Relatively mild winter climate. Where is ductwork system located? Where will furnace be located? Can you install a high eff 95+% efficient furnace?

You need a load calculation especially for cooling.

FROGs are notorious for being difficult to heat and cool. Usually the reason is poor insulation qualities and poor ductwork sizing/design.

Here are your fuel comparison calculation for both 80% and 95% eff furnaces. These numbers to be used as a guide only. I will assume rates posted are all inclusive costs for each fuel type.

80% furnace
Cost per 100,000 btu of useable heat
Electric baseboard: $2.90
Heat pump: $1.17
Natural gas: $1.26

95% furnace
Cost per 100,000 btu of useable heat
Electric baseboard: $2.90
Heat pump: $1.17
Natural gas: $1.06

My advice is to forget the HP unless there is no difference in cost between AC and HP condenser which is highly unlikely. The leverage between the two fuels,is simply not there like it was 10 yrs ago. Country is awash in nat gas supply.

IMO

Thanks tigerdunes. You are a huge help!

The duct work is in the attic and so is the furnace. The insulation in the attic is blown in and looks to be about 12 inches deep.

I think you are right about the ROG. It's both poorly insulated and poorly ducted.

One of the furnace quotes I got was for a 95% model. But I'm trying to decide if it's worth it. From your numbers above ($0.20 difference/therm between the 80 and 95) the most I would save in a month is about $25. That was the highest month ever and we used 125 therms. Does that sound about right?

The other thing I'm trying to decide is whether to get the furnace with VS blower. One of the 80% Carrier furnaces that I've looked at has the VS motor. Does this seem like a good option?

Thanks
MB

You will have to decide on best efficiency furnace for your application. Rely on advice from your dealer plus cost differential

But definitely 2 stage var speed furnace correctly sized whether 80% or 95% efficient. With correct two stage thermostat and pleated filter media cabinet if you don't already have one.

IMO

Variable speed motors are quieter and more efficient than standard PSC motors, and features such as ramping profiles and dehumidify on demand allow for greater comfort during the summer by removing more humidity. However, there can be consequences if you put them on a poor duct system. The motor will overwork itself trying to overcome the restrictive ductwork, leading to increased energy usage and a shorter lifespan. It should be at your contractor's discretion whether a VS blower will work well for you. Hopefully you are working with someone you trust and not someone you think is trying to push more expensive equipment on you. I say, if your ducts can handle it, go for it!

I realize Wilmington location has relatively mild winter climate. However, you normally do not install high eff condensing furnaces in an unconditioned/uninsulated attic envelope. This issue bears discussion with your installing dealer as far as 80% versus 95+% eff condensing furnaces and potential for freeze ups however small the risk.

IMO

Thank you tigerdunes and hvtech42 for your replies. They are very helpful.

I now have estimates for both Carrier and Rheem systems. Based on their input and this discussion we decided on straight AC condenser with 80% gas furnace.

The Carrier contractor who gave me the estimate based his recommendation on what the service tech told him (the service tech was the original person who diagnosed the evap coil leak). So the person giving me the estimate has never actually been to my house (so no load calculation yet). So basically it's a direct replacement for the 5T system we have now. Here is the system:

24ACC660 condenser (single stage, Performance 16)
58CVA110 NG furnace (Infinity, VS, 2 stage)
CNPV 6024ALA coil
Carrier digital thermostat (not sure which one but I doubt an Infinity control)
Fix ductwork to make FROG a second zone
AHRI# 6390769
SEER 15
EER 12.5
Cost $9,930
(to upgrade to the Performance 17 with 2 stage compressor he said would cost another $2,000 - AHRI# 6389260, SEER 16, EER 12.5)
1 year labor warranty
To upgrade to 10 year labor warranty is $980

The Rheem contractor came to my house and was very friendly and seemed knowledgeable. He didn't take any measurements but thought that the 5T replacement was correct given our high ceilings, etc. He can return to do a load calculation. Here are the Rheem systems:

RASL060JEC condenser (Prestige 2 stage communicating)
RGPE10EARMR NG furnace (100K BTU, VS, 2 stage, 80%,communicating)
RCFLHM6024CC Coil
2 Rheem communicating thermostats
Fix ductwork to make FROG second zone
AHRI# 4051285
SEER 16.5
EER 11.5
10 year parts warranty
5 year condenser replacement (he said Rheem replaces entire outdoor unit if compressor goes bad in first 5 years)
1 year labor warranty
$9,890 - $1,200 rebate = $8,690

RARL061JEC condenser (Prestige 2 stage, communicating)
R96VA1002521MSA NG furnace (100K BTU, 96%, VS, 2 stage, communicating)
RCFNHM6024CC Coil
2 Rheem digital communicating thermostats
Fix ductwork to make FROG second zone
AHRI# 6676602
SEER 16
EER 12
10 year parts warranty
5 year condenser replacement
1 year labor warranty
$9,990 - $800 rebate = $9,190

Strange thing is if I combine the Rheem RARL condenser (step below the RASL) with the Rheem 80% furnace, the SEER is 16 and EER goes up to 12.5.

