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.

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.

V

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.

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.

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.

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?

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

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)?

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.

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?

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.

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.

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!

Feli,

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.