plastic to become brittle. My covers on my handler are currently being held together with copious amount of duct tape to keep cold air from cooling the attic instead of my home.

The re-usable electrostatic filter died on it last year. I pulled all the guts out and just slide a normal filter into the emptied box with the controller unplugged. The electrostatic filter is also made of plastic and one of the latches has broken so I now use a screwdriver to rotate the latch instead of the plastic thumb screw.

 

[danski0224]

Are you in the habit of replacing functional parts before they break? Just swap a coil every 5 years or so?

Typical lifespan is 15-20 years.

I always suggest that it's replaced when the homeowner has some control over the downtime.

Got people that complain here about replacing old and working equipment.

Got people here complaining about their old AC or heat that broke when it's needed.

No one wants to spend money.

Everyone is "moving soon".

Pick your poison.

 

[danski0224]

I've run--until it breaks-- two microwaves, two dishwashers, a washer/dryer set, two televisions. I did no maintenance on any of them.

Not the same. Not a valid comparison.

 

[danski0224]

And what exact maintenance would have prevented the known galvanic corrosion of the copper coil tube ends that is a known issue with this design?

Nothing you can do. They are made like that, presumably so the manufacturer can save some money.

Only choice is an all aluminum coil, if it's available.

Pretty sure that the issue is actually the end sheet rust pinching the copper tubes, not galvanic corrosion.