HVAC replacement question

[nash031]

Quote:

Originally Posted by Revlefty My DW is one of those people who will be running the air conditioner nine months out of the year--in Illinois! She always claims we can put more clothes on but she can't take any more off.

Keep that woman. My wife is afraid that when we get A/C, I am going to freeze her out of the house. I have mentioned on several occasions that she can don a sweatshirt, but when it's hot in the house, I can't take my skin off... as it is, I sit around in shorts with no shirt and just sweat watching football on a Saturday...

[MuirWannabe]

Quote:

Originally Posted by Texas Proud What do you mean six..... more like nine!!! I do not know the construction of others, but from what I am told, the Trane has a lot of aluminum which does not degrade like copper.... so the unit is still putting out the same cooling years later... I was told that with copper the SEER drops over the years... Also, I was surprised when I was told that my unit is 4 tons for a 2700 sq.ft. house.... I would think 5 tons just for a downstairs is way too big... what do you have for the upstairs

TP,

Now that I'm becoming more educated I think 5 ton is too much for downstairs as well. My upstairs unit is a 3 ton. That's 8 ton of AC for a 3000 sqft house.

The more educated I've become the more confused I've become. Ignorance can be bliss if not expensive. Now I've got further concerns about my duct work sizing and returns sizing and what that can and cannot allow. Along with how a dual capacity unit fits into the picture.

I know this is generally a DIY group here. But I'm feeling overwhelmed after getting 3 estimates all with different opinions and all badmouthing the other guys ideas and approaches. This combined with the useful info I've learned through this thread. So, I'm planning to hire an independent home energy auditor to come out and do the full test on our house and provide a comprehensive independent evaluation on this replacement project as well. They will know they are not getting any of the actual work. Just the assessment. I think this may cost ~$200 alone but would be worth it to help me end up with the correct answer.

Think of it as a fee only FA. Any thoughts on this approach? Anyone done one of these home energy audits?

Muir

[Walt34]

Quote:

Originally Posted by MuirWannabe So, I'm planning to hire an independent home energy auditor to come out and do the full test on our house and provide a comprehensive independent evaluation on this replacement project as well. They will know they are not getting any of the actual work. Just the assessment. I think this may cost ~$200 alone but would be worth it to help me end up with the correct answer. Think of it as a fee only FA. Any thoughts on this approach? Anyone done one of these home energy audits?

Given the current state of the estimates that seems a wise decision. Since he won't have anything extra to gain he is less likely to steer you wrong.

[meierlde]

Just for reference my house has 3 units totally 8 tons for 3400 sf , but they are heat pumps, so because its in the Tx hill country and has gotten into the single digits, it may be the heating that controls the size of the units.

Note that although it is shaded in the summer the south wall of the house is about 70 door walls.

[Texas Proud]

Quote:

Originally Posted by meierlde Just for reference my house has 3 units totally 8 tons for 3400 sf , but they are heat pumps, so because its in the Tx hill country and has gotten into the single digits, it may be the heating that controls the size of the units. Note that although it is shaded in the summer the south wall of the house is about 70 door walls.

That does seem to be a bit overkill on the AC side....

I would not buy extra on heat pumps in Texas.... even when it gets to the single digits I bet you are having secondary heating kick in which sounds like you have electric.... I would have gone for gas, but that might not be an option...

[Texas Proud]

Quote:

Originally Posted by MuirWannabe TP, Now that I'm becoming more educated I think 5 ton is too much for downstairs as well. My upstairs unit is a 3 ton. That's 8 ton of AC for a 3000 sqft house. The more educated I've become the more confused I've become. Ignorance can be bliss if not expensive. Now I've got further concerns about my duct work sizing and returns sizing and what that can and cannot allow. Along with how a dual capacity unit fits into the picture. I know this is generally a DIY group here. But I'm feeling overwhelmed after getting 3 estimates all with different opinions and all badmouthing the other guys ideas and approaches. This combined with the useful info I've learned through this thread. So, I'm planning to hire an independent home energy auditor to come out and do the full test on our house and provide a comprehensive independent evaluation on this replacement project as well. They will know they are not getting any of the actual work. Just the assessment. I think this may cost ~$200 alone but would be worth it to help me end up with the correct answer. Think of it as a fee only FA. Any thoughts on this approach? Anyone done one of these home energy audits? Muir

I have never done it, but it does sound like a good plan... as Walt has said, he would not have anything to gain in steering you wrong (unless of course they try and sell energy savings items)....



