This furnace has an 80,000 BTU input, which multiplied by 80%, translates to a 64,000 BTU output. Your 28 year old furnace is probably around 80% as well, so 92,000 x 80% = 73,600. A bit more output than the new one would have. But that doesn't mean the new one is undersized - most old furnaces are oversized, and if anything it may still be oversized!

You need a Manual J load calculation to determine the proper size for your new furnace. At the very least post your ZIP code and basic information about your house. Square footage served by this unit, year constructed, anything else about its construction it might be useful to know, so someone here can give a ballpark estimate for what size you need.

 

For that AHRI number they show a very specific model number for the Indoor Coil. Shows the 4TXCC009DS3, is that the coil they plan on installing? If your looking at getting rebates from your state that’s the combo for that AHRI number. Did they mention rebates to you, as chances at 16 SEER and 13 EER it would meet the minimum threshold for rebates.

Have them do a comprehensive startup/commissioning report on your system of choice.

Here’s one as a guide: https://www.google.com/url?sa=t&rct...%202015-07-07_clean_fillable_508.pdf?5ace-789f&usg=AOvVaw1DkTbUviGtreMqRxxNNbzS

 

ZIP _ _ _ _ _ ?

_ Follow the HVAC Design Process for Reasonable sizing.

. Do you Really need a furnace?
Manual J calculation & an Operating Cost comparison
will inform you of the benefits & options.

Natural Gas: $_._ _ / Therm
. Electricity : $0._ _ _ / kw-hr

 

^^^^^ What he said!

 

Thanks for the replies! Yes, my current furnace is Carrier model 58RAV075-111JC with a 92,000 BTU/H input. Based on the first reply, perhaps I may be OK then with a 13% less output (64,000 vs 73,600 BTU/H), given our short winters? I realize this cannot be answered assuredly without a manual J. The contractor said the next higher TRANE furnace model in the series (S8X1C100) is a match for a 5 Ton AC, not a 4 Ton.

The house is a 1993 construction, 3900 SF with about 1950 SF served by this system (downstairs). Most of the windows face N or S. Zip code 77479.

The coil specified is indeed 4TXCC009DS3. The quote indicates a $175 centerpoint rebate, but also includes a 10% discount from the contractor. This is a smaller company with a long association with the community, and good reviews on Angi, Google etc. Another quote for the same system from a bigger HVAC company, also with good reviews, is significantly higher.

The startup commisioning report is a good idea!

The same contractor quoted a 20 SEER with XV20i condensing unit and the XC80 communicating furnace for 3.5k more, but I'm not inclined to pay more for a more complex system, notwithstanding the energy savings. Let me know if this would be shortsighted.

 

Thanks for the replies!

Yes, my current furnace is Carrier model 58RAV075-111JC with a 92,000 BTU/H input.
Based on the first reply, perhaps I may be OK then with a 13% less output (64,000 vs 73,600 BTU/H),
given our short winters?

I realize this cannot be answered assuredly without a manual J.

The contractor said the next higher TRANE furnace model in the series (S8X1C100) is a
match for a 5 Ton AC, not a 4 Ton.

The house is a 1993 construction,
3900 SF with about 1950 SF served by this system (downstairs).
Most of the windows face N or S.

Zip code 77479.

Energy assessment can be provided based on natural gas and electricity use.
Monthly energy use for EACH of the last 12 months is needed.

Blower Door Test Results: _ _ _ _ CFM50 ???

Dehumidifier is necessary in SE TX.

Window Type: Double or Single

...Glass Area per Floor
__ Main: 260 Sq Feet ??
__ Upstairs: 230 Sq Feet ??

Ceiling: R-30
Walls : R-11+

Manual J is required for actual equipment selection ( Manual S).
2-Stage Heat Pump would likely be my equipment selection
to enhance the humidity control, the air distribution and eliminate the furnace necessity.

Oversizing [ > 3 X for Furnace, design temp 34'F ] is definitely as issue here.

Design Temperature = 95.2'F
Q. Sensible < 41,000 BTU/HR is highly likely for 1993 Well-Built residence.

https://mn.gov/commerce-stat/pdfs/home-energy-guide.pdf

 

The XV 20i is a great system but I would suggest if you decide to check into it more to look at the 95% furnace that goes with it. In my market there is not a lot of price difference between the two but 90%+ furnaces sell more than 80% and in general the more sold the cheaper. The point being here for the price difference the 15% savings doesn't take long to pay the difference back.

 

Cooling Capacity
$0.118 / kw-hr

Do you spend < $1,050 for Cooling?
________ < 9,000 KW-hours Annual

Heating Capacity
$0.90/ Therm Natural Gas

Do you spend < $280 for Heating?
__________ < 300 therms / year

 

Thanks, again, for replying!

Based on the humidity control being an important factor, here're my current thinking on the potential options

1. XR16 condensing unit (4 Ton, #4TTR6048J1) + S8X1 furnace (80kBUTH input S8X1C080M5PSC) and 4TXCC009DS3 coil [AHRI# 207148158] with a whole house dehumidifier added now, or in future

2. XV20i condensing unit (4TTV0048A1) + XC80 furnace (TUD2C080ACV42) + 4TCXX007DS3 coil [AHRI# 8704108] with a recommendation from contractor to change ducts within a year or two if going this route, to avoid problems running at low air flow

(There was also a suggestion above to consider the 95% furnace for Option 2. Another suggestion was for a 2 stage heat pump with no furnace. Is there Trane model numbers for the outside unit and air handler you can suggest for the heat pump option?)

Initial cost is higher for Option 2. With the whole house dehumidifier added for Option 1, they are similar. After adding recommended duct replacement, Option 2 again pulls ahead in installed cost.

My new questions for the forum:
- For humidity control, are both options equally effective?
- With the added complexity of the XV20i and XC80 units, will this system be harder/more expensive to maintain, service, and get parts for?

Thanks!

 

Thanks, again, for replying!


There was also a suggestion above to consider the 95% furnace for Option 2. Another suggestion was for a 2 stage heat pump with no furnace.

Is there Trane model numbers for the outside unit and air handler
you can suggest for the heat pump option?

Manual J is required for actual equipment selection ( Manual S).

2-Stage Heat Pump would likely be my equipment selection
to enhance the humidity control, the air distribution and eliminate the furnace necessity.

No meaningful responses to Posts # 4, 8 & 9.

 

Heat pump numbers are easy. Drop the second "T" and replace it with "W" as in 4TWR6048 would be opt 1. The numbers/letters after the 8 may be different but those first 8 are the model family.& size. The rest of the numbers are major/minor changes mainly.