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Posted by btbic (My Page) on
Mon, Jun 2, 08 at 13:26

Well, I think I have narrowed down my choice in replacing the upstairs unit with a 3 ton Trane 13 Seer and Furnace

The model numbers are:

TUD060R9v3 Furnace
4TTX5036a1 or 4TXCB036BC (not sure which one is the 13 SEER)

My question is another vendor quoted me an 80k BTU as opposed to the 60K BTU. Does that make a difference in what I am looking for? I essentially have 4 rooms upstairs I am trying to keep cool, but am clueless as to the importance of BTU's. Most of the people in my neighborhood have 3 tons for the upstairs as well and are happy, but they all have no idea how many BTU's they got.

Any help is appreciated.


Follow-Up Postings:


Three ton is 36,000 BTUs.
The units are Rated in Nominal Tons per hour.

However, the nominal BTU/hr rating of some range from 36,000 down to around 34,000-BTU/hr.

Additionally, with high indoor temperatures & very high humidities a nominal 36,000-BTU/hr could go considderably higher.

Example, Goodman Expanded Data: a 3-ton condenser 13-SEER GSC130363A, with a 4-ton evaporator coil:
1434-cfm or 478-cfm per ton of cooling
85 OAT Outdoor Ambient Temp
80 IDB Indoor Dry Bulb
71 IWB Indoor Wet Bulb or 63% Relative Humidity
Nominal BTU/hr of 39,500
At 75 OAT outdoor Ambient Temp
other figures the same, nominal listed @ 40,500-BTU/hr.

Moderate outdoor temps with high indoor temps & a high latent humidity heatload through the evaporator coil boils refrigerant at its fastest rate, which transfers more heat outdoors per unit of time.
- udarrell

Here is a link that might be useful: Optimizing Evaporator BTUH Heat-Load Input



I believe the question of btu's is regarding the furnace and not the condenser.

To the OP:

A load calc (heat gain/loss calc called a Manual J) determines the heating load for the structure.

Gas furnaces are rated by input btu's but the efficiency determines the output btu's. Example: a 100,000 btu furnace, 80% efficiency, produces 80,000 btu per hour. An 80,000 btu furnace, 95% efficiency, puts out 76,000 btu per hour.



First of all, the AC condenser you have listed is Trane's XL15i model-depending on configuration generally called a 15 SEER model. I will assume you are sized correctly/

Here are the ARI performance metrics per your model numbers.

1420829 Active OEM XL15I TRANE 4TTX5036A1 4TXCB036BC3 *UD060R9V3 35200 12.00 14.25 CEE Tier 1

this has the condenser model, the evap coil model, and the furnace model with cooling BTUs of 35,200; 12.00 EER, 14.25 SEER stated in previous thread, an 80% furnace with today's energy costs is a dinosaur even with hotlanta. you should change the XL15i AC condenser for the HP condenser version. The HP version will easily pay for itself.

2.with a two story home and only one system, it is doubtful that you will get comfortable, even heating/cooling unless you have zoning controls and/or good ductwork sizing/design and your dealer can help balance the floors with manual dampers. that is a big if!

3.Use a HW VisionPro IAQ stat for controlling blower speed for best dehumidification.

12,000 BTUs=1 ton for both cooling and heating; therefore three tons of cooling are 36,000 BTUs

for your furnace at 80% eff, you are looking at apprx 50 KBTUs.


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