Sorry for the long post, but what do you think? I thought having the top of the line Rheem condenser (RASL) with the 80% furnace would be a great system. The SEER is 16.5 but what do you think about the EER of only 11.5? Is it because it's a 2 stage condenser?

Are you surprised that by combining the RARL condenser (the step below the RASL) with the 80% furnace, the EER actually goes up?

Is there a real difference between the 2 Rheem evap coils?

A Bryant contractor came to my house today and did measurements for a load calculation and will send estimates tomorrow. A Trane person is coming tomorrow.

Between the Carrier and Rheem systems, it seems to me the Rheem is a clear winner. I would get 2 stages on both AC and furnace and it would be fully communicating. And it costs less. What am I missing?

Thanks so much.
MB

The RASL series should be 1-2 units more efficient than the RARL series. It's possible that the numbers sent by Rheem to AHRI were in error or AHRI transcribed them incorrectly. Having said that, strange things sometimes happen with the larger capacity systems, especially when the matching coils are different.

As far as the 80% vs 95% furnace is concerned, the main difference will be the availability of a PVC vent pipe option vs the existing metal flue vent.

You need to focus less on the brand and more on the contractor. All of the brands you mention getting quotes for will last a long time and do a good job heating/cooling if they're installed and taken care of properly. So far I would cross off the Carrier guy for the simple fact that he is putting in a 5 ton because it's what you have already. The fact that the Rheem guy at least knew what a load calc is and offered to do one puts him ahead of a lot of contractors. However, it is better if they do one without prompting like it seems the Bryant guy will. And a 100K BTU furnace in a house of that size in a mild climate is insane, although I realize they are spec'ing them because they need enough airflow for a 5 ton. It usually takes a bit more than higher-than-average ceilings to justify sizing like that.

I certainly would not want an oversized furnace to justify a 5 ton AC condenser without first seeing a load calculation for cooling in writing on software letterhead.

And while another poster disagrees, I would never purchase an Infinity furnace without Infinity controller.

I see nothing wrong with Rheem. To be clear, you are in a true coastal environment or are inland?

IMO

Tigerdunes, our house is about 0.5 mile from the Cape Fear river and probably 3 miles to the ocean as the crow flies (10-15 minute drive). So we are not directly on the water.

Regarding sizing, the Bryant guy spent significant time doing measurements and was very knowledgeable. I'm looking forward to what he says today. He also mentioned that the furnace was way over sized but was put there because of the 5T condenser.

I was thinking the same thing about crossing the Carrier person off the list. I have been impressed both with the Rheem and Bryant people.

Thanks again.
I'll post back with the results from load calculation.

MB

That close, you are considered to be in a coastal environment. I would ask Rheem about any salt water shield they offer for evap coil and condenser. That would be my major concern with Rheem.

TD

OK, so the Trane guy came today and he was great. He emailed me a copy of his load calculation.

The software is Wrightsoft. The first page looks like the summary:

Total area 2296 sq ft (276 up, 2020 down)
Heating load 52728 (7083 up, 45645 down)
Cooling load upstairs 4989
Cooling load downstairs 36247
Cooling load entire house 36952
Other equipment loads 0
Equip. @ 1.00 RSM 36952
Latent cooling 6682
Total cooling load 43634
(I don't understand why some of these cooling numbers don't add up?)
Htg AVF (cfm) 1510 (203 up, 1307 down)
Clg AVF (cfm) 1510 (204 up, 1482 down)
(Why don't cooling numbers add up?)

Based on this he recommended the following:
TUD2B080A9482A XL80 furnace
4TWX8048E1000B XL18i HP
4TXCD050BC3HCA Coil
Connect to existing line set
Fix ductwork for FROG
TOTAL Cost $13,293.75 (includes $700 Trane rebate and $300 Progress Energy rebate)

Can I get your opinions on this? The contractor was great, but I am a bit in shock at the cost (especially compared to the Rheem quote I got). I really don't want to spend $13K on this system.

Thanks so much
MB

I would ask him to explain the load calc, I would also question his choice of furnace. The XL80 has 2 stages, but no variable speed blower. Besides all the other benefits, you need a variable speed blower to get the advertised efficiency on that heat pump and not having one on a system this expensive is just ridiculous. Also that furnace is only designed to be used with a single stage outdoor unit. I suspect he might have just made a clerical error in selecting it.

