Gas and Oil Home Heating Furnaces - replacing existing system

My central carrier airconditioner is more than 20yrs old and the blower motor stopped working. I replaced with a similar motor and after running for few minutes it over heated and stopped. I wired it in the same way it was wired before. Now called the technician and they said that it may the blower bearing is worn out and needs replacing. quoted 400 - 500 dollars for that.

They also suggested to replace the furnace and the airconditioner and quoted 4000 dollars for lennox 11 seers (HS 29 3 ton) outdoor unit and a lennox 80% G50 100,000 btu. this includes all the installation. They also mentioned that this would save me utility bills.

I am confused whether to get it repaired or replaced. if repairing it is it a good option and is the price fair? if replacing it is this a good price ? is lennox a good brand ? should i choose some other brand and if which brand?

Thank you

The following is advice from “Consumers Report” 1998…Quote:

CHOOSING A CONTRACTOR
A successful central-cooling purchase depends most of all on finding a contractor who will size and install the equipment correctly and will charge a reasonable fee. Central-air systems are generally sold and installed by independent contractors who also sell furnaces, heat pumps, and other equipment. In recent years, so-called consolidators have been buying up independent contractors to create national chains.
Neither independents nor chains are necessarily the better choice. As with hiring any other service provider, the first step to selecting a heating and cooling contractor is to canvass friends and family for recommendations. You might also contact your electric utility, which may have a list of firms it recommends. Finally, check the yellow pages under "air-conditioning contractors."
We recommend contacting at least three contractors, especially if you don't have a strong personal recommendation for a particular firm. Arrange to have each visit your home to prepare a bid, and ask:
· Are you licensed, insured, and bonded? If state or local law requires it (check with government offices), make sure the contractor has a valid air-conditioning contractor's license. And ask to see proof that the company is insured against liability.
· Are any of the company's technicians nationally certified? If not, do some plan to seek certification? Two industry groups--the Air Conditioning Contractors of America (ACCA) and North American Technical Excellence (NATE)--have recently begun certification programs to identify technicians who have met their standards of proficiency. So far, no more than a few hundred technicians across the country have qualified. Still, even an interest in certification may point to a contractor whose staffers seek excellence. If a contractor does employ certified staffers, insist that those technicians do the work.
· Will you prepare a complete cooling-load calculation and a duct design? Assessing cooling loads and designing the duct system on a room-by-room basis using standard industry calculations takes considerable work. But it results in a more accurate (and often lower) estimate than one that uses rule-of-thumb sizing. Contractors are not likely to do that free, but the good ones are likely to include it as part of their installation price.
· Will your company also maintain the system? Most contractors both install systems and maintain them. Ask if the contractor will extend the labor warranty offered by the equipment manufacturer--perhaps to the length of the manufacturer's parts warranty. Also, consider negotiating a service contract as part of the purchase price; see Caring for your cooler, below.
Be wary of bids that are considerably lower than the rest; they may exclude key services or parts. Once you've narrowed your choice, ask for and check the contractor's references, and check any complaints with the Better Business Bureau before you sign a contract. (End of quote.)

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BUY A NEW INDOOR COIL and don't buy from a dealer who hasn't explained why (or doesn't know why). This is why:

If you don't…you may as well buy a 10 Seer unit and save some money because the old coil will severely limit the performance and life expectancy of any new unit.

Check Amana at http://www.amana-hac.com/Products/INDOORCOIL.html

I like the detailed info at http://www.climatemakers.com/coil.htm

Also (Tips for Buying a New Air Conditioner) at http://hes.lbl.gov/hes/makingithappen/nrr.html

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HEATING AND COOLING EQUIPMENT SIZING:

Equipment is very seldom undersized. OVERsizing is the rule. Comparison to other homes will be misleading. Most air conditioners and heaters are too big...which is good for the seller and bad for the buyer.

You can have the calculations done by a local contractor as a part of the bidding process. Request the calculations to be done in writing and ask for them to conform to Manual J. Expect to pay for this service.

You can also go to the web. One such location is:
http://www.comfort-calc.com/price.html
Download their forms and you will get an answer. The best calculations conform to Manual J by Air Conditioning Contractors of America (ACCA). Ask them about the basis for their calculations.

See: http://www.proctoreng.com/articles/bigger.html for an excellent look at sizing air conditioners.

Another view of proper sizing is at http://www.buildingscience.com/501c.PDF
They find that even 80% of Manual J sizing is more than adequate in Tucson, AZ.

I suspect that your old unit is a belt drive. If the blower bearing is damaged, worn, and tight...the motor will slow down just BEFORE the motor shuts down and the motor will not coast. It may even stop before the motor safety clicks off.

If the motor is overheating for internal electrical reasons it may overheat and shut off with the belt OFF. Try it and feel the motor after 3 or 4 minutes. In any case internal electrical problems in the motor will cause it to shut down without slowing down and it will coast to a stop.