Home A/C unit died-- by design.

[dogememe]

long term reliability from gree hasn’t been great nor parts. they’re also just loud compared to AUX, Midea. they do use a hot vapor line to heat the bottom pan for heat pump usage which is very intuitive. they also have a crank case heater which i’m not sure ever turns off so they use a bit more power than the others. regardless like I said it’s a great system, just not my preference. same thing with an “american” inverter system. it’s all marked up Midea technology. look at the bosch, top dollar for again, a midea built system lacking the features of midea or ACIQ/mrcool/senville. Carrier rebrands the midea EVOX line with quite literally just a name and paint job but sells it at a 100-150% markup because it has “carrier” on it.

Well ours is already installed and I paid zero so it’s firmly in the not my problem camp BUT I do appreciate the information and more knowledge is always better.

I’m slightly miffed they didn’t give us a smart thermostat. I asked for that and even offered to buy the one I wanted. Oh well.

 

[BrendanC]

Well ours is already installed and I paid zero so it’s firmly in the not my problem camp BUT I do appreciate the information and more knowledge is always better.

I’m slightly miffed they didn’t give us a smart thermostat. I asked for that and even offered to buy the one I wanted. Oh well.

pull the cover off of your air handler and look for an A B and G terminal. if it is there, you really should get Gree’s communicating thermostat. you are missing out on quite a bit of efficiency and comfort if you’re using a standard 24v thermostat. also, make SURE there is a surge protector at the outdoor condenser and the air handler. if there isn’t one, they’re about $40 each on amazon and a 5 minute job to add if you’re handy.

 

[Rand]

Could you link the surge protector you would use?

 

[BrendanC]

Could you link the surge protector you would use?

https://a.co/d/05080vTn for each appliance at disconnect properly pigtailed.

https://a.co/d/0a99GmQ3 at electrical panel on seperate 30amp breaker.

 

[oil pan 4]

This is the kind of engineered obsolescence, designed-to-fail stuff that just infuriates me.


Our home A/C is a Trane XB10 from 2005, about 3 tons IIRC. It just died. Technician found the leak with his sniffer at the evaporator, which is a tube-and-fin style. IT has copper tubes with aluminum fins, pretty typical. At the end of each tube there are u-bends of copper brazed/soldered on to plumb all the tubes together. Also quite typical.

Ah, but the header plate at the end? GALVANIZED STEEL. Now, you might already know that zinc touching copper is going to cause galvanic corrosion of the copper. There's no way the engineers at Trane did NOT know this.

But who cares? That means when the evaporator fails in 15 years because of corrosion they could have prevented, you won't be able to get a replacement part (naturally, out with the old) so they'll get to sell you and entirely new system for $10,000+ because they decided to use cheaper galvanized steel instead of aluminum for the header plates.


So now the question becomes: Now what? What do I get to replace this rusty old dumpster fire of an HVAC system that has never worked very well in 20 years?


Since the furnace also needs to go (it's very rusty), I'm thinking just biting the bullet for a whole new system. The ducting in the house seems fine. But I'm pretty frustrated that my 2005 HVAC system is essentially no different from a 1960s unit-- single speed fan, single speed compressor, constant output furnace.


Best I can tell, I the smart call for my part of Indiana is a higher capacity heat pump with variable speeds on the compressor and fan and then have the gas furnace backup for when the heat pump cant keep up.


Sometimes being an engineer means living a life of frustration when you can see every defect of design right in plain sight. Especially when it costs you a small fortune.

This is why I hate central hvac. Its designed to fail and costs a fortune to replace.
I've gone to using mini splits and windows units.

 

[Hohn]

This is why I hate central hvac. Its designed to fail and costs a fortune to replace.
I've gone to using mini splits and windows units.

I think if I ever have to buy A/C again (may it not be soon) that's almost certainly the route I will take.

 

[TooManyWheels]

....but you are much more efficient and comfortable than someone with even a two stage system. inverter systems are hard to beat if installed right.

It occurred to me that it might be possible to put numbers to this.

My initial assumption was that a system that modulated down to 25-30% capacity just *must* be having the coil warmer than the dewpoint. But Google, assuming it is correct, says a typical number for a system at the low end of it's capacity would be about 55 degrees. Plugging some typical interior temp and humidity figures for our house into a dewpoint calculator says anything lower than 60 is dehumidifying.

So I may be rethinking my preference for a two-stage condenser.

But now I'm wondering about the respective *rates* of dehumidification. I'm wondering if the house may get cool before it gets dry, having longer run times with a relatively warmer evaporator. Not to mention I'm still worried about the repair costs of a vastly more sophisticated system.

