Systems comparison (HP vs. AC/Furnace) + thoughts on the nest

SanMAugust 20, 2014

Hi Everyone, After receiving many quotes to replace our 15+ year old 5 ton AC/furnace setup for a 3,000 sqft house, we've got it narrowed down to two choices. Both include replacement of all ductwork as it is in pretty bad shape (rusty, holes, fallen insulation, weird combos of rigid & flex). Also, I've received a mix of suggestions for 5 ton vs. 4 ton total, but the two companies below spent the most time doing the manual J calc and said the house is right at 4.

1) Trane -
Downstairs - 2 ton - XR A/C 14.5 SEER (4TTR6024B1000A) XV 95% Furnace 60,000 BTU (TUH1B060A936)
Upstairs - 2 ton XR Heat Pump 15.5 SEER (4TWR5024G1000A) + air handler (TAM7A024) + aux heat (BAYEVAC05LG1AA)
Total cost - $19,900

2) Carrier (all performance series)
Downstairs - 2 ton - A/C 15.5 SEER (24ACC630A003), 2 stage 95% furnace (59TP5A060E17--14)
Upstairs - 2 ton - A/C15.5 SEER (24ACC630A003), single stage 80% furnace (58PHA070---1--16)
Total cost - $18,133

Both companies have very positive ratings/reviews on Angie's list.

I'm leaning towards option 2 based on price, but wondering what others think. Option 1 sales guy says furnace upstairs is overkill and would require running gas line and extra flue in roof. Option 2 says he didn't think we had room in our electrical panel to add a HP. Also a HP isn't good for covering 4 bedrooms/2Bath upstairs since when it gets cold it will freeze and switch to defrost mode.

Finally, I can save about $3-400 on each quote by supplying my own thermostat. I really, really like the look of the nest and personally think most thermostats are ugly. I've seen mixed reviews online, with people both loving and hating them. System performance is obviously important, but I also don't want to walk by two thermostats each day and wish I had something better looking. Thoughts on The Nest? Anything else that looks similar?

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Should have mentioned we are in Charlotte, NC. Energy rates are $0.0936/kWh and gas is $1.04/therm from Nov-March and 1.01 rest of year.

    Bookmark   August 20, 2014 at 10:40PM
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The model numbers for the Carrier AC condensers are 2.5 tons, not 2 tons. Is this what the contractor intended to quote?

There are better thermostats than the Nest for the same amount of money. The Nest was designed by people who make things look good. It seems they did not put much effort into how to control HVAC systems properly. I am not sure the Nest is the best choice.

    Bookmark   August 21, 2014 at 9:24AM
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The Trane systems quoted are better equipment. I would not use a Nest Period.

On Trane, a two stage thermostat for downstairs like HW Prestige 2.0, upstairs HP system HW Mdl #8321.

I would want a load calc for each zone. What size living area for downstairs and upstairs?

It should be noted you were quoted var speed furnace and var speed air handler from Trane dealer, much better than the Carrier quote.

I recommend filter box cabinets for each system. Both floors have adequate returns?

You want minimum R8 insulation for both ductwork systems. Now would be the time to add additional returns if indicated.


This post was edited by tigerdunes on Thu, Aug 21, 14 at 9:52

    Bookmark   August 21, 2014 at 9:40AM
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Thank you for the replies. I did some follow-up and have some adjustments. The Trane furnace had the correct model number, but the name is wrong. It would actually be an XR 95% furnace. The salesman apologized and said it was a cut and paste error from another quote he prepared for me. This means that setup isn't variable speed.

Also, rechecked my notes and I had the wrong company for the 4-ton. The Trane dealer said right at 4, the carrier dealer said 5. others have said either 4.5 or 5, but I think many of them are defaulting to match the current 5 ton system.

Another consideration is that we may eventually want to add a room over the garage which would be an additional 500 sqft (single room). If in doubt, would it be worth oversizing in case we do the addition, or would that require a system change no matter what (gulp)?

Finally, we will be using current supply & return vents downstairs (some in each room). The upstairs will have a single return added. All ductwork will be insulated with R8.

This post was edited by SanM on Thu, Aug 21, 14 at 21:15

    Bookmark   August 21, 2014 at 9:11PM
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I always hate to read posts like this last one.

I would tell Trane dealer to honor the XV95 or you intend to walk.


    Bookmark   August 22, 2014 at 9:59AM
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The additional 500 sq. feet would increase the heating and cooling loads. If are serious about doing this you first have to determine how you would supply this room. It may not be feasible to tie into the existing duct work.

The new room would probably put you above 4 tons. It may turn out the upstairs could be a 3 ton 2-stage condenser, and the downstairs is a 2 ton unit.

A better option would be to install a mini split for the new room. This makes the planning easier and will make it a lot easier to control the temperature in that room.

    Bookmark   August 22, 2014 at 10:41AM
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Thanks tigerdunes, I was frustrated, but this is also one of about 6 quotes i've had the guy put together over the past 2 weeks. He has been really nice to work with in every other way, so I don't want to force him to lose money on a simple mistake. It does make me nervous about his attention to detail though.

