Home A/C unit died-- by design.

[BrendanC]

surge protector required at service entrance and disconnect. other parts of the world have been on VFD systems for years. a lot of HVAC techs are just scared of new technology and speak on things they are not educated in. anyone can get their EPA cert and do HVAC. i’ve done multiple central air conditioners. edit- supposed to be quoting 4wd on the post about his HVAC guy replacing VFD’s.

 

[Hohn]

We put in a new mini-split AC/Heat pump 3 years ago. The AC efficiency (50% less electrical use) and quietness is so much better than the 25 year old unit it replaced. The compressor and condenser fan have variable speed motors and when running slow you literally can't hear them. The heat pump is ok, but puts out little heat below 30F and virtually no heat below 15F, but above 40F it's great. The heat pump is advertised to put out heat below 0F and that's just a bunch of hogwash. Have gas backup for cold weather and you'll be fine.

It’s pretty rare that we even see single digits here.

I like the idea of heat pump plus a small aux gas furnace in the 20-30k BTU range.

I don’t blame a heat pump for falling off rapidly at low temps (pulling heat from already cold air is tricky), but I would share your disappointment at performance not meeting claims. Heat pump COPs can be 3-4 in moderate temps, which is very good considering pure resistive heating is 1.0.

It’s not just the the upgrade to newer, higher efficiency that I looking forward to, but it’s the chance to re-engineer the system and fix the flaws from a cookie cutter spec home slapped together which marginal workmanship and perhaps eliminate one of my larger frustrations with my home.

 

[Hohn]

Yep, my guy said every time there’s a nasty thunderstorm - he’s got a VFD system to deal with …

It’s the unfortunately reality of newer tech— it’s fragile and intolerant of marginal conditions.

It’s like the world class athlete that has very picky dietary requirements. Well, ok. But you better perform.

When properly integrated with stable power and good ground/bond modern systems can be as reliable as any, if not more so. But they can be quite unforgiving of corner cutting.

 

[Hohn]

My ac tech told me the variable speed units are not worth buying they break way more often and cost over two grand sometimes more to repair compared to a normal one and for the most part it's going to run about the same. The warranty is almost worthless from what he told me and said they blame the home owner or installer and don't care.

The might be the case.

I think that having service from the same people who sold it and installed it goes a long way.

 

[Hohn]

My old 1994 Trane XL- - - 4 ton ac unit except for a couple of capacitors, has been basically trouble free for 32 years. When it fails another Trane will take its place.

View attachment 350480

If I had one of those I’m sure it would still be in service also. The don’t make them like they used to.


Although in fairness to Trane— this unit was in a spec home/subdivision and I”m sure wasn’t their flagship of the era. And even as a builder-grade unit, it still took 20 years to fail.

Design flaw (imo) aside, that’s not a bad run in the bigger picture.

 

[4wd]

It’s the unfortunately reality of newer tech— it’s fragile and intolerant of marginal conditions.

It’s like the world class athlete that has very picky dietary requirements. Well, ok. But you better perform.

When properly integrated with stable power and good ground/bond modern systems can be as reliable as any, if not more so. But they can be quite unforgiving of corner cutting.

I have to deal with industrial VFD - so decided that a two stage was the next step up. We only have “hot” and “really hot” LOL

 

[JavierH19]

surge protector required at service entrance and disconnect. other parts of the world have been on VFD systems for years. a lot of HVAC techs are just scared of new technology and speak on things they are not educated in. anyone can get their EPA cert and do HVAC. i’ve done multiple central air conditioners. edit- supposed to be quoting 4wd on the post about his HVAC guy replacing VFD’s.

It's not that they don't know but they do it for more money because more ac problem calls = more money. On their own home systems they have soft starts, surge protectors, the best quality contactors and capacitors, the best brazed or silver soldered joints, better quality driers, and properly epoxy coated coils to make their systems last forever.

There are so many hvac techs that don't even put service caps so it will leak refrigerant so you'll call them for a recharge every year and if you ask why they didn't put them they'll act dumb or like one lying clown did to me said no it's bad and dangerous if it has a leak it will explode so it best to have them open which was total bullcrap he just wanted it to leak. I bought caps myself and put them on and threw his number away.

 

[wwillson]

Yep, my guy said every time there’s a nasty thunderstorm - he’s got a VFD system to deal with …

Our house was also brought up to current electrical code. This includes better grounding and a whole house surge protector. Lots of lightning and zero problems.

Old grounding code was much less stringent.

 

[QwikKota]

I would be leery of any proprietary thermostat based systems, FYI. Our fancy Lennox POS uses a table style digital thermostat that uses specific comms between the outside unit, the blower and God knows what else. I replaced it myself when it failed once with a used T-stat at the tune of $400 and coddled it along for a few years (multiple resets due to it not sensing inside temps). Finally I had a local company swap it out with a newer version that did not use a smart hub (direct wire) for $1200. They wanted $1400 and I begged and pleaded to give me a discount. This is a 20 SEER true variable speed unit with inverter driven condensing unit, not a 2 speed unit. I heard they are nearly $20k installed now for a full replacement. Did I mention I hate Lennox??

 

[TooManyWheels]

I have to deal with industrial VFD - so decided that a two stage was the next step up. We only have “hot” and “really hot” LOL

I've come to the same conclusion. The current single stage is not uncomfortable, but I want the better dehumidification of the two stage. We have a variable frequency system in the upstairs bedrooms but actually do not want a continuously variable system for the downstairs, as it only dehumidifies when the coil is below the dewpoint. Plus it's one less inverter board to worry about.

Was looking seriously at duel fuel but don't see the advantage of a heat pump over a two stage furnace in our climate. When the current twenty six year old Carrier condenser bites the dust it will be replaced by a two-stage.....wait for it....Carrier.

Current gas furnace is only eleven years old and works fine, but I do see the advantage of a two stage (vs a heat pump for that part of the temp spectrum). Want to stay with 80%, which will be legally outlawed by end of 2028, so that will be replaced between now and then.

 

[TooManyWheels]

Did I mention I hate Lennox??

I monitor a few AC forums. They hate them too, placing them on par or just slightly above Goodman/Amana.