HVAC questions

I just got out of a horrible, dysfunctional, relatonship with my last Air Conditioner.

A Lennox, it was fixed at 8 months, 20 months, and died at 8 years. We sweated through 2.5 years without A/C while we scrounged enough to replace it.

Learned a lot of little coping mechanisms and realized that it was also saving us $200 a month in electrical.

The replacement is an off-brand (Gibson?) and seems to work well. What I noticed was: It’s a good 20% larger, and the hot air coming off it isn’t as hot as it was on the Lennox.

So, question time:

  1. The installer mentioned that 8-10 years is now the accepted lifespan of a system. Really? :frowning:

  2. While it may seem that ‘less hot air’ coming off the Condenser would mean it’s not working as well, I’m of the opinion it’s not working as hard…which means the compressor isn’t working as hard…which should translate to a little more longevity…right?

  3. The online AC reviews I found were rather polar, either people rating them 5 stars wonderful, or 1 star awful (like my Lennox)…leading me to believe it’s a self-selecting population and not one to rely on. But how on earth do you make an educated choice on something like this then?

When you say it is 20% biggger, I’m assuming you mean the outdoor unit, that would probably explain why it appears less hot, there is more air circulating to remove the same heat.

Yeah, I should have been more specific. The Condensing unit was replaced after the compressor seized. Originally, I added a hard start kit to the condenser fan motor…then I swapped out the Condenser Fan motor as it had stopped turning, THEN added a hard start kit to the compressor. That all lasted about a week before the compressor seized entirely.

I don’t have the gear to work with refrigerant…it was at that time I gave up and started saving money for an expert.

The Condensing unit is 20% larger…Just wondering if less heat means less wear on the compressor. Not so much that it lasts longer, but I suspect the older unit was undersized.

I just replaced a 10 year old Lennox system myself with a 2nd Lennox system. I moved into the house in 2007. I heard the same “10 years” general lifespan remark, but I kinda figured that was because the climate here in San Antonio is so hot, not that 10 years is the rule of thumb anywhere. My previous system hadn’t died but it was shown to me that it was at the point where it could fail at any moment. I got yearly “checkup” with the local contractor and noticed the numbers they used to measure it effectiveness went over a cliff between the spring 2011 and the spring 2012. What’s more, the old R-22 refrigerant is getting more and more expensive since it was banned in new installations in 2010.

As for online reviews, I’d wouldn’t put much stock in them. I have no problem with my system since it was installed a month ago but I haven’t gone to any websites to write any 5 star reviews about it… it is working as it should be! I would think that the 1 stars are people who got lemon systems or had a bad experience with the contractor and 5 stars may tend to be fake reviews posted to offset the angry 1 star reviews. :slight_smile:

I am liking this image.

Gibson is not an off brand. The channges is ac equipment and efficiencies of newer equiupment are so much higher that they have lot less to be given off.
I think the differences in the reviews are more of an installers results.

Snerk! :smiley:

Well, I (an admitted expert in LOTS of things, none of them being HVAC) hadn’t heard of 'em.

I’ve seen 5 years and 25 years…it all depends on a number of factors. The leading reasons (in order as far as I know) of a non-abused compressor/condenser unit to fail are…

  1. Improper wiring. While the running current of an AC unit might call for 20-30 amps and get wired with #10ga wire, their starting current is much higher. They should be wired between the service and a nearby disconnect at 45-60 amps (with #6 wire). At the disconnect, the service condenser motors endure are more properly fused, as opposed to circuit breakers (and that last 3-5 feet is where it’s setup for 30 amps). Preceding based on an average unit for a modest home.

  2. at installation, the installer didn’t add the proper amount of lubricant, leading to increased wear or seal failure.

  3. The unit, during the off season is never run, so lubricant never is replenished to seals, which dry out and then leak. Before it was common for the AC to turn on in cars automatically when the defroster setting is selected, it was common advice to run your ac at least once a month.