Does that new info make the carrier equipment/price combo the better option?

Great idea with the mini split mike. That would probably be the best route.

    Bookmark   August 22, 2014 at 8:33PM
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I emailed the carrier dealer about the larger size of the system and the less efficient furnace upstairs. here is part of his response. Does this make sense to you guys?

2 stage equipment only comes in even numbers (2,3,4 ton). The problem I have is all ac systems are different out tonnage. The "best" system that you are looking at is 27,600 output in the ideal time of the day. With your sq footage with 2 floors you are In between 4 and 5 ton. If you install a 2 stage 2 ton, I feel it will run all ac calls in 2 stage defeating the purpose of energy-saving. We like to use a less energy efficient furnace for the second floor due to the fact that all the heat will rise from the first floor to the second and not allowing the benefits of a higher efficient system.

    Bookmark   August 22, 2014 at 10:02PM
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There are so many wrong things in the Carrier dealer statements that I don't where to begin.

It is true that 2-stage equipment comes in whole ton sizes. It is also true that the actual output of all 2 ton systems is not exactly 24,000 BTUs. The SEER rating takes into account in the output versus energy input. You have to pay attention to the net output if the cooling load is very close to the size you are trying to use.

A good 2-stage thermostat will start 2-stage equipment in the low stage and keep it there until the temperature is satisfied. This is more efficient than a larger single stage. The thermostat will go to the high stage if there is a big delta between ambient temperature and programmed temperature. This usually occurs coming out of a set back period.

The logic about using a lower efficiency furnace on the upper lower is nonsense. The heat load may be less than the first floor in some cases, but it still has to be heated. If the furnace is going to installed in the attic, some contractors will use an non-condensing furnace (80% AFUE) in order not to have to deal with the condensate water freeze ups. A good contractor will know how to install high efficiency furnace in attics. If the furnace is in a conditioned space then there is no reason not to use the highest AFUE furnace you can afford.

I am not getting good feelings about this contractor. Are there any other choices?

    Bookmark   August 23, 2014 at 8:42AM
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Thanks Mike, the amount of time you and tigerdunes spend helping people on this site is amazing and very appreciated.

This was the 4th quote we've gotten. (not including a 5th contractor that never returned our calls) I've thrown out a Lenox dealer who didn't spend much time in the house and basically quoted an exact replacement for our old system. I also threw out another trane dealer who has a good reputation in the area, but was pushing very hard for high end systems and priced the items we really wanted thousands more than other 3 quotes. That leaves me with the 2 mentioned. Perhaps I need to get one more, but we felt very comfortable talking with the carrier dealer. We also let him know that we did not need top of the line on efficiency or features and would be frustrated if he quoted us as such. We wanted something that made sense if we planned to be in the house for less than 10 more years. Perhaps this contributed to the lower end furnace upstairs. Carrier seems to quote in a good, better, best format. He initially recommended going with the "better" option of lower SEER A/C and "comfort"level furnaces (similar specs up and down) for a couple thousand less, but since we aren't really sure about moving, I wanted to step it up a bit.

The other wrinkle is that the carrier dealer has a sister company that does moisture and mold remediation. You may remember a post I made a while ago about my crawlspace & ductwork being a mess and a trunk line running up the inside of a large chimney to allow the single system to reach the attic. We've decided to do things right by switching to two systems and the carrier dealer was able to speak most intelligently about the situation. The sister company has been the best to work with for crawlspace remediation quotes, offers the longest warranty (25 yrs) and they've collectively agreed to negotiate a TBD additional discount if we go with both companies in a sort of package deal.

I've asked the carrier dealer to come back with a hybrid quote that includes all "performance" level equipment with high efficiency furnaces on both floors, but keeping the system at 14 SEER instead of 15.5. Still waiting on that and will let you know when I get it.

Given the information above, do you still think we need to walk away and find another contractor?

Finally, Tigerdunes asked about living space split in an earlier post. There is about 1,740 down and 1,300 up. There is a large opening at the front of the house for stairs and an overlook to the foyer. 6 rooms downstairs (incl 1 half-bath) & 6 rooms up (including 2 full bath).

    Bookmark   August 23, 2014 at 9:57AM
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It appears you are leaning toward Carrier.

I have no problem with the downstairs system as quoted. You list a 2 ton system but the model number is in fact a 2 1/2 ton Performance 16 AC condenser. I would want the 2 1/2 ton. What matching evap coil did dealer quote? You want the Performance Edge Thermidistat. No substitute is acceptable. And do not go lower than the Performance16.

I do have a problem though with the upstairs system. That furnace is too large. Ask dealer for recommendation even if that includes a HP system which is not a bad idea for better sizing.

Post back.


    Bookmark   August 23, 2014 at 11:08AM
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Thank you Tigerdunes. I just sent a follow-up email to request using a smaller system upstairs. I'll also ensure I get the performance edge Tstat. I hadn't seen it before, and it actually looks pretty nice. dealer originally said he would start by pricing in 2 mid-range wifi enabled Tstats valued at $400 total and we could go up or down, or I could provide my own.

You said not to go lower than performance 16, but did you mean not to go below 16SEER, or that I could go below 16 SEER as long as it was part of the performance 16 series? Also, I reviewed the carrier website and didn't see much difference btw the performance 16 and performance 13 (24ACB3) other than 2 decibels of sound. Is it really worth the extra cost?

I used the following website to calculate savings over 10 years with 14 vs. 16 SEER and it didn't seem to justify the extra upfront cost. I'll have to double check once I get the latest quote back though. (zone 3, 9.36 cents/kWh)

    Bookmark   August 23, 2014 at 12:15PM
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I would stay with the Performance series of AC Condensers.

What model evap coil were you quoted? Should be a Carrier ALA suffix model. no third party brand is acceptable. The evap coil model and size determines the performance and efficiency numbers for AC cooling.

You can weigh the cost difference between the Performance 16 and 13 AC models. Expect no more than 10% savings in operational costs.


    Bookmark   August 23, 2014 at 12:51PM
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Sorry, I missed a key part of your prior response. The evap coil is only quoted as a matched carrier model CNPHP3017. I checked on the carrier website and didn't see anything ending in ALA. Is that something specific I need to ask about?

    Bookmark   August 23, 2014 at 1:11PM
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ALA is Carrier's aluminum coil. Yes, a big deal and both verify and insist on it.

Carrier has finally caught up on aluminum coils as they had many problems with leaking copper coils not so many years ago.


    Bookmark   August 23, 2014 at 1:19PM
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Here is the AHRI matching number on Carrier dealer's downstairs system quoted. I believe he is mistaken on the coil so I used the model that is close.
You might ask him for the AHRI matching number.

6389691 Active Systems CARRIER PERFORMANCE SERIES PURON AC CARRIER AIR CONDITIONING 24ACC630A**30 CNPH*3117AL* 905 59*P5A060E17**14 28400 13.00 16.00 1 RCU-A-CB 220 Yes


    Bookmark   August 23, 2014 at 4:12PM
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Sorry for the delay, was a busy week. Connected with the dealer and talked through some things though. Have two new options to consider. First, here are some clarifications:
1. yes the coils are ALA. According to the dealer, this is all their company uses now.
2. My sqft calcs were a little off. downstairs is more like 1,550 vs 1,450 upstairs. dealer is adamant that 2.5 tons is necessary upstairs based on his calculations. Seems flexible on everything else, so I think he really believes what he saying.

ok, here are the new packages:
1) Downstairs - 59TN6A060V17 infinity series 96% furnace & 14 SEER 24ACB330A003 AC unit
Upstairs - 58CVA070 infinity series 80% furnace & 14 SEER 24ACB330A003 AC unit

2)Downstairs - 59TP5A060E17 performance series 95% furnace & 14 SEER 24ACB330A003 AC unit
Upstairs - 58PHA070 performance series 80% furnace & 14 SEER 24ACB330A003 AC unit

He threw in the infinity furnace as an option that would provide additional comfort due to the variable speed air. The performance series sounds pretty good too, but not quite as fancy. We talked about the 80% upstairs and he said that based on our attic, we were at risk of the condensate freezing up (as mentioned in previous reply). He said he'd install a higher efficiency if we wanted, but he didn't think it was worth the risk based on the limited savings we would see and the additional upfront cost. The same argument applied to moving up to infinity series A/C units to match the furnaces- not worth the upfront costs unless we were going to stay in the house for 10+ years.

Looking for final thoughts on these two setups. How would you describe the comfort difference between infinity and performance series? can it really be worth $1,400?

    Bookmark   August 28, 2014 at 10:55PM
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Your house is similar in size than mine, so the load calculations would be similar. The 2.5 tons is probably correct for the second floor, but I have my doubts you need 2.5 tons for the first floor. You would have to have a lot of south and west windows in order to raise the heat load to be similar to the second floor.

Do these prices include the Carrier rebates? I think $31,000 is very over priced considering you are getting one furnace which is 80% AFUE and the condensers are the Performance series. Then he wants another $1400 to upgrade to the Infinity series condensers. Did he say these would be single stage or 2-stage.

Get more quotes from additional Carrier dealers. I would think this job could be done for $5000 less than what you have been quoted.

    Bookmark   August 29, 2014 at 8:29AM
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Thanks Mike and sorry for the confusion on price. $31,000 would be WAY overpriced! The numbers represented two completely different options. The infinity series would be 16,400 total, the performance series would be 15,000. both quotes include replacement of all ductwork in attic and crawl-space.

Option one is 2 stage heat and variable fan. Option two is only 2 stage heat downstairs and multi-speed fan, but not completely variable. AC on both options is single stage.

    Bookmark   August 29, 2014 at 12:03PM
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