Need Help Making Final Decision on HVAC

Feli123April 25, 2012

I am coming down to the final decision on choosing a replacement HVAC system for my 1900 sq ft ranch home and need to decide, do I go with the basics or pay for all the extras that have been proposed?

Currently, I have a Trane XB furnace, manufactured in 2007 (80,000 BTUs), a 3 ton ADP coil (2006), and a 2 ton Carrier 38TKB AC from 1991. The AC is not working at all right now. I am thinking of changing the AC with Carrier Perf. 16 (24ACC6) and the coil (CNPVP) and install new duct work. Total cost ... $6,700 (I think about $2,200 of the cost is for installing new duct work, and the remaining $4,500 is for the AC equipment).

My main question is, does it makes sense to keep the current Trane XB furnace or also replace it for an additional $2,000 with a new Carrier 66,000 BTU furnace, 80% AFUE (58CVA070-12)? The current furnace seems to work fine, but it is a one stage, not variable. Does it really make a difference if I have variable or not? Does replacing an 80,000 BTU furnace with a 66,000 BTU furnace make sense when we have had a problem getting sufficient air to all the bedrooms.

If I don't change the furnace, does that mean I have to stick with one stage AC? Does a two stage AC really make a difference?

-If I add a new variable furnace ... the total would now be $8,800.

-If I go to a two stage Infinity 17 AC (#24ANB724) ... total is $9,250.

-If I go to Infinity 21 (#24ANB124) ... total is $10,050.

-If I go to a 95 + efficient condensing furnace ... total $11,500.

I really wanted to pay no more than $6,000 because we just bought the house and there is a lot of other stuff to fix (windows, doors, roof, fence etc.) ... so would it be ok if I just replaced the AC and coil right now, and fixed duct work (i.e. would this give me hot air in winter, cold air in summer, at a decent efficient rate), or do all these "extras" make sense (as the companies selling me these systems are telling me).

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When we went to replace our system, we chose to replace all the components at the same time since matched systems perform more efficiently and since the heat pump was going, we figured the other parts would too soon thereafter.

    Bookmark   April 25, 2012 at 3:54PM
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If you replaced only the AC and coil you would have a mismatched system. This is what you have today. It works, but the efficicency is unknown. I am confident it will be more efficient than what you have now.

I agree it is a shame to throw out your 5 old year furnance. However putting in a complete new system for only $2100 more is attractive.

You must get a variable speed furnace if you get a 2-stage AC. The 2-stage is nice if you have humid summers. It helps improve comfort and may allow you to set the thermostat a few degrees higher than you normally would.

In summary it is OK but not ideal to what you are proposing.

    Bookmark   April 25, 2012 at 3:59PM
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I hope the contractor performed a (real) heat calc. Your present furnace has an output of 74,000 BTU (92.5% AFUE). The propoed furnace is a NOMINAL 70,000 BTU unit. Actual input is 66,000 BTU (according to info I found), which at 80% AFUE, is an output of 52,800 BTU.

First question is why are you considering a less efficient furnace? Being a lower output, the available airflow should be less, which, with renewed ductwork, COULD work in your favor, assuming correct sizing.

Design of the ductwork is critical.

Since the furnace and a/c are single stage, a variable speed blower would probably not benefit you, assuming proper duct design.


    Bookmark   April 25, 2012 at 3:59PM
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The Tran web site state Trane XB furnaces have a 80% efficiency.

The Carrier 58CVA70 has a 2-stage gas valve and variable speed blower. The AFUE is also 80%. The output will be less than that of the Trane.

    Bookmark   April 25, 2012 at 4:10PM
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Is it a good thing or a bad thing that the output of the proposed furnace will be less than that of the current Trane furnace? I notice on the carrier website that the Infinity 80 (which I think is what the #58CVA070-12 is) is not Energy Star certified and does not have a media filter cabinet. Is this important?