How quickly does your AC cool down your house I remember someone on another thread way back when said that the proper sized AC unit is one that run all day long on the hottest day of the year.... and keeps you cool...

But the rule of thumb can be bad... and the original unit can also be the wrong size based on house orientation and trees.... as an example, my last house was about 2200 or so s.f. I had an original 4 ton unit.... during the hottest days, the house would get warm... when it was 105 outside, it was in the 80s inside... I replace it with a 5 ton and that worked great...

I now have 2700 s.f. and was told I have a 4 ton... even when hot it cycles on and off... keeps the inside cool at all times... I had thought I had a 5 ton just because how it can cool down the house quickly... I still need to go outside and see if what I am being told is correct or not....

[MuirWannabe]

Quote:

Originally Posted by Texas Proud I have never done it, but it does sound like a good plan... as Walt has said, he would not have anything to gain in steering you wrong (unless of course they try and sell energy savings items).... How quickly does your AC cool down your house I remember someone on another thread way back when said that the proper sized AC unit is one that run all day long on the hottest day of the year.... and keeps you cool... But the rule of thumb can be bad... and the original unit can also be the wrong size based on house orientation and trees.... as an example, my last house was about 2200 or so s.f. I had an original 4 ton unit.... during the hottest days, the house would get warm... when it was 105 outside, it was in the 80s inside... I replace it with a 5 ton and that worked great... I now have 2700 s.f. and was told I have a 4 ton... even when hot it cycles on and off... keeps the inside cool at all times... I had thought I had a 5 ton just because how it can cool down the house quickly... I still need to go outside and see if what I am being told is correct or not....

Our house cools down well but the units cycle off and on. I'll update this thread after the audit occurs and let y'all know if that was worthwhile. I've already looked into it enough to revise my $200 estimate upwards to $300+ for this service. That's a hefty sum even in relation to the $8000+ I'll be spending on the HVAC replacement. It better be worth it.

Thanks TP for starting this thread and allowing me to glom on to it. And thanks to others like Walt, Nash, and Wahoo for helping.

Muir


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[Telly]

Quote:

Originally Posted by Texas Proud ............ I remember someone on another thread way back when said that the proper sized AC unit is one that run all day long on the hottest day of the year.... and keeps you cool...

Yeah, I've often heard that said... and rejected it! Why?

No reserve.

Add some people or some activity to that house, and it warms up, and there ain't nothin' you can do about it, until after the sun goes down and it starts to catch up.

Can't use a set-back (actually a "set-up" in this case) thermostat to advantage if no one is going to be home during the day. If you do, you will come home after work to a hot house, with the AC running 100%, and way behind. Might as well stay at work till 8-9 PM or so

Or you set the temp up for when you are off on a trip for days, and return during the day... and swelter for hours as it's behind and chugging away and not getting there.

No reserve for any aging effects.
Reciprocating compressors had valve plates that implemented reed valves for cylinder input and output. As the metal loses some of its springiness over the years, the valves don't seal as tight and as fast as they used to, which shows up as a less-efficient compressor, as if the compressor lowered its displacement. With no reserve, the effect will start to show up on the hottest days first, as not being able to keep up, until the heat load lessens. That is the way all of our reciprocating compressors went, when a compressor was the problem. But having some reserve added years onto the useful life of them in a system.
Also, a loss of even a small amount of refrigerant in a system with no reserve will show up right away.

I don't know (yet) what the wear-out effects of scroll compressors are.