 

[BrendanC]

It occurred to me that it might be possible to put numbers to this.

My initial assumption was that a system that modulated down to 25-30% capacity just *must* be having the coil warmer than the dewpoint. But Google, assuming it is correct, says a typical number for a system at the low end of it's capacity would be about 55 degrees. Plugging some typical interior temp and humidity figures for our house into a dewpoint calculator says anything low than 60 is dehumidifying.

So I may be rethinking my preference for a two-stage condenser. Although I'm still worried about repair costs.

so that is actually something i tuned with my installs. you can set minimum inverter speed. i had to bump up from 15% to 20% to make sure the coil gets below dew point. my house was always 60-68% humidity. now i cruise in the mid 50’s and get down in the 40’s at night time when its set to 73°. keep in mind, this is a 1978 home (original owner was the GC so it isn’t built sloppy) that isnt up to new air seal/insulation code in Houston Texas.

 

[TooManyWheels]

so that is actually something i tuned with my installs. you can set minimum inverter speed. i had to bump up from 15% to 20% to make sure the coil gets below dew point. my house was always 60-68% humidity. now i cruise in the mid 50’s and get down in the 40’s at night time when its set to 73°. keep in mind, this is a 1978 home (original owner was the GC so it isn’t built sloppy) that isnt up to new air seal/insulation code in Houston Texas.

My home was built a year later, and has had similar humidity to yours. We're currently running a standalone dehumidifier, which runs most of the day to get it down to about 50%. Thanks for the note on the adjustment, that's very helpful.

 

[BrendanC]

My home was built a year later, and has had similar humidity to yours. We're currently running a standalone dehumidifier, which runs most of the day to get it down to about 50%.

time for an inverter central air system! i actually used to sleep at 70° but still in the 60% humidity. raised it to 73° and it feels the same if not a little better.

 

[Hohn]

It occurred to me that it might be possible to put numbers to this.

My initial assumption was that a system that modulated down to 25-30% capacity just *must* be having the coil warmer than the dewpoint. But Google, assuming it is correct, says a typical number for a system at the low end of it's capacity would be about 55 degrees. Plugging some typical interior temp and humidity figures for our house into a dewpoint calculator says anything lower than 60 is dehumidifying.

So I may be rethinking my preference for a two-stage condenser.

But now I'm wondering about the respective *rates* of dehumidification. I'm wondering if the house may get cool before it gets dry, having longer run times with a relatively warmer evaporator. Not to mention I'm still worried about the repair costs of a vastly more sophisticated system.

Variable speed setup as I understand don't actually change the coil temp, they check the amount of flow required to maintain the temperature because the heat transfer across the coil is lessened by lower fan speed.

I could be mistaken on this.

 

[Hohn]

Well, new Lennox system is in and boy is it a treat.

It has four variable degrees of freedom: Compressor speed; condenser fan speed, air mover speed, and furnace fuel flow.

This means that the system can no only vary the air mover fan speed, but vary the coil temp and furnace output indecent of fan speed.


This is a real advantage for dehumidification because the system can essentially target humidity level and temperature levels independently. You can actually set a humidistat separately from the thermostat.

Right now it's 75F and 50% humidity in the house and it's the perfect sleeping temperature (cooler). With the old system, we'd sleep at 73 or 74 typically.

I'm guessing that day time we will be quite comfortable at 78-80 or so depending on activity level.

Other observations:

The new condenser is MUCH larger:

There is ZERO copper, zinc, or iron in the coils:

The smart thermostat is pretty trick, too-- it has temp and humidity sensors outdoors on the condenser as well as indoor temp and humidity sensing at the 'stat. It's a touch screen, wi-fi and all that and talks to a phone app. Blah blah.

Obviously I have no indication of durability or quality in the first day of usage. But I can say the performance is VERY GOOD. I'm quite excited about this upgrade.

 

[RhondaHonda]

What did that system set you back? I have 3 Lennox systems that are 12 years old and a Carrier that is 9 years old. Had to replace the A coil on one Lennox system a year ago but otherwise they keep chugging along.

 

[Hohn]

What did that system set you back? I have 3 Lennox systems that are 12 years old and a Carrier that is 9 years old. Had to replace the A coil on one Lennox system a year ago but otherwise they keep chugging along.

An arm and a leg frankly. All done around 15k.

But I'll break even on energy consumption somewhere around retirement. Maybe. Possibly.

 

[RhondaHonda]

An arm and a leg frankly. All done around 15k.

But I'll break even on energy consumption somewhere around retirement. Maybe. Possibly.