I thought the same thing about the furnace.

I'm probably going to have to eliminate the Trane due to the cost alone.

Does something in the load numbers stand out to you as questionable (besides some of the numbers not adding up exactly)? I may not be reading it correctly.

The Trane quote is really a mess , especially furnace selection and load calc for cooling not to mention absurd pricing.

Should be XV80 furnace 80 K size. Prestige 2.0 thermostat.

Looks like a 3 1/2 ton AC condenser is minimum required.

I question the need for a 5 ton AC condenser as quoted by both Carrier and Rheem dealers.

IMO

I would give the contractor a chance to explain it. I'm confused like you on how he got 36952 sensible cooling load from 4989 upstairs and 36247 downstairs. Assuming that 43634 total cooling load is correct, a 4 ton heat pump would be right since the XL18i is 2 stage and only comes in full ton increments. It may not kick into 2nd stage much during the summer, but in the winter that little extra capacity for heating will be nice so you don't have to rely on the furnace as much. With a 2 stage units inside and out, it is crucial that you get a thermostat that can handle that. I agree with tigerdunes that the Prestige IAQ would be the best choice.

So the second Trane guy came over today. He was very knowledgeable and is a previous installer. He sketched out how he wanted to rework the ducts to make the FROG a separate zone. He is the only one to do this and his duct idea was simple and made good sense. He did a load calculation and said we need a 3.5 ton system but gave a quote for xl18i so a 4T was recommended. I am starting to believe the 4T recommendation because he is the second one to recommend that size (we have a 5T now). It's also what my next door neighbor has now (he replaced with a Trane unit within the last year) and he is happy. Here is the system recommended:

4TTX8048
UH2C080A9V
Unspecified coil (I'll call him next week and get model number)
Trane XL824 thermostat

I looked on AHRI and I couldn't find this system. I could only find this condenser with the 100k BTU furnace. Do I need to specify the larger furnace?

The quote was for $11,500 - $300 Progress rebate = $11,200

It's expensive but almost $4000 less than the identical system from the other Trane dealer.

Can I get your thoughts?

Thanks so much.
MB

The model number he gave for the furnace is invalid, that's probably why you couldn't find it. I think he meant TUH2B080A9V which would be an 80,000 BTU XV95 furnace.

With help from the forum, I got 3 consistent load calculations and a bunch of quotes. I have settled on the American Standard contractor who was knowledgeable and had a fair price. Here is my final choice:

AUD2C080B9V4
4A7A7048A1
4TXCD063
AHRI# 5942858

I am going to add a 5" media cabinet as recommended here. TFM245B0FR0. The contractor recommended getting the largest filter (24" wide) even though the furnace is 21" wide (said it improves air flow).

My last question deals with the thermostats. I've read all the forum posts and am still a little confused. I've asked for a quote on the Honeywell Prestige IAQ 2.0 as recommended here. The contractor is recommending 803s, however. Should I insist on the Honeywell? The contractor made it sound like the 803 does the same thing but from reading here it seems like the 803 just overcools to de-humidify whereas the Honeywell slows the blower speed. Is that correct? Is it possible to have one Honeywell Prestige downstairs that controls both the downstairs and FROG (with a temp and humidity gauge installed in the FROG)?

Let me know any final thoughts before I sign the contract.

Thanks so much.
MB

>The contractor is recommending 803s, however. Should I insist on the Honeywell? The contractor made it sound like the 803 does the same thing but from reading here it seems like the 803 just overcools to de-humidify whereas the Honeywell slows the blower speed. Is that correct? Is it possible to have one Honeywell Prestige downstairs that controls both the downstairs and FROG (with a temp and humidity gauge installed in the FROG)?

Yes, I would get the Prestige IAQ, with a Redlink sensor in the FROG if you'd like. Add a Redlink gateway if you'd like to control over the internet. I would make sure they wire it correctly, the fact that they are advising you away from it suggests they are unfamiliar with how to set it up. I can see no other reason they'd recommend the 803, the Prestige means more of a profit for them.

I agree with hvteck on thermostat selection. Because of your location, insist that dehumidify on demand be set up.

As far as system, I think it's a good choice. Matching number below. Appears to be AS equivalent to Trane's XV80 along with XR17 condenser. Excellent numbers.

5942858 Active Systems AMERICAN STANDARD PLATINUM XM AMERICAN STANDARD, INC. 4A7A7048A1 4TXCD063BC3 1370 1095 *UD2C080B9V4 50000 13.00 18.00 1 RCU-A-CB 344 Yes

I do disagree about the filter cabinet. I would want the 21" size to fit the furnace correctly. Needs to handle 1600 CFMs.

IMO