Another way of looking at this, is an analogy... Who would want a car that is only capable of accelerating to 70 MPH, if the highest speed limit one would see is 70 MPH? any takers?

Or maybe a 300 mile car trip, with a car that should get 30 MPG on the trip... so only need 10 gallons of gas in the tank

Some reserve is good in almost all things

Back to AC for a moment, many contractors do not want to size a system that close anyway, as they will get a call-back on the hottest day, and there will be nothing they can do other than swapping out major components, and they can't stay in business doing things like that.

[Texas Proud]

Quote:

Originally Posted by Telly Yeah, I've often heard that said... and rejected it! Why? No reserve. Add some people or some activity to that house, and it warms up, and there ain't nothin' you can do about it, until after the sun goes down and it starts to catch up. Can't use a set-back (actually a "set-up" in this case) thermostat to advantage if no one is going to be home during the day. If you do, you will come home after work to a hot house, with the AC running 100%, and way behind. Might as well stay at work till 8-9 PM or so Or you set the temp up for when you are off on a trip for days, and return during the day... and swelter for hours as it's behind and chugging away and not getting there. No reserve for any aging effects. Reciprocating compressors had valve plates that implemented reed valves for cylinder input and output. As the metal loses some of its springiness over the years, the valves don't seal as tight and as fast as they used to, which shows up as a less-efficient compressor, as if the compressor lowered its displacement. With no reserve, the effect will start to show up on the hottest days first, as not being able to keep up, until the heat load lessens. That is the way all of our reciprocating compressors went, when a compressor was the problem. But having some reserve added years onto the useful life of them in a system. Also, a loss of even a small amount of refrigerant in a system with no reserve will show up right away. I don't know (yet) what the wear-out effects of scroll compressors are. Another way of looking at this, is an analogy... Who would want a car that is only capable of accelerating to 70 MPH, if the highest speed limit one would see is 70 MPH? any takers? Or maybe a 300 mile car trip, with a car that should get 30 MPG on the trip... so only need 10 gallons of gas in the tank Some reserve is good in almost all things Back to AC for a moment, many contractors do not want to size a system that close anyway, as they will get a call-back on the hottest day, and there will be nothing they can do other than swapping out major components, and they can't stay in business doing things like that.

All good arguments.... but still does not take away from the theory...

IN THEORY, the best AC is one that..... you know the rest...



Also, the AC manufacturers have now addressed this with a variable system.... the AC guys were telling me that if you install one it will likely run all day long.... with the unit adjusting between 30% and 100% to cool the house... the sensors are there to tell the unit that it is getting hotter and to spool up.... if the system was not so expensive, I would look at getting one...

[Looking4Ward]

Interesting thread. We purchased a 3,400sf two-story foreclosure in the Austin area about five years ago.

Our chief concern was the home (built by one of the better home builders in Texas) only had a 5 ton A/C unit. We noticed most others in the same subdivision had at least two units, some even three.

Even the home inspector agreed it was undersized and recommended a second unit be added. We negotiated an additional $5K back from the bank at closing because of this.

We never added the second unit, and we've since been thru several of the hottest summers on record, one with over 90 100+ degree days.

I can tell you that keeping cool in this house has NOT been an issue. It will maintain the 78 degree setting we keep it at during the day and will bring it down to the 72 degree setting we like to have when we sleep.

Our electric bill for this size home with 105-110 degree summer days has never been more than $275. That is comparable to a 1900sf lake house that I had with a 4 ton unit which always felt "clammy" because the A/C unit was probably over-sized and didn't run long enough to remove all the humidity.

So 78 in that house actually felt warmer than 78 in this house, where the A/C runs longer and doesn't cycle as much. Incidentally, the longer an A/C unit is allowed to run, the more efficient it is. Those frequent start-up cycles are real energy hogs.

My point is, definitely have a heat load manual J study done. The science is far more perfect than a contractor's estimate.

[photoguy]

Quote:

Originally Posted by nash031 Keep that woman. My wife is afraid that when we get A/C, I am going to freeze her out of the house. I have mentioned on several occasions that she can don a sweatshirt, but when it's hot in the house, I can't take my skin off... as it is, I sit around in shorts with no shirt and just sweat watching football on a Saturday...