That doesn’t sound as bad as I expected. My mom just got an 80% furnace and base model AC for $14k 2 years ago. They threw in a 4” media filter. I told her to call around but she’s stubborn. Her stuff was working fine by the way and the same company inspected it 2x a year. She just thought it was time.

I’ve had the one service call ever and just change the filters and humidifier pads.

 

[QwikKota]

I guess my Lennox experience didn't scare you off. I will say that the new thermostat that directly wires to the furnace/blower has been rock solid compared to the old version that used a smart hub in between. Knock on wood! My unit looks the same outside. Mine is an XC20. 19.5 SEER or something similar. From what I've heard, that install cost is pretty decent for an inverter driven system.

I have my t-stat set to overcool to bring down the humidity and set it at 55% but it never gets below 60%. Our house has bad insulation and thin single pane windows though. It could be a setting speed the installer didn't adjust as mentioned above. He could barely get the thing booted up initially. This was 2015 when this was all voodoo.

 

[Hohn]

I guess my Lennox experience didn't scare you off. I will say that the new thermostat that directly wires to the furnace/blower has been rock solid compared to the old version that used a smart hub in between. Knock on wood! My unit looks the same outside. Mine is an XC20. 19.5 SEER or something similar. From what I've heard, that install cost is pretty decent for an inverter driven system.

I have my t-stat set to overcool to bring down the humidity and set it at 55% but it never gets below 60%. Our house has bad insulation and thin single pane windows though. It could be a setting speed the installer didn't adjust as mentioned above. He could barely get the thing booted up initially. This was 2015 when this was all voodoo.

Our setup I set to max dehumidification (which is 50%, can't be set lower) and it's sitting right now as I type this at 75F and 50% humidity on the button. The system sits loafing alone silently almost all day now. My wife says she's never even heard it throttle up the blower to audible once the house achieved set point a couple hours after install.

Poor air sealing will defeat any effort to dehumidify by a/c alone. You'll end up with a house that's 68F and has a dew point of 68F. Air carries vapor. But vapor also carries vapor.

One nice thing about relatively more recent construction is that they took air sealing a bit more seriously-- house wrap, tuck tape, etc.

Your Lennox experience didn't particularly scare me away because YMMV is a huge factor in these systems-- the local installer's skill and familiarity really matters. My local installer has the highest Lennox certification as well as independent ACA certification. They've carried the Lennox line for 8 years after dropping Carrier after nearly 20 years of Carrier relationship. (Carrier was screwing them with parts availability, leaving customers with high end $20k systems with failures they couldn't fix because a $900 board was backordered 4 months).

I wasn't sold on Lennox so much as our local dealer who is highly regarded. My limited experience with Lennox, however, has always been favorable in the past.

 

[vwmaniaman]

Our home in Kentucky has 2 levels and we have a 4 ton AC cooling 3500 sq. ft. Our upstairs at front yard ground level has 12 inches of fiberglass in the attic cross laid. Our central unit is in the lower level or bright basement part. I am not sure of its age but last spring it needed some R22 added to it and it lasted about 3 weeks. I ordered some stop leak that some veterans invented and recharged it myself I have the equipment to do that and then it went through the entire summer here. When I put the gauges on it this spring it only needed about 8 ounces to bring it back to full. I have not added anymore to it this summer. It still cooling and dehumidifying very well. It must be about 30 years old. My wife and I are inn our 70's and if I can keep it working like it currently is I will be very happy. Our last electric bill was $191 and we keep ours at 76 degrees and use our ceiling fans.. Our refrigerator is old and it runs a lot and we use a dehumidifier that kicks in if the humidity gets over 50%. Our last month was very hot here and the month before was hot but not as bad and the electric that month was $63. Everyone tells us we need a smaller house but we have hobby's and use the space.

 

[Hohn]

Variable speed setup as I understand don't actually change the coil temp, they check the amount of flow required to maintain the temperature because the heat transfer across the coil is lessened by lower fan speed.

I could be mistaken on this.

I was able to confirm that the coil temp of this Lennox system is fairly constant because it has an electronic expansion valve that can maintain a fairly constant superheat.

The interesting thing is that because of how the system modulates, as it throttles down, you actually have less airflow per ton of cooling. That means that it becomes *more* effective at dehumidification as it throttles down because the air has more dwell time on the coil.

This setup will especially work well when you get to the time of year where it's crazy humid but not particularly hot. Regular single-stage A/C struggles because it links cooling to dehumidification in 1:1 ratio-- the only way the dehumidify is to crank the thermostat down.

This system is much smarter.