It seems like most people think it is better to change everything at once. If I do pay $2,000 more to change out the furnace for the Carrier, it is only $450 more to upgrade to the two stage Infinity 17 AC (#24ANB724) or $1,250 to upgrade to the Infinity 21 (#24ANB124). Are they basically the same, but one has a higher SEER? I would probably go with the Infinity 17 if that was the only difference.

    Bookmark   April 25, 2012 at 5:01PM
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It is important the furnace and the AC be sized properly. The contractor should have done a load calcualtion. Ask him to review it with you. If he is confident the smaller furnace is adequate based a a real calculation then you should be fine.

The media filter cabinet is usually an extra add on. Ask about this.

The Infinity 17 furnace is 2-stage. I personally it worth the extra $450. The Infinity 21 is not worth the extra money in your climate.

Are you getting the Infinity controller?

    Bookmark   April 25, 2012 at 8:28PM
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The $2100 more is a good deal probably should take that. I am going to strongly agree with the heat load/loss calculations and air flow suggestions by Mike _home and veesubotee. Excellent advice very crucial information! I'd start there before making any decision. Good luck to you.

Here is a link that might be useful: heatandcooldiy

    Bookmark   April 25, 2012 at 9:49PM
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Thanks for the tips. This contractor looks pretty good and he is going to come back for a second visit to do a heat load/loss calculation/Manual J. If we go from a 2 ton to a 2 1/2 ton, he said it would only be a few hundred more. If we get the new variable furnace, we would also get a new thermostat (#SYSTXCCUIDO1) -- is that what you mean by an "Infinity controller"?

From the discussion here, I guess I am leaning towards getting the furnace and the Infinity 17. Do you think with a totally new system, it makes sense to pay $160 per year for a maintenance plan (two inspections per year)?

    Bookmark   April 26, 2012 at 10:05AM
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That model number you have stated is the Infinity controller.

I think the calculation will show the 2 ton AC is undersized. Don't be surprised when the contractor says you need a 2.5 ton condenser. Is he offering the Carrier rebate?

In my opinion a once a year inspection is sufficient. Ask if you have the option to pay less for one visit per year.

    Bookmark   April 26, 2012 at 11:32AM
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This dealer is offering Carrier rebate: $150 for the 24ACC6 or $1,100 if we go with either the Infinity 17 or Infinity 21.

For the furnace, why are media filter cabinets important? Don't all furnaces have places where you can put a filter? The HVAC closet is a tight space right now, so I don't know if size is an issue in putting these in. How much do they cost?

Another dealer proposed that we go with the Performance Boost 80 (#58PHA070). Isn't the Infinity 80 (#58CVA070-12) better?

    Bookmark   April 27, 2012 at 2:05PM
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I think the Media cabinet folks are refereing to allows you to use a 4"-thick filter. These larger filters require less change-out, like once a year rather than once a month or 3 months.

    Bookmark   April 27, 2012 at 2:40PM
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Media cabinets are simple metal enclosures which hold a 4 inch filter. They are not expensive. You may not have the room to install it, so in that case you will get a 1 inch filter.

The Infinity 80 is a 2-stage furnace, the Performance Boost 80 is single stage. Carrier offers a better rebate on the Infinity equipment so the net cost increase over the Performance is not significant.

    Bookmark   April 27, 2012 at 4:53PM
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I went with the top of the line Bryant modulating gas furnace and two stage AC. It is much better then the 1999 York two stage furnace and one stage AC back then. It quite pleasant since you hardly hear it unless there is a quick temperature increase or drop usually happens base on you thermostat settings for morning or night or the outdoor temperature changes fast. Otherwise; you do not heard it at all!

    Bookmark   April 29, 2012 at 7:51PM
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HVAC Equipment will last the same age no matter which one you buy even the cheapest one as long as it is installed properly. The reason why one cost more is due to efficiency. If you have high utilities bill, then go for a high efficiency, if not then go middle, if low go for the least expensive. sometimes it is not worth to spend $2000 more just to save $40 a year on utilities. Higher efficiency means more parts, means more money for repairs down the road, especially with two stage A/C and Variable speed motor.

    Bookmark   May 3, 2012 at 12:51AM
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