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I had service people come in and check for charging. They measured the cold air coming out and it was cold (I felt it myself) so it was working.
Otherwise, I don't think anyone checked if the condenser was clean or the fins perfect. I would think they were in 20 year used condition. The motors seemed fine (occasionally the start up cap blew which I replaced myself a couple times for $20).
If the motors weren't running efficiently, wouldn't that simply raise the power draw but otherwise the performance is the same? In otherwords, it might work like an 8 SEER instead of 10???
Motors running a few percent slow would not allow compressor to run a full effiency which would tmean the refrigerent doesn't cool as much which means it has less capability to cool the air passing over the coils. It can eventually get the air cool but it takes longer. Tubes have scale buildup which means they can't transfer heat as efficently which again means it takes longer to get the same amount of heat transferred.
In general. It is a 20 year old system. Some of it is just the accumulation of small issues. If you track how long it takes the new system to cool the house I'll bet even properly maintained it will take longer in 10 years and even longer in 20 years. It is just that the change is gradual and not noticed.
For example? How would the installation of the new unit be significantly different than the builder unit if the ducts and other hardware were the same?
Yes installation definitely makes a difference. In my split AC I can feel cold air coming out or rather leaking from multiple spots from the system containing the A coil and furnace
Would you guys conclude that if my 1997 10 SEER 3 ton unit was installed properly AND there was no wear out, it indeed would (other than power draw) perform as well as my 2017 14 SEER 3 ton unit?
I've experienced this twice, with two different homes.
Why does a 12 SEER 3 ton builder grade A/C seem so much weaker (takes longer to cool) than a new dealer Lennox or Carrier 12 SEER 3 ton? The SEER and BTU specs are exactly the same but that dealer A/C works so much better.
I think the installers drop n' go. Adjusting the blower helps a lot... not all installers read the manual or know what the DIP switches do on an air handler.
Would you guys conclude that if my 1997 10 SEER 3 ton unit was installed properly AND there was no wear out, it indeed would (other than power draw) perform as well as my 2017 14 SEER 3 ton unit?
"Tonnage" vs actual cooling capacity can differ among brands, and will differ based on the specific components chosen within those brands - i.e. The indoor coil and outdoor condenser - there's nearly always more than one "acceptable" matching coil and condenser. A "4 ton" goodman may deliver several thousand more or less btu's than a "4-ton" carrier. There is a lot of math involved and more than one parameter that needs to be looked at to determine if a unit is operating as designed. Things like amp draw, outdoor temp, humidity & static pressure of the ductwork. There's way more to it than the temperature of the air coming out of one duct.
The easiest way to see if your new system is properly installed is to look at the repair / work order for the installed system. Does it show things like a measured amp-draw for the system? Does it show inlet temps, outlet temps,outdoor temps, line pressures, wet bulb, & static pressures? if you don't check everything, you can't know that the refrigerant charge is correct.. Hvac manufacturers have charts that come with every system that specify this data.. "With this condenser and this coil, with this temperature, you should be seeing x,y & z.. ".
If you then want to talk about "performance", you'll need to measure more than just "this cools my house down faster"..
An oversized unit will cool (parts of) your house down super fast.. It'll also be drafty & uncomfortable, allow the humidity to creep up, amp up your electric bill & die years before a properly sized unit.
No matter how the coils looked, they were 20 year old coils. They build up a layer of material that doesn’t easily wash away. This results in a reduction of heat transfer. If there is blockage in the coils then you also have a reduction in air flow across the coils. An older fan motor can also generate more heat than when new. While you may not feel the heat, this heat is transferred to the air moving through the unit. New motor won’t generate that much heat. There are way too many variables to consider other than the difference between a 20 year old brand and a new brand of the same capacity being the reason for the difference in cooling.
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