Am I limited to what seer a/c I can buy due

[jns]

...due to my furnace? It is a basic thermopride, I do NOT believe it is
2 stage. It is only a couple years old, but no bells and whistles.
I was looking at info on a website that said if I wanted a 16- 21 seer
a/c, I would have to have a 2 stage furnace and/or air handler.
Am I forced to buy a 13/14 seer due to my furnace?

[motoguy128]

To meet any ratings, you need to have a matched system. To get the highest ratings, you need to have a variable speed blower or ECM blwoer which uses less electricity. It doesn't matter that's it's 2 stage, only that it has the more efficint blower motor. However, most of the higher end furnaces that have these motors are also 2 stage. Although some midrange furnaces have a similer version of these motors in singel stage furnaces.

So if you repalce the A/C without repalcing the furnace or air handler, your actually SEER ratigns will be unknown.

Look at it this way. If I took a new fuel efficient 2.5L 4 cylinder engine made by Ford that gets 34mpg in the new Ford Fusion and stuck it in a 1985 Ford Taurus (assuming it would fit) who knows what mileage I would get. Would it be better than the old POS engine it had in it? It would certianly make more power and accelrate better. But since that combination isn't tested, I won't have an official EPA fuel economy number.

The highest advertised ratings BTW, are with 2.0Ton or 2.5 Ton sizes matched with an air handler. Furnaces always have slightly lower perforamnce numbers due to their dimensions and air resistance the heat exchangers in the airflow.

[RyanHughes]

So if you repalce the A/C without repalcing the furnace or air handler, your actually SEER ratigns will be unknown.


You can still determine the SEER rating. It just wouldn't account for the furnace/air handler, and would be listed in the AHRI database as just the air conditioner and indoor coil. Usually, without the ECM motor, 13/14 SEER is the most one can achieve.

[motoguy128]

You can still determine the SEER rating. It just wouldn't account for the furnace/air handler, and would be listed in the AHRI database as just the air conditioner and indoor coil. Usually, without the ECM motor, 13/14 SEER is the most one can achieve.

That statement is somewhat contradictive, since normally SEER ratings include the power consumed by the furnace/air handler. You are still just taking a WAG without a matching air mover. That's why you get a increase in SEER when using a ECM blwoer. It simply consumes less power.

The AHRI database will give you a baseline for a particular indoor ourdoor combination, but without knowing how much energy will be used to get proper airflow yu still won't know the actual rating. The closest thing you could do it use another furance with similar dimensions and blower.

You could probably estimate it within about 1.5 SEER and 1 EER. I do agree, that without a ECM motor, around 13-14 SEER is about the best you can get with most units. Espeically since above 16 SEER, you're looking at a 2 stage compressor, which won't match well if at all without a VS (ECM) air handler or furnace.


To the OP, you can still buy a new "standard efficiency" (13 SEER is the minumum, you can no longer pruchase 1 0SEER systems) outdoor unit and indoor coil in a standard efficncy if you don't want to replace your furnace now. It will probably rate around 10-12 SEER on your furnace with the correct airflow. You can then pruhcase a matching furnace later and improve your unit's performance. I would however, recommend if at all possible repalcing both, if the furnace is more than 10 years old.

[RyanHughes]

I think the SEER/EER ratings themselves are deceiving to the homeowners. :cool: Without ideal ductwork, proper refrigerant charge, proper installation, etc. you just don't know what your "actual" operating efficiency is.

[motoguy128]

I think the SEER/EER ratings themselves are deceiving to the homeowners. :cool: Without ideal ductwork, proper refrigerant charge, proper installation, etc. you just don't know what your "actual" operating efficiency is.


I completely agree!:) The system is even worse the mpg ratings for cars.

I find it amusing, that you can take a base model builder grade 14 SEER Carrier A/C and pair it to a midrange single stage furnae and meet get to 16SEER/13EER. But yet fail to match those ratings with a premium 17SEER 2 stage unit with a premium 2 stage VS furance... probably costing almost twice as much. Ther may be a big difference in comfort and quality, but that's not how it's marketed.


What's worse, it that I'd estiamte that at least 25% of the "pro's" out there don't really understand the ratings system either.

I think twice that don't understand the tax credits. My MIL got 3 quotes... and all 3 claimed the equipment would meet the tax credits and even listsed the credit as a line item in the final cost (one even listed an amount higher than $1500:rolleyes:). On closer examination, NONE of thsoe system meet the tax credit requirements.:eek:


In hte HVAc industry, you can' normally purchase a 13 SEER 2 stage system if you have a small home and care more abotu comfort than efficincy. The auto industry by comparison, has the opposite problem. You can't really find a economical luxury car. Meaning it's assumed that small cars much be cheap and not premium features or premium suspension system unless they are high performance sports cars. In the HVAC industry it's assumed that if you want lots of comfort with a modulating furnace or 2 stage comrpessor, you MUST want it in a 95% furnace or a 16+ SEER A/C.