Should I get a new furnace?

[st6_guy]

Need some advice:

- My central AC unit is on it's last leg, it's at least 25 years old, the original from the house, and I am suprised it lasted through the summer. It's rusty, noisy, and likely not efficient.

- The furnace is 10 years old (1993), and still works good, but some portion above the furnace (I think condenser) needs to be replaced to match the new AC uint. There is no access panel in the duct work, so they basically have to make one. And I need a new humidifier.

At least a few people have told me it's always best to get BOTH furnance and the AC done at the same time so they are a matched pair, and properly installed. I don't know too much about heating and cooling except I know I need an AC unit.

Advice is welcome.

[Roger Roney]

I would probably have some advice and direction for you, but since you do not appear to answer questions asking for further information or results, (roof vent thread,) I choose not to ask or advise you at this time.

[Divegeek]

Let me start off by stating that I am not a licensed HVAC person. I have though worked for my father who is off and on for the last 18 years. If the furnace put in in '93 is a quality name brand furnace of at least 90% efficiency I would not replace it. You can tell if it is at least 90% efficient by the type of flue vent it has. If it is a plastic type of piping (PVC) it is at least 90% efficient. Meaning that less than 10% of the heat created by the burning of the gas goes out the exhaust system. If you have a metal flue or chimney, I would probably replace it. Heating fuel prices are predicted to double in the next couple of years so you definately want to make sure that your furnace is efficient and that your house is WELL INSULATED. As for the efficiency rating of your air conditioning unit, that is expressed typically in SEER's. If we lived in an area of the country where you would be using your ac more than 3 or 4 months of the year, I would recomend that you get a more efficient one, but for people in Michigan my father doesn't recomend it, because it would take you too long to see a return on the investment in the difference in price of the units. The other thing, when picking a contractor make sure that you use one that runs a computerized heat loss/gain profile of the house. This takes into account insulation, number and type of doors and windows and tells them what size furnace and air conditioner to put in, rather than guessing. I have seen houses that had furnaces two sizes too big put in them because some idiot contractor didn't run the analysis, because he was either too cheap or too dumb. This causes efficiency problems.