  4. Bad luck, not leveled well enough, planetary misalignment, etc

Where exactly are the transmission lines?

Bubbadog suddenly realizes that High Voltage Alternating Current is not the subject and quietly leaves.

Info. I have a Bryant installed in 1995 still going strong. It is fused at 25 amps, #10 wire, and a very short run. The condenser almost sits under the meter with the breaker box inside.

It replaced a Sears where the people that took money to run one wire about 15 feet to the furnace a non code splice and another wire running out to the condenser. I ran one wire directly to the condenser. I used the other wire to put the fridge on its own 20 amp circuit.

If i may weigh in…

  1. Units are much larger now because they are required to be much more efficient. Air conditioning is all about moving heat from one place to another. That’s achieved through a 2 step heat transfer process; heat is transferred into your evaporator inside, and transferred to the environment outside via your condenser.

Improved efficiency is accomplished in part by larger coil surfaces to effect heat transfer. So… bigger coils produce more efficient heat transfer.

The notion that units last 8-10 years is complete unadulterated bull IME/IMO. That lie is propagated by the industry (that wants to sell units) and contractors (that want to sell units). IME a well maintained unit will last 15-20 years----if it was installed using best practices.

  1. The heart and soul of the unit is the compressor. Only one manufacturer makes their own compressor. Everyone else is buying from Danfoss, Tecumseh, Bristol, or Copeland. So in all cases almost, competing brands are using many of the same parts.

You can buy an older compressor technology that works well (reciprocating) or a newer technology (scroll). I recommend scroll, and Copeland is the gold standard for scroll compressors.

  1. There’s no correlation between the air you feel and the longevity of the unit. There are many variables, and its nor practical to list them here. Heres some basic info that will give you a thumbnail sketch as to your unit: The air temp difference between the return air going to the furnace, and the supply air at your register should be 15-20°. For example…if the return air is 75°, the temps at your register should be 55-60°. Thats a 15-20° “delta.”

  2. You are infinitely better off choosing your contractor for an HVAC system than the brand. Every brand has many models and many features/ efficiencies. So…any brand will have the features and efficiency you wish. Educate your self on those features. Educate your self on the best contractor that will meet your needs. The name on the front is the least important item.

  3. We routinely help DIYers and advertise that will help DIYers. That said, an A/C system is not for the untrained, and unlike a TV or toaster it is not “plug and play.” As a result I find online reviews to be relatively worthless. The installation (and the quality of that installation) has more to do with the units performance and longevity than the brand.

Pick the right people, and educate your self on the features you want. Whatever brand they sell you will be happy with.


The compressor is working the same. (although all motors are more efficient then older motors, right?)

The same amount of heat is being moved but it is dispersed in a larger coil and more airflow. It is essentially being “diluted” if that makes sense.

Thanks, guys, all very helpful information. Any truth to the rumor that extra money spent in a more efficient unit won’t be gained back in improved efficiency, or is it one of those ‘it depends’ things?

(And one week in, the Gibson’s just peachy. Five Stars!)

"In rush’ current isn’t a factor, and the wire can be sized for normal running load. (RLA)

“Locked rotor amps” (LRA) is typically 3-8 times RLA, but is in effect for a split second and wire is sized for RLA, not LRA.

Great question. Installed correctly you’ll always get your money back.

The question is: “when?”

The answer is based on at least these variable:

  1. the quality of the envelope. Better envelopes mean lower run times which drag out paybacks.

  2. lifestyle. If you use setback tstats and use higher temps in the summer the unit will run less----which will drag out paybacks.

I’d guess the average home will get all their money back (that “money” being the premium you paid for a higher efficiency unit) in the form of lower utility bills in 3-8 years. After that its money in the bank.

Anybody who tells you you’ll see 50% reductions etc in utility bills is misinformed or lying.

And this solves voltage drop?

No it doesn’t address it. If the run is long enough the wire must compensated for voltage drop.

Thats pretty common in commercial applications, where the runs can be very long, but is a lot less common in residential homes.