You could always try wearing a wet towel (my dad's version of natural air conditioning)


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[frank]

I wonder if you ever thought of contacting a trade school that does hvac training. I did that once and they installed my system at just about what it cost to buy the equipment. the instructor is a professional heating and air person and does all the calculations, designs whatever system you need and oversees the installation and checks the preformance of the system. the instructor could probably figure what size system you need and you would have an unbiased opinion. just a thought.

[MuirWannabe]

A few updates from my situation. Lessons learned.

1. There is no independent home energy audit provider. I wanted to find someone who would do an energy audit of my house along with recommendations for my downstairs AC/furnace replacement. But reality is most folks who do this also are in the business and therefore want to sell your solution and not just independently recommend. And even those who are not in the business but really are energy auditors all have ties to fellow companies they quickly bring into the picture. So independent recommendations quickly disappeared for me as a myth not to be found.

2. Cost quotes varied widely. The first quote I recieved for a 5 ton 18 SEER two stage Trane was the cheapest at $8200. But I have now received 3 other quotes ranging from $9800-11,700. And some of those are for 16 SEER 'lesser' units. Pretty amazing variance. I'm almost skeptical of the first quote since noone else came close to this lower amount. But that is too big a difference to ignore so I'm planning to move forward with this.

3. I did have the manual J calculation performed by two of the quote providers. In both cases it indicated I need the 5 ton unit even though I already have a 3 ton upstairs unit and my house is only 3000 sqft. It also confirmed my returns are adequate to supply a 5 ton. But they did discover a portion of my ducting needed to be upgraded from 10 inch to 12 inch to allow maximum utilization of airflow when the 5 ton is fully going. Doing this more comprehesive calculation was a good idea.

That's a few of the lessons I've learned so far. Still have not done the actual replacement so will update if any more major lessons are learned. I hope this is helpful to someone else. It's been quite an educational process for me and I'm still concerned I'm screwing up. Dang it's a bunch of money.

Muir

[Looking4Ward]

I had a 4-ton unit go out on a rental last year. Quotes from A/C companies were coming in at $4-$5K to replace it.

Found a licensed contractor on Craigslist who replaced it with a new 4 ton 16 SEER for $1800, hauling off of the old unit included.

Once you've determined what size/brand/model you need, check Craigslist in your area for a licensed A/C contractor selling wholesale.

[springnr]

Muir, to confirm ballpark accuracy you can check the manual j you received with this calculator, manual j has interpretation room, experience counts. I think some contractors prefer to match existing so the customer can't fault them for a bad sizing choice.

HVAC Load Calculation - Maunualj - Whole House Loadcalc

HVAC talk forum map of contractors: Ask Our Pros Contractor Locator

The HVAC talk forum can critic your estimates, similar to a boglehead forum portfolio check. Example critic, tiger's recommendation and informative thermostat comment.
Need help sizing AC unit for 3 level Townhome

[nash031]

My first two quotes are also in, and it portrays exactly the reason why I'll get a third next week!

First guy:

- Ducting is good for A/C (based on inspection)
- Recommended also replacing the furnace (original with house, Rheem Criterion II gas).
- 3 ton unit (for 1600 square feet, single story, close to water in San Diego)

$3800 for simple A/C install, $5400 to replace furnace as well.

Second:

- Ducting probably needs to be replaced (note: this is based on me telling him age, type, etc.)
- Recommended replacing furnace
- 4 ton unit recommended (neither guy did the full load calculation)

$4500-5500 for furnace and A/C install
$5500-6500 for upgraded furnace and A/C (multi-stage, variable speed, reduced noise)
$5500-8000 for all that plus replaced duct work

So, a home inspector and one A/C installer said our ducting is fine. The third (no visual inspection) said to replace it. Pricing is close to in line, but I think 4 tons is too much (to wit: the 2700 square foot, 2 story house with west-facing windows next door has a 4.5-ton unit), and get the feeling he'll try to "up sell" me on everything. I don't believe I need a variable speed, multi-stage install for my application. It doesn't get THAT cold, and rarely gets THAT hot...

