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====== Mary Info ======

Passed away 10/13/2019 4:48 a.m.

===== Carrier 92 Furnace =====

==== Specs ====

Working on fixing Mary's Carrier 92 Furnace. This is a gas furnace with an air conditioner add-on.

^Manufacturer|Carrier Corporation, Indianapolis, Indiana, made in Mexico|
^Furnace Model|58MXA060-12|
^Furnace Product|58MXA060-F-17112|
^Furnace Serial|2705A00464|
^Date of Manufacture|Jul 2005|
^Motor H.P.|1/3|
^Max Unit Amps|7.2|
^Refrigerant|22, kPa 2068, maximum working pressure PSIG 300|
^Refrigeration Evaporator|252N|
^Refrigeration Model|519DXS030000MAAA|
^Refrigeration Serial|2989X77603|

{{:maryinfo:crc3265.pdf|Carrier 58MXA Manual}}

==== Symptoms ====

The symptoms:

  * Air flow going through the vents is very low
  * Air temperature coming through the vents is only slightly warm
  * Opened up the air conditioner chamber below the furnace. The air is only slightly warm here. The specs on the furnace panel indicate that the temperature rise should be 30 - 60 degrees.
  * While watching the flames, when the main blower starts, the flames are heavily pushed back away from the heat exchanger on two of the three flames, proving a Heat Exchanger failure. (I got hints on how to determine Heat Exchanger failure by watching a couple of YouTube videos.)

Did some disassembly and testing. The main blower motor seems to be running fine. It has 3 speeds and by adjusting the wiring, saw that the motor can run in all of the speeds. I configured it to run at the highest speed, but it still doesn't blow a lot of air through the vents.

Climbed under her house twice. Directly under the furnace is a rectangular plenum. Opened this and saw that it was clean. Reached up and blew through the air conditioner coils from below. Coils seem clean and not much debris got blown out. Sealed up the plenum using reflective duct tape.

The duct work looks OK, although was not able to fully examine it. While climbing over a part of it, broke it open, a duct near the under-house access. Fixed it by using ordinary duct tape and wrapped it several times.

3/28/2018: Operated the furnace with the panel opened below the heat exchanger. A moderate amount of air flows out, and it is somewhat warm, but doesn't seem warm enough. We operated the furnace for a few hours with this open, and it cycled somewhat normally, although her gas fireplace was running also, augmenting the heat. 

3/29/2018: Planning to open the burner chamber and see if I can examine the heat exchanger. It has some "rusticles" showing from the blower compartment. I'm not sure if the burner is working well enough. I see 3 flames, but maybe it has 4 burners. Also the heat exchanger could be plugged.

3/30/2018: There is obvious heat exchanger failure. When the main blower starts, two of the three flames are blown back away from the heat exchanger. Opening the heat exchanger area to see what needs to be replaced. There are several "blades" and I see rust but haven't yet opened up the area to see how many need to be replaced.

Heat Exchanger 320723-751 replacements:

  * http://www.technicalhotandcoldparts.com/carrier-320723-751-heat-exchanger-kit.html  $110 each.
  * https://www.repairclinic.com/PartDetail/Heat-Exchanger/320723751/2356484   $114.40 each.

3/31/2018: The furnace didn't seem to have broken heat exchangers. They were very rusty, but didn't see cracks. I'm thinking that the problem is leak between the intakes of the heat exchangers and the large metal plate. It was very rusty at this joint, and there was a lot of water on exchangers 2 and 3. Planning to order some gasketing material:

  * {{https://www.doityourself.com/forum/gas-oil-home-heating-furnaces/454459-high-temp-felt-gasket.html|Article mentioning solution}}
  * {{https://www.patriot-supply.com/products/showitem.cfm/LYNN_9650|Gasket Order Page, Patriot}}
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