where do you live. how big a house? window types? folks can't recommend anythign without all teh info.

whatever you do, MAKE SURE they run a manual J to verify the system sizing. it can be a big mistake to just replace with the same size you had before, they are not correct many times.

I also have been given a quote for an Armstrong unit.
I'm afraid I don't know a manual J from an automatic K - what does this mean?
I live in South Wester Ohio, in a 2,400 sq ft, 2 storey house. 4 Bedrooms, about 10 years old, double pane glazed windows.
Not sure if that's all that's needed for now?

andeew

first you need a load calculation for both heating and cooling.

what is size of existing unit? did it cool adequately or did it ever struggle to keep you comfortable?

don't you have reasonable electric rate?

if so, i would add a properly sized heat pump.

and if this was my home I would replace everything, both inside and outside unit with Carrier's Performance 15 HP (25HPA mdl) and Infinity two stg var speed furnace with Infinity Controller.

whay is brand,mdl,size of existing furnace?

And a Manual J is HVAC jargon and refers to the software package that professional dealers use to accurately size new residential HVAC equipment.

let me know if you have any further questions.
IMO

My existing AC is a 3 tonne unit - we were very satisfied with it's performance until it stopped working.

The furnace is a Goodman Cat4, output is 72,400 BTU, model # is GMPN080-4 Rev B

Why do you recommend replacing the furnace at the same time? How log should an HP/Furnace last if well maintained?

andeew

you can not get your best performance/efficiency numbers without a var speed blower on either an air handler or furnace.

I would go witrh HP and change out everything both inside and outside unit. That way you can go with a high performance HP.

But if you elect to keep existing furnace then go with a good basic HP with matching evap coil like Carrier's Comfort 13 HP Puron mdl(25HCA3).

IMO

I realize it is different for each situation, but generally speaking, does the payback in improved efficiency make economic sense? I get electricity at about7c per unit but I don't remember what I pay for gas. My existing system is a 10 seer AC and 90% furnace.
How long should I expect a brand new HP and furnace to last?

andeew

probably not. generally speaking if you currently have a 10 SEER AC, you will get 5% savings for each increase in SEER for your AC dollar. it's all about how you want to spend your money. but definitely there would be a nice payback over a HP vs the comparable AC model. lots of bang for the buck!

IMO

Your contractor needs to be helping you with this decision if you don't feel like you are getting that help keep looking for contractors you need to ask yourself a few questions like what is your present financial situation, how long are you going to live in this house, how important is resale value to you when you answer these questions your contractor will be able to find a system that will fit into both your budget and your long term plans

Here is a link that might be useful: Air Conditioning and Heating Repair Made Easy

The contractors I have contacted for quotes have all been very helpful - I can't help thinking that they are also salesmen, I just need the impartial advice from the enthusiasts here to help me make a good decision.
I can spend between $2,500 and $5,000 for a new heat pump or $5,000 - $?,000 on the full system. I have the funds available to do either I'm just struggling to make the choice that makes the most financial sense.