Sooner or later the time is going to come when you will have to replace that old gravity furnace.  It may happen when you discover parts are no longer available to repair that old blower.  Or, it may happen after you've called every dealer in town to come repair it, and find that no one wnats to work on it anymore.

If its your time to replace that old "octopus" in your basement, here a few tips that can make it somewhat easier for you -

• Realize that its not going to be a simple in and out thing.  Your neighbor may have gotten a new furnace and air conditioner for $4500, and had it installed in one day.  That's not going to happen for you.

1. Whoever does the work is going to spend at least half a day just cutting up the old furnace, and taking it out.
2. Your old duct work is now obsolete.  All of it will need to be redone.
3. Asbestos is likely to be a major consideration.  Odds are, all of that gray or white tape around the pipes and furnace are asbestos.  No reputable HVAC dealer is going to touch it.  By law you need to hire an asbestos abtement company to remove, and properly dispose of all the asbestos.  Many people chose to remove the asbestos themselves, but realize you are putting yourself, and your family at risk.
4. If you are taking this opportunity to add air conditioning, odds are you are looking at a whole house electrical upgrade.  Many older homes still have glass fuses rather than breaker boxes, and while you can adapt your old style fuse box to accept 220 volts - it is not a good idea.  You really need a breaker system, and at least 100 amps of power coming into your house.
5. You're going to be tempted to save a $1000 or more redoing the duct work.  Don't do it!  Your dealer needs to build a minimum of a four foot trunk line to run the individual supplies off of.  If they suggest running round pipe out of the plenum (top of the furnace) be very leary, especially if you have a two story house, and are adding air conditioning.  Without a trunk line air flow will not be good. 
6. You are going to need more return air.  Old homes normally have one or two central returns, rather than an individual return air register in each room.  Normally in an older home you have one return in the main room, and one at the bottom of the stairs.  Not enough.  If you are adding air conditioning, you will need to add retun air to the upstairs.
7. Realize that no matter what you do - When you add air conditioning, the upstairs will likely be 5 to 7 degrees warmer than the downstairs.  It's just the nature of the beast.  Unless you are willing to spring for a separate system for the upper level, this is the best you can do.
8. Expect the whole process to take 2 1/2 to 3 days, sometimes longer.  Add another day or two, if you need to do asbestos abatement.
9. Someone needs to take a good hard look at your chimney.  It may need a new liner.  If you are installing a high efficiency furnace, it will no longer use your chimney.  Instead two PVC pipes will be run out the side of the house.  One is to exhaust carbon monoxide, the other brings combustion air into your furnace.  If you still have a gas water heater, code in most area still requires your contractor to install a new chimney liner, if the old one is bad.
10. A humidifier is a really good option to consider.  That new furnace is going to dry out the air in your house rather quickly.  You need to add moisture to make your home more comfortable.
11. Do expect your installers to clean up after themselves, take all of the old equipment away, and to show you how to use and maintain your new equipment.

Finally, it may sound like a lot of work, but - The truth is, You have the easy part.  Once you pick the right dealer, they should take care of all the details for you.

If you need some tips on picking a new furnace, or on what to expect when your comfort consultant arrives at your door, see my other guide:  Furnace Buying Guide

I hope you found this guide helpful..  If you feel I should add something to it, please contact me, and I will be glad to consider adding it. 

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