DIY Furnace and A/C Repacement


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Old 12-04-14, 11:00 AM
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DIY Furnace and A/C Repacement

AHHHH WE'RE ALL GOING TO DIE!!!

Now that that's out of the way. MY wife and I recently bought a house, this house has a 26 year old central heating and cooling system. The fuel is natural gas...

The furnace is a Lennox Conservator III G16. The furance works great. its been inspected twice before we bought it, checked out perfectly both times. It is also hungry, and way oversized. How can I tell? Because of short cycling. I have a programmable thermostat that holds the house temp between +/- 1. Even when its in single digit temps out the unit runs only for a few minutes at a time.

The AC is also a Lennox, but not sure of the model number. It does not do a very good job cooling, and judging by age alone, I am going to have a hard time finding someone to simply recharge it for me. The evap and condenser coils are clean.

A little background on me, I am a engineer, I did construction, commissioning, and start-up of thermal water treatment plants before going into controls, I have done my own electrical, carpentry, and plumbing work. I have always pulled permits and had my work inspected. I have no doubt I could pull off a furnace install with "contractor quality" and have it pass inspection.

I am planning taking a proactive approach and purchasing the major equipment in the early spring, then in spring, while we are between the heating and cooling season, I will replace the furnace and AC.

The furnace, to me, is pretty straight forward. I will familiarize myself to the local codes, pull the permit, go to town, I will pre-measure and purchase connecting duct work to mate the new furnace to the existing household duct work (which inspected well is properly sized).

The AC poses a little bit more of a challenge. I will have the system drained and vacuumed. I will remove the old, install the new, then hire someone to vacuum, leak-test and charge the new. I will of course have the whole system inspected and signed off before I commission the puppy.

I plan on going with a Goodman Furnace and AC. Consumer Reports rate them well, and I can buy them as a DIY installer. I am going to get a high efficiency two stage furnace. I just need to get to the sizing portion.

Why DIY? Two Reasons, I want to replace the system before it fails and cheap daycare cost me $18K/year, so money is a little on the tight side. Otherwise I would likely play the system to be installed.

I do find it interesting, the opposition to DIY furnace installs
 
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Old 12-04-14, 11:22 AM
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Be sure and do a Manual J. What's the sq. footage of your house and BTU on the furnace?
 
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Old 12-04-14, 11:57 AM
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The Lennox is 135,000 BTUs

The house was built in 1988 and is 2500 square feet of finished living space with, with maybe another 800 square feet of un-finished living space. The house has a walk out basement, most of the subterranean wall composes the unfinished living space in the basement, or a little less than half of the basement. That also where the utility room is at. I have a lot or space to work in.

I am in the process of installing ridged foam around the rim joist, sealing it with expanding foam. I am going to hold off on installing the ridged foam in the utility room until I have poked the holes for the furnace install.

I was considering using Manual J for the heat load calculation. Thank you!
 
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Old 12-04-14, 01:49 PM
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Is an equipment warranty of any importance to you? If yes, then you probably cannot self install. Even though Goodman equipment is sold over the Internet to anyone Goodman makes it clear that they WILL NOT WARRANT any self-installed equipment.

I have an extensive background in HVAC equipment and I DO know a bit about sheet-metal work but when it came time to replace my furnace I did not even consider DIY for two reasons, number one is because I wanted the warranty coverage and number two I wanted the work completed in one day.
 
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Old 12-04-14, 02:23 PM
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I don't know of any manufacturer who will honor the warranty on homeowner installed installed equipment nor any bought online. A lot of these online sellers claim "full factory warranty" or something of the sort but every manufacturer I know of will disclaim that statement.
 
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Old 12-05-14, 05:14 AM
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In this particular case, I don't care about warranty. I can replace the unit 2 or 3 times before I would approach the cost of paying a contractor to install the system.

Plus the Magnuson–Moss Warranty Act protect the consumer from manufactures not honoring warranty. Having reviewed Goodman's Warranty, the statement is in direct violation of the act.

Plus I can diagnose and fix, controls, mechanical, electrical, and chemical issues in an industrial setting, I can handle a furnace.
 
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Old 12-05-14, 06:25 AM
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Plus I can diagnose and fix, controls, mechanical, electrical, and chemical issues in an industrial setting, I can handle a furnace.
For YOU this is your safety net. Furnaces are a collection of simple circuits and interlocks that are easy to troubleshoot--but you may be on the hook for parts costs. Really not a big concern IMO.
There may be a couple specialized pieces of equipment you need for setting it up to operate at best efficiency. This is where my expertise ends.
 
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Old 12-05-14, 12:01 PM
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Plus the Magnuson–Moss Warranty Act protect the consumer from manufactures not honoring warranty. Having reviewed Goodman's Warranty, the statement is in direct violation of the act.
So in addition to your other talents you are also a lawyer.

Good luck on your plan but why did you even ask the questions if you had already made up your mind? I have a good friend who along with his father (a retired sheet metal worker) installed a new furnace. One positive in DIY is that the equipment IS well built and rarely is there a problem. I do urge you to do the gas pressure testing as well as the heat gain across the heat exchanger tests, something that not even certified installers always do.

For what it is worth, I am planning on removing my furnace and adding a cooling coil, maybe later this month as I will have a strong young man to help. It will entail changing the gas line, the vent piping and major revisions to the return air duct.
 
 

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