As of today, I'd go with the first guy, but will see where the third estimate comes in and what he recommends for the furnace and ducting.

[nash031]

Quote:

Originally Posted by Looking4Ward I had a 4-ton unit go out on a rental last year. Quotes from A/C companies were coming in at $4-$5K to replace it. Found a licensed contractor on Craigslist who replaced it with a new 4 ton 16 SEER for $1800, hauling off of the old unit included. Once you've determined what size/brand/model you need, check Craigslist in your area for a licensed A/C contractor selling wholesale.

This seems like a great idea... difference being I think you already had refirgerant hosing and electrical wiring installed? (I'm a full new install, so I doubt I could get such a deal!)

[Senator]

I just installed a furnace in one of my rentals. A 95% 110 BTU Goodman modulating furnace.

They are not that hard to install. Total cost, including giving a few bucks to a friend that helped, was $2,000. It would have been $4,000+ at a dealer.

[MuirWannabe]

Nash,
I never could get a straight answer either. Had 4 different companies come out and provide quotes. Also spoke to several others over the phone. They all told me conflicting things. And yes, I got tired head and caved. Plus I wanted to get my AC going again. So, I just went with the cheapest guy for $8300. And yes, that was the cheapest quote received. So far, all seems okay but its just been a week. I think I have the Taj Mahal of HVAC systems. The process was defeating but it is nice to have it done.

[nash031]

Quote:

Originally Posted by nash031 My first two quotes are also in, and it portrays exactly the reason why I'll get a third next week! First guy: - Ducting is good for A/C (based on inspection) - Recommended also replacing the furnace (original with house, Rheem Criterion II gas). - 3 ton unit (for 1600 square feet, single story, close to water in San Diego) $3800 for simple A/C install, $5400 to replace furnace as well. Second: - Ducting probably needs to be replaced (note: this is based on me telling him age, type, etc.) - Recommended replacing furnace - 4 ton unit recommended (neither guy did the full load calculation) $4500-5500 for furnace and A/C install $5500-6500 for upgraded furnace and A/C (multi-stage, variable speed, reduced noise) $5500-8000 for all that plus replaced duct work So, a home inspector and one A/C installer said our ducting is fine. The third (no visual inspection) said to replace it. Pricing is close to in line, but I think 4 tons is too much (to wit: the 2700 square foot, 2 story house with west-facing windows next door has a 4.5-ton unit), and get the feeling he'll try to "up sell" me on everything. I don't believe I need a variable speed, multi-stage install for my application. It doesn't get THAT cold, and rarely gets THAT hot... As of today, I'd go with the first guy, but will see where the third estimate comes in and what he recommends for the furnace and ducting.

So the third quote is in:

- No need for duct work. 3 out of 4 say this.
- 3 ton A/C. 3 out of 4 (same dissenter) say this.
- Replace furnace. 4 out of 4 say this.

1st quote: $3800 A/C only; $5400 A/C and Furnace
2nd quote (the dissenter): $4500 - $5500 A/C and Furnace (4 ton...)
3rd quote: $4400 A/C; $5400 both

(The "4th" is recommendation of home inspector and family expertise.)

So, the second guy hasn't actually seen the house, but I'd hesitate giving him business if he's set on 4 tons for a 1600 sqft house by the ocean. Giving him the benefit of the doubt, I would hope he'd come out and recommend against replacing the ducting and come down on his sizing recommendation. If that's the case, it might bring his price down some as well. (Edit: just looked up the price difference between 3 ton 13 SEER and 4 ton 13 SEER; it's about $200, so not particularly significant in this application).

Part of me says to call the 2nd guy, have him come look, and see if that changes his mind. Part of me says go with one of the other two, both of whom seem reasonable and whose proposals are in line.

Any thoughts/suggestions?