So I’m trying to make some decisions about the HVAC replacement soon, I’ve been reading online a fair amount but I am still totally overwhelmed. (Of course)

I went back through the thread from a few weeks ago, and noticed that Steve recommended against a higher SEER rating and I thought part of the implication was that we don’t need/want a unit that has variable speed. But I’ve heen reading about the differences and it sounds like the variable speed is especially good for a humid climate. But I wonder about the noise, and whether it’s overkill or not. And if we don’t need it, that would save us money of course.

Steve or anyone else, any additional thoughts about that?

Here are the models the local company has quoted me for. I am focusing on 2 and 3 right now.

1. 20 SEER– 3‐ton Lennox XP20 – variable capacity with CBA38MV variable speed airhandler

2. 16 SEER– 3‐ton Lennox XP16 – two stage with CBA38MV variable speed air handler

3. 15 SEER– 3‐ton Lennox ML14 – single stage with CBA27 with high efficiency blower

4. 15 SEER– 3‐ton Lennox ML14 – single stage with CBA25UHV with high efficiency blower

At some SEER rating there will be a big jump in price to the next highest rating.

Don’t make that jump - there is no payback.

Steve, right, so there are two factors though. One is the money question, which is usually discussed in terms of savings in electric bills. The other is the comfort level in the house.

So first the money question: I am not even considering the 20 SEER machine that was in the quotes I received. It's too expensive. But for the two middle ones, the 16 SEER unit has more rebates with it, so although there's maybe a $2500 jump from 15 to 16, when you factor in the rebates, that difference in price becomes much smaller.

Now, is there a difference in the monthly electric bill? From what I can find online, the actual savings in a year's worth of bills is probably not that big. So that alone isn't reason to get the 16 SEER model.

But what I'm more concerned about is comfort level in the house. If the difference is purchase price is not *that* huge, but the variable speed one is going to be better when it's super humid but not that hot, well, that might be reason to consider it.

In one of your earlier posts, I had the impression that you didn't think very highly of the variable speed units, but is that just because there's not a big difference in monthly bills? Or do they not perform the way they're supposed to?

I don't think variable speed compressors provide enough additional value to justify their cost. The amount of electricity you save will be minor and the added complexity increases the the likelihood of breakdown in the future.

OTOH, he humidity claim is interesting and not something we consider out here. I understand the engineering behind the idea and it makes sense, but I wonder how often the unit will run on low speed if the house is reasonably well weather stripped.

Maybe ask people at work if they have two speed compressors on their air conditioning systems and if they have trouble controlling humidity when the temps get lower.

I can answer that question from a different perspective. We had two-speed compressors in our house in Arizona. Our issue (obviously) was cooling in the summer. We also have humidity for a portion of that summer, though nothing like you have in your location, SK.

I really liked the two-speed option. It ran (almost continuously) during the worst of the summer, but there was a "turbo charge" option that would kick in late in the afternoon on hot days. I felt like the house maintained a more even cool throughout the entire place. I also felt like it handled humidity better, because it was drying the air out at low speeds. It was also quiet. The high speed option made noise. Not awful, but not quiet.

Our power bills went down significantly but I don't know that I can attribute it to the two-speed. We were replacing ancient units and I think any newer system would have reduced our bills.

What Steve says about repairs makes sense. We moved when the units were about 10 years old, and had no issues. We were also religious about annual maintenance, which probably helped.

My 2c!

It sounds like the units ran in low speed most of the time and only kicked in to high speed when the weather got really hot. That makes sense, particularly if the house was newer/well insulated. It also makes some sense to use a two speed model if you are likely to run it all night - something we don't need to do here.

I may have talked myself in to going to the two speed unit if the price jump isn't too drastic.

The jury remains out. I will comment everyone’s comments soon but first this:

https://homeguides.sfgate.com/...itioners-102483.html

I also need to read about the diff b/w twonstage and true variables (multi stage)...

That’s a good article.

Yes, and it says it was updated in 2018, but OTOH the only study cited is from 2006...

When I read about the two-stage or multi-stage, it makes sense to me that they would be better at deal with humidity because the air is moving more.

But that article has the key phrase -- "real-world performance."

Other relevant issues.... I'm not in a "mild climate" so maybe a two-stage is warranted. Or, conversely, my house is probably pretty leaky, so a single stage is better.

I was really hoping to get this decision made today and off my place, but I have a gazillion tabs open with articles about this, and it's not getting any clearer....

Here's another one that TL;DR says the savings in electric bills might not justify the expensive but the increased comfort level does... Of this is on a seller's website, so...

https://advanced-air.com/help-...oner-worth-the-price

quote:

Originally posted by ShiroKuro:
When I read about the two-stage or multi-stage, it makes sense to me that they would be better at deal with humidity because the air is moving more.

More of the time, yes. More air no. You get more air on high speed, but letting the unit run on low more of the time might keep humidity levels more even.

I'm guessing you have a single stage unit on your current house and IIRC it's about the same age . Have you noticed objectionable swings in humidity in that house?

From the article:

quote:

Uneven cooling. Since the air conditioner doesn’t run long and quickly shuts off, it doesn’t mix the air in your home very well. This leads to uncomfortable hot and cold spots in your house.

If your air conditioner runs a short cycle and quickly shuts off then the unit is oversized. Quite a bit oversized, actually.

quote:

Uncomfortable humidity. To remove humidity, your AC needs to run for long periods of time. Shorter cycles with a 14-SEER won’t remove much humidity, leaving your home feeling sticky and uncomfortable.

That has not been my experience. A properly sized A/C will keep a house right around 50% relative humidity without any special controls.

The wild card is that you get cool but humid days in your area. I do know that high humidity will cause an A/C to run longer cycles without cooling the house much because wringing out water happens before lowering air temp. What I don't know is how this translates to HVAC performance in your climate.

quote:

More of the time, yes. More air no. You get more air on high speed, but letting the unit run on low more of the time might keep humidity levels more even.

By more, I meant more often, as in the system stays on longer, but at a lower level. That makes sense to me intuitively and it seems like it would be great for humid days.

quote:

I'm guessing you have a single stage unit on your current house and IIRC it's about the same age . Have you noticed objectionable swings in humidity in that house?

Our rental house is about 10 years older than the house we bought, but the AC unit is newer. But, it is a single-stage. And it works fine most of the time, temp and humidity wise. It's when it's not hot but super humid that I am less than pleased with it. So that's another draw to the two-stage for me...But only if the "real world performance" at least matches the description for the most part.

Also here's another difference b/w the rental and our new house: in the new house, we want to have heating and cooling to the finished basement room. The rental house has an unfinished basement, we never go down there, and there are no add-on vents down there the way there are in the new house. And I suspect the ductwork in the rental house has not been modified the way it appears to be in the new house.

Also, I would prefer a quieter model than what the rental house has, but that's not really a deal-breaker.

There are so many variables, I'm kind of stuck right now.

Nina, do you remember the make of the unit you had?

I'm reading about how Lennox parts can be harder to get, and the local company which I would prefer to go with only offered me Lennox models in their quote, I will ask if they do other models or not, but I think I need to find another local company. I definitely don't want to go with HD or Lowe's.

The only other thing I can say is if you are happy with what you install you will forget about the additional cost pretty quickly.

If you are not you will never forget it.

quote:

The only other thing I can say is if you are happy with what you install you will forget about the additional cost pretty quickly.

If you are not you will never forget it.

Truer words were ne’er spoken.

Ugh.