Lost Effiency of Armstrong Ultra

[RomulanSpy]

Question about effiency of a 3 ton Armstrong Concept A/C built and installed in 1993 by subcontractor when building our house. I'm guessing 10 SEER but how much has it lost in those 15 years of heavy use (deep South).

It has gotten annual tuneups (except for last spring) and filter changes regularly. Basically, I'm crunchin' the numbers to see how long it'd take to break back even on a new, 4 ton, Amana 18 seer system with dual fuel heat

My tech examined ductwork, return, etc and said basically all had to redone. He wrote out a detailed quote of 10K and change.

This guy is a credit to your guys profession and honest about my needs.
So in a nutshell, (probably) is it STILL a 10 SEER unit or or we lookin' at single digits now

Thanx ahead for any/all help.

[dash]

If the duct system is undersized,it was never 10 SEER.

Why does the duct system need to be replaced?

Where are the ducts located?

What city/state are you in?

[beenthere]

Why the increase from 3 ton to 4 ton.
Just because your going 2 stage, doesn't mean you can oversize by a ton.

A 4 ton in first stage is going to have around 3 tons of capacity.
But may not remove as much humidity as your current A/C. Meaning you could have to set the stat lower, and use more electric then you do now.

[hvacrmedic]

You won't even break even.

A generous calculation: amortizing over the expected lifetime of the new system.
10,000/15yr = 666.67 per year, cost of system. Assume an optimal energy savings of 30% over the old system (you won't get 18SEER out of the new system in the deep south). About 1/2 the energy bill is heat and air, so you get only a 15% total energy savings per year with the new system. Assume energy is costing 3,000 per year. 15% of that is 450 dollars per year energy savings. That means that you'll be spending over 200 dollars more a year for the new system for as long as the old system would have lasted. Give or take. But what's a couple hundred a year one way or the other anyway. You want to be comfortable right? Put in the new system. I don't know if dual fuel is going to save you any money though. Back up heat will seldom run in the deep south, and electric back-up running with the heat pump will still be cheaper than gas, if it's set up correctly. At no point is gas going to be cheaper than the heat pump alone to run unless your rates are way different than mine. A lot of dual fuels going in around here lately, but we don't get into it unless the customer is adamant about having it.

[dash]

You won't even break even.

A generous calculation: amortizing over the expected lifetime of the new system.
10,000/15yr = 666.67 per year, cost of system. Assume an optimal energy savings of 30% over the old system (you won't get 18SEER out of the new system in the deep south). About 1/2 the energy bill is heat and air, so you get only a 15% total energy savings per year with the new system. Assume energy is costing 3,000 per year. 15% of that is 450 dollars per year energy savings. That means that you'll be spending over 200 dollars more a year for the new system for as long as the old system would have lasted. Give or take. But what's a couple hundred a year one way or the other anyway. You want to be comfortable right? Put in the new system. I don't know if dual fuel is going to save you any money though. Back up heat will seldom run in the deep south, and electric back-up running with the heat pump will still be cheaper than gas, if it's set up correctly. At no point is gas going to be cheaper than the heat pump alone to run unless your rates are way different than mine. A lot of dual fuels going in around here lately, but we don't get into it unless the customer is adamant about having it.

If you replace :

$10,000 investment ,your tax free return,using the above numbers,is 4.5% .

Or you can pay $450.00 a year ,times 5 years,or $2250.0 ,that could have gone towards the new system,just for keeping it,if it lasts that long.

Now if you make some upgrades like insulation,window tint,etc.,you may need a smaller system and saving will increase.

Depending on why your ducts are being replaced,meaning their current condition,you could see much larger saving.

[hvacrmedic]

If you replace :

$10,000 investment ,your tax free return,using the above numbers,is 4.5% .

Or you can pay $450.00 a year ,times 5 years,or $2250.0 ,that could have gone towards the new system,just for keeping it,if it lasts that long.

Now if you make some upgrades like insulation,window tint,etc.,you may need a smaller system and saving will increase.

Depending on why your ducts are being replaced,meaning their current condition,you could see much larger saving.

If they can get the annual energy savings to exceed the annual amortized price of the system, then it would be foolish not to replace it. It would literally not only pay for itself, but it would put money in their pocket. It's sometimes difficult to convince a customer of that. To them it can sound as though you've fabricated the whole argument just to make a sale. I have to give credit to those customers out there, like this one, that take the time to investigate this aspect of purchacing a new system. Of course the price here also includes duct upgrades, whereas normally there is only the price of the system itself to consider. If the numbers above were run again with just the system, the savings would be apparent.

[RomulanSpy]

Re: 18 SEER just trying to maximize efficiency but he said we could step down 3 ton Amana or Trane for around 7 K.

He said the ductwork that was installed, "has some problems....strange bends...which is causing some hot spots and cold spots (unfort. my bathroom)"

Also the he basically said if we went with the 18 SEER Amana the ductwork would have to be improved to realize that much savings.

The ducts are in the attic, and it is well ventilated up there.

Right now I just need some serious and objective advice.

[beenthere]

Your installer has no real idea what size system your house needs. If he did, he wouldn't be giving you the choice of a 4 or 3 ton unit.
Get some more estimates.

[RomulanSpy]

and thanx again for all the